Synthetic light generation method, light utilization method, light source unit, imaging method, and measuring apparatus

Abstract

To provide an optical detection method or an optical imaging method with high reliability or high accuracy, or to provide an application technique using the method.SOLUTION: At least a part of an optical path that starts from a light source or an optical path that reaches an optical detector is made of a plurality of optical paths. In a predetermined part of the middle of the optical path, light having passed through the plurality of optical paths is mixed. The mixed light is used for optical detection or optical imaging. The difference in the length of the optical paths between light passing through the plurality of optical paths may be larger than a coherent distance. Also, the above means may be combined with means of feeding back the difference to characteristics of light used for optical detection or optical imaging on the basis of a predetermined characteristic of a target body. Alternately, the means may be used alone, or the means may be developed into an application technique, an application material, or an application program using the means.SELECTED DRAWING: Figure 8A

Description

Technical Field

[0001] Embodiments of the present invention relate to a synthetic light generation method for obtaining a signal from a detection object using light (or detecting a predetermined optical property), a light utilization method, a light source unit, an imaging method, and an optical detection method.

[0002] Furthermore, it may be applied to application fields using the above optical detection or imaging. This application range includes substances (generation) capable of detecting internal structures and internal activity states using light, and management methods and manufacturing methods for predetermined states using light.

[0003] And not limited to the above, it may also include a calculation method for predicting the optical properties of the detection object.

Background Art

[0004] Optical detection methods and optical imaging methods are noncontact / noninvasive methods, so the burden on the detection object during detection is significantly reduced. As a result, the above detection methods and imaging methods using light are suitable for observing the natural state of the detection object and measuring minute changes. Therefore, these methods are widely used in a very wide range of fields.

[0005] Correspondingly, the application fields of these optical detection technologies and optical imaging technologies are also expanding. Some of this application field also includes substances (generation) capable of detecting internal structures and internal activity states using light, and management fields and manufacturing fields for predetermined states using light.

[0006] As these technologies are applied in a wide range, higher accuracy or higher reliability has been demanded for detection results and measurement results using light. Also, as a means for confirming the reliability and credibility of detection / measurement results using light, high-precision collation confirmation with theoretical support is also required.

Prior Art Documents

Patent Documents

[0007] [Patent Document 1] Japanese Patent Application Publication No. 6-167640 [Patent Document 2] Japanese Patent Application Publication No. 2-240545 [Patent Document 3] JP 2013-122443 A [Patent Document 4] JP 2003-500255 A [Patent Document 5] Patent No. 5098028 Summary of the Invention [Problem to be solved by the invention]

[0008] One way to improve the detection accuracy and reliability of optical detection and imaging technologies is to reduce optical noise (noise components generated by optical factors) that gets mixed into detection signals and optical images.

[0009] As an example of a specific means for achieving this, Patent Document 1 discloses a method for improving detection accuracy by reducing the coherence of light and lowering the amount of optical noise in the detection / measurement system. However, there is a limit to the speckle reduction that can be achieved within the scope of the disclosure in Patent Document 1, and there is a demand for even higher accuracy or reliability.

[0010] For the above reasons, there is a demand for optical detection methods and optical imaging methods that can achieve higher reliability or higher accuracy, or for application (utilization) development technologies that utilize these methods (including (the creation of) substances that can detect / measure / assess internal structures or internal activity states using light, or the provision of manufacturing methods and methods for managing specified states that enable improved manufacturing efficiency and improved control accuracy). There is also a demand for measurement devices and light sources to realize the above methods.

[0011] As another story related to the above, as a means of verifying the reliability and credibility of the results of the above optical detection and imaging, there exists a computer simulation method using various quantum chemistry calculation softwares. However, with existing quantum chemistry calculation softwares, it takes an enormous amount of calculation time to calculate the n-th overtone vibration of a polymer. Therefore, there is a demand for a calculation method that can simply and quickly perform the characteristics of the n-th overtone and combination tones limited to specific atomic groups within a polymer.

Means for Solving the Problem

[0012] Light in which lights with different optical lengths are combined (or mixed) is used for optical detection or optical imaging. Also, the above difference value of optical length may be longer than the coherence length. Furthermore, within the light obtained by the above combination (or mixing), the traveling direction or the direction of electric field vibration may be the same or similar.

[0013] Also, the above means may be applied to application development technologies using an optical detection method or an optical imaging method. That is, state management using the above light may be performed. Furthermore, it may be applied to the production of a predetermined substance or the evaluation of a manufactured product in which a chemical state or its change or a physicochemical (or physical) state or its change or a structure or its change or a form or its change that can be detected, measured, or managed using light occurs (during the manufacturing process). Also, not limited to that, it may be applied to the functional substance itself manufactured or evaluated by the above method.

[0014] The following means may be executed independently separately from the above means, or the following means may be used in combination with the above means. The following means are: 1) Measure a predetermined characteristic of an object to be the target of optical detection or optical imaging, 2) Based on the measurement results, feedback is provided on the characteristics of the light used for optical detection or optical imaging. Here, the above-mentioned predetermined characteristics are related to the wavefront characteristics of the light used for optical detection or optical imaging, or the influence on the propagation directions of some parts within the light. Also, the above-mentioned "characteristics of the light" mean wavefront characteristics or characteristics that change the propagation directions of some parts within the light.

[0015] On the other hand, not limited thereto, in order to theoretically predict the phenomenon meant by the optical characteristics of the object obtained from the optical detection results or optical imaging results, the following calculation method may be performed. α] Calculate the potential characteristics involved in the group vibration within a predetermined region contained in this object. β] Utilize the result to predict the absorption wavelength or absorption wave number (frequency) of the light.

Brief Description of the Drawings

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Mode for Carrying Out the Invention

[0017] Regarding the light source unit, measurement device, near-infrared microscope, optical detection method, imaging method, calculation method, state management method, and manufacturing method in this embodiment, an explanation will be given below with reference to the drawings. First, a table of contents regarding the content of this embodiment is shown so as to easily grasp the overall explanation. Chapter 1 Basic Configuration of the Measurement Device Showing this Embodiment Chapter 2 Influence on Optical Noise of Partial Coherence 2.1 Section Outline of the Explanation Procedure of this Embodiment Aimed at Reducing Optical Noise 2.2 Explanation of the situation where white light has partial coherence and definition of terms 2.3 Influence of partially coherent light on optical imaging 2.4 Influence of partially coherent light on measurement of spectral characteristics 2.5 Mathematical expression of an example of the influence of partially coherent light on spectral characteristics 2.6 Influence and wavelength range regarding detection / imaging using near-infrared light Chapter 3 Optical noise reduction method in this embodiment related to partial coherence 3.1 Basic principle for optical noise reduction 3.2 Utilization of emitted light in different directions 3.3 Optical property modification member having a wavefront splitting function 3.4 Synthesis (mixing) between split wavefronts 3.5 Mathematical expression of light intensity when using partially incoherent light (optical noise reduction effect) 3.6 Ingenuity in the structure of the optical property modification member 3.7 Comparison with prior art using wavefront splitting 3.8 Optical property modification member having an optical waveguide function 3.9 Synthesis (mixing) of emitted light from different regions 3.10 Application examples regarding synthesis (mixing) of emitted light from different regions 3.11 Method for reducing partial coherence and application examples regarding electromagnetic waves with wavelengths longer than infrared light 3.12 Simple explanation regarding the method for controlling the partial coherence of light Chapter 4 Method for mixing / separating coherent light and partially incoherent light 4.1 Structural example inside a measurement device using both coherent light and partially incoherent light 4.2 Method for mixing and separating coherent light and partially incoherent light Chapter 5 Interaction with light inside the object to be measured 5.1 Influence of light scattering, light absorption, and multiple scattering occurring inside the object 5.2 Relationship between the factors of scattering / absorption and the scattering cross-section 5.3 Scattering cross-section and characteristics of light scattering 5.4 Detection characteristics using backward scattered light (reflected light) 5.5 Formulation regarding interaction with electromagnetic waves inside the measurement object 5.6 Effects on measurement results and considerations based on differences in partial coherence of the irradiation light Chapter 6 Feedback method for wavefront aberration generated in the optical path 6.1 Principle of wavefront aberration generation inside the object (transparent parallel plate) 6.2 Wavefront aberration correction method 6.3 Common part of wavefront aberration characteristic detection methods 6.4 Wavefront aberration characteristic detection method using partially incoherent light 6.5 Wavefront aberration characteristic detection method using coherent light Chapter 7 Calculation method for the n-th harmonic characteristics limited to specific functional groups in polymers 7.1 Optical noise reduction method and absorption band wavelength prediction attributed to group vibrations in specific functional groups 7.2 Mathematical expression regarding group vibrations within functional groups 7.3 Significance of group vibration analysis within functional groups 7.4 Simulation method for absorption band wavelengths attributed to group vibrations Chapter 8 Functional biomaterials 8.1 What are functional biomaterials 8.2 Classification from the perspective of how functional biomaterials exert their unique functions 8.3 Examples of functional biomaterials that exert functions through amino acid sequences or three-dimensional structures 8.4 Examples of functional biomaterials that exert functions as structures within the active region or enzymes 8.5 Examples of functional biomaterials that exert functions in parts related to the production process Chapter 9 Genome editing processing using functional biomaterials 9.1 Examples of dealing with affected parts related to DNA damage and current problems 9.2 Structure and operating principle of carriers for nuclear transport in cells 9.3 Manufacturing method of carriers for nuclear transport in cells (compatible with mass production) Chapter 10 Manufacturing method and process management of functional biomaterials 10.1 Manufacturing Method and Basic Procedures for Process Management 10.2 Geographically Distributed Mass Production Process 10.3 Estimation of Functional Biomolecules Using Non-Interfering Near-Infrared Light 10.4 Optical Properties of Functional Biomolecules in This Embodiment 10.5 Manufacturing Method of Functional Biomolecules Manufactured in an Extracellular Environment Chapter 1 Basic Configuration of the Measuring Device Showing This Embodiment The basic configuration of the measuring device using the optical detection method and imaging method in this embodiment will be described with reference to FIGS. 1A to 1C. The basic configuration of this measuring device is all composed of a light source unit 2 and detection units 4 and 6. The light source unit 2 emits irradiation light 12 that hits the first light, and irradiates the irradiation light 12 onto an object 10 (detection object) that is the object of measurement or detection.

[0018] Here, the object 10 is not limited to living organisms such as animals, plants, and microorganisms (including bacteria and viruses), but may also be a single biological constituent such as nucleotides, amino acids / proteins, lipids (including phospholipids), and carbohydrates. In addition, other than that, organic substances such as plastics or inorganic substances that transmit at least part of the light may also be acceptable. Also, the form of the detection object 10 is not limited to solids, but may also be in a liquid or gaseous state. And the size of the single detection object 10 can be arbitrarily selected from the maximum order of meters (the size of humans and elephants) to the minimum size of atoms and molecules.

[0019] The second light obtained from this object 10 (that is, the light after the irradiation light 12 is reflected / transmitted / absorbed / scattered inside or on the surface of the object 10) is projected as detection light 16 onto the detection units 4 and 6. As a result, the optical properties of the object 10 (detection object) are detected or measured.

[0020] The optical properties of the object 10 obtained here include not only the light quantity properties after reflection / transmission / absorption / scattering of the object 10 and their temporal changes, optical phase properties, spectral properties (wavelength spectrum), imaging (extracted video / image), and image analysis results (such as spatial frequency characteristic analysis results), but also any optical properties may be included in the detection target.

[0021] Also, based on the results obtained by the detection units 4 and 6, the emission characteristics of the irradiation light 12 from the light source unit 2 may be controlled via the feedback unit 8. As specific examples, not limited to the steady emission amount control of the irradiation light 12 and the temporal change control of the emission amount, the phase distribution and light amount distribution of the irradiation light 12 immediately before irradiation of the object 10 may be controlled. Also, any other arbitrary control may be performed.

[0022] The characteristics of the measuring device when the irradiation light (first light) 12 irradiated on this object 10 is divergent, parallel, or convergent are shown in FIGS. 1A, 1B, and 1C, respectively. Also, in any of FIGS. 1A, 1B, and 1C, (a) is at the time of transmitted light detection (including forward scattered light detection), (b) is at the time of reflected light / scattered light detection, (c) shows the structure when the light source unit 2 and the detection unit 6 are integrated and housed in the measuring device 30.

[0023] In FIGS. 1A(c), 1B(c), and 1C(c), a part of the optical path between the irradiation light (first light) 12 and the detection light (second light) 16 is made common using the beam splitter 20. Thereby, an effect of facilitating miniaturization of the measuring device 30 is produced.

[0024] On the other hand, in the structure without using the beam splitter 20 in FIGS. 1A(b), 1B(b), and 1C(b), the relative position between the light source unit 2 and the detection unit 6 in the measuring device 30 can be arbitrarily set. As a result, there is an effect of increasing the flexibility of the measurement environment.

[0025] The light source 70 that emits the irradiation light 12 within the light source unit 2 (a specific example will be described later with reference to Fig. 10A) generally emits divergent light. Therefore, in the structures of Figs. 1B and 1C where parallel light or focused light is irradiated onto the object 10, it is necessary to mount a collimating lens 26 or a condenser lens 98 within the light source unit 2. In contrast, in the structure that directly utilizes the divergent light as shown in Fig. 1A, such mounting is unnecessary, resulting in the effect of reducing the cost and size of the entire measuring device 30.

[0026] When using the parallel irradiation light 12 as shown in Fig. 1B, the degree of freedom in the installation position of the object 10 with respect to the traveling direction of the irradiation light 12 increases. Therefore, it is suitable for optical property measurement when the object 10 is in a gaseous state or dispersed in a solvent in a liquid state. Thus, in this embodiment regarding the manufacturing method and state management method, the parallel irradiation light 12 as shown in Fig. 1B may be used.

[0027] In this case, the object 10 in a gaseous state or dispersed in a liquid medium is enclosed within the measurement sample column 34 in the transparent glass container 36. Here, the measurement sample column 34 is provided with an injection port 42 with a lid 46 and an outlet port 44 with a lid 46, facilitating the replacement of the object 10.

[0028] Furthermore, inside the transparent glass container 36, a reference sample column 32 partitioned by the wall 9 is also installed. Similarly, lids 46 are attached to the injection port 42 and the outlet port 44 of the reference sample column 32, enabling the inside of the reference sample column 32 to be evacuated. Moreover, without being limited thereto, the inside of the reference sample column 32 may be filled with only the liquid solvent before the dispersion of the object 10.

[0029] The transparent glass container 36 is movable relative to the measuring device 30. In particular, the moving direction 38 of this glass container is non-parallel (it may be orthogonal) to the traveling direction of the irradiation light 12. Therefore, after first measuring the optical properties in the reference sample column 32, the optical properties in the measurement sample column 34 may be measured, and the results of both may be compared. By comparing the two in this way, there is an effect of enhancing the detection accuracy of the optical properties obtained as the result of the measurement / detection. As a method for comparing the two, the difference between the measurement data after arithmetic processing (which may include normalization) may be taken, or the division processing (difference processing on a logarithmic scale) between the two may be performed. The measuring device 30 has a unique optical transmission characteristic (function), and the above-mentioned optical transmission characteristic is included in the optical properties obtained from the measurement sample column 34. On the other hand, when performing the division processing (difference processing on a logarithmic scale) between the optical properties of the measurement sample column 34 and the reference sample column 32, the optical transmission characteristic in the measuring device 30 is removed, and there is an effect of obtaining the optical properties of the object 10 alone.

[0030] The irradiation light (first light) 12 is scattered / absorbed by the detection object 10 in a molecular state that has vaporized (or is dispersed in a liquid medium). In FIG. 1B(b), the side scattered light at this time is detected as the detection light (second light) 16. On the other hand, in FIG. 1B(a), the transmitted light amount loss due to total scattering and absorption is detected. Also, when a mirror surface 48 is formed on the bottom surface of the transparent glass container 36 as shown in FIG. 1B(c), the transmitted light amount loss is detected in the same manner as in FIG. 1B(a). On the other hand, when the mirror surface 48 is not formed, the backward scattered light is detected as the detection light (second light) 16. By using the parallel irradiation light 12 in this way, various scattered light detections in the front / back / side directions are possible, and there is an effect of improving the detection accuracy.

[0031] When irradiating the object 10 with the convergent irradiation light 12 as shown in FIG. 1C, it converges at each of the points α, β, and γ inside the object 10 (the converging method will be described later in Chapter 7). As a result, there is an effect that the measurement / detection of the optical properties limited to a specific location inside the object 10 can be performed. In FIG. 1C(a), the forward scattered light can be measured / detected, in FIG. 1C(b), the side scattered light can be measured / detected, and in FIG. 1C(c), the backward scattered light can be measured / detected.

[0032] Chapter 2 Influence on Optical Noise of Partial Coherence (Chapter 2] Partial Coherence affecting Optical Noise) The following Chapter 2 will explain that white light also has the characteristics of partial coherence and can generate optical noise.

[0033] 2.1 Overview of the Explanation Procedure of the Present Embodiment for Reducing Optical Noise Reduce the optical noise mixed in the measuring device 30 shown in FIGS. 1A to 1C to improve the detection accuracy and reliability of optical detection or optical imaging. As a method for reducing the optical noise, in the present embodiment, at least one of the optical characteristics of the irradiation light (first light) 12 and the detection light (second light) 16 is changed. As the optical characteristics to be changed, (1) Reduce optical noise related to partial coherence (using an optical characteristic changing member) (2) Perform only one of the wavefront aberration or the feedback of the partial change in the traveling direction caused by the object 10, or perform both in combination.

[0034] Regarding the above (2), measure the influence on the irradiation light 12 or the detection light 16 in at least a part of the detection units 4 or 6, and change the optical characteristics of the irradiation light 12 via the feedback unit 8. Similarly, the inside of the detection units 4 and 6 may be controlled to change the optical characteristics of the detection light 16 (details will be described later in Chapter 6).

[0035] Prior to explaining specific embodiment examples regarding the above (1) in Chapter 3, Chapter 2 will explain the principle by which partially coherent light generates optical noise.

[0036] In addition, in order to verify the reliability and credibility of the findings obtained by optical detection or optical imaging, in this embodiment, computer simulations using quantum chemistry calculation software may be used in combination. And the method of this embodiment for theoretically calculating the characteristics of the n-th harmonic and the coupling sound limited to specific functional groups in the polymer will be described later in Chapter 7.

[0037] Section 2.2 Explanation of the Situation Where White Light Has Partial Coherence and Definition of Terms (Section 2.2) Occasion of Partially Coherent White Light and Definition of Technical Terms) It is known that monochromatic laser light generated from a semiconductor laser element (Laser Diode Tip) has coherence (Cohetency). Correspondingly, for example, white light emitted from a small light source 70 such as a tungsten halogen lamp (Tungsten Halogen Lamp) also has partial coherence.

[0038] For example, as shown in Fig. 2A, take the case where the light (white light) emitted from point α on the surface of the tungsten filament 50 and the light (white light) emitted from point β are simultaneously observed at point γ. When the "amplitude correlation" between the two is very strong, or when the "phase shift value" between the two is constant over time, the light of the two is called coherent light (Coherent Light). And in this case, "interference" occurs between the light of the two at point γ.

[0039] On the contrary, when there is no "amplitude correlation" between the two, or when the "phase difference changes completely independently" between the two, it is called incoherent light (Incoherent Light). And in this case, "interference" does not occur between the light of the two at point γ. And the light intensity observed at point γ is obtained by simply adding the light intensity obtained alone from point α and the light intensity obtained alone from point β.

[0040] By the way, most light other than the laser light that emits steadily is in an intermediate state between the above-mentioned coherent state and incoherent state. This state that is neither completely coherent nor completely incoherent is generally called partial coherence. Also, light in such a state is called partially coherent light.

[0041] When this partially coherent light is scattered, reflected, or transmitted by the object to be detected, partial "interference" occurs in the subsequent optical path, causing speckle noise. Therefore, when obtaining a signal from the object to be detected using light (detecting predetermined optical characteristics at a specific site within the object to be detected) or acquiring image information from the object to be detected, the quality and characteristics of the detection signal and image deteriorate due to the influence of speckle noise caused by the "optical interference phenomenon".

[0042] In this embodiment, as will be described later, a unique method of "(A) making the emission directions, different emission regions, different divided wavefronts, and different divided amplitudes of light mutually incoherent" and "(B) combining (mixing) the multiple mutually incoherent lights" is proposed. Therefore, in the description of this embodiment to be described later, the term "partially incoherent (including a state that is not completely incoherent but is somewhat incoherent)" is specifically used to mean that the light used for signal detection and imaging is "made partially incoherent". Thereby, the difference between this embodiment and the prior art is clarified.

[0043] In the optical operation corresponding to the above (B), the operation of combining mutually partially incoherent lights (partially incoherent light) is expressed as "mix" in the description of this embodiment. Also, the light obtained by the above mixing is called "mixed light".

[0044] In this description of the present embodiment, an operation of combining lights that have passed through different optical paths regardless of the interference state is expressed as "combine". That is, the lights to be combined may have interference (including partial coherence), or may be in a non-interference (including partial non-interference) state.

[0045] Depending on the optical operation method of combining lights in a wide wavelength range that have passed through a plurality of different optical paths, there are cases where it exhibits a mixed characteristic of having "partial non-interference in short wavelength components" and "partial coherence in long wavelength components". Also in this case, the combining operation is called "combine", and the light obtained as a result of the combination is expressed as "combined light" in this description of the present embodiment.

[0046] Also, the lights obtained by the above-described synthesis (or mixing) may have the same or similar propagation directions or electric field vibration directions. As a result, the lights before synthesis (or mixing) that pass through different optical paths pass through at least partially the same optical path after synthesis (or mixing).

[0047] First, the fundamental principle that causes the "interference property of light" described so far will be explained. Here, for the sake of ease of explanation, the concept of "indeterminacy regarding the light emission time of light within the frequency width Δν (cannot be uniquely defined within the time width Δt)" is used. However, as a general method for explaining the interference property of light, there is much content in the latter half of this section (Section 2.2).

[0048] Consider the case where white light emitted from point α on the surface of tungsten filament 50 in FIG. 2A passes through an optical narrow-band band-pass filter (wavelength selection filter) 52 that allows only light within the wavelength range from λ0 - Δλ / 2 to λ0 + Δλ / 2 and arrives at point γ at a distance R. At this time, the frequency (vibration number) range of the light that can pass through the narrow-band band-pass filter (wavelength selection filter) 52 is from ν0 + Δν / 2 to ν0 - Δν / 2.

[0049] Also, let the distance from this γ point to the β point on the surface of the tungsten filament 50 be R + δ. Let the propagation speed of light in vacuum be represented by C. The time when the light arriving at the γ point simultaneously departs from the β point is naturally considered to be earlier than the time when it departs from the α point by Δt = δ / C …(B·1) only.

[0050] However, there also exists the following Uncertainty Principle for light. 1 ≧ Δt·Δν …(B·2) That is, among multiple optical phenomena occurring within the time range Δt defined by the above equation (B·2) (for example, the emission of photons at multiple different positions, etc.), it is interpreted that it is difficult to identify the detailed temporal sequence. That is, the light emissions from multiple different positions occurring within the above time range Δt are regarded as "emitting light almost simultaneously".

[0051] By the way, between the central wavelength λ0, the wavelength range Δλ, the central frequency (vibration frequency) ν0, and its range Δν of the light that can pass through the optical narrow-band bandpass filter (wavelength selection filter) 52, (λ0 - Δλ / 2)×(ν0 + Δν / 2) = λ0×ν0 = C …(B·3) since the relationship holds, if we consider Δλ×Δν / 4 ≒ 0 in equation (B·3), Δν ≒ Δλ × C / λ0 2 …(B·4) the relationship is derived. Then, substituting equations (B·1) and (B·4) into equation (B·2), we get δ ≦ λ0 2 / Δλ …(B·5) That is, within the range where the optical path length difference δ in Figure 2A satisfies equation (B·5), all the light emitted from different positions (α point and β point) on the surface of the tungsten filament 50 is interpreted as "emitted almost simultaneously". In particular, the length satisfying the right side of equation (B·5) is called the coherence length. That is, the coherence length l CL is l CL ≡ λ02 / Δλ …(B·6) is expressed by the relational expression of

[0052] Therefore, within the range that satisfies the above formula (B·5), the lights have a relationship of partially coherent lights with each other. Also, although the formula (B·5) is not satisfied, the relationship between lights having a relationship close to the formula (B·5) is called low coherence. In particular, in the description text of this embodiment (although not used as a general term but to show uniqueness), the light controlled (operated) in the situation of departing from the above formula (B·5) is particularly called the above-mentioned partially non-interfered light.

[0053] In the example shown in FIG. 2A, the wavelength range Δλ in the formula (B·6) is set by using the optical narrow-band bandpass filter (wavelength selection filter) 52. However, not limited thereto, the wavelength range Δλ (wavelength resolution) that can be separated and detected in the detection unit 6 (FIGS. 1A to 1C) in this embodiment may be applied to the above formula (B·6).

[0054] For example, the above formula (B·6) can be used with the wavelength range that can be detected by one detection cell in the one-dimensional line sensor 132 installed in the spectroscope 22 in FIG. 14E as Δλ.

[0055] On the other hand, the value of the wavelength resolution (half-value width) of the spectroscope 22 itself in FIG. 14E may be applied to the above formula (B·6) as the above wavelength range Δλ. Here, the wavelength resolution (half-value width) of the spectroscope 22 shown as an example in FIG. 14E is greatly affected by the width of the slit 130 (or the pinhole width) W.

[0056] When the light with wavelength λ near the central wavelength λ0 is incident on the blazed diffraction grating 126, the diffraction angle θ is θ ≒ χ·λ …(B·7) is approximated as. Here, χ represents the diffraction angle coefficient with respect to the incident wavelength of the diffraction grating. When λ in this formula (B·7) is replaced with Δλ, the following formula is obtained. Δθ ≒χ·Δλ …(B·8) Furthermore, if the distance between the condenser lens 134-2 and the one-dimensional line sensor 132 is represented by SL, the amount of displacement ΔY on the one-dimensional line sensor 132 corresponding to Δθ is ΔY = SL·Δθ ≒ SL·χ·Δλ …(B·9) is obtained.

[0057] On the other hand, if the imaging magnification (lateral magnification) of the condenser lens 134-2 is M, the width of the slit 130 (or the pinhole width) W is ΔY = M·W / 2 …(B·10) Since there is such a relationship, from equations (B·9) and (B·10), Δλ ≒ M·W / (2SL·χ) …(B·11) This relationship holds. Substituting this equation (B·11) into the above equation (B·6) gives l CL = 2SL·χ·λ0 2 / (M·W) …(B·12) The characteristic equation is obtained.

[0058] Therefore, in this embodiment, according to the characteristics of various photodetection elements (or optical elements such as the optical narrow-band bandpass filter 10 (wavelength selection filter) in FIGS. 2A, 2B, or 4) that depend on the width W of the slit 130 and other parameters M, SL, χ in the measuring device or the near-infrared microscope device, the optical noise components such as the speckle noise of the irradiation light (first light) 12 or the detection light (second light) 16 are reduced (δ>l CL is achieved), and the optical system structure in the light source unit 2 or the detection unit 6 may be designed.

[0059] In the above, the optical system in the light source unit 2 or the optical system in the detection unit 6 is designed according to the characteristics (optical characteristics of the optical element (FIGS. 2A, 2B, or 4)) affected by the width W of the slit 130 (or the pinhole width) in the spectroscope 22 to reduce optical noise components such as speckle noise (δ>l CLSpecific examples have been described. However, not limited to this, in this embodiment, the optical noise components such as speckle noise are reduced (δ>l) according to the characteristics of the monitor camera 24 shown in FIG. 7 (wavelength separation performance / resolution, etc.), or the detection characteristics (wavelength separation performance / resolution, etc.) of various photodetectors (not shown) and the optical characteristics of optical elements. CL Devises may be made.

[0060] So far, a relatively narrow wavelength range Δλ has been taken as an example for explanation. However, not limited to this, for example, even when the wavelength range Δλ is very wide such as "white light", equations (B·5), (B·6), and (B·12) are applicable.

[0061] For example, when roughly estimating the wavelength range Δλ of white light emitted from a tungsten halogen lamp to be about 2 μm (0.5 μm to 2.5 μm) and the central wavelength λ0 to be about 1.2 μm, the coherence length l CL is 0.72 μm. That is, even for white light emitted from a plurality of different light-emitting points, interference occurs (partial coherence state) between white lights with the optical path length difference δ up to the measurement point (γ point) being 0.72 μm or less. And not limited to the above tungsten filament 50 as the light source, the same phenomenon occurs for white light emitted from any light source. For example, for a light source that emits white light simultaneously from a wide area (that is, even when the light-emitting area of the light source is very wide), the same phenomenon (interference) occurs between white lights emitted from minute light-emitting areas that satisfy equation (B·5).

[0062] In many cases, instead of explaining the coherence length using the concept of "uncertainty in the emission (light emission) time within the time range Δt" as described above, it is often explained as the distance at which interference can occur between different wave trains as follows.

[0063] For example, consider the case where white light emitted from a light-emitting point propagates in the same direction (e.g., the z-axis direction) within a space. Assume that at the location where t = 0 and z = 0, the phases of all wavelength lights included in the white light (the position in the z-axis direction where the electric field amplitude value becomes the "maximum value") coincide. The electric field amplitude distribution region for all wavelengths that is localized within the range of the coherence distance in this vicinity is defined as a "wave train".

[0064] Citing the above-described calculation example of the coherence distance, when the wavelength range included in white light is 0.5 μm to 2.5 μm, the range where one wave train is defined is -0.36 μm ≤ z ≤ 0.36 μm (= 0.72 μm ÷ 2). Since this 0.36 μm is shorter than the shortest wavelength of 0.5 μm, within the same wave train, the phases of all wavelengths are almost aligned.

[0065] Therefore, when a part between two adjacent wave trains in the z-axis direction overlaps, interference occurs with all wavelength lights within the overlapping region.

[0066] 2.3 Influence of Partially Coherent Light on Optical Imaging Within the range that satisfies equation (B·5), light emitted from different positions (point α and point β) on the surface of the tungsten filament 50 (light source) in FIG. 2A is all interpreted as being "emitted almost simultaneously". Therefore, as shown in FIG. 2B, for the light that has passed through the optical narrow-band bandpass filter 10, the phases (the positions of the valleys in the light propagation direction) of the electric field amplitudes 54 are all considered to be the same.

[0067] An example of the interference phenomenon that occurs when the partially coherent light having this characteristic passes through an "optical transmission object 56 having a fine uneven structure on one side" is shown in FIG. 3. In FIG. 3(a), since there is no uneven structure on the surface of the optical transmission object 56, there is no cancellation effect (based on the interference caused by the phase shift) between adjacent partially coherent lights 60.

[0068] In Figure 3(b) of one side, the surface of the light-transmitting object 56 has an uneven structure with a step d. Here, assuming the refractive index of the light-transmitting object 56 is n, the optical path length after passing through this interior by a mechanical distance d is "nd". On the other hand, the optical path length after passing through a distance d in a vacuum is d. Therefore, the difference δ in the optical path length between the light passing through the upper path (in a vacuum with a thickness d) in Figure 3(b) and the light passing through the lower path (the light-transmitting object 56 with a thickness d) in Figure 3(b) is δ = (n - 1)d …(B·13) When δ = λ0 / 2, the partial coherent light passing through the upper path and the lower path in Figure 3(b) interferes (cancels out), and the intensity of the direct light becomes "0". When the amount of transmitted light is detected by the detector 6, the difference between Figures 3(a) and (b) (the influence of interference) appears as optical noise.

[0069] Figure 3 shows an example of the influence on the optical imaging of the fine uneven structure during light transmission in the optical path, but it is not limited to this. Similar phenomena (interference between reflected light and scattered light) also occur in light reflection and light scattering in the optical path.

[0070] In the explanation using Figure 2A, the coherent distance was explained as the range where interference occurs between "the irradiation light 12 emitted (released) from the light source" (Figures 1A to 1C). However, it is not limited to this. Similar interference effects also occur between "the light (partial coherent light) reflected or scattered (including transmission) within the minute region within the object 10 (Figures 1A to 1C)", which is the object of observation, measurement, and detection.

[0071] Figure 4 shows an example where the irradiation light 12 travels from right to left, and the light backscattered by a part of the minute light scatterer 66 within the object 10 is used as the detection light 16 (see Figures 1A to 1C). Consider the case where the backscattered light at points α and β within the minute light scatterer 66 is detected (measured) at point γ. When the difference δ between the optical path length from point β to point γ and the optical path length from point α to point γ satisfies the relationship of Equation (B·5), optical interference occurs at point γ between the light from points α and β.

[0072] Furthermore, if the surface of the object 10 has a fine uneven structure, an interference phenomenon occurs as in the description of FIG. 3, and light intensity variations in the detection direction occur in the detected light quantity. As a result, it has a great adverse effect on optical imaging. Also, not limited thereto, even when the refractive index inside the object 10 is non-uniform (has a refractive index distribution), an interference phenomenon (unnecessary light intensity variations in the detection direction) similarly occurs, having a great adverse effect on optical imaging.

[0073] 2.4 Influence of Partially Coherent Light on Measurement of Spectral Characteristics When the irradiation light 12 or the detection light 16 (FIGS. 1A to 1C) is partially coherent light, the reason for the deterioration of optical imaging due to the influence of interference (speckle noise) was explained in Section 2.3. Also, not limited thereto, the reason for having a great adverse effect on the detection signal obtained after photoelectric conversion and the measurement results of the spectral characteristics (such as light absorption characteristics) of the object 10 itself will be explained.

[0074] As an example of the structure of the object 10 in FIGS. 1A / B / C(a), a light-transmissive object 58 having a fine uneven structure (step with height d) on one side is shown in FIG. 5. And as the incident light having partial coherence passing through here, FIG. 5(a) shows the case of long-wavelength light 68, and FIG. 5(b) shows the case of short-wavelength light 62.

[0075] Between the light passing through the upper part of the step d and the light passing through the lower part, a difference in optical path length δ corresponding to Equation (B·13) occurs. In the state of FIG. 5(b) where the relationship “δ≈λ” is satisfied with respect to the wavelength λ of the incident light in vacuum, the phases of the light passing through the upper part of the step d and the light passing through the lower part match. Therefore, in this state, the reduction in the light quantity of the transmitted light is small.

[0076] On the other hand, when the relationship “δ≈λ / 2” holds in the state of FIG. 5(a), a “cancellation phenomenon of the directly transmitted light quantity due to interference” occurs between the light passing through the upper part of the step d and the light passing through the lower part. As a result, a reduction in the directly transmitted light quantity occurs.

[0077] When the directly transmitted light quantity changes depending on the wavelength of the incident light in this way, a large error occurs in the measurement results of the spectral characteristics (such as light absorption characteristics) of the object 10 itself to be measured.

[0078] As a characteristic of the light-transmitting object 58 in FIG. 5, an example having only a fine concavo-convex structure on one surface was used for explanation. However, it is not limited thereto, and an optical interference phenomenon also occurs inside the light-transmitting object 58. That is, in an inorganic dielectric, an organic substance (a polymerized polymer), or a living body that is an object through which light can pass with a predetermined thickness, light scattering occurs in each minute region. When the traveling directions after exiting from the object are different and the multiple scattered lights coincide with each other, optical interference similar to that in FIG. 5 occurs.

[0079] FIG. 23A shows the experimental results of measuring the wavelength change of the transmittance for a polyethylene sheet having a thickness of 30 μm and flat both surfaces (detailed experimental conditions will be described later). In FIG. 23A(a), the measurement is performed with near-infrared light having a high partial coherence, and as it moves to FIG. 23A(c), the near-infrared light has a high partial non-coherence. As it moves from FIG. 23A(a) to FIG. 23A(c), the transmittance at a wavelength of 1.360 μm sequentially increases from 85.3 to 85.80% and 87.2%. The change at the same wavelength for the same sample (object 10) is considered to be due to the difference in the partial non-coherence of the near-infrared light used for the measurement.

[0080] That is, when light passes through the polyethylene sheet, the multiple scattered light generated inside the polyethylene sheet also passes through to the rear of the polyethylene sheet. When the partial coherence of the detection light 16 after passing through this polyethylene sheet is high, the detection lights 16 traveling in the same direction interfere with each other to reduce the intensity of the direct-propagating light. On the other hand, when the partial non-coherence of this detection light 16 is high, it is considered that the decrease in the intensity of the direct-propagating light due to the interference between the detection lights 16 traveling in the same direction is small.

[0081] For ease of explanation, the influence on the spectroscopic characteristic measurement results was explained using the example of FIG. 5 in which parallel light passes through the object 10. However, it is not limited thereto, and for all the structures shown in FIGS. 1A to 1C as the measurement apparatus of this embodiment, the phenomena in Sections 2.4 or 2.3 also occur.

[0082] Furthermore, as described in Section 2.3 with reference to FIG. 4, the above phenomenon also occurs when measuring spectroscopic and absorption characteristics using the reflected light from the minute light scatterer 66. Therefore, even in a near-infrared microscope for measuring the minute light scatterer 66, as shown in FIG. 7 in this embodiment, an optical noise reduction element or a partial coherence reduction element 64 may be used to reduce optical noise.

[0083] In the microscope according to this embodiment shown in FIG. 7, the irradiation light (first light) 12 irradiated from the light source 70 is converted into parallel light by the collimating lens 26 and then condensed by the objective lens 25 at a specific location inside the object 10. The light reflected at this specific location is imaged as detection light (second light) 16 on the spectroscope 22 and on the monitor camera 24.

[0084] As a specific optical path, the detection light (second light) 16 obtained from inside the object 10 becomes parallel light by the objective lens 25 and is separated from the optical path of the irradiation light (first light) 12 by the beam splitter 20. Then, it is separated by the beam splitter 18 in the detection unit 6 into different traveling directions. The separated detection light (second light) 16 is condensed by the detection lenses 28-1 and 2 on the monitor camera 24 and on the spectroscope 22 (specifically, on the pinhole or slit 130 shown in FIG. 14E). The combination of the objective lens 25 and the detection lenses 28-1 / 2 forms an imaging optical system between the specific location inside the object 10 to be detected or measured by this microscope and the detection positions (imaging surface, pinhole or slit 130) of the spectroscope 22 and the monitor camera 24. Thereby, only the characteristic signal at a predetermined position in the depth direction inside the object 10 can be extracted.

[0085] In the microscope of this embodiment, an optical noise reduction element or a partial coherence reduction element 64 (the detailed structure and operation will be described later in Chapter 3) may be inserted in the middle of the optical path. Thereby, the partial non-coherence of the irradiation light (first light) and the detection light (second light) 16 is improved, and the optical noise based on optical interference is reduced.

[0086] In addition, near-infrared light within the wavelength range defined in Section 2.5 may be used as the light for the microscope device. In this embodiment, the microscope device using the above-mentioned near-infrared light is particularly referred to as a "near-infrared microscope device".

[0087] Section 2.5 Mathematical Expression of the Influence of Partially Coherent Light on Spectral Characteristics When using partially coherent light for measuring the spectral characteristics (such as absorption characteristics) within the object to be measured, it was qualitatively explained in Section 2.4 that the detection signal characteristics deteriorate due to the influence of speckle noise caused by optical interference. In this Section 2.5, a specific model example will be used for quantitative (mathematical) explanation.

[0088] As panchromatic light sources from the visible region to the near-infrared region (panchromatic, emitting many different wavelength lights simultaneously in a wide wavelength range), tungsten-halogen lamps and xenon lamps are known. These structures have halogen-based gases (iodine or bromine compounds) or xenon gas encapsulated around the tungsten filament. And from an optical perspective (with an accuracy of the order of the wavelength of light), the thickness of the quartz glass vessel encapsulating these gases has no uniformity, and there are thickness irregularities depending on the location. Therefore, during the process of the panchromatic light generated inside the vessel passing through the vessel, optical interference occurs due to the thickness irregularities of the vessel.

[0089] This situation model is shown in FIG. 6. Assume a case where the divergent light generated near the tungsten filament 50 of the light source 70 becomes parallel light after passing through the vessel 67 and then through the collimating lens 26 with a focal length F. Here, the radius of the aperture (Pupil Area) of the collimating lens 26 is normalized to "1". And with the optical axis of this collimating lens 26 as a reference, the angle between the traveling direction of the light generated from the α point near the tungsten filament 50 and passing through the β point on the surface of the vessel and the collimating lens 26 aperture is η, and the radius of the position where this light passes through the aperture of the collimating lens 26 is represented by r. Next, the refractive index inside the vessel (quartz glass) 67 of the tungsten-halogen lamp is denoted as n, and its thickness is denoted as T.

[0090] When the angle η is small enough, the relationship between the angle ρ of the light propagation direction inside the bulb (quartz glass) 67 of the tungsten-halogen lamp can be obtained from Snell's law ρ ≒ η / n …(B·14) Therefore, when the mechanical distance τ when passing through the bulb (quartz glass) 67 of the tungsten-halogen lamp, when the angle η is small enough, it can be approximated as follows for convenience τ = T / cosρ ≒ T …(B·15) Consider the case where the thickness of the bulb (quartz glass) 67 of the tungsten-halogen lamp at the γ point on the bulb surface is thinner by d than the periphery. Also assume that the angle when generated from the α point, passing through the γ point, and then exiting the bulb 67 and heading towards the collimating lens 26 is η. Since the light passing through the β point and the γ point travels in the same direction, interference occurs due to the characteristics of partial coherence

[0091] Using the approximation of equation (B·15), the optical path length difference δ between the light passing through the β point and the γ point is the same as equation (B·13). Then the composite wave ψ after passing through the bulb (quartz glass) 67 of the tungsten-halogen lamp via the β point or the γ point, when the wave number is k and the light propagation direction is z ψ(r) = e ikz + Ae ik[z+(n-1)d] = e ik[z+(n-1)d / 2] { (1 - A)e -ik(n-1)d / 2 + 2Acos[k(n - 1)d / 2]} = e ik[z+(n-1)d / 2] ×{ (1 + A) cos[k(n - 1)d / 2] - i(1 - A)sin[k(n - 1)d / 2)}…(B·16) Here, the amplitude of the light passing through the γ point is set to "1", and the amplitude of the light passing through the β point is set to "A".

[0092] Although the distribution of the thickness deviation of the bulb (quartz glass) 67 of the tungsten halogen lamp is non-uniform, the calculation is advanced by simplifying the calculation model and assuming that "the thickness deviation d of the bulb is uniformly distributed". The area of the radius r and width dr on the aperture plane of the collimating lens 26 is 2πrdr, and all the composite waves Ψ passing through the aperture of the collimating lens 26 are

[0093]

Number

[0094] becomes. Therefore, when the light intensity Ic of this composite wave Ψ is normalized by the maximum value, from k = 2π / λ

[0095]

Number

[0096] is obtained. The second term of equation (B·18) indicates that "when light interference occurs partially during the measurement of the spectroscopic characteristics using partially coherent light, the detected light amount changes cosine-wave-like depending on the measurement wavelength".

[0097] Not limited to the thickness deviation of the bulb (quartz glass) 67 of the tungsten halogen lamp, a phenomenon similar to the above occurs when interference occurs between partially coherent lights for any reason. Due to some reason in the light source unit 2 or the detection unit 6 (in FIGS. 1A to 1C), an optical path length difference δ occurs, and the composite wave ψ of different coherent lights (when the vibration directions also coincide) traveling in the same direction is the same as equation (B·16) ψ = e ikz + Ae ik(z+δ) = e ik[z+δ / 2] { (1 + A) cos(kδ / 2) - i(1 - A)sin(kδ / 2)}…(B·19) but here |ψ| 2 ≡{ (1 + A) 2 cos2(kδ / 2) + (1 - A) 2 sin2(kδ / 2)} 1 / 2…(B·20) And

[0098] [Number]

[0099] If we set it as..., the formula (B·19) becomes ψ = |ψ|e ik(z+δ / 2+σ) …(B·22) and can be transformed. And the formula (B·22) means that "the composite wave ψ formed by synthesizing two plane waves with different phases becomes a single plane wave with a phase of δ / 2 + σ". Furthermore, for the same reason, when synthesizing multiple plane waves with partial coherence of 3 or more, a single plane wave can be obtained.

[0100] (For example, when there is no spherical bulb 67, etc.) Let Ψ0 be the composite wave for all the light passing through the collimating lens 26 when there is no factor causing optical interference at all, and let Ψ1 be the new composite wave generated by the factor causing optical interference. When each of the composite waves Ψ0 and Ψ1 has partial coherence, a "change in the detected light amount in the detected wavelength direction" similar to the formula (B·18) occurs from Ψ0 + Ψ1 obtained by further synthesizing the two.

[0101] Next, as a calculation model different from the above, consider the characteristics when "the wall surface of the spherical bulb 67 of the tungsten halogen lamp is regarded as a flat parallel plate and the divergent light heading towards the collimating lens 26 passes through it". Here, for the simplicity of calculation, it is regarded that "the amplitude distribution of the light passing through the collimating lens 26 is constant everywhere".

[0102] Let the NA (Numerical Aperture) value of the collimating lens 26 be represented by NA. Then, from Figure 6, r = η / NA …(B·23) becomes. Here, the formula (B·14) which approximates Snell's law is used, but for the formula (B·15), the following approximate formula with slightly higher accuracy is used.

[0103] [Number]

[0104] The second term on the right side of this equation (B·24) corresponds to "d" in equation (B·13) (or equation (B·16)).

[0105] Similar to the previous calculation model, since the area with radius r and width dr on the aperture plane of the collimating lens 26 is 2πrdr, all the composite waves Ψ passing through the aperture of the collimating lens 26 are

[0106]

Number

[0107] given by. Here, v ≡ r 2 When setting it as such, from rdr = (1 / 2)dv, the integration result of equation (B·25) becomes the following equation.

[0108]

Number

[0109] Here, replacing ψ in equation (B·16) with Ψ, setting "A = -1", d = -T·NA 2 / (2n 2 ) …(B·27) When replacing, it is proportional to equation (B·26). Therefore, the normalized optical intensity Ic regarding the composite wave Ψ is obtained by performing the above replacement on equation (B·18)

[0110]

Number

[0111] is obtained. According to the second term on the right side of equation (B·28), the detection intensity changes periodically in response to the change of the measurement wavelength λ. Also, the period of the detection intensity change corresponding to the measurement wavelength λ changes with the thickness of the parallel flat plate (the tube sphere 67) or the NA value of the collimating lens 26.

[0112] The parallel light after passing through the collimating lens 26 in Fig. 6 passes through the object 10 and enters the detection unit 6 as shown in, for example, Fig. 1B(a). In the detection unit 6, as shown in, for example, Fig. 14E, after being condensed by the detection lens 28-2, a signal including the characteristics of formula (B·28) is detected or measured using the spectroscope 22. However, not limited thereto, a signal including the characteristics of formula (B·28) can be detected or measured using any of the optical systems shown in Figs. 1A to 1C. That is, formula (B·28) shows that "when a parallel plate (such as the wall of the bulb) transparent to the diverging light path or converging light path of partially coherent light is arranged in the optical path from the light source 70 to the photodetector 80 (Fig. 8B), in principle, due to the influence of light interference, optical noise whose intensity changes periodically according to the wavelength λ change can occur".

[0113] In formula (B·28), the change amount of the periodically generated optical noise becomes very large. When formula (B·27) is substituted into formula (B·13), the maximum value δmax of the optical path length difference is δmax = -(n - 1)T·NA 2 / (2n 2 ) …(B·29) and is given by. In formula (B·29), when the thickness T of the parallel plate (such as the wall of the bulb) increases, δmax > l CL will result (the calculated value of the actual coherence distance l CL will be described later in section 2.7). In this state, light interference between the light passing through the center and the peripheral part of the aperture of the collimating lens 26 does not occur inside the spectroscope 22.

[0114] The approximation of formula (B·24) holds only in a range where the value of ρ is sufficiently small. Furthermore, the uniformity of the thickness of the bulb 67 of the tungsten halogen lamp made of quartz glass is not very high, and large thickness unevenness is expected. Also, the amplitude distribution of the aperture of the collimating lens 26 deviates greatly from uniformity. As a result, actually, an optical noise amount much smaller than that of formula (B·28) is observed.

[0115] In a panchromatic light source such as a tungsten halogen lamp or a xenon lamp, a difference in optical path length can occur within the bulb disposed around the tungsten filament. As a result, the panchromatic light emitted from the light source (including the above bulb) often contains an optical noise component such as in formula (B·28).

[0116] When actually measuring the amount of the optical noise component in the emitted light from the above panchromatic light source, it is not as large as given by formula (B·28). Due to the various factors described above, it is considered that the amount of the optical noise component decreases from formula (B·28).

[0117] When actually examining the emitted light from a plurality of types and a plurality of tungsten halogen lamp light sources (including the bulb), the optical noise component (the coefficient of the second term on the right side of formula (B·28)) was about 0.1 to 1.0% when the DC component (the coefficient of the first term on the right side of formula (B·28)) was set to "1".

[0118] For comparison with the above, the amount of the optical noise component allowed for a panchromatic light source will be described. When direct parallel light passes through a polyethylene film with a thickness of 30 μm, as shown in Fig. 23A, the light absorption amount of the absorption band attributed to the second overtone of the group stretching vibration of the methylene group (-CH2) changes by about 0.5% (details will be described later in Chapter 5 etc.).

[0119] Therefore, the amount of the optical noise component allowed for a panchromatic light source needs to be at most an average of 0.5% or less (desirably an average of 0.1% or less) at worst. Not limited to the experimental conditions of Fig. 23A, there is also a need to measure with a sample (film) thinner than 30 μm. Therefore, the amount of the optical noise component needs to be an average of 0.05% or less or 0.02% or less. Here, the above amount of the optical noise component is defined as the ratio of the optical noise component (corresponding to the coefficient value of the second term on the right side of formula (B·28)) when the DC component (the coefficient of the first term on the right side of formula (B·28)) is set to "1".

[0120] With respect to the optical noise components originally contained in the polychromatic (non-monochromatic) light source light, which is about 0.1 to 1.0%, due to the influence of a globe or the like, it can be reduced to an average of 0.5% or less (alternatively, an average of 0.1% or less, preferably an average of 0.05% or less, or 0.02% or less) according to the embodiment described in Chapter 3. On the other hand, as described in "Problems to be Solved by the Invention", in the prior art such as Patent Document 1, there is a limit to reducing optical noise, and it was difficult to reduce optical noise to an average of 0.5% or less (alternatively, an average of 0.1% or less, preferably an average of 0.05% or less, or an average of 0.02% or less). And as shown in FIG. 9, the embodiment examples described later in Chapter 3 comprehensively present all methods for effectively reducing the optical noise generated by the influence of optical interference.

[0121] Therefore, as a result of performing some optical noise reduction process on the irradiation light 12 (or detection light 16) obtained from a non-monochromatic light source containing a globe or the like inside the light source, when the amount of optical noise components in the irradiation light 12 (or detection light 16) achieves an average of 0.5% or less (alternatively, an average of 0.1% or less, preferably an average of 0.05% or less, or an average of 0.02% or less), it can be regarded as having implemented any one or a combination thereof of all (described in Chapter 3) the embodiments of the present invention.

[0122] 2.6 Influence on Detection / Imaging Using Near-Infrared Light and Its Wavelength Range The spectroscopic characteristics (absorption characteristics) and light scattering characteristics detected in the visible region or the infrared region (mainly the wavelength regions of mid-infrared light and far-infrared light) appear as relatively large changes. Therefore, regarding the signals obtained in the visible region or the mid / far-infrared region, the influence of optical noise is not much of a problem. However, in nature, there are few substances that are transparent to visible light, and the types of measurement objects that can be measured with visible light up to a depth inside the surface are limited. In addition, since water molecules absorb mid-infrared light and far-infrared light well, it is difficult to use mid-infrared light and far-infrared light for measuring the internal characteristics of a measurement object that is slightly wet or has a wet surface.

[0123] In contrast, near-infrared light with a wavelength range within 0.7 to 2.5 μm has excellent transmission characteristics for dielectrics, organic substances, and living organisms. Therefore, it is appropriate to utilize near-infrared light for measuring the characteristics inside the measurement object 10 composed of these substances. Particularly, due to its excellent light transmittance in living organisms, near-infrared light is called the "window of life."

[0124] For visualizing (imaging) the activity state inside a living body, f-MRI (Functional Magnetic Resonance Imaging) is often used. Particularly when dealing with imaging, the Pulse Fourier Transform Spectroscope is frequently used aiming at increasing the processing speed. However, since the pulse width for excitation in this method (Pulse Width of Magnetical Excitation) is on the order of microseconds, it has the drawback that it cannot detect changes faster than that.

[0125] On the other hand, in activities inside a living body (biological reactions, biochemical reactions, or catalytic reactions), the reaction is often completed at a high speed of less than microseconds. Therefore, with the above f-MRI (or NRI), it is impossible to detect the activities inside a living body that occur at high speed. On the other hand, if a high-speed photodetector (or imaging device) is used, it is possible to detect high-speed changes inside a living body using near-infrared light. Therefore, near-infrared light is suitable for detecting high-speed changes (activities) inside a living body (less than microseconds).

[0126] However, although near-infrared light has good transmission characteristics for dielectrics, organic substances, and living organisms, conversely, the absorption and scattering of near-infrared light in these substances are small. Therefore, the amount of signal change obtained by near-infrared light from a specific region inside the measurement object 10 is extremely small.

[0127] As shown by the experimental data in Fig. 23A as a specific application example, the difference in light transmittance between the actually measured minimum value at a wavelength of 1.213 μm and the interpolated value (at the same wavelength position) estimated from the envelope connecting its periphery is very small, about "0.5%".

[0128] Since the amount of signal change using near-infrared light is extremely small in this way, it is necessary to reduce optical noise to obtain a sufficient signal-to-noise ratio (S / N ratio). Therefore, when detecting or measuring the characteristic state or its change in a specific region inside the object 10 using near-infrared light, the optical noise reduction method using this embodiment becomes particularly important.

[0129] In particular, when using near-infrared light, the optical noise reduction techniques in imaging described in Section 2.3 and signal detection (after photoelectric conversion) and measurement of spectroscopic characteristics (e.g., wavelength dependence of absorption characteristics and light scattering characteristics) described in Section 2.4 become important.

[0130] However, the optical noise reduction method described in this embodiment is not unsuitable for detection signals obtained using the visible region or the mid / far-infrared region. Applying the optical noise reduction method described later in Chapter 3 and subsequent chapters to detection signals obtained using the visible region or the mid / far-infrared region also reduces the amount of noise and further improves the S / N ratio.

[0131] In addition to the method of this embodiment for optical noise reduction specifically described in Chapter 3 and subsequent chapters, the following limitation of the used wavelength range may be used in combination. As a result, a sufficient S / N ratio can be obtained, and the accuracy and reliability of signal detection and measurement are improved.

[0132] The above combination particularly has a great effect when detecting or measuring the composition, structure, activity state, or its change inside a living body using near-infrared light. This is because there are many substances in the living body that absorb light in a specific wavelength range for near-infrared light defined within the range of 0.7 to 2.5 μm. Therefore, the near-infrared light within the specific wavelength range absorbed by the above substances is absorbed in large amounts in the living body, and the amount of detected signal is significantly reduced. Therefore, using light with a wavelength avoiding the above specific wavelength range for detection and measurement can prevent an unnecessary decrease in the amount of detected signal.

[0133] Examples of substances that absorb light in a specific wavelength range within the near-infrared region include oxygen concentration indicator substances such as hemoglobin, myoglobin, cytochrome oxidase, and pyridine nucleotide (their absorption characteristics are described in detail in Patent Document 2). Hemoglobin and myoglobin (especially in the deoxidized state) have a sharp increase in absorbance in the wavelength range of 850 nm or less. Therefore, as the wavelength range of use limited in this embodiment, a range of 875 nm to 2500 nm including some margin is desirable.

[0134] On the other hand, the absorbance of oxidized cytochrome oxidase slightly increases when it reaches 940 nm or less. Therefore, considering the absorbance characteristics of the above-mentioned oxidized cytochrome oxidase, a range of 950 nm to 2500 nm including some margin is more desirable.

[0135] Water molecules exist as in-vivo substances that strongly absorb near-infrared light. From the description in Patent Document 3, the region with the largest absorption within the specific wavelength range related to these water molecules has a central wavelength of 1.91 μm and a half-value range of absorbance of 1.894 to 2.061 μm. Therefore, light limited within the range of 875 nm or more and 1890 nm or less, or 950 nm or more and 1890 nm or less, avoiding the absorption of oxygen concentration indicator substances and water molecules in the living body, may be used to detect or measure the composition, structure, activity state, or changes thereof inside the living body.

[0136] Furthermore, there is also absorption of water molecules in the region with a central wavelength of 1.43 μm and a half-value range of absorbance of 1.394 to 1.523 μm. Therefore, the composition, structure, activity state, or changes thereof inside the living body may also be detected or measured using light within the range of 875 nm or more and 1390 nm or less (or 950 nm or more and 1390 nm or less) and within the range of 1530 nm or more and 1890 nm or less, avoiding that region.

[0137] Furthermore, the absorption of water molecules (although with relatively low absorbance) also exists in the region with a central wavelength of 0.97 μm and a half-value range of absorbance from 0.943 to 1.028 μm. Therefore, light within the range of 1028 nm or more and 1890 nm or less, or 1028 nm or more and 1390 nm or less, which avoids the above absorption range of water molecules, may be used to detect or measure the composition, structure, activity state, or changes thereof inside the living body.

[0138] Substitute the above wavelength range into Equation (B·6) to estimate the value of the coherence length l CL In this embodiment, it was explained in Section 2.2 that the value of the coherence length l CL may be set in relation to (adapted to) the detection characteristics within the detector 6. Consider the wavelength resolution (half-value width) of the spectrometer 22 example shown in Fig. 14E to be 5 nm for high performance and 50 nm for relatively low performance.

[0139] Therefore, when Δλ = 5 nm, the coherence length l CL ≒ 0.18 mm at λ0 = 950 nm, the coherence length l CL ≒ 0.21 mm at λ0 = 1028 nm, and the coherence length l CL ≒ 0.71 mm at λ0 = 1890 nm.

[0140] On the other hand, when Δλ = 30 nm, the coherence length l CL ≒ 30 μm at λ0 = 950 nm, the coherence length l CL ≒ 35 μm at λ0 = 1028 nm, and the coherence length l CL ≒ 0.12 mm at λ0 = 1890 nm.

[0141] Since the maximum value among the above estimated coherence lengths is "0.71 mm", some margin may be taken and measures may be taken to reduce optical noise so that the coherence length l CL is approximately 1 mm or more.

[0142] Chapter 3 Optical Noise Reduction Method in this Embodiment Related to Partial Coherence (Chapter 3] Optical Noise Reduction Method of Exemplary Eembodiment regarding Partial Coherence) In Chapter 2, a situation was described where optical noise may be mixed in the partially coherent light generated from a panchromatic light source such as a tungsten halogen lamp or a xenon lamp due to the influence of the bulb surrounding the filament. In Chapter 3, the method of this embodiment for reducing the optical noise based on the optical interference will be described.

[0143] 3.1 Section Basic Principle for Optical Noise Reduction (Section 3.1) Basic Principle to Reduce Optical Noise) The basic principle for reducing the optical noise in this embodiment will be described with reference to FIGS. 8A and 8B. Inside a measuring device having any of the configurations of FIGS. 1A to 1C, an optical path (or at least a part of the optical path starting from the light source 70 or at least a part of the optical path reaching the photodetector 80) from the light source 70 in the light emitting unit 2 through the object 10 (the object to be detected or measured) to the photodetectors 80 in the detection units 4 and 6 is composed of a plurality of optical paths. Then, the plurality of optical paths are combined or mixed at a predetermined location in the middle of the optical path.

[0144] Here, in accordance with the definition of terms in Section 2.2, the mixed light generated immediately after "mixing" has partial non-coherence (Partial Incoherent), and the partial coherence before mixing is significantly reduced. On the other hand, the combined light generated immediately after "combination" allows either the state of "partial coherence" or "partial non-coherence". Also, in the combined light, an intermediate state between the two may be acceptable. For example, in the short wavelength component of the combined light, it may have partial non-coherence, and in the long wavelength component, it may have partial coherence.

[0145] The above-mentioned predetermined location where a plurality of optical paths are combined or mixed may be any one of the optical combining (mixing) unit 102 in the middle of the optical path, a specific region (optical combining / mixing location) 200 within the object 10, or at least inside the photodetector 80, as shown in FIG. 8A or FIG. 8B.

[0146] Particularly, when there is a predetermined location (optical combining (mixing) unit 102 in the middle of the optical path) in the middle of the optical path, the above-mentioned predetermined location exists within a local region in the optical axis direction of the combined light (mixed light) 78 (that is, the above-mentioned predetermined location is localized at a specific position in the optical axis direction).

[0147] On the other hand, in the direction of the plane perpendicular to the optical axis (optical cross-section), this predetermined location does not necessarily have to be localized. Therefore, the lights 201, 202, and 203 passing through each optical path may be combined or mixed simultaneously across the entire optical cross-section. Moreover, without being limited thereto, the above-mentioned predetermined location (optical combining (mixing) unit 102 in the middle of the optical path) may be arranged within a local region in the direction of the plane perpendicular to the optical axis (optical cross-section).

[0148] Also, at the above-mentioned predetermined location where a plurality of optical paths are combined or mixed, it is better that at least one of the traveling directions of the lights passing through different optical paths or the directions of the vibration planes of the electric fields substantially coincide (not necessarily exactly coincide).

[0149] Particularly, when there is a predetermined location (optical combining (mixing) unit 102 in the middle of the optical path) in the middle of the optical path, it passes through the optical path in the state of the combined light (mixed light) 78 as shown in FIG. 8A(a) or FIG. 8B(a). If the traveling directions between the lights 201, 202, and 203 passing through different optical paths do not coincide at this predetermined location (optical combining (mixing) unit 102), as the optical path of the combined light (mixed light) 78 becomes longer, the lights 201, 202, and 203 separate from each other again and the partial non-coherence decreases.

[0150] Even when the optical path of the combined light (mixed light) 78 is short, there is a risk that the objective lens 25, detection lenses 28-1, 2, etc. in FIG. 7 will act and the lights 201, 202, 203 will be separated again within the object 10, in the spectroscope 22, or on the monitor camera 24. Therefore, when the traveling directions of the lights 201, 202, 203 that have passed through different optical paths coincide at the above-mentioned predetermined location (the light combining (mixing) unit 102 in the middle of the optical path), the detection signal accuracy and the sharpness of the image will be improved.

[0151] Similarly, when a photo-detector or a polarization beam splitter is arranged in the detection units 4, 6 to measure the polarization characteristics of the detection light 16, by making the directions of the vibration planes of the electric fields between the lights 201, 202, 203 that have passed through different optical paths coincide at a predetermined location (the light combining (mixing) unit 102 in the middle of the optical path), the detection signal characteristics will be improved.

[0152] And within the above-mentioned plurality of optical paths, the optical arrangement may be made such that the difference δ in the optical path lengths of each other is greater than the coherence distance l CL In this way, the optical interference between the lights that have passed through different optical paths at the above-mentioned predetermined location is inhibited, and the optical noise can be reduced. When such an optical arrangement is made, the characteristics of the light that has passed through a plurality of optical paths at the above-mentioned predetermined location are changed (that is, the partial coherence is reduced and the partial non-coherence is increased). As a result, the lights that have passed through different optical paths are "mixed" at the above-mentioned predetermined location.

[0153] Since no optical interference occurs between the lights that have passed through different optical paths and become partially non-coherent light, the optical noise can be reduced. This effect will be described in detail mathematically in Section 3.5, but conceptually, the mutually different vibration periods and mutually different phases of the optical noise components generated in different optical paths (corresponding to the second term on the right side of Equation (B·28) or Equation (B·18)) are intensity-added to average (smooth) the optical noise characteristics. Therefore, the greater the number of added terms, the better the averaging = smoothing effect. Therefore, the greater the number N of divisions (corresponding to the above-mentioned number of added terms) for dividing into this plurality of optical paths, the greater the reduction effect of the optical noise.

[0154] By reducing the optical noise based on optical interference in this way, it is possible to reduce the adverse effects on the optical imaging described in Section 2.3. Moreover, not only that, but it is also possible to reduce the adverse effects on the measurement of spectral characteristics described in Section 2.4 and the optical detection using the general detection light 16.

[0155] As described above, in this embodiment, the difference δ between the optical path lengths in the plurality of optical paths is optically arranged to be larger than the coherence length l CL so that the optical characteristics are changed (the mutual partial coherence decreases and the partial incoherence increases) in the above-mentioned predetermined location or in the optical path after combination. By the way, when the partially coherent light passing through two different optical paths is combined at the above-mentioned predetermined location, if the traveling directions and the directions of the vibration planes of the electric fields of the two are significantly different at the above-mentioned predetermined location, it is difficult for optical interference to occur originally. In that case, even if the method of this embodiment is implemented, the optical noise reduction effect will be diminished. Therefore, in order to exhibit the optical noise reduction effect according to this embodiment, it is desirable that the traveling directions and the directions of the vibration planes of the electric fields of the two at the above-mentioned predetermined location coincide to a certain extent.

[0156] In this embodiment, as shown in FIG. 8A or FIG. 8B, the value of the above-mentioned number of optical paths (number of divisions of the optical path) N of the plurality is set to "3 or more" (desirably 4 or more (examples such as FIG. 13A)). However, it is not limited thereto, and it may be 8 or more or 9 or more as shown in FIG. 13B(a) or FIG. 12C(c).

[0157] By the way, the above-mentioned detector 80 includes all optical detection functional units with a built-in photoelectric conversion function. Specific examples of this optical detection functional unit include not only semiconductor photodetectors composed of a single photodetection unit having a photoelectric conversion function, but also avalanche (internal signal multiplication type) detectors, photomultiplier tubes, etc. Also included are line sensors in which a plurality of detection cells are arranged in a one-dimensional direction, area sensors in which a plurality of detection elements are arranged in a two-dimensional direction, and position sensors (position detection sensors) that detect the position of a light spot irradiated within a predetermined surface area, etc., as photodetectors composed of a plurality of photodetection units (photodetection cells). Furthermore, cameras with built-in these photoelectric conversion elements (monitor camera 24 in FIG. 14D) and the spectroscope 22 in FIG. 14E are also included in the above-mentioned detector 80.

[0158] Furthermore, for the light source 70 described above, it is desirable to use a panchromatic light source such as the tungsten halogen lamp, xenon lamp, incandescent lamp, or fluorescent lamp described in Section 2.5.

[0159] In Section 2.5, using Equation (B·28), it was explained that when a transparent parallel plate is placed in the optical path of the divergent light emitted from the light source 70, the intensity distribution of the transmitted light can vary periodically in response to changes in the measurement wavelength λ. This phenomenon occurs regardless of whether a panchromatic light source or a monochromatic (single wavelength or narrow wavelength range) light source is used. It occurs.

[0160] As another method of obtaining high-precision spectroscopic characteristics (or absorption characteristics) by using this light in a spectroscope, "selectively irradiate the object 10 with light in only a narrow wavelength band at the same time, and sweep the irradiated wavelength in a time series" may be performed. When this method is adopted, the intensity of the narrow wavelength band light irradiated at the same time can be monitored simultaneously, and the result can be fed back to the detected light amount to remove the component of the change in the irradiated light amount for each measurement wavelength λ. However, in the above method, since a "wavelength sweep time" for measuring spectroscopic characteristics (or absorption characteristics) is required, it is difficult to detect and measure "rapid changes" in the object 10.

[0161] In contrast, when a panchromatic light source is used as the light source 70 and (according to this embodiment) partially incoherent light is irradiated onto the object 10, and the detected light intensities at a plurality of wavelengths are simultaneously detected / measured by, for example, the spectroscope 22 in FIG. 14E, "rapid detection / measurement" becomes possible. As a result, there is an effect that "rapid changes" inside the object 10 can be accurately detected and measured.

[0162] However, not limited thereto, a monochromatic light source such as an LD (Laser Diode) or an LED (Light-emittind Diode) may be used as the light source 70.

[0163] FIG. 8A shows an example of this embodiment in which the optical path in the light source unit 2 from the light emission source 70 to the specific region α in the object 10 is composed of three optical paths. In this embodiment, it is not necessary to limit it to three optical paths, and as described above, it may be set (divided) to more (four or more optical paths, eight or more optical paths, nine or more optical paths). It may also be possible. Also, it is not necessarily required to configure the optical path immediately after the light emission source 70 with a plurality of optical paths, and it may be divided into a plurality of optical paths from the middle of the optical path after the light emission source 70.

[0164] In the light source unit 2 shown in FIG. 8A, a plurality of optical paths having different optical path lengths are formed (FIG. 8B). Further, a light combining (mixing) unit 102 that combines (or mixes) the light that has passed through the plurality of optical paths may be disposed in the light source unit 2.

[0165] In the embodiment of FIG. 8A(a), a light combining (mixing) unit 102 is installed in the light source unit 2. And this light combining (mixing) unit 102 corresponds to the "predetermined location" in the middle of the optical path in the light source unit 2 described above. Also, the "predetermined location" (light combining (mixing) unit 102) in this state corresponds to the "middle of the optical path" as the combining / mixing location in FIG. 9 described later.

[0166] That is, in the embodiment of FIG. 8A(a), the optical path from the light emission source 70 to the light combining (mixing) unit 102 is composed of three optical paths, the first / second / third, and the lights 201, 202, 203 that have passed through each optical path are combined (mixed) by the light combining (mixing) unit 102. After that, the lights 201, 202, 203 are gathered into the combined light (mixed light) 78 and irradiated into the specific region α inside the object 10.

[0167] In the embodiment of FIG. 8A(b), the entire optical path in the light source unit 2 is composed of three optical paths, the first / second / third, and is combined (mixed) at the specific region (combining / mixing location) 200 in the object 10. Therefore, in this case, the specific region (combining / mixing location) 200 in the object 10 corresponds to the "predetermined location" in the middle of the optical path.

[0168] In this state, the "predetermined location" (specific region (photosynthesis / mixing location) 200 within the object 10) corresponds to the "specific region within the object 10 (including imaging on the detection surface 86, etc.)" as the synthesis / mixing location in FIG. 9 described later.

[0169] In both FIGS. 8A(a) and (b) of the present embodiment, with respect to the optical path length difference δ between the first / second / third optical paths, δ > l CL is satisfied. Therefore, the partial coherence between the lights 201, 202, and 203 passing through the first / second / third optical paths is reduced, and they become partially incoherent lights with respect to each other.

[0170] Therefore, as shown in FIGS. 8A(a) or (b), when the partial coherence of the irradiation light (first light) 12 (in FIGS. 1A to 1C) in the light source unit 2 is reduced (changed to a partially incoherent light), the accuracy of imaging on the specific region α (200) within the object 10, signal detection (after photoelectric conversion), and spectroscopic measurement (measurement of, for example, the wavelength dependence of the absorption characteristics and light scattering characteristics) is improved, and highly reliable results can be obtained.

[0171] That is, as described later in Section 5.3 using FIG. 23A, multiple scattering occurs inside the object 10. Therefore, when partially coherent light is used as the irradiation light (first light) 12 for irradiating the object 10, light interference occurs between the multiple scattered lights, which has an adverse effect on imaging, signal detection, and spectroscopic measurement (a large optical noise component is mixed in). Moreover, as described in Section 2.3, there is also an adverse effect of light interference caused by the fine uneven structure on the surface of the object 10 and the non-uniformity of the refractive index distribution inside the object 10.

[0172] As shown in FIGS. 8A(a) or (b), when the partial coherence of the irradiation light (first light) 12 is reduced (changed to a partially incoherent light), the light interference that may occur due to the inside or surface of the object 10 described above is reduced.

[0173] FIG. 8B shows an example of the present embodiment in which the optical paths in the detection units 4 and 6 from a specific region β in the object 10 to the photodetectors 80 in the detection units 4 and 6 are composed of three optical paths. In the present embodiment, it is not necessary to limit to three optical paths, and as described above, it may be set (divided) to more (four or more optical paths, eight or more optical paths, nine or more optical paths). Also, it is not necessarily required to configure the optical path immediately after the β region in the object 10 with a plurality of optical paths, and it may be divided into a plurality of optical paths from the middle of the optical path after the object 10.

[0174] In the embodiment of FIG. 8B(a), a photosynthesis (mixing) unit 102 is installed in the detection units 4 and 6. And this photosynthesis (mixing) unit 102 corresponds to the "predetermined location" in the middle of the optical paths in the detection units 4 and 6 described above. Also, the "predetermined location" (photosynthesis (mixing) unit 102) in this state corresponds to the "middle of the optical path (of the detection light 16)" as the synthesis / mixing location in FIG. 9 to be described later.

[0175] That is, in the embodiment of FIG. 8B(a), the optical path from the β region in the object 10 to the photosynthesis (mixing) unit 102 is composed of three optical paths, the first / second / third, and the lights 201, 202, 203 that have passed through each optical path are synthesized (mixed) by the photosynthesis (mixing) unit 102. After that, the lights 201, 202, 203 are gathered into the synthesized light (mixed light) 78 and reach the photodetector 80.

[0176] In the embodiment of FIG. 8B(b), all the optical paths in the detection units 4 and 6 are composed of three optical paths, the first / second / third, and are synthesized (mixed) on the photodetector. Therefore, in this case, the photodetector 80 corresponds to the "predetermined location" in the middle of the optical path.

[0177] The "predetermined location" (photodetector 80) in this state corresponds to the "detection surface 86 in the detector 80" as the synthesis / mixing location in FIG. 9 to be described later.

[0178] In both FIG. 8B(a) and (b) in the present embodiment, regarding the optical path length difference δ between the first / second / third optical paths, δ>l CL is satisfied. Therefore, the partial coherence between the lights 201, 202, and 203 passing through the first / second / third optical paths is reduced, and they become partially non-coherent lights with each other.

[0179] A list of cases regarding the method of embodying the basic concept (basic principle) of the present embodiment shown in FIGS. 8A and 8B is shown in FIG. 9.

[0180] Using FIGS. 8A and 8B, after configuring at least a part of the optical path (s) in the light source unit 2 or in the detection units 4 and 6 with a plurality of optical paths, a structure / configuration for synthesizing / mixing the light that has passed through each optical path is shown. However, not limited thereto, in this embodiment, “plural optical paths ⇒ synthesis / mixing” may be performed across the light source unit 2 and the detection units 4 and 6, or “plural optical paths ⇒ synthesis / mixing” may be performed both in the light source unit 2 and in the detection units 4 and 6.

[0181] Moreover, not only that, for example, like the near-infrared microscope apparatus shown in FIG. 7, an optical noise reduction element or a partial coherence reduction element 64 that performs “plural optical paths ⇒ synthesis / mixing” may be arranged in both the light source unit 2 and the detection unit 6. By arranging them in this combined manner, a significant reduction in the amount of optical noise caused by optical interference becomes possible, and high precision and high reliability of the detection signal can be ensured.

[0182] The column representing the options for the method of configuring a plurality of optical paths immediately after the light emitting source 70 in FIG. 8A corresponds to the column of “optical path state before synthesis / mixing” in FIG. 9. That is, in this embodiment example, for the irradiation light (first light) 12 emitted from the light emitting source 70, either a method of configuring a plurality of optical paths by utilizing the “diversity of light emission states” or a method of performing an “optical path splitting operation” on the irradiation light (first light) 12 to configure a plurality of optical paths (described in the column of optical path state / operation), or a combination of both can be adopted.

[0183] Also, when configuring a plurality of optical paths by utilizing the above “diversity of light emission states”, either one or both of different “light emitting regions” and “light emission methods” (described in the column of detailed content) may be utilized.

[0184] For example, when there is "spread in the light-emitting region" instead of light emission only from a single point, separate lights emitted from different light-emitting regions can be combined and used as irradiation light (first light) 12. On the other hand, when there is spread in the emission direction of the emitted light from the light source 70, the light emitted in different directions (regarding different light emission directions as a plurality of optical paths) can be combined and used as irradiation light (first light) 12.

[0185] Regarding the detection light (second light) obtained from the β region in the object 10 to be detected or measured shown in FIG. 8B, the "different light-emitting regions" included in the "diversity of light emission states" (in the optical path state / operation column) and the "optical path splitting operation" (in the optical path state / operation column) exist as options in this embodiment. That is, in this embodiment, either one of the above two methods, or a combination of both, may be performed.

[0186] For example, even when the object 10 to be detected or measured has the micro-structure shown in FIG. 4 (the micro-light scatterer 66), the optical path length difference δ between the light obtained from the α point and the light obtained from the β point is greater than the coherence length l CL (δ > l CL ) When the optical arrangement (FIG. 8B) is made (to conform to the "different light-emitting regions"), the partial coherence between the two can be reduced and the optical noise level can be reduced.

[0187] Regarding either the irradiation light (first light) 12 in FIG. 8A or the detection light (second light) 16 in FIG. 18B, either the method of "Wave Front Dividing" or the method of "Amplitude Dividing", which are specific "detailed contents" included in the "optical path splitting operation" (in the optical path state / operation column), or a combination of both can be selected.

[0188] "Wavefront splitting" means a method of spatially splitting an optical cross-section on a cutting plane perpendicular to the optical axis along the propagation direction of light. And after wavefront splitting, the optical cross-section shapes of individual split lights often deform (compared to before wavefront splitting). Also, when wavefront splitting is performed using a transparent parallel plate, the propagation directions of individual split lights coincide with each other. Even if the propagation directions of each split light coincide with each other, in this embodiment, it is regarded that "individual split lights after wavefront splitting pass through different optical paths".

[0189] On the other hand, in "amplitude splitting", it is split into a plurality of optical paths with different propagation directions while maintaining the optical cross-section shape. And it is often amplitude-split by optical elements such as a beam splitter or a polarization beam splitter.

[0190] The method of "combining or mixing light in multiple optical paths" specifically changes or controls the light propagation direction for each of these multiple optical paths. However, it is not limited to this, and any method may be used as the "light combining / mixing method".

[0191] First, the "light combining / mixing method" applicable to all states / operations in the "Detailed Content" column will be described. In FIGS. 8A and 8B for explaining the basic principle of reducing optical noise, lights 201, 202, and 203 passing through the first / second / third optical paths with different optical path lengths gather toward a predetermined location. This predetermined location corresponds to the light combining (mixing) unit 102 or a specific region (light combining / mixing location) 200 (α point) within the photodetector or the object 10.

[0192] Therefore, including this entire optical path, it is described as the "light combining / mixing method" in FIG. 9. Also, as a supplementary explanation of the meaning of the "light combining / mixing method", it is specified as a method related to [changing / controlling the path for each optical path]. And in the description text of this embodiment, the general term for an optical member that changes or controls the path for each of a plurality of different optical paths is called an "optical characteristic changing member". Therefore, all individual optical elements or combinations of those optical elements described in the "light combining / mixing method" column in FIG. 9 (changing / controlling the path for each optical path) correspond to the "optical characteristic changing member".

[0193] The functions that this optical property changing member can have include (A) the function of changing / controlling the optical path length for each of a plurality of optical paths (corresponding to the "optical path length change 76" function in FIG. 10 described later) and (B) the function of combining (or mixing) a plurality of optical paths at a predetermined location. In the description of this embodiment, an optical member that exhibits at least one of the above functions (both functions may be exhibited simultaneously) is referred to as an optical property changing member.

[0194] Also, as the physical structure of this optical property changing member, it may be integrally arranged at a single location in the optical path. Moreover, not limited thereto, a plurality of members dispersed in the optical path may also be arranged in combination. When arranged in this dispersed manner, the functions may be separated such that a part of the optical property changing member bears the function of (B) above, and the remaining part arranged at a different position bears the function of (A) above. As an example of changing / controlling the light traveling direction for a plurality of optical paths configured by any of the methods of "different emission regions", "different light emission methods", "wavefront splitting", and "amplitude splitting", a refractive element such as a lens may be used. Also, in this embodiment, the above-mentioned "refractive element" may include not only a spherical lens but also an aspherical lens, a Fresnel lens, a prism, a transparent parallel plate, and the like.

[0195] Moreover, not limited thereto, diffraction-related elements, light reflection elements, and light phase conversion elements may also be used. Here, the above-mentioned diffraction-related elements include a diffraction grating, a hologram element, etc., and may be blazed with the microplanes inclined.

[0196] Also, the light phase conversion element means an optical element that locally or globally changes the phase of the light (irradiation light 12 or detection light 16) after passing through or reflecting from this element. To realize its function, the light phase conversion element has a fine refractive index distribution inside or a fine uneven structure on the surface. Also, in this embodiment, the light phase conversion element includes a random phase shifter, a defuser, a sanded surface or a sand-sprayed surface having a surface with a specific period or a random fine uneven structure.

[0197] In addition, for the path change / control (photosynthesis / mixing method) for each of the plurality of optical paths, a waveguide element that forms or integrates an optical guiding path on an optical fiber or a predetermined plate to guide the traveling direction of light may be used.

[0198] As another method, instead of changing / controlling the light traveling direction to a "predetermined location", only the light that has gathered at the "predetermined location" among the lights with a plurality of traveling directions may be extracted. This method corresponds to "synthesis / mixing light extraction at the detection unit 6" in FIG. 9. For example, the photodetectors 80 in the detection units 4 and 6 in FIG. 8B perform "photodetection (photoelectric conversion) of only light at a specific localized location". Then, by forming an imaging relationship (confocal relationship) between the "specific localized location" on the photodetector 80 and the "predetermined location β" in the object 10 within the detection units 4 and 6, it becomes possible to detect / measure substantially only the information of the "predetermined location β" (details will be described later in Section 3.9 using FIG. 20).

[0199] In addition, a prism or a special lens may be additionally used in the optical path of the light emitted from "different light emitting regions" to collect the light emitted from a wide light emitting region. As described in Section 2.2 using FIG. 2A, when the optical path length difference δ between the light reaching from point α to point γ and the light reaching from point β to point γ is wider than the coherence distance l CL the partial coherence between them decreases (the partial non-coherence increases), and the optical noise level decreases. For that, it is desirable that the distance between point α and point β is increased. Therefore, a prism or a special lens may be used in the optical path to collect the light emitted from a wide light emitting region (details will be described later in Section 3.9 using FIGS. 24A and 24B).

[0200] Note that the special lens means a lens in an aspherical state. Specifically, it may include a lenticular lens, a cylindrical lens, a Fresnel lens, etc.

[0201] As a method of "combining / synthesizing" the light split into a plurality of optical paths by "amplitude splitting", a polarization reflecting element, a polarization transmitting element (e.g., a polarization beam splitter, etc.), or a non-polarizing beam splitter may be used. Further, as a means for aligning the directions of the electric field vibration planes between the lights that have passed through different optical paths, a phase plate, an analyzer, or a polarization beam splitter may be additionally used.

[0202] As described above using FIGS. 8A and 8B and as will be described later using FIG. 10, the lights that have passed through a plurality of optical paths are combined / synthesized at the "combining / synthesizing location" with respect to the "optical path state before combining / synthesizing" in FIG. 9. In this process, an optical path length change 76 is generated to change the optical characteristics of the combined light (mixed light) 78 (decrease the partial coherence and increase the partial incoherence).

[0203] The "combining / synthesizing location" and "spatially identical region" in FIG. 9, and the "light combining (mixing) section 102" in FIGS. 8A and 8B correspond to the above-described "predetermined location". As a specific example within this embodiment when this predetermined location is arranged in the optical path of the irradiation light 12 or the detection light 16, the core region 142 inside the optical fiber 100 may be adapted (details will be described later in Section 3.4 using FIG. 14A). Also, not limited thereto, in this embodiment, the location after passing through the optical phase conversion element may be adapted (details will be described later in Section 3.4 using FIG. 14B).

[0204] When the "predetermined region where the lights that have passed through a plurality of optical paths are combined or mixed" described at the beginning of Section 3.1 is the "specific region 200 within the object 10", for the reasons described above, it includes "imaging on the detection surface 86, etc." (details will be described later in Section 3.9 using FIG. 20). Therefore, in this case, the method of "extracting the combined / mixed light with the detector 6" in the "light combining / synthesizing method" column is used.

[0205] On the other hand, when the "predetermined region where light that has passed through a plurality of optical paths is combined or mixed" described at the beginning of Section 3.1 is set to "inside the photodetector 80", it corresponds to the "detection surface 86 inside the detector 80" in the "Combination / Mixing Location" column of FIG. 9. As described above, the "photodetector 80" in the present embodiment includes not only a photodetector composed of only a single photodetection cell, but also any photodetection functional unit incorporating a photoelectric conversion function. Therefore, when a camera is used, the imaging surface (detection surface) 86 in the monitor camera 24 shown in FIG. 14D corresponds to the above "predetermined location".

[0206] Also, in the spectroscope 22 shown in FIG. 14E as a type of "photodetector 80", the pinhole or slit 130 corresponds to the above "predetermined location". And this embodiment example corresponds to the "pinhole or slit 130" in the "Combination / Mixing Location" column of FIG. 9.

[0207] Using FIG. 10, the basic principle of the optical noise reduction method in the present embodiment will be explained from another perspective. As shown in FIG. 10(a), in the present embodiment, basically, an optical path length change 76 is caused for a part 74 of light different from a part 72 of the light emitted from the light source 70. Here, the amount δ of the optical path length change 76 is preferably larger than the coherence distance l defined by Equation (B·6) (or Equation (B·12)). Then, the two are mixed to generate mixed light 78 (synthetic light may also be used). Therefore, by this method, the optical characteristics of the mixed light 78 are changed, the partial coherence is reduced, and the partial incoherence is increased. Therefore, according to the basic principle of the present embodiment shown in FIG. 10, when viewed along the optical path proceeding from the light source 70, synthetic light (mixed light) 78 is generated after the optical path length change 76 is made. CL Incidentally, the amount δ of the optical path length change 76 does not necessarily have to be larger than the coherence distance l at all wavelengths. This is because the coherence distance l defined by Equation (B·6) (or Equation (B·12)) varies greatly depending on the target center wavelength λ0 as described in the latter half of Section 2.7. Therefore, when broadband light is generated from the light source 70, the above coherence distance l is set at the shortest wavelength to be used.

[0208] Incidentally, the amount δ of the optical path length change 76 does not necessarily have to be larger than the coherence distance l at all wavelengths. CL This is because the coherence distance l defined by Equation (B·6) (or Equation (B·12)) CL varies greatly depending on the target center wavelength λ0 as described in the latter half of Section 2.7. Therefore, when broadband light is generated from the light source 70, the above coherence distance l is set at the shortest wavelength to be used.CL It only needs to be larger. In this case, partial coherence remains on the long-wavelength side in the combined light 78.

[0209] An embodiment in which the optical operation of FIG. 10(a) is performed in the light source unit 2 is shown in FIG. 10(b). In this case, the combined light (mixed light) 78 is irradiated onto the object 10 as the irradiation light (first light) 12.

[0210] On the other hand, an embodiment in which the optical operation of FIG. 10(a) is performed in the detection units 4 and 6 is shown in FIG. 10(c). That is, after changing the optical path length 76 of a part 74 of the detection light (second light) 16 obtained from the object 10, it is combined (mixed) with a part 72 of the remaining light. Then, the obtained combined light (mixed light) 78 reaches the photodetector 80.

[0211] FIG. 8A corresponds to FIG. 10(b), and FIG. 8B corresponds to FIG. 10(c). The optical path length changes 76 occurring in FIGS. 8A and 8B are explicitly shown in FIG. 10.

[0212] Also, as described in the first part of this section 3.1, inside the optical path of the combined light (mixed light) 78 in FIG. 10 (at least the starting position of the optical path of the combined light (mixed light) 78), it is desirable that the traveling direction of the light (or the direction of the vibration plane of the electric field) belonging to a part 72 of the light originally and the traveling direction of the light (or the direction of the vibration plane of the electric field) belonging to a part 74 of the light coincide. Thereby, re-separation inside the object 10 and on the photodetector 80 is suppressed, and a good image and a highly accurate detection signal can be obtained.

[0213] The material used for the above-described optical property changing member or the material used for the substrate of the optical property changing member will be described. In particular, the points to note for material selection when using near-infrared light described in section 2.6 as the irradiation light 12 or the detection light 16 will be described below. Here, the optical property changing member is premised on various optical members described in the column of "Light combining / mixing method [changing / controlling the path for each optical path]" in FIG. 9. However, it is not limited thereto, and it may be applied to any optical element material.

[0214] Among the entire optical property changing member or its entire base material, it is desirable to select a material with high light transmittance for the portion through which the irradiation light 12 and the detection light 16 pass. As relatively inexpensive and readily available transparent plastic resins, acrylic resin PMMA (Poly-Methyl-Metacrylate) and polycarbonate resin PC (Polycarbonate) are known. However, these plastic resins contain a large amount of functional groups composed only of carbon atoms and hydrogen atoms (such as methyl groups and methylene groups).

[0215] The above-mentioned functional groups have the property of absorbing near-infrared light as described in Section 2.6. And the light at the center wavelength of the absorption band attributed to the first overtone of the stretching vibration occurring within the above-mentioned functional groups is particularly strongly absorbed. The center wavelength of this absorption band is included in the range of approximately 1710 nm to 1795 nm. For example, when the light at the center wavelength passes through a 1-mm-thick transparent acrylic resin PMMA (Poly-Methyl-Metacrylate) plate, the light absorption amount is large enough that the transmitted light amount is approximately halved. Therefore, when using near-infrared light for the irradiation light 12 and the detection light 16, it is better to avoid using transparent plastic resin as the material of the optical property changing member or its base material. And it is desirable to use an inorganic material instead of an organic material as a material with high light transmittance for near-infrared light.

[0216] As inorganic materials with high light transmittance, optical glass (Optical Glass), CaF2, MgF2, or LiF, KBr, etc. are known. Therefore, these inorganic materials are suitable for the optical property changing member (or the base material of the optical property changing member).

[0217] By the way, for manufacturing convenience, a large amount of hydroxyl groups (-OH groups, Hydroxyl Group) are mixed into general optical glass. And the center wavelength of the absorption band attributed to the first overtone of the stretching vibration of the hydroxyl group is in the range of 1395 nm to 1595 nm or in its vicinity. Therefore, the light passing through the optical glass with a large amount of hydroxyl groups mixed therein undergoes light absorption in the above wavelength range.

[0218] Therefore, when using near-infrared light in the wavelength range described in Section 2.6 as the irradiation light 12 or the detection light 16, it is desirable to select a material with a low hydroxyl group content (or the base material of the optical property changing member) as the material of the optical property changing member. As a result obtained from experiments, specifically, the necessary condition for the allowable amount of hydroxyl group incorporation is "100 ppm or less". In particular, when performing highly accurate near-infrared spectrum measurement, "1 ppm or less" is desirable. By selecting a material with a hydroxyl group incorporation amount within the above allowable range, light absorption within the wavelength range from 1395 nm to 1595 nm can be avoided, and the effect of enabling highly accurate spectroscopic property measurement in the entire wavelength range of near-infrared light is produced.

[0219] As a specific method for obtaining a light-transmissive material within the above allowable range, when ordering materials, "glass materials with low hydroxyl group incorporation and controlled production management", "fused silica glass", or "fused silica" may be specified. All of these perform material production while ensuring low humidity and controlling temperature in an environment with low cleanliness (inside a clean room). By performing material production in a clean room set to low humidity, the mixing of water vapor in the air is prevented, and the amount of hydroxyl group incorporation is suppressed within the above allowable range. By adopting such a production method, the incorporation of impurities that cause material deterioration can be prevented, and the purity of the produced material is increased. As a result, the long-term storage stability of the light-transmissive material is guaranteed, and the characteristics (performance) of the optical property changing member created using it have the effect of lasting for a long time.

[0220] Section 3.2 Utilization of Emitted Light in Different Directions In Section 3.1, a list of detailed optical noise reduction methods in this embodiment was outlined using the case-by-case table in Figure 9. And for each of its individual detailed specific examples, it will be described after Section 3.2. The examples of this embodiment described after Section 3.2 are only examples, and all combinations within Figure 9 are included in this embodiment.

[0221] An example of a method of using the "different light emission directions" in the "optical path state before synthesis / mixing" column of FIG. 9 and using an "optical reflection element" as a means of "changing the path of a specific optical path" and performing "synthesis / mixing" between different optical paths in the middle of the optical path of the irradiation light 12 is shown in FIG. 11.

[0222] Light is emitted in all directions from a tungsten filament 50, which is a type of light-emitting source 70 in the light source unit 2. In many cases, only the forward-emitted light 84 (corresponding to the first optical path) is used as shown in FIG. 11(a).

[0223] In contrast, in the present embodiment, a rear mirror 82 of the optical reflection element is arranged on the rear side, and the rear-emitted light 88 (corresponding to the second optical path) is returned inside the tungsten filament 50. The distance of reciprocation from the tungsten filament 50 to the rear mirror 82 brings about an optical path length change 76. Comparing with the calculation example in the latter half of section 2.7, the difference δ in the optical path length generated here is much larger than the coherence length l CL by far.

[0224] The rear-emitted light 88 (the second optical path) that has passed through the inside of the tungsten filament 50 passes through the same optical path as the forward-emitted light 84 (the first optical path). As a result, the forward-emitted light 84 (the first optical path) and the rear-emitted light 88 (the second optical path) are mixed.

[0225] In the example of the present embodiment shown in FIG. 11, since the partial coherence of the mixed light is significantly reduced, even if a transparent parallel plate is arranged in the middle of this divergent optical path, the optical noise level can be suppressed to be relatively small. Moreover, not only that, but in the example of the embodiment of FIG. 11, there is also an effect that the light emitted from the tungsten filament 50 can be effectively utilized.

[0226] 3.3 Wavefront splitting function optical property changing member In Section 3.3, a specific example of this embodiment will be described when "wavefront splitting" is performed in the "optical path splitting operation" of FIG. 9. Here, as an optical element used for performing this "wavefront splitting", an example using a refractive element or a diffraction-related element will be described. However, it is not limited thereto, and a light reflection element, a light phase conversion element, or a waveguide element may also be used. For example, as shown in FIGS. 12C to 13C described later, a light reflecting surface having different steps for each region may be configured, and the optical path length (after reflection) may be changed according to the reflection location in the optical cross-section 92.

[0227] Also, in the example of this embodiment described in Section 3.3, as the content in the "synthesis / mixing location" column of FIG. 9, "in the optical path of the irradiation light 12 and the detection light 16" is set.

[0228] An example of this embodiment using a "diffraction-related element" or a "refractive element" as the "light synthesis / mixing method" of FIG. 9 is shown in FIG. 12A. A blazed diffraction grating or a prism 128 is arranged in a partial region of the optical cross-section (the region through which the transmitted light 110-1 passes) in the optical path of the irradiation light 12 and the detection light 16 to change the traveling direction of the transmitted light 110-1.

[0229] Thereafter, the transmitted light 110-1 and the transmitted light 110-2 are synthesized or mixed by the transmission diffraction grating 120. At this time, the traveling directions of the first-order diffracted light of the transmitted light 110-1 and the zero-order light of the transmitted light 110-2 are made to coincide.

[0230] The optical path lengths between the blazed diffraction grating or the prism 128 and the transmission diffraction grating 120 are different for the transmitted light 110-1 and the transmitted light 110-2. Thus, in the example of this embodiment in FIG. 12A, the optical characteristics of the synthesized light (mixed light) 79 are changed (the partial coherence is reduced and the partial incoherence is increased) by utilizing the optical path length change generated due to the difference in the traveling paths of light.

[0231] An example of this embodiment using a transparent parallel plate as a refractive element used to realize "wavefront splitting" in FIG. 9 is shown in FIGS. 12B to 13C. When the refractive index in the transparent parallel plate is n and its thickness is d, a difference in optical path length δ shown in Equation (B·13) occurs between the first optical path traveling straight in the transparent parallel plate and the light passing through the second optical path traveling straight in a vacuum (air) with a length d.

[0232] And in the example of this embodiment shown in FIGS. 12B to 13C, the optical characteristics of the combined light (mixed light) 78 are changed (the partial coherence is reduced and the partial incoherence is increased) by utilizing the change in the optical path length δ of the transmitted light generated due to the difference in refractive index. Therefore, the optical element formed by combining the transparent parallel plates 94, 114, and 116 shown in FIGS. 12B to 13C is included in a type of optical characteristic changing member (or split-wave optical path length conversion element 90).

[0233] As shown in FIG. 12B, the cut surface 95 of the parallel plate is parallel to the optical axis of the transmitted light with high precision. Therefore, the light passing through the optical characteristic changing member (split-wave optical path length conversion element 90) is wavefront-split at the boundary line 97 of the cut surface (of the parallel plate) in the transmitted light cross-section 92. Since the optical path length is different for each of the wavefront-split transmitted lights, they pass through different optical paths.

[0234] Another example of the embodiment regarding the optical characteristic changing member (split-wave optical path length conversion element 90) shown in FIG. 12B is shown in FIG. 12C. First, the long side direction of the transparent parallel plate 114-2 with a thickness t is arranged in the X-axis direction. Then, as shown in FIG. 12C(a), with the long side direction of the transparent parallel plate 114-1 with a thickness of 5t in the X-axis direction, it is overlaid (adhered) on the transparent parallel plate 114-2 with a thickness t. As a result, three regions with thicknesses of 0t, 1t, and 6t are formed along the Y-axis direction.

[0235] Next, the long side direction of the transparent parallel plate 114-3 with a thickness of 2t is arranged in the Y-axis direction. Then, with the long side direction of the transparent parallel plate 114-4 with a thickness of 2t in the Y-axis direction, it is overlaid (adhered) under the transparent parallel plate 114-3 with a thickness of 2t as shown in FIG. 12C(b). As a result, three regions with thicknesses of 4t, 2t, and 0t are formed along the X-axis direction.

[0236] Next, as shown in Fig. 12(c), Figs. 12(b) and 12(a) are overlaid (bonded). Then, the transmission direction 96 of the partially coherent light is made to coincide with the Z-axis direction from bottom to top. As a result, when viewed in the cross-sectional direction of the light cut in a direction perpendicular to the light passing direction 96, the optical path is divided into 9 regions. And the thicknesses passing through the parallel plate 114 in each optical path are 10t, 8t, 6t, 5t, 3t, t, 4t, 2t, and 0t in order from the upper left. The difference δ in optical path length for each optical path passing through each region is given by Equation (B·13).

[0237] In the first half of Section 3.1, it was explained that the greater the number N of divisions (corresponding to the above-mentioned addition numbers) for dividing the optical path, the greater the effect of reducing optical noise. Therefore, when light is divided into N different optical paths by an optical property changing member corresponding to at least any one of all the items described in the "Detailed Content" column in the column of "Optical Path State Before Synthesis / Mixing" in Fig. 9 (for example, not limited to wavefront division including the embodiment of Fig. 11C, but also amplitude division and different light emission directions), the differences δ in optical path length generated when passing through all the optical paths may be set to be different from each other. In the embodiment of Fig. 12C, the above conditions are satisfied. That is, the differences δ in optical path length generated in all the light passing through the 9 regions divided on the optical cross-section (passing through 9 different optical paths) are different.

[0238] Explaining the above content in another expression method, it is as follows. That is, as an optical property changing member, a plurality of optical paths are divided by combining refractive elements with different thicknesses (not limited to parallel plates, but also including prisms and lenses). When the thickness of the refractive element in each optical path is mt (m is an integer), all the divided optical paths take different values of m. Note that the characteristics as this optical property changing member are not limited to the structure of Fig. 12C, but also apply to the structures of Figs. 13A to 13C. Furthermore, the above characteristics may be applied not only to the "Wavefront Distribution" in the column of "Optical Path State Before Synthesis / Mixing" in Fig. 9, but also to the "Amplitude Distribution" and "Different Light Emission Directions".

[0239] In the present embodiment, with respect to at least any one of all the items described in the "Details" column in the "Optical path state before synthesis / mixing" column of FIG. 9 (for example, not limited to wavefront splitting including the embodiment example of FIG. 11C, but also amplitude splitting and different light emission directions), the optical path length difference δ between lights passing through different optical paths is the coherence distance l given by formula (B·6) (or formula (B·12)). CL It is desirable that the optical arrangement be such that it is larger than CL . In the embodiment example of FIG. 9(c), the minimum value of the thickness difference between different regions is t. Therefore, considering formula (B·13) for the above reasons, (n - 1)t > l CL = λ0 2 / Δλ …(B·29) the optical arrangement may be set to satisfy the condition of. For example, when the refractive index of the refractive element is 1.5, the value of t may be set to 2 mm or more from the calculation example in anticipation of the margin in the latter half of section 2.7. On the other hand, while making the upper limit value of the used wavelength smaller than 1.89 μm and aiming for miniaturization of the entire optical system, the value of t may be set to 1 mm or more. Furthermore, when detection units 4 and 6 (or photodetectors) with a Δλ value larger than 5 nm are used, the value of t may be set to 0.5 mm or more, desirably 0.3 mm or more.

[0240] Another way of expressing this content can also be explained as follows. That is, in an optical property changing member that divides into a plurality of optical paths by combining refractive elements with different thicknesses (not limited to parallel flat plates, but also including prisms and lenses), when the thickness of the refractive element in each optical path is mt (m is an integer), t satisfies the condition of formula (B·29). Note that the characteristics as this optical property changing member are not limited to the structure of FIG. 12C, but also apply to the structures of FIGS. 13A to 13C. Furthermore, the above characteristics may be applied not only to the "wavefront distribution" in the "Optical path state before synthesis / mixing" column of FIG. 9, but also to the "amplitude distribution" and "different light emission directions".

[0241] Furthermore, when combining both of the above as application examples of the present embodiment, the characteristics of the optical property changing member can be expressed as follows. That is, in an optical property changing member that can be divided into N optical paths, when the thickness of the refractive element in each optical path is mt (or the optical path length generated when passing through each optical path is mδ) (m is an integer), different values of m are taken in all N optical paths, and the (B·29) formula (or δ>l CL ) is satisfied.

[0242] In the optical property changing member shown in FIG. 11C, a combination of three divisions along the Y-axis direction and three divisions along the X-axis direction (adhering) is used to divide it into nine regions. Such a division method is called "XY division" in the description text of the present embodiment. This XY division is not limited to FIG. 11C, and any number of divisions can be selected as long as the number of divisions in one axial direction is 2 or more (for example, a total of 4 divisions of 2 divisions in the Y-axis direction × 2 divisions in the X-axis direction).

[0243] Also, in FIG. 11C, the X-axis and the Y-axis are orthogonal to each other, but it is not limited thereto. For example, the X-axis and the Y-axis may be obliquely intersecting (the X-axis and the Y-axis intersect at an angle other than 90 degrees). Furthermore, as another wavefront division method, "X-axis division" that divides only along one axis (X-axis) direction may be performed. As another example, the optical property changing member may be separated into a portion divided in the X-axis direction and a portion divided in the Y-axis direction, and dispersed and arranged at different positions on the optical path.

[0244] Regarding another wavefront division method, the "angle division" method, it will be described with reference to FIGS. 13A to 13B. In this method, for the (circular) transmitted light cross-section 92, the division boundary line 97 between the optical paths with the center of the circle as the reference is divided in the angular direction. Even if angle division is performed in the middle of the optical path, there is an effect that good imaging characteristics can be obtained because the deterioration of the MTF (Modulation Transfer Function) characteristics at the imaging part does not occur.

[0245] For example, as shown in Fig. 13A(a), the cross-section 95 of the transparent parallel flat plate 94-1 with a thickness Ta of, for example, 2t is arranged horizontally. Next, a transparent parallel flat plate 94-2 (Fig. 13A(b)) with a thickness Tb of, for example, 3t, whose cross-section 95 is arranged vertically, is stacked (adhered) below it to form an optical property changing member having the structure shown in Fig. 13A(c). Then, the light transmission direction 96 is set so as to be parallel to the cross-section 95. As a result, the transmitted light cross-section 92 is angularly divided into four quadrants where the boundary portions 97 of the cross-sections are orthogonal to each other.

[0246] In the optical property changing member shown in Fig. 13A(c), the thicknesses of the locations (each region) through which each optical path passes as seen from the light transmission direction 96 are Ta (for example, 2t), Ta + Tb (for example, 5t), Tb (for example, 3t), and a thickness of "0" in order from the first quadrant. Thus, at the thickness mt, the value of m is different for each location (each region) through which each optical path passes (the value of m is 2, 5, 3, 0 in order from the first quadrant), and it satisfies the formula (B·29) as t (for example, 0.3 mm or more).

[0247] In Fig. 13A(c), it is an optical property changing member formed by adhering and integrating the transparent semi-circular parallel flat plates 94-1 and 94-2. However, it is not limited to this, and a plurality of them may be dispersedly arranged in the optical path. In this case, they may be arranged at predetermined angles (for example, 45 degrees each when two are dispersedly arranged) so that the regions divided from each other do not overlap.

[0248] An application example of Fig. 13A(c) is shown in Fig. 13B. A structure in which two sets of optical property changing members having the structure of Fig. 13A(c) are overlapped with each other shifted by 45 degrees is shown on the right side of Fig. 13B(a). The thicknesses of this optical property changing member are 10t, 7t, 4t, 2t, 0, 3t, 6t, and 8t for each optical path (divided region).

[0249] Shift when overlapping (adhering) two sets of optical property changing members having the structure of Fig. 13A(c) An example where the angle is set to 30 degrees instead of 45 degrees is shown at the left end of Fig. 13B(b). On the other hand, a transparent semi-circular parallel plate 94-5 with a thickness of 1t and a transparent semi-circular parallel plate 94-6 with a thickness of 3t are overlapped (adhered) with a 90-degree shift (the figure in the center of Fig. 13B(b)), and an optical property changing member formed by overlapping (adhering) the set at the left end thereon is shown at the right end of Fig. 13B(b). In this structure, the transmitted light cross-section 92 is divided into 12 regions (the number of divided optical paths N = 12).

[0250] In the right-end figure of Fig. 13B, it is an optical property changing member formed by adhering and integrating the transparent semi-circular parallel plates 94-1 and 94-2. However, it is not limited to this, and a plurality of them may be dispersedly arranged in the middle of the optical path. In this case, they may be arranged with a predetermined angle shift (for example, 22.5 degrees each when two elements at the right end of Fig. 13B are dispersedly arranged) so that the divided regions do not overlap each other.

[0251] In this embodiment, the method of dividing the transmitted light cross-section 92 in the radial direction with respect to the circular shape (optical path division) is called "radial division". Examples of combining wavefront division of the transmitted light cross-section 92 by this radial division and angle division are shown in Fig. 13C.

[0252] Two transparent cylindrical parallel plates 116-1 and 116-2 with a thickness of 9t are overlapped and an optical property changing member configured by overlapping (adhering) them on the right-end structure of Fig. 18B(a) is shown on the right side of Fig. 13C.

[0253] In the structure on the right side of Fig. 13C, the transmitted light cross-section 92 is divided into 24 (3×8), and at the same time, 24 different optical paths (the number of optical paths N = 24) are formed. Also, when the thickness of each optical path (divided region) is set to mt, all positive integer values from 0 to 28 excluding 1, 5, 14, 23, and 27 as the value of m are assigned to each optical path (divided region).

[0254] In the right diagram of Fig. 13C, angular division and radial division are simultaneously performed within the integrated optical property changing member. However, not limited to this, a plurality of optical property changing members that exhibit the same function may be dispersedly arranged in the optical path. As an example, a part that performs angular division and a part that performs radial division within the optical property changing member may be separated from each other and dispersedly arranged on the optical path.

[0255] In the embodiment examples shown from Fig. 12C to Fig. 13C, they are equally divided in the X / Y direction, angular direction, and radial direction. However, not limited to this, in this embodiment, they may be non-equally divided for each divided optical path (each divided region). Also, the number of optical paths N (or the number of divisions) generated by the optical property changing member may be set to any value of 2 or more. Furthermore, in this embodiment, the transmitted light cross-section 92 may be wavefront-divided by any other method.

[0256] As schematically described in Section 3.1 and detailed using mathematical formulas in Section 3.5, the larger the number of optical paths N (or the number of divisions) generated by the optical property changing member, the greater the optical noise reduction effect. And in the wavefront division method that changes the thickness of the refractive element for transmitted light and the step amount for reflected light, as can be seen from the example of 24 divisions (N = 24) in the right diagram of Fig. 13C, the number of optical paths N (or the number of divided regions) generated by the optical property changing member can be arbitrarily set to increase. Furthermore, an optical arrangement that makes the light amounts passing through each of the N-divided optical paths substantially equal becomes easy.

[0257] In comparison, in the amplitude division shown in Fig. 9, it is difficult to divide into many optical paths while ensuring the same intensity. Even if a plurality of amplitude division planes capable of amplitude division are formed, the divided light close to the maximum intensity is limited to only two optical paths. And the intensity of the other divided optical paths tends to decrease significantly.

[0258] As an optical property changing member having a wavefront division function, a prism having an inclination between the light incident surface and the light exit surface may be used, or one surface may be made non-planar. However, in this case, an optical axis shift is likely to occur for each optical path after transmission.

[0259] In contrast, as shown in FIGS. 12B to 13C, when a transparent parallel flat plate is used as a constituent element of the optical property changing member and the light transmission direction 96 is set in the direction perpendicular to the plane thereof, there is no "optical axis deviation after transmission", and there is an effect that "all optical paths after transmission (after emission) are kept parallel". Thereby, the combining (mixing) operation between different optical paths becomes easy. Further, for example, even if the objective lens 25, the detection lenses 28-1 and 28-2 are arranged as shown in FIG. 7 after the combining (mixing) operation, it is difficult for a positional deviation to occur in the vicinity of the focal point, so that a clear image and a highly accurate detection signal can be obtained.

[0260] When the wavefront splitting function is used to change the optical properties of the irradiation light (first light) 12 and the detection light (second light) 16, a boundary line (wavefront splitting boundary line) with different optical properties after the change appears in the cross section perpendicular to the light traveling direction. As a specific example of this wavefront splitting boundary line, the boundary line 97 of the cut surface shown in FIGS. 12B and 13A corresponds.

[0261] By the way, for example, in a light source 70 (FIGS. 11, 14A, and 14B) using a tungsten filament 50 or the like, heat is generated during light emission. And in many cases, a mechanical fan is used for cooling this light source 70. When this mechanical fan rotates, minute mechanical vibrations are generated, and there are cases where these mechanical vibrations are propagated to the "optical property changing member having a wavefront splitting function". Then, due to the influence, the wavefront splitting boundary line vibrates slightly mechanically.

[0262] In the description of the material used for the optical property changing member (or its base material) made at the end of Section 3.1, the existence of a material having a large absorption band in the near-infrared region was described. Therefore, when an "optical property changing member having a wavefront splitting function" is created using a material having a large absorption band in the near-infrared region, noise components may be mixed into the detection signals of the light having wavelengths within the absorption band obtained from the detection units 4 and 6 (FIGS. 1A, 1B, and 1C). This noise component is generated in synchronization with the mechanical vibration of the wavefront splitting boundary line. In order to remove this noise component, it is advisable to consider the material selection of the "optical property changing member having a wavefront splitting function" in the same manner as the description at the end of Section 3.1.

[0263] That is, it is desirable to use an inorganic material instead of an organic material for the material of the "optical property changing member having a wavefront splitting function (or its base material)". Examples of such inorganic materials include optical glass, CaF2, MgF2, LiF, KBr, etc.

[0264] In particular, a low-OH material that satisfies the condition that the mixing amount of hydroxyl groups contained in the material of the "optical property changing member having a wavefront splitting function (or its base material)" is "100 ppm or less" (desirably "1 ppm or less") is suitable. Specific examples include 'glass materials with less hydroxyl group mixing and controlled production', 'fused silica glass', 'fused silica', etc.

[0265] By considering the material selection of the "optical property changing member having a wavefront splitting function (or its base material)" in this way, an effect is produced in which high-precision spectroscopic characteristics with less influence of mechanical vibration mixing are obtained.

[0266] 3.4 Synthesis (mixing) between split wavefronts The method of synthesizing / mixing light after using the optical property changing member described in 3.3 will be described in this 3.4. As described in 3.1 with reference to FIG. 10, after splitting into a plurality of optical paths using the optical property changing member, light passing through different optical paths is synthesized or mixed. The optical path state before the synthesis / mixing described here is not limited to only wavefront splitting, and any state (item) in the "optical path state before synthesis / mixing" column of FIG. 9 may be adapted. Also, a combined state of each item may be used. FIGS. 14A and 14B show an example of the combination of "different light emission directions" and "wavefront splitting".

[0267] That is, in the embodiment examples of FIGS. 14A and 14B, the state (item) of different light emission directions in the emission direction directly toward the collimating lens 26 and the emission direction toward the rear mirror 82 from the light source 70 (tungsten filament 50) is utilized. At the same time, an optical property changing member that combines a transparent parallel plate 94-1 with a thickness Tb and a transparent parallel plate 94-2 with a thickness Ta to split the wavefront is arranged in the optical path.

[0268] Also, in the first half of Section 3.4, as the item corresponding to the "Synthesis / Mixing Location" column in Fig. 9, the content corresponding to "in the optical path (of the irradiation light 12 or the detection light 16)" is described. And in the second half of Section 3.4, the content corresponding to "the detection surface 86 in the detector 80" and "the pinhole or slit 130" is described. And first, the explanation starts from the content corresponding to "in the optical path (of the irradiation light 12 or the detection light 16)".

[0269] The optical system corresponding to the photosynthesis (mixing) unit in Fig. 8A(a) is composed of a combination of a condenser lens 98 and an optical fiber 100 in Fig. 14A. All the light passing through the entire optical path after passing through the optical property changing member having this wavefront splitting function is in a parallel state. When this light is condensed by the condenser lens 98, the equiphase surfaces of all the light are planes perpendicular to the optical axis on the condensing surface. And this state is the same as the state where "the traveling directions of the light passing through different optical paths are the same" described in the first half of Section 3.1.

[0270] And this condensing surface corresponds to "a predetermined location existing within a local region in the optical axis direction" described in the first half of Section 3.1. And the entrance surface of the optical fiber 100 is made to coincide with this predetermined location. And in the process of passing through this optical fiber 100, the light passing through each optical path wavefront-split by the optical property changing member is mixed. As a result, the combined light (mixed light) 78 is emitted from the exit surface (the exit 108 of the combined light) of the optical fiber 100.

[0271] The part from the rear mirror 82 in Fig. 14A to the left entrance of the optical fiber 100 may be housed inside the light source unit 2 in Figs. 1A to 1C or Figs. 7, 8A, 10(b). And the exit 108 of the combined light on the right side of the optical fiber 100 may be arranged near the object 10.

[0272] The optical fiber 100 has very high flexibility, and the length of the optical fiber 100 can be set to an arbitrary length (for example, 50 m or less). Thereby, there is an effect of isolating the object 10 from the heat and vibration generated near the light emitting source 70 (tungsten filament 50).

[0273] In the "Photosynthesis / Mixing Method" column of FIG. 9, a "light phase conversion element" (including a random phase shifter, a diffuser, a sanded surface, etc.) that has a fine concavo-convex structure on its surface and locally changes the phase of transmitted light or reflected light is described. A specific embodiment using this method is shown in FIG. 14B.

[0274] Similar to FIG. 14A, as different optical paths, light in different light emission directions (front and rear) is utilized. Also, the optical property changing member formed by combining the transparent semi-circular parallel plates 94-1 and 2 is not limited to the structures shown in FIGS. 12C to 13C, and any structure that enables wavefront splitting may be used.

[0275] The "light phase conversion element" described in the "Photosynthesis / Mixing Method" column of FIG. 9 corresponds to a transparent flat plate (photosynthesis unit 102-2) 104 having a random fine concavo-convex structure on one side. And the light passing through any optical path is simultaneously diffused by this fine concavo-convex surface and travels in a wide range of directions. From this feature, a part of the light diffused from any position on this fine concavo-convex surface also travels in a specific direction that coincides. By the way, as described in Section 3.3, in "wavefront splitting", the optical paths of light passing through (or reflecting) at different positions on the transmitted light cross-section 92 (FIG. 12B or FIG. 13A) are different from each other. Therefore, the light extracted in a specific traveling direction after passing through (or reflecting from) the "light phase conversion element" is in a state where "the traveling directions of light passing through different optical paths coincide" (which is consistent with the description in the first half of Section 3.1).

[0276] As a specific method for extracting the light traveling in a specific direction after passing through (or reflecting from) the "light phase conversion element", for example, as shown in FIG. 14E, only the light passing through the pinhole or slit 130 on the condensing surface of the detection lens 28-2 may be extracted. Alternatively, as shown in FIG. 14D, the imaging surface (detection surface) 86 of the monitor camera 24 may be arranged on the condensing surface of the detection lens 28-2, and the light irradiated only on specific pixels therein may be detected.

[0277] As described above, even if the traveling light in a specific direction after passing through (or being reflected by) the "optical phase conversion element" is not deliberately extracted, light mixing (or synthesis) occurs within the wavefront 106 of the traveling light that is separated from the transparent flat plate (photosynthesis unit 102-2) 104 having a random fine uneven structure on one side by a predetermined distance or more. In this way, light mixing (or synthesis) may be performed by utilizing the light diffraction phenomenon.

[0278] When light is mixed (or synthesized) using the "optical phase conversion element" in this way, the mixing (or synthesis) occurs regardless of the traveling direction of the light at a certain distance or more. Therefore, since high-precision optical arrangement and optical axis alignment are not required for the generation of the synthesized light (mixed light) 78, there is an effect that it is easy to manufacture a large amount of inexpensive measuring devices.

[0279] Furthermore, as shown in FIG. 14B, an optical phase conversion element may be directly adhered to a part (light exit) of the optical property changing member (composed of the transparent semi-circular parallel plates 94-1 and 94-2) to integrate the optical property changing member and the optical phase conversion element. As a result, since the integrated optical element has both an optical path separation (division) function and a light synthesis / mixing function, it is easy to modify an existing measuring device (or microscope device).

[0280] In FIG. 14B, the integrated element of the optical phase conversion element (the transparent flat plate (photosynthesis unit 102-2) 104 having a random fine uneven structure on one side) or the optical property changing member is arranged in the light source unit 2. However, it is not limited thereto and may be arranged in the detection unit 6, or may be arranged to be shared by both the light source unit 2 and the detection unit 6 as shown in FIG. 7. (In this case, the integrated element of the optical phase conversion element or the optical property changing member corresponds to the optical noise reduction element or the partial coherence reduction element 64.) An example of a method using a "diffraction-related element" in the "Photosynthesis / Mixing Method" column of FIG. 9 is shown in FIG. 14C. In FIG. 14C, a blazed diffraction grating 124 is used as the diffraction-related element, but it is not limited thereto, and any optical element having a function of synthesizing (mixing) light using diffraction may be used. Generally, diffraction-related elements are often used for splitting transmitted light or reflected light. However, when looking at the optical path where the light is split from the reverse direction, the light takes a form in which it is synthesized (or mixed). Utilizing this feature, the synthetic light (mixed light) 78 is generated.

[0281] A transparent parallel plate 114-1 and 2 are combined to form an optical property changing member using wavefront splitting. And at least a part of the exit of this optical property changing member, an optical element for changing the light traveling direction such as a Fresnel prism (blazed hologram) 122 is arranged. Note that this optical element for changing the light traveling direction and the optical property changing member may be adhered and integrated.

[0282] And the transmitted light 110-1 whose traveling direction has been changed is synthesized with the transmitted light 110-2 that has passed only through the transparent parallel plate 114-1 at the blazed diffraction grating 124. Therefore, the combination part of the Fresnel prism (blazed hologram) 122 and the blazed diffraction grating 124 becomes the light synthesis (mixing) part 102-3, corresponding to the light synthesis (mixing) part 102 in FIG. 8A(a) or FIG. 8B(a).

[0283] Note that in the present embodiment example of FIG. 14C, transmitted lights 110-1 and 2 are used. However, it is not limited thereto, and synthetic light (mixed light) 78 may be generated using reflected light.

[0284] An embodiment example corresponding to the "detection surface 86 in the detector 80" in the "Synthesis / Mixing Location" column of FIG. 9 is shown in FIG. 14D. By using this embodiment example, an enlarged image of the minute light scatterer 66 can be clearly imaged.

[0285] With the combination of the objective lens 25 and the detection lens 28-2, the imaging surface (detection surface) 86 in the monitor camera 24 becomes an imaging surface for the minute light scatterer 66. A part of this imaging optical system (or confocal optical system) is used for light synthesis / mixing. In the imaging optical system (or confocal optical system), light starting from one point converges to one point on the imaging surface regardless of the optical path. And at the position of the converging point on this imaging surface, the light that has passed through all the optical paths is synthesized / mixed.

[0286] Therefore, when an optical characteristic changing member that divides (separates) into a plurality of optical paths with different optical path lengths is arranged in the optical path of the imaging optical system, the optical arrangements shown in FIGS. 8B(b) and 10(c) are configured. As another way of looking at it, the light synthesis (mixing) unit 102-4 combining the detection lens 28-2 in FIG. 14D and the imaging surface (detection surface) 86 in the monitor camera 24 may be made to correspond to the light synthesis (mixing) unit 102 in FIG. 8B(a).

[0287] The spectroscope 22 shown in FIG. 14E has a structure that measures the spectroscopic characteristics only for the light passing through the pinhole or slit 130 arranged at the entrance. That is, the light passing through the pinhole or slit 130 is returned to parallel light by the condenser lens 134-1, and wavelength separation is performed using diffraction by the blazed diffraction grating 126. Then, each wavelength-separated light is condensed onto the one-dimensional line sensor 132 by the condenser lens 134-2. The spectroscopic characteristics are measured by detecting the light quantity distribution irradiated on this one-dimensional line sensor 132.

[0288] And also in the other application embodiment shown in FIG. 14E, the imaging optical system (or confocal optical system) is used to synthesize (mix) the light that has passed through a plurality of optical paths with different optical path lengths. In this case, only the light obtained from the optical axis of the objective lens 25 in the minute light scatterer 66 passes through the pinhole or slit 130 arranged at the imaging position (or confocal position).

[0289] As a device for measuring the spectroscopic characteristics of only a local region within the minute light scatterer 66, the imaging position (or confocal position) of the local region is made to coincide with the position of the pinhole or slit 130 at the entrance of the spectroscope 22. However, not limited thereto, the pinhole or slit 130 existing alone may be arranged at a predetermined position in the optical path (imaging position (or confocal position) corresponding to the local region within the minute light scatterer 66).

[0290] When the parallel plates 94-1 and 2 are arranged in the diverging optical path or the converging optical path within the imaging optical system, unnecessary optical interference occurs as shown by the formula (B·28) in Section 2.5. Moreover, as will be described later in Chapter 6, the imaging image deteriorates due to the influence of spherical aberration. Therefore, in the present embodiment examples of FIGS. 14D and 14E, the optical property changing member composed of the transparent semi-circular parallel plates 94-1 and 2 is arranged in the optical path in a parallel state. As shown in FIG. 22 as a specific embodiment example of this, the irradiation light 12 is made parallel between the collimating lens 26 and the condenser lens 98. And in the optical path in this parallel state, the transparent semi-circular parallel plates 94-1 and 2 which are optical property changing members are arranged. However, not limited to the above example, any form of optical property changing member described in the "Photosynthesis / Mixing Method" column of FIG. 9 may be arranged in the optical path (parallel light beam) in a parallel state. As a result, an effect is produced in which unnecessary optical interference is removed to remove optical noise and the imaging image can be sharpened.

[0291] Note that the optical property changing member arranged in the parallel optical path is not limited to FIGS. 14D and 14E, and any member having the function of "wavefront splitting" or "amplitude splitting" in FIG. 9 may be used.

[0292] In Section 3.4 until now, mainly the method of mixing or synthesizing the light that has passed through a plurality of optical paths divided by "wavefront splitting" has been mainly described. However, as described in the "Detailed Content" column of FIG. 9, the light that has passed through a plurality of optical paths divided by "amplitude splitting" may be mixed or synthesized.

[0293] In the case of mixing light that has passed through a plurality of optical paths divided by "amplitude division" in this exemplary embodiment, the directions of the vibration planes (of the electric fields) in the mixed light may be made to coincide. For example, when the vibration planes (of the electric fields) are inclined with respect to each other (not completely coinciding) between the lights passing through the two optical paths divided by "amplitude division", the directions of the vibration planes of both may be made to coincide at the stage of the mixing process (or the combining process). As an example of this specific method, only the light components having a predetermined vibration plane may be extracted (transmitted) using the analyzer 496 or the polarization beam splitter 492 shown in FIG. 33.

[0294] If the direction of the vibration plane in the mixed light is deflected using the above analyzer 496 or polarization beam splitter 492, the mixed light becomes linearly polarized light. However, in this exemplary embodiment, it is sufficient that the polarization characteristics in the mixed light coincide, and circularly polarized light or elliptically polarized light may also be used. Further, the above operation is not limited to the case of mixing or combining the lights that have passed through a plurality of optical paths divided by "amplitude division", and may be applied to any method described in the "Detailed Content" column of FIG. 9.

[0295] When performing signal detection / measurement (including spectroscopic characteristic detection), imaging, or wavefront aberration characteristic detection / measurement in the detection unit 6 (FIGS. 1A to 1C) using the above mixed light, for example, a "polarization plane operation" (an optical operation related to the vibration plane of a specific electric field) as shown in FIG. 33 may be performed. If the polarization characteristics in the mixed light are different (between different optical paths before mixing), there is a risk that the partial coherence is improved and the optical noise increases due to the "polarization plane operation" inside the detection unit 6. Therefore, when the polarization characteristics (or the direction of the vibration plane, etc.) in the mixed light coincide, even if the "polarization plane operation" is performed inside the detection unit 6, an increase in optical noise can be suppressed, and stable signal detection / measurement (including spectroscopic characteristic detection), imaging, or wavefront aberration characteristic detection / measurement can be performed.

[0296] 3.5 Expression of the light intensity formula when using partially incoherent light (optical noise reduction effect) (Section 3.5) Light Intensity Formula of Partially Incoherent Light indicating Optical Noise Reduction Effect) In Section 3.1, the situation where optical noise is reduced by the method of this embodiment was qualitatively described. In this Section 3.5, the implementation effect will be quantitatively described using mathematical formulas.

[0297] Consider the case where the transmitted light cross-section 92 is evenly divided into N (equally divided into N regions) by the angular division shown in the examples of FIGS. 13A to 13B. As already described in Section 2.5, for example, the uniformity of the thickness T of the bulb (quartz glass) 67 of the tungsten halogen lamp in FIG. 6 is low. Therefore, if the average thickness of each of the N-divided regions is Tm, the average thickness Tm shows different values for different regions m.

[0298] Due to the function of the optical property changing member in FIGS. 13A to 13B, the lights passing through different optical paths show partial non-coherence with each other. As a result, at the place where they are mixed, the synthesis (summation) on the amplitude characteristic expressed by Equation (B·19) does not occur. Instead, at the mixing place, the transmitted light intensities (light amounts) of different optical paths are simply added.

[0299] From the above situation, the light intensity characteristic after mixing partially incoherent light is transformed with respect to Equation (B·28)

[0300]

Number

[0301] and is transformed as follows.

[0302] The second term on the right side of Equation (B·30) indicates the amount of optical noise generated due to optical interference. Since different average thicknesses Tm are possessed for different optical paths in the numerator of this second term, the periods of change corresponding to the measurement wavelength λ are different. It is considered that the maximum value of the fluctuation amplitude of the second term on the right side is reduced by averaging between cosine waves having these different periods.

[0303] Comparing the formula (B·28) showing the detected intensity distribution of the partial coherent light with the formula (B·30) showing the detected intensity distribution of the partial incoherent light, it can be seen that the optical noise level is significantly reduced by adopting the method of this embodiment. Although the angular division in FIGS. 13A to 13B is taken as an example here for explanation, it is not limited thereto, and similar results to the above can be obtained for all the "optical path states before synthesis / mixing" in FIG. 9.

[0304] As described at the end of Section 2.6, due to the influence of the bulb inside the light source, etc., most of the irradiation light 12 (or detection light 16) obtained from a panchromatic (non-monochromatic) light source contains optical noise components of about 0.1 to 1.0% on average. In the example of this embodiment, due to the effect of the formula (B·30), the amount of the optical noise component is reduced to 0.5% or less on average (or 0.1% or less on average, desirably 0.05% or less on average or 0.02% or less on average). Here, the amount of the optical noise component is defined as the ratio of the optical noise component (the average amplitude value of the second term on the right side of the formula (B·30)) to the direct current component (the coefficient of the first term on the right side of the formula (B·30)) when the direct current component is set to "1". Note that the experimental data in FIG. 23A(c) cited in Chapter 5, etc., shows that the optical noise component is significantly reduced (satisfying the above numerical values).

[0305] When the average thickness Tm for each different optical path is all the same, the formula (B·30) completely coincides with the formula (B·28), so the reduction effect of the periodic light quantity variation (optical noise) according to the change in the measurement wavelength λ does not appear. By the way, the formula (B·30) represents a state where the partial coherence is reduced and the partial incoherence is increased between the lights passing through different optical paths. However, the method of this embodiment for reducing the optical noise is not an absolutely universal method, and in a situation where strong light interference occurs in the optical system (for example, all Tm are the same), the reduction effect of the optical noise weakens.

[0306] Even when the average thickness Tm for each different optical path does not all match, if the value of the number N of divided optical paths is small, beats occur in the second term on the right side of equation (B·30). For simplicity of explanation, the case of N = 2 will be described. Even in the situation where T1 ≠ T2, there exist values of wavelength λ for which the value of the second term on the right side of equation (B·30) becomes 1 / 2 and values of wavelength λ for which it becomes -1 / 2. Since the interval (wavelength difference) between the two is much wider than the period of equation (B·28), if the detection / measurement wavelength range is set to a narrower range than that, an optical noise reduction effect appears. However, an optical system configuration in which the above beats are less likely to occur is preferred.

[0307] Therefore, in the present embodiment, the value of the number N of divided optical paths is preferably "3 or more", more preferably 4 or more, 8 or more, 9 or more. In order to increase the value of the number N of divided optical paths, in this embodiment example, a plurality of items described in the "Detailed Content" column of FIG. 9 may be combined and used.

[0308] 3.6 Device Structure Improvements for Optical Property Changes In this 3.6 section, the precautions and technical improvements when using an optical property change member having the wavefront division function described in 3.3 section will be described. As an example, an optical property change member is configured by combining (adhering) a transparent semi-circular parallel plate 94-1 with a thickness T and a transparent semi-circular parallel plate 94-2 with a thickness 2T.

[0309] When light reflection occurs at the interface between the adhesive layer 112 and the transparent semi-circular parallel plate 94-1 or 2 as shown in FIG. 15(a), light interference occurs between the reflected light and the direct light, increasing the optical noise. Also, as shown in FIG. 15(a), there is a risk of light reflection occurring at the interface between the transparent semi-circular parallel plate 94-1 or 2 and the air, causing unnecessary light interference.

[0310] Furthermore, when the cut surface 95 of the transparent semi-circular parallel plate 94-2 is inclined with respect to the optical axis of the transmitted light 110-2 as shown in Fig. 15(c), or when the boundary line 97 of the cut surface spreads, that portion becomes a shadow and an unnecessary loss of the amount of transmitted light occurs. Further, when the parallelism between the parallel surfaces of the transparent semi-circular parallel plate 94-2 decreases, the propagation angle ζ of the transmitted light 110-1 after passing through the transparent semi-circular parallel plate 94-2 (the angle formed with the propagation direction of the transmitted light 110-2) increases, and it is likely that the propagation directions will not match after mixing (refer to the description in the first half of Section 3.1).

[0311] To prevent light reflection at the interface between the transparent parallel plates 114-1, 2 and the adhesive layer 112, the interfaces of both may be arranged substantially parallel to the optical axes of the transmitted lights 110-1, 2 as shown in Fig. 16A(a). As another method, in this embodiment, the refractive index of the adhesive layer 112 may be adjusted to match the refractive index of the material to which it adheres (i.e., the glass material constituting the transparent parallel plates 114-1, 2).

[0312] Also, to prevent light reflection (and the resulting light interference) on the front and back surfaces of the transparent semi-circular parallel plates 94-1, 2 in Fig. 15(b), antireflection coating layers 118-1 to 3 may be provided on the front and back of the transparent semi-circular parallel plates 94-1, 2. That is, not only in the "wavefront splitting" of the "detailed content" in Fig. 9 but also in all items, antireflection coating layers 118-1 to 3 are formed at the interface between the optical property changing member and air (vacuum) to prevent light reflection. As a result, unnecessary light interference can be prevented, and the effect of preventing an increase in optical noise can be achieved.

[0313] To prevent the loss of the amount of transmitted light due to the boundary line 97 of the cut surface and the cut surface 95 described with reference to Fig. 15(c), the manufacturing accuracy of the optical property changing member is improved. That is, the width of the boundary line 97 of the cut surface within the optical property changing member is set to 1 mm or less (preferably 0.5 mm or less, or 0.2 mm or less). Also, when the maximum thickness of the optical property changing member is T and the inclination angle of the cut surface 95 with respect to the optical axis of the transmitted light 110-2 is η, the manufacturing accuracy is defined such that the value of Ttanη is 1 mm or less (preferably 0.5 mm or less, or 0.2 mm or less).

[0314] At the beginning of Section 3.1, it was explained that "the light passing through multiple optical paths is combined or mixed at a predetermined location". To enable this, the allowable range of the manufacturing accuracy of the optical property changing member (for example, the parallel accuracy within the optical property changing member, etc.) is defined.

[0315] For example, in the embodiment of FIG. 14E, it is combined or mixed at the pinhole or slit 130 portion. Therefore, it is necessary for the light passing only through the transparent semi-circular parallel plate 94-1 and the light that has also passed through the transparent semi-circular parallel plate 94-2 to simultaneously pass through the pinhole or slit 130.

[0316] Let the inclination angle between both planes constituting the transparent semi-circular parallel plate 94-2 with a refractive index n be θ. And when the inclination angle of the traveling direction of the light after passing through the transparent parallel plate is ζ, approximately ζ ≒(n - 1)θ …(B·31) the following relationship holds. Let the focal length of the detection lens 28-2 be "F". And let the value of half of the pinhole radius / slit width W be "a". Based on the position where the light passing only through the transparent semi-circular parallel plate 94-1 is focused on the surface of the pinhole or slit 130, let the deviation amount of the position where the light that has also passed through the transparent semi-circular parallel plate 94-2 is focused on the surface of the pinhole or slit 130 be D. Then, D≒Fζ can be approximated. And since the condition for this light to pass through the pinhole or slit 130 is D < a, summarizing the above

[0317]

Equation

[0318] the following relationship holds. Therefore, the manufacturing accuracy of the optical property changing member (for example, the parallel accuracy within the optical property changing member) is defined so as to satisfy the above conditions.

[0319] 3.7 Comparison with the Prior Art Using Wavefront Division The difference between the prior art described in [Patent Document 1] explicitly stated in [Prior Art Documents] and this embodiment will be explained here.

[0320] In [Patent Document 1], as shown in FIG. 17, the optical path lengths are changed using optical fibers 100-1 and 100-2 and they are mixed using a collimating lens 136. However, in this prior art, the traveling directions of the light after mixing do not match. That is, since the outlets of optical fibers 100-1 and 2 are arranged on the front focal plane of the collimating lens 136, the traveling directions of the light that has become parallel by the collimating lens 136 are different from each other as α and β. As a result, the equiphase surfaces (wavefronts) are inclined with respect to each other between the traveling directions α and β of the light after passing through the collimating lens 136, and highly accurate optical synthesis or optical mixing cannot be performed. Therefore, the effect of reducing partial coherence is insufficient.

[0321] Furthermore, as shown in FIG. 8A or FIG. 10(b), in this embodiment, after making the traveling directions of the combined light (mixed light) 78 all coincide (regardless of the optical paths before synthesis / mixing), the object 10 is irradiated. Based on this, when irradiating the object 10 with focused light as shown in FIG. 1C or FIG. 7, all the light can be efficiently irradiated within a specific region α in the object. Then, for example, regarding the measurement or observation of a local specific region within the minute light scatterer 66 as shown in FIGS. 14D and 14E, there is an effect that high signal detection accuracy, high imaging accuracy, and spectroscopic characteristic measurement accuracy can be ensured.

[0322] 3.8 Section Optical property changing member having an optical waveguide function An example of this embodiment using the "waveguide element (optical fiber / optical waveguide)" described as an optical element used in the "optical synthesis / mixing method" column in FIG. 9 will be described. In this example of the embodiment, by making the length of the waveguide element longer than a predetermined distance, the optical path length is changed for each optical path of the light passing through the waveguide element to reduce partial coherence. Note that the optical path length for each optical path of the light passing through the waveguide element may be made longer than the coherence distance given by Equation (B·6) or Equation (B·12). That is, the above-mentioned predetermined distance may correspond to the coherence distance.

[0323] The range of the maximum incident angle ε entering from the entrance of the optical fiber 100-2 into the interior is defined by NA (strictly speaking, in a vacuum (air), NA = sin ε). When the value of ε is sufficiently small, NA ≒ ε. Also, at this time, the incident angle within the core region 142 of the optical fiber 100-2 is represented by ξ. If the refractive index within the core region 142 of the optical fiber 100-2 is represented by n, from Snell's law, the approximation ε ≒ n×ξ holds.

[0324] Estimate the value of the optical path difference δ generated between the light passing through the optical path traveling straight through the central part within the core region 142 of the optical fiber 100-2 and the light passing through the optical path also passing near the interface between the core region 142 and the cladding layer 144.

[0325] As shown in Fig. 18(a), the optical path passing near the interface between the core region 142 and the cladding layer 144 draws a curve. For simplicity of calculation, approximate this curve as a straight line. That is, consider that the optical path within the core region 142 travels straight and undergoes total reflection near the interface between the core region 142 and the cladding layer 144.

[0326] The optical path length difference δ per unit length of the optical fiber 100-2 between this optical path and the optical path traveling straight through the central part within the core region 142 * is δ * ≒ { (1 / cos ξ) - 1}n …(B·33) Therefore, when the total length of the optical fiber 100-2 is L, the total value of the optical path length difference δ after passing through the optical fiber 100-2 is δ = Lδ * is longer than the coherence length l given by Equation (B·6) or Equation (B·12) CL The condition for this is, from Fig. 18

[0327]

Equation

[0328] is given by. If the total length L of the optical fiber 100-2 is made longer than the length satisfying this (B·34) equation, the partial coherence of the light passing through the optical fiber 100-2 will decrease.

[0329] The above formula (B·34) is not a conditional formula that holds only for the optical fiber 100-2, but is also applicable to any waveguide element (such as an optical waveguide formed (integrated) on a substrate).

[0330] 3.9 Method for Combining / Mixing Emitted Light from Different Regions An explanation of this embodiment using the "different light-emitting regions" in FIG. 9 will be given. Also in this case, basically, the basic principle described in Section 3.1 is followed. That is, in this embodiment, the difference δ in the optical path lengths between each other up to a specific region (or measurement point) γ in the object 10 is the interference distance l given by formula (B·6) or formula (B·12) CL Light generated from a plurality of light-emitting regions (for example, the α region and the β region near the tungsten filament 50 in FIG. 2A) that is longer than this is mixed and irradiated onto the object 10. Alternatively, the detected light 16 (the light detected by the photodetector 80 in FIG. 8B or FIG. 10) after passing through the object 10 may include the combined light or mixed light of the light generated from the α region and the β region.

[0331] In this Section 3.9, a basic embodiment method in which the content already described in FIG. 8A is applied to "different light-emitting regions" (FIG. 9) will be outlined using FIGS. 19A and 19B. Thereafter, specific embodiments thereof will be described using FIGS. 20 to 21C and FIGS. 24A and 24B.

[0332] In Section 3.9, as an example of different light-emitting regions, a light-emitting source 70 using a tungsten filament 50 will be described. However, it is not limited thereto, and all light-emitting sources 70 having the characteristic of emitting light simultaneously from a relatively wide region may be adapted to the description content. Also, here, an example of the "same light-emitting source 70" having different light-emitting regions is used for the description. However, it is not limited thereto, and different light-emitting regions may be dispersedly arranged across different light-emitting sources. That is, in this embodiment example, light emitted from a plurality of different light-emitting sources may be mixed and used as irradiation light (first light) 12 (Figs. 1A to 1C). And in this case, a plurality of different light-emitting sources are built into the light source unit 2 of Figs. 1A to 1C. Also in this case, in the photosynthesis (mixing) unit 102 (Fig. 8A(a)), as described in Section 3.1, it is desirable that the traveling directions (or the directions of the vibration planes of the electric fields) of the light emitted from a plurality of different light-emitting regions substantially coincide.

[0333] Fig. 19A shows a basic embodiment method in which the content already described in Fig. 8A(b) is applied to "different light-emitting regions" (Fig. 9). In Fig. 19A(a), an optical path changing element 210 corresponding to a kind of optical property changing member is arranged between the light-emitting source 70 (tungsten filament 50) and the object 10. On the other hand, in Fig. 19A(a), it is not present, and the light emitted from the light-emitting source 70 (tungsten filament 50) is directly irradiated onto the object 10.

[0334] In both Fig. 19A(a) and (b), an α region corresponding to a specific region 200 in the object serves as a photosynthesis / mixing location. Here, not all the light emitted from the light-emitting source 70 (tungsten filament 50) passes through the α region in the object 10. Only a part of the light emitted from the light-emitting source 70 (tungsten filament 50) passes through the α region, but only the light that has passed through this α region is selectively extracted by the detection unit 6. And this α region corresponds to the "specific region 200 in the object 10" or "(including imaging on the detection surface 86, etc.)" in the "synthesis / mixing location" column of Fig. 9, and the details will be described later with reference to Fig. 20.

[0335] The differences δ1 and δ2 in the optical path lengths from a plurality of light-emitting regions within the same light source 70 to the α point corresponding to the specific region 200 within the object are the coherence lengths l given by equation (B·6) or equation (B·12). CL If they are longer than the coherence length l, the partial coherence between the lights emitted from each light-emitting region decreases.

[0336] Due to the geometric arrangement in Fig. 19A(a), the values of the respective optical path length differences δ1 and δ2 become smaller as the distance between the light source 70 (tungsten filament 50) and the object 10 increases. Conversely, as the distance between the light source 70 (tungsten filament 50) and the object 10 decreases, the values of the respective optical path length differences δ1 and δ2 decrease to the distance between the light-emitting regions on the light source 70 (tungsten filament 50).

[0337] Therefore, when the distance between the light-emitting regions on the same light source 70 is longer than the coherence length l given by equation (B·6) or equation (B·12), the partial coherence always decreases regardless of the distance between the light source 70 (tungsten filament 50) and the object 10. Therefore, in this embodiment, the width (length) of the wide light-emitting region in the light source 70 may be set to be longer than the coherence length l given by equation (B·6) or equation (B·12). CL Particularly, when a tungsten filament 50 is used as the light source 70, the widths of the light-emitting regions are different in the vertical and horizontal directions. In this case (when the widths (lengths) of the wide light-emitting regions in the direction of the light source 70 are different), the length of the widest part of the light-emitting region in the light source 70 may be made longer than the coherence length l. CL It may be set longer.

[0338] CL It may be set longer.

[0339]

[0340] CL By the way, when the distance between the light source 70 and the object 10 is sufficiently short and the widest width of the light-emitting region in the light source 70 is the same as the coherence length l, only partial non-coherence can be obtained between the lights emitted from the light-emitting regions at both ends within the light source 70. In this case, partial coherence is maintained between the lights emitted from the light-emitting regions near the center within the light source 70.

[0340] The greater the value of the number of optical paths N for which the optical path length difference δ between each other is longer than the coherence distance l CL is desirable, as explained in the first half (or Section 3.5) of Section 3.1. Therefore, from the viewpoint of the optical noise reduction effect, it is better that the width of the light emitting region in the light source 70 is wider. Therefore, as a condition for always being able to exhibit the optical noise reduction effect regardless of the distance between the light source 70 and the object 10, the length at the widest part of the width of the light emitting region in the light source 70 is N×l CL is desirably wider. Here, the value of N is "2 or more", and more preferably 3 or more, 4 or more, 8 or more.

[0341] In other words, the optical system may be arranged so that the object 10 is irradiated with light emitted from a wide light emitting region wider than N×l CL in the light source 70. Moreover, not limited to that alone, the optical system may be arranged so that the light emitted from a wide light emitting region wider than N×l CL in the light source 70 reaches the photodetector 80 (FIG. 8B or FIG. 10(c)) in the detection units 4 and 6 via the object 10.

[0342] In Section 3.1, two types of functions that the optical property changing member can exhibit were explained. The optical path changing element (optical property changing member) 210 used in FIG. 19A(b) changes the optical path (mainly the traveling direction) of the light emitted from the light source 70 to perform "(A) changing / controlling the optical path length for each optical path".

[0343] That is, for the light emitted from a plurality of different light emitting regions on the light source 70 (tungsten filament 50), the traveling direction (optical path) is changed by the optical path changing element (optical property changing member) 210.

[0344] As the above optical path changing element (optical property changing member) 210, an optical phase conversion element or a diffraction related element described in the "Light synthesis / mixing method" column of FIG. 9 may be used. Thereby, the light passing through the above optical path changing element (optical property changing member) 210 is diffused. And a part of the diffused light reaches the α region in the object 10 of the specific region (light synthesis / mixing place) 200 in the object.

[0345] As described above, the differences δ1 and δ2 in the optical path lengths from a plurality of light-emitting regions within the same light source 70 to the α point within the object 10 increase as the distance between the light source 70 and the object 10 decreases. However, since the light source 70 (tungsten filament 50) generates a large amount of heat and vibration (such as the rotational vibration of a cooling fan), it is difficult to arrange the light source 70 and the object 10 close to each other. As a countermeasure, an optical path changing element (optical property changing member) 210 is arranged between the light source 70 (tungsten filament 50) and the object 10. By approaching the object 10, the differences δ1 and δ2 in the optical path lengths from the plurality of light-emitting regions within the light source 70 are increased, resulting in an effect of making it easier to reduce the partial coherence.

[0346] Actually, divergent light is emitted from each light-emitting region within the light source 70. However, consider the case where substantially parallel light from each light-emitting region within the light source 70 reaches the optical path changing element (optical property changing member) 210 as the optical path of light that coincides with the photosynthesis / mixing location in the specific region 200 within the object 10, as will be described later. In this case, similar to the description of FIG. 19A(a), if the width (length) of the wide light-emitting region in the light source 70 is longer than the coherence distance l CL the partial coherence of the combined light is likely to decrease.

[0347] Also, similar to FIG. 19A(a), in FIG. 19A(b) as well, it is desirable that the length at the portion where the width of the light-emitting region within the light source 70 is the widest is wider than N×l CL (the value of N may be "2 or more", 3 or more, 8 or more, etc.). And in the method of FIG. 19A(b) as well, the optical system may be arranged so that the light emitted from the wide light-emitting region wider than N×l CL within the light source 70 irradiates the object 10. Further, the optical system may be arranged so that the light emitted from the wide light-emitting region wider than N×l CL within the light source 70 reaches the photodetector 80 (FIG. 8B or FIG. 10(c)) in the detection units 4 and 6 after passing through the object 10. Here, these conditions are not limited to FIG. 19A and may also be applied to FIGS. 19B(a) and 19B(b).

[0348] The method shown in FIGS. 19A(a) and (b) sets a specific region 200 within the object as a photosynthesis / mixing location by selectively extracting only the light that has passed through the α region within the object 10 in the detection units 4 and 6. In contrast, the method of FIGS. 19B(a) and (b) installs a photosynthesis (mixing) unit 102 inside the light source unit 2 to generate synthesized light (mixed light) 78. In this case, the differences δ1 and δ2 in the optical path lengths from the plurality of different light-emitting regions within the light-emitting source 70 to reach the photosynthesis (mixing) unit 102 are made longer than the coherence length l CL to reduce their partial coherence with each other.

[0349] And FIG. 19B shows a basic embodiment method in which the content already described in FIG. 8A(a) is applied to "different light-emitting regions" (FIG. 9).

[0350] In FIG. 19B(a), the light emitted from the plurality of different light-emitting regions within the light-emitting source 70 directly reaches the photosynthesis (mixing) unit 102. On the other hand, in FIG. 19B(b), an optical path conversion element (optical property changing member) 210 similar to that in FIG. 19A(b) is disposed between the light-emitting source 70 and the photosynthesis (mixing) unit 102.

[0351] Specific embodiment examples of setting the α region of the specific region 200 within the object as a photosynthesis / mixing location in FIGS. 19A(a) and (b) are shown in FIG. 20. Here, FIG. 20(a) corresponds to FIG. 19A(a), and FIG. 20(b) corresponds to FIG. 19A(b). And in both FIGS. 20(a) and (b), the α region within the object 10 corresponds to the "specific region 200 within the object" in the "synthesis / mixing location" column of FIG. 9.

[0352] Inside the detection unit 6, a spectroscope 22 and a monitor camera 24 are installed. These detect the detection light (second light) 16 obtained from the object 10 and measure the inside of the object 10. Here, the position of the imaging surface (detection surface) 86 (see FIG. 14D) in the monitor camera 24 and the position of the pinhole or slit 130 (see FIG. 14E) in the spectroscope 22 are in an imaging (confocal) relationship with the α region (α point) in the object 10. Therefore, the monitor camera 24 and the spectroscope 22 selectively extract signals obtained from the α region (α point) in the object 10. Arranging the detection surface in this way corresponds to "(including imaging on the detection surface 86, etc.)" in the "Synthesis / Mixing Location" column of FIG. 9.

[0353] On the other hand, the light emitted from a plurality of different light-emitting regions in the light source 70 (FIG. 20(a)) or the light after passing through the optical path conversion element (optical property conversion member) 210 spreads as diffused light. And a part of the light emitted from all the different light-emitting regions in the light source 70 passes through the α region in the object 10. Therefore, using the imaging optical system in the detection unit 6, the light emitted from a plurality of different light-emitting regions in the light source 70 is substantially synthesized / mixed within the α region (α point) in the object 10.

[0354] In FIG. 20, the monitor camera 24 and the spectroscope 22 are used for signal detection. However, not limited to this, in this embodiment, any signal detection means (light detector 80 in a broad sense) may be arranged at the imaging position (confocal position).

[0355] Specific embodiment examples regarding FIGS. 19B(a) and (b) are shown in FIG. 21A. Here, FIG. 21A(a) corresponds to FIG. 19B(a), and FIG. 21A(b) corresponds to FIG. 19B(b). In FIG. 21A, as an example of the light detector 80, the spectroscope 22 is used. However, not limited to this, as a means for detecting the signal obtained from the object 10, a light detector 80 having an arbitrary function may be used.

[0356] In Fig. 21A(a), the collimating lens 26 serves as part of the function of the photosynthesis (mixing) unit 102 in Fig. 19B(a). That is, the divergent light emitted from the plurality of light-emitting regions (regions α, β, and γ) within the light source 70 is partially synthesized (mixed) on the collimating lens 26.

[0357] However, the equiphase surface (wavefront) after passing through the collimating lens 26 has a relationship in which the light-emitting regions are inclined with respect to each other for each of α, β, and γ (the directions of light propagation do not coincide). Therefore, in this state, as in Fig. 17, it is not in a completely synthesized (mixed) state.

[0358] The light after passing through the collimating lens 26 undergoes multiple scattering and diffusion inside the object 10. In the detection unit 6, only the parallel light in which the "directions of propagation are the same as each other" among the detection light 16 that has passed through the object 10 is extracted and detected by a combination of the detection lens 28 and the pinhole or slit 130. Therefore, in the embodiment shown in Fig. 21A(a), the photosynthesis (mixing) unit 102 is constituted by a combination of the collimating lens 26 and the object 10 (multiple scattering inside), (strictly speaking, the combination including the detection unit 6).

[0359] As an optical path changing element 210, which is a type of light characteristic changing member in Fig. 19B(b), in Fig. 21A(b), a phase conversion element 212 (specifically, a diffuser, a random phase shifter, a sanded surface, etc.) is used to further diffuse the directions of propagation of the light emitted from the light-emitting regions α, β, and γ within the light source 70 (change the direction of light propagation to a more spreading direction). As a result, the light emitted from the light-emitting regions α, β, and γ is included in the parallel light after passing through the collimating lens 26 (within the collimated light, the directions of propagation of the light that has passed through different optical paths emitted from the light-emitting regions α, β, and γ coincide).

[0360] And similar to Fig. 21A(a), in Fig. 21A(b) as well, only the parallel light component of the light that has passed through the object 10 is selectively detected by a combination of the detection lens 28 and the pinhole or slit 130 within the detection unit 6.

[0361] Therefore, in Fig. 21A(b), the collimating lens (strictly speaking, the combination including the detection unit 6) corresponds to the photosynthesis (mixing) unit 102 in Fig. 19B(b).

[0362] In Fig. 21A(b), the irradiated light 12 after passing through the collimating lens 26 contains a large amount of non-parallel components. As a specific method for making the traveling directions of the combined light (mixed light) 78 irradiated on the object 10 coincide and further improving the partial non-interference property, a beam expander may be arranged between the collimating lens 26 and the object 10, and a pinhole may be arranged at the condensing part in the middle.

[0363] Fig. 21B shows another embodiment example in which a phase conversion element 212 is used as a means for realizing an optical path change element 210 that realizes the function of “(A) changing / controlling the optical path length for each of a plurality of optical paths” among the functions of the optical property change member. In a panchromatic light source such as a tungsten halogen lamp or a xenon lamp, a halogen-based gas (iodine or bromine compound) or xenon gas is enclosed in the bulb. Then, a fine uneven shape is formed on the inner wall or the outer wall of the bulb 214 to give it phase conversion characteristics. As a result, the optical paths emitted from a plurality of different light emitting regions on the light emitting source 70 (for example, the tungsten filament 50) are changed, and the optical path length for each of the plurality of optical paths is changed / controlled.

[0364] Furthermore, a rear mirror 82 is used to combine (mix) the light that has passed through different optical paths. When using a bulb (and the rear mirror 82) having phase conversion characteristics on the inner wall or the outer wall as shown in Fig. 21B, there is an effect that light with a reduced partial coherence can be generated at a very low cost. Also, not limited thereto, an optical phase conversion element or a diffraction-related element described in the “Photosynthesis / Mixing Method” column in Fig. 9 may be arranged near the bulb 214.

[0365] In addition, since the light reflected by the rear mirror 82 becomes parallel light, an optical property changing member having a wavefront splitting function such as those shown in FIGS. 12A to 13C, which is not shown, may be arranged in the optical path of the parallel light. Moreover, not limited thereto, a light combining (mixing) unit 102-1 composed of a condenser lens 98 and an optical fiber 100 shown in FIG. 14A may be arranged behind this optical property changing member. Further, as the optical fiber 100 used at this time, a bundle-shaped optical fiber 300 used in FIG. 21C may be used.

[0366] Another embodiment of the optical path changing element (optical property changing member) 210 in FIG. 19B(b) will be described with reference to FIG. 21C. The optical path changing element (optical property changing member) 210 corresponds to a combination of an imaging lens 215, a collimating lens 26, and a bundle-shaped optical fiber group 300 (optical fiber 100).

[0367] In particular, the bundle-shaped optical fiber group 300 (optical fiber 100) has a function of collecting the emitted light from a very wide emission region (each region (each point) of α, β, γ) on the light source 70 and irradiating the object 10. Further, it also exhibits the effect of blocking the influence of the heat generated from the tungsten filament 50 of the light source 70 and the vibration from the cooling fan between the entrances and exits of the bundle-shaped optical fiber group 300 (optical fiber 100).

[0368] The diffused light emitted from different emission regions (each region (each point) of α, β, γ) on the light source 70 is imaged by the imaging lens 216 on the incident surface of the bundle-shaped optical fiber group 300 (optical fiber 100). Here, if the width of the light incident region of the bundle-shaped optical fiber group 300 (optical fiber 100) is represented by "D" and the imaging magnification of the imaging lens 216 is represented by "M", the light emitted within the range of D / M as the width of the wide-area emission region on the light source 70 can pass through the bundle-shaped optical fiber group 300 (optical fiber 100). Here D / M > N·l CL …(B·35) (l CLIt is given by the formula (B·6) or (B·12), and it is desirable that N satisfies a positive number of 1 or more (where N is desirably 2 or more, 4 or more, 8 or more). In particular, when using the bundle-shaped optical fiber group 300 (optical fiber 100), the value of "D" can be increased, so N can be made larger. As a result, the partial coherence between the lights passing through the bundle-shaped optical fiber group 300 (optical fiber 100) can be greatly reduced (the partial incoherence is greatly increased).

[0369] The lights emitted from each region (each point) of α, β, and γ on the light source 70 are imaged at each point of ε, ζ, and η within the light incident region of the bundle-shaped optical fiber group 300 (optical fiber 100). Since the bundle-shaped optical fiber group 300 (optical fiber 100) transports the incident light as it is, each light is emitted from each point of ε, ζ, and η within the light emission region.

[0370] Each light emitted from each point of ε, ζ, and η within the light emission region of the bundle-shaped optical fiber group 300 (optical fiber 100) becomes parallel light after passing through the collimating lens 26, but the traveling directions of this parallel light are shifted from each other (the equiphase surfaces (wave surfaces) of the parallel light are inclined to each other).

[0371] In order to make the traveling directions of the lights emitted from each point of ε, ζ, and η within the light emission region of the bundle-shaped optical fiber group 300 (optical fiber 100) coincide, the phase conversion element 212 is used as the optical property changing member. The optical property changing member used here exhibits a function corresponding to "(B) combining (mixing) a plurality of optical paths" described in Section 3.1. Also, this phase conversion element (optical property changing member) 212 corresponds to the light combining (mixing) unit 102 in Fig. 19B(b).

[0372] Since this phase conversion element (optical property changing member) 212 diffuses transmitted light (converts it into diffused light when parallel light is transmitted), a large amount of non-parallel light components are included in the irradiation light 12 irradiated onto the object 10. On the other hand, with the combination of the detection lens 28 and the pinhole or slit 130, only the parallel light components after passing through the object 10 are selectively extracted for signal detection. Therefore, strictly speaking in FIG. 21C, the phase conversion element (optical property changing member) 212 and the combination of the detection lens 28 and the pinhole or slit 130 constitute the light combining (mixing) unit 102.

[0373] Part of the specific embodiment examples of FIGS. 19A and 19B are shown in FIGS. 20 to 20C. However, not limited to the above specific embodiment examples, any other specific methods for realizing FIGS. 19A or 19B may be used. That is, as the functions that the optical property changing member can have in Section 3.1 (A) The function of changing / controlling the optical path length for each of a plurality of optical paths (corresponding to the function of "optical path length change 76" in FIG. 10 described later) and (B) It was explained that the function of combining (or mixing) a plurality of optical paths at a predetermined location is included. Any form of the optical property changing member that realizes this "(B) combination (or mixing) of a plurality of optical paths" may be used as the light combining (mixing) unit 102 in FIG. 19B. Also, any form of the optical property changing member that realizes the above "(A) changing / controlling the optical path length for each of a plurality of optical paths" may be used as the optical path changing element (optical property changing member) 210 in FIG. 19A(b) or FIG. 19B(b). Furthermore, as this optical property changing member, any optical element described in the "light combining / mixing method" column in FIG. 9 or a combination thereof may be used.

[0374] In FIGS. 20(b), 21A(b), or 21B / C, the phase conversion elements 212 and 214 are used to change the optical path (propagation direction) of light. However, with optical phase conversion elements 212 and 214 having arbitrary characteristics, it is not always possible to efficiently reduce partial coherence. The experimental system used to measure the characteristics of the optical phase conversion element 212 and the reduction effect of partial coherence is shown in FIG. 22. Also, the optical system in FIG. 22 also corresponds to other application examples of this embodiment.

[0375] In the experiment, as the "optical path state before synthesis / mixing" in Fig. 9, three types of items, namely "different light emitting regions", "different light emission directions", and "wavefront division", are combined.

[0376] Here, the radius of curvature of the rear mirror 82 is 19 mm, and the focal lengths of the collimating lens 26 and the condenser lens 98 are both 25.4 mm (resulting in an imaging magnification M = 1). Also, the diameters of the parallel light beams at the apertures of the collimating lens 26, the condenser lens 98, the expand lens 218, and the detection lens 28 are all made to coincide at 25 mm.

[0377] Also, the width D of the light incident region of the bundle-shaped optical fiber group 300 (optical fiber 100) is set to 5 mm. As a result, the value on the left side of equation (B·35) becomes 5 mm. The length of the spiral tungsten filament 50 used here is about 5 mm, and the emitted light from almost the entire wide light emitting region of the light source 70 can irradiate the object 10. Also, the length of the bundle-shaped optical fiber group 300 (optical fiber 100) is made 2 m, and the influence of the heat generated from the tungsten filament 50 of the light source 70 and the vibration from the cooling fan is blocked between the entrance and exit of the bundle-shaped optical fiber group 300 (optical fiber 100).

[0378] For the combination of the transparent semi-circular parallel plates 94-1 and 2 and the combination of the transparent semi-circular parallel plates 94-3 and 4, two sets of optical property changing members that divide the angle by 45 degrees as shown in Fig. 13B(a) are used. In order to increase the number of divided optical paths, they are installed at an angle rotated by 22.5 degrees relative to each other. Here, the value of "t" shown in Fig. 13B(a) is 1 mm, and optical glass commonly called BK-7 is used. Also, for the adhesion between the transparent semi-circular parallel plates 94-1 and 2 and the adhesion between the transparent semi-circular parallel plates 94-3 and 4, an adhesive with the same refractive index as BK-7 is used.

[0379] Also, the focal lengths of the expand lens 218 and the detection lens 28 were set to 50 mm and 250 mm. Also, after passing through the optical phase conversion element (optical property changing member) 212, the light is diffused (becomes diffused light). However, by using the combination of the detection lens 28 and the pinhole or slit 130, only the parallel light component after passing through the object 10 was extracted and detected.

[0380] As the object 10, a polyethylene film with a thickness of 30 μm that appears transparent in the visible range was used. The polyethylene film of the object 10 is not turbid with respect to near-infrared light either. Therefore, by using the combination of the detection lens 28 and the pinhole or slit 130, substantially only the components of the parallel light (light emitted from the α region, β region, and γ region and incident on the object in a form with the same traveling direction) incident on the object 10 were selectively extracted and detected.

[0381] One side of the phase conversion element (optical property changing member) 212 was made into a sanding surface (Sand Treatment Plate) with different sand grain sizes. Also, an antireflection coating was applied to the other flat surface of the phase conversion element (optical property changing member) 212.

[0382] Figure 23A shows the measurement wavelength dependence of the detection light quantity ratio (transmittance) before inserting the object 10 when the detection light quantity before inserting the object 10 was normalized uniformly to 100%. Also, the change in the measurement results when changing the sand grain size used for generating the sanding surface of the optical phase conversion element (optical property changing member) 212 was examined. Figure 23A(a) uses #1200 sand grains (the average surface roughness Ra (Average Value of Roughness) is 0.35 μm). Also, Figure 23A(b) uses #800 sand grains (the average surface roughness Ra is 0.48 μm), and Figure 23A(c) uses #400 sand grains (the average surface roughness Ra is 1.2 μm).

[0383] The difference value between the transmittance at a wavelength of 1.213 μm and the transmittance at a wavelength of 1.360 μm increases as it moves from Fig. 23A(a) to Fig. 23A(c). However, the change between Fig. 23A(a) and Fig. 23A(b) is relatively small (a large effect appears when it reaches Fig. 23A(c)).

[0384] On the other hand, the difference in light transmittance between the actually measured minimum value at a wavelength of 1.213 μm and the interpolated value (at the same wavelength position) estimated from the envelope connecting its periphery is approximately the same at about "0.5%" for both (a), (b), and (c) of Fig. 23A.

[0385] Fig. 23A shows the change in relative transmittance, while Fig. 23B shows the change in absorbance. Here, the absorbance refers to the value obtained by expressing the common logarithm of the reciprocal of the above transmittance. It can be seen from Fig. 23B that the difference between the maximum absorbance value at a wavelength of 1.213 μm and its periphery shows almost similar values regardless of the sand grain size. On the other hand, the height of the overall baseline in Fig. 23B changes significantly with the sand grain size. The causes of the maximum absorbance value and the overall baseline at the above wavelength of 1.213 μm will be described in detail later in Chapter 5.

[0386] In the absorbance characteristics of Fig. 23B, the lower the height of the baseline, the higher the measurement accuracy of the spectral characteristics (absorbance characteristics). Therefore, the measurement accuracy is the highest for #400 (the average surface roughness Ra is 1.2 μm). On the other hand, the measurement accuracy changes slightly between #800 (the average surface roughness Ra is 0.48 μm) and #1200 (the average surface roughness Ra is 0.35 μm).

[0387] The above average surface roughness Ra represents the average amount of fine mechanical unevenness on the sanded surface. Therefore, the average amount of phase difference δ generated after passing through the sanded surface is obtained by substituting the value of "Ra" into "d" in equation (B·13). Assuming that the refractive index n of BK-7 at a wavelength of 1.213 μm is approximately 1.5, when Ra = 1.2 μm, δ = 0.6 μm. This value is approximately half of the wavelength of 1.213 μm. Similarly, the average value of the phase difference corresponding to Ra = 0.48 μm is 1 / 5, and the average value of the phase difference corresponding to Ra = 0.35 μm is 1 / 7.

[0388] Therefore, when a phase conversion element (optical property changing member) 212 is used in this embodiment, it can be said that the effect will be produced when the average value of the phase difference generated by it becomes 1 / 6 or more (preferably 1 / 5 or more, or 1 / 4 or more) of the wavelength used. [Patent Document 1] also describes an example of using a diffraction grating or a diffuser to reduce optical noise. [Patent Document 1] However, there is no disclosure at all regarding the performance of the optical phase conversion element and the diffraction-related element required to actually exert an effect, nor is there any disclosure regarding the relationship with the optical characteristics / optical arrangement in the detection unit 6.

[0389] Since the optical path length difference between the optical paths of light emitted from wide light-emitting regions (light-emitting points) separated from each other in the light source 70 becomes large, it has been described in the first half of Section 3.9 that it is desirable to "irradiate the object 10 with the light emitted from the wide light-emitting region (light-emitting point) in the light source 70 or to detect it with the photodetector 80." An application example of an embodiment that realizes this method is shown in Figures 24A and 24B.

[0390] 24A, the illumination light 12 emitted from a wide light-emitting region (from light-emitting point β to γ) in the light source 70 is reduced in size by an imaging lens with an imaging magnification M and passed through an entrance region of the optical fiber 100. The illumination light 12 that has passed through the exit region of the optical fiber 100 is converted into parallel light by the collimating lens 26 and is then irradiated onto the target object 10.

[0391] However, the present invention is not limited to this and may be configured so that the light is focused (imaged on the emission area of ​​the optical fiber 100) on a local area in the target object 10 by the collimator lens 26. Also, although only one optical fiber 100 is illustrated in Fig. 24A, the present invention is not limited to this and may be configured so as to use a bundle-type optical fiber group.

[0392] Furthermore, in Fig. 24A, the imaging system is constituted by only one imaging lens 216, but it is not limited thereto, and the imaging system may be constituted by a plurality of lenses. As a specific example thereof, as shown in Fig. 22, the imaging system may be constituted by a collimating lens 26 and a condensing lens 98. Furthermore, as described in the last part of Section 3.4, an optical characteristic changing member having a wavefront splitting function (or other functions) may be arranged with respect to the irradiation light in a parallel state (parallel light beam) formed by the collimating lens 26 and the condensing lens 98. As an example of this optical characteristic changing member, Fig. 22 shows an example of a combination of transparent semi-circular parallel plates 94-1 and 94-2.

[0393] The imaging lens 216 in Fig. 24A functions as an "(A) changing / controlling the optical path length for each of a plurality of optical paths" as an optical characteristic changing member. Therefore, this imaging lens 216 is included in a kind of the optical path conversion element 210 described in Fig. 19B(b).

[0394] On the other hand, the optical fiber 100 in Fig. 24A functions as an "(B) combining (or mixing) a plurality of optical paths" as an optical characteristic changing member. Also in Fig. 24B, the optical fiber 100 exhibits the same function. Therefore, this optical fiber 100 corresponds to the optical combining (mixing) unit 102 described in Fig. 19B(b).

[0395] As described in Fig. 24A, the core diameter in the incident region of the optical fiber 100 is represented by "ΔD". Also, the imaging magnification (lateral magnification) of the imaging lens 216 is set as "M". Also in this case, when the condition in which D in the formula (B·35) is replaced with ΔD is satisfied, the combined light (mixed light) 78 (Fig. 10(b)) in the optical fiber 100 shows partial non-coherence.

[0396] From another perspective, the optical path length difference δ between the lights entering the optical fiber 100 is considered. First, the α point (α region) on the light source 70 is arranged on the optical axis of the imaging lens 216. Next, consider the optical path that passes through the center point of the imaging lens 216 after being emitted from the β point (β region) on the light source 70 and reaches the inner end of the incident region of the optical fiber 100 (the boundary position between the core region and the cladding layer). The angle between this optical path and the optical axis of the imaging lens 216 is represented by η. Also, the distance from the light source 70 to the incident region of the optical fiber 100 is denoted as "SF".

[0397] The distance between the α point (α region) and the β point (β region) on the light source 70 is ΔD / (2M). Therefore, when η is sufficiently small,

[0398]

Equation

[0399] is approximated as. On the other hand, the optical path length difference δ between from the α point (α region) to the incident region of the optical fiber 100 and from the β point (β region) to the incident region of the optical fiber 100 is

[0400]

Equation

[0401] is given by. Therefore, the condition for the light to be mixed in the optical fiber 100 and the partial coherence to decrease (the partial incoherence to increase) is

[0402]

Equation

[0403] becomes (N is a positive number greater than or equal to 1). Also, the above coherence distance l CL is given by equation (B·6) or (B·12). Here, when applying an approximate equation similar to equation (B·24) to the left side of equation (B·38),

[0404]

Number

[0405] It is transformed as follows. Looking at the approximate formula of (B·39), it can be seen that the ratio of the core diameter ΔD in the incident region of the optical fiber 100 to the imaging magnification (lateral magnification) M of the imaging lens 216 is an important factor. That is, it is desirable to make the imaging magnification (lateral magnification) M of the imaging lens 216 as small as possible and the core diameter ΔD in the incident region of the optical fiber 100 as large as possible. Furthermore, the distance SF from the light source 70 to the incident region of the optical fiber 100 is preferably short.

[0406] That is, in the optical arrangement of FIG. 24A, when set to satisfy the formula (B·38) or (B·39), optical noise (generated, for example, by the influence of a tube ball inside the light source 70) can be reduced. Note that the above imaging magnification M is not limited to the case where one imaging lens 216 is used, and the imaging magnification (lateral magnification) at the time of forming an arbitrary imaging optical system (confocal optical system) may be applied to the above formula.

[0407] As a means for realizing the function of "(B) synthesis (or mixing) of a plurality of optical paths" borne by the optical characteristic changing member, a phase conversion element 212 was used in FIG. 21A(b), FIG. 21C, or FIG. 22. However, in this method, the efficiency of the light used for signal detection in the detection units 4 and 6 is low. In comparison, by using the combination of the imaging optical system (confocal optical system) of FIG. 24A (or FIG. 24B) and the optical fiber 100, not only can the object 10 be efficiently irradiated with partially incoherent light, but it also has the effect of efficiently guiding the light to the photodetectors 80 in the detection units 4 and 6 so that signal detection can be performed by the photodetectors 80.

[0408] The range of the incident angle of light that can be incident into the optical fiber 100 from the incident region of the optical fiber 100 is represented by the NA value. The NA values of many commercially available optical fibers 100 are relatively small values such as 0.22, for example. Therefore, if the formula (B·38) or (B·39) is satisfied, only a part of the irradiation light 12 emitted from the light source 70 passes through the imaging lens 216. A method for improving this and increasing the utilization efficiency of the irradiation light 12 and reducing the value of SF in the formula (B·38) or (B·39) is shown in FIG. 24B.

[0409] In the application example of the present embodiment shown in FIG. 24B, an optical path conversion element 210 is disposed in the incident region (or in the vicinity thereof) of the optical fiber 100 to increase the substantial NA value of the light that can be incident into the optical fiber 100. As a specific example of the optical path conversion element 210, a micro concave lens 230 may be used. However, not limited thereto, as the optical path conversion element 210, any optical element having a function of expanding the range of the incident angle of the light that can be incident into the optical fiber 100 may be used.

[0410] Also, a concave lens or a cylindrical concave lens 240 is disposed at a position close to the light source 70 to simultaneously achieve a function of reducing the imaging magnification M of the imaging system from the light source 70 to the micro concave lens 230 (optical path conversion element 210) and a function of reducing the value of the mechanical distance SF therebetween.

[0411] In FIG. 24B, a collimating lens 26 and a condenser lens 98 are disposed between the light source 70 and the optical fiber 100 to make the irradiation light 12 parallel therebetween. However, not limited thereto, only one imaging lens 216 may be disposed between the light source 70 and the optical fiber 100, and a concave lens or a cylindrical concave lens 240 may be disposed in the optical path.

[0412] When a light source 70 such as a tungsten filament 50 having a significantly different width of the light emitting region in the longitudinal direction and the short transverse direction is used, a cylindrical concave lens 240 or the like may be disposed to change the imaging magnification M in the longitudinal direction and the short transverse direction of the light emitting region.

[0413] In the optical arrangement of FIG. 24B, astigmatism occurs near the incident region of the optical fiber 100. Here, the phenomenon in which the condensing positions with respect to the longitudinal direction and the short-side direction of the light-emitting region are displaced on the optical axis near the incident region of the optical fiber 100 for the light emitted from the α point on the light source 70 is called this astigmatism. However, if the imaging magnification M is set to be smaller than "1", the amount of this displacement can be set smaller. As a result, regardless of astigmatism near the incident region of the optical fiber 100, a large amount of light can be guided into the core region 142 in the optical fiber 100.

[0414] As another method of changing the imaging magnification M in the longitudinal direction and the short-side direction of the light-emitting region, instead of arranging the cylindrical concave lens 240 between the light source 70 and the collimating lens 26, two cylindrical concave lenses may be arranged at a place where the irradiation light 12 becomes parallel between the collimating lens 26 and the condensing lens 98 to form a beam expander.

[0415] Also, in FIG. 24B, the transparent semi-circular parallel plates 94-1 and 2, which are optical characteristic changing members having a wavefront splitting function, are arranged in the optical path of the irradiation light 12 in a parallel state to reduce the partial coherence of the irradiation light 12 (increase the partial incoherence). However, not limited thereto, any optical characteristic changing member (and its combination) described in the "Light Synthesis / Mixing Method" column in FIG. 9 may be arranged in the optical path.

[0416] As the internal structure of the light source unit 2 in FIG. 1A (or FIG. 1B or FIG. 1C), it may be configured as in FIG. 24B (or FIG. 24A or FIG. 24C). The light source 70 generates heat, and in some cases, a fan is used for cooling, which may become a vibration source. When the optical fiber 100 is arranged between the object 10 and the light source 70 as described above, there is an effect of protecting the object 10 from the influence of heat and vibration.

[0417] As another method of changing the imaging magnification M in the longitudinal direction and the short-side direction of the tungsten filament 50 in the imaging (confocal) optical system shown in FIG. 24B, instead of using the spherical lens in FIG. 24A, an aspherical lens may be used, or a prism 220 or a lenticular lens 222 may be arranged in the optical path.

[0418] That is, in FIG. 24C, in both (a) and (b), the optical fiber 100 is used for the photosynthesis (mixing) unit 102. And as the optical path conversion element 210 in FIG. 24C(a), an imaging lens 216 and a prism 220 are combined. Also, as another application example of an embodiment, in FIG. 24C(b), a combination of an imaging lens 216 and a lenticular lens 222 is used for the optical path conversion element 210.

[0419] 3.10 Application Examples Regarding the Synthesis / Mixing of Emitted Light from Different Regions When mixing (or synthesizing) the light emitted from different regions within the same light source 70, the method of changing the optical path length between different optical paths was described in Section 3.9. Based on this, the partial coherence of the light after mixing (synthesizing) can be reduced (the partial incoherence can be increased). In this section, the technology will be developed to explain the method of 'expanding the optical path length difference between different optical paths' and the method of'more efficient mixing (synthesizing)'.

[0420] Both FIG. 21C and FIG. 22 show that the entrance of the handle-shaped optical fiber group 300 (optical fiber 100) corresponds to the imaging position with respect to the light source 70 (tungsten filament 50). As a method of forming this imaging optical system, in FIG. 21C, only one optical path changing element 210 (imaging lens 216) is used. In contrast, in FIG. 22, a combination of a plurality of optical path changing elements (collimating lens 26 and condensing lens 98) arranged at spatially different positions is used to form the imaging optical system. Using a combination of a plurality of optical path changing elements arranged at spatially different positions (the collimating lens 26 and the condensing lens 98 in FIG. 22) to form the imaging optical system can expand the 'optical path length difference between different optical paths' compared to configuring the imaging optical system with a single optical path changing element 210 (the imaging lens 216 in FIG. 21C). As a result, there is an effect of 'further reducing the partial coherence' by configuring the imaging optical system by combining a plurality of optical path changing elements arranged at spatially different positions. The basic principle will be explained below.

[0421] FIG. 51 shows an imaging optical system that forms an emission image of a light source 70 (tungsten filament 50) at an entrance of an optical fiber 100 (photosynthesis (mixing) unit 102). Here, FIG. 51(a) shows an imaging optical system configured by only one imaging lens 216 (optical path conversion element 210). On the other hand, FIG. 51(b) shows an imaging optical system configured by a combination of a plurality of optical path changing elements (collimating lens 26 and condensing lens 98) arranged at spatially different positions.

[0422] The state of the irradiation light 12 passing between a plurality of optical path changing elements (collimating lens 26 and condensing lens 98) may basically be a diverging light state or a converging light state. For example, as shown in FIGS. 22 and 24B, consider an optical system in which an optical property changing member that changes the optical path length for each of the divided optical paths by wavefront splitting the irradiation light 12 (light cross section) is inserted between a plurality of optical path changing elements (collimating lens 26 and condensing lens 98). Then, regarding the examples of FIGS. 22 and 24B in which this optical property changing member is composed of a combination of transparent parallel plates 94-1 to 4, when the parallel plates 94-1 to 4 are arranged in the optical path of the diverging light or the optical path of the converging light in the imaging optical system, it is generally known that aberration occurs in the imaging optical system. Therefore, the irradiation light 12 passing between a plurality of optical path changing elements (collimating lens 26 and condensing lens 98) is preferably in a parallel light state. By using the parallel light state in this way, an effect is produced in which an accurate imaging pattern with less aberration with respect to the light source 70 (tungsten filament 50) can be formed at the entrance of the optical fiber 100 (photosynthesis (mixing) unit 102).

[0423] The core diameter ΔD of the optical fiber 100 made of a generally available inorganic material (for example, made of fused silica glass) is mostly 1.0 mm or less. On the other hand, the standard length in the longitudinal direction of the tungsten filament 50 used in a tungsten halogen lamp (twice the distance ι between point α and point β) is 4 cm, which is more than 40 times the core diameter ΔD. Therefore, it is necessary to reduce the light emission image of the tungsten filament 50 to 1 / 40 or less and form an image at the entrance of the optical fiber 100. For this purpose, as shown in Fig. 51(a), in order to reduce and form an image to 1 / 40 or less with only one imaging lens 216, it is necessary to arrange the imaging lens 216 near the entrance of the optical fiber 100.

[0424] The distance from the tungsten filament 50 to the entrance of the optical fiber 100 is represented by SF. And the light emitting point on the light source 70 (tungsten filament 50) on the extension of the optical axis of the imaging lens 216 is defined as point α. And it is set so that this point α coincides with the midpoint in the longitudinal direction of the tungsten filament 50. Consider the case where the irradiation light 12 emitted from point β located at the end face in the longitudinal direction of the tungsten filament 50 passes through the center of the optical axis of the imaging lens 216. The angle between this irradiation light 12 and the optical axis of the imaging lens 216 is expressed by η. Also, the distance between point α and point β is represented by ι.

[0425] When the imaging lens 216 is arranged near the entrance of the optical fiber 100 as described above, η ≒ tan -1 (ι / SF) …(B·42) can be approximated.

[0426] And the difference value δ between the optical path length until the irradiation light 12 emitted from point β passes through the imaging lens 216 and reaches the entrance of the optical fiber 100, and the optical path length until the light emitted from point α reaches the entrance of the optical fiber 100, when the η value is sufficiently small, δ = SF{( cosη) -1 - 1} ≒ SF·η 2 / 2 …(B·43) It can be expressed by an approximate formula. As shown in Equation (B·43), the optical path length difference δ varies with the square of the angle η. However, when the imaging optical system is composed of only one imaging lens 216 (optical path changing element 210), the value of the angle η cannot be set large.

[0427] The coherence length l given by Equation (B·6) or (B·12) CL and the natural number N (it is essential that it is "1" or more, but a value as large as possible of "2" or more or "4" or more is desirable) and the above optical path length difference δ δ ≧ N·l CL …(B·44) When the relationship of is satisfied, the partial coherence of the light passing through the photosynthesis (mixing) unit 102 (optical fiber 100) decreases (the partial non - coherence increases).

[0428] However, in the imaging optical system composed of only one imaging lens 216 (optical path changing element 210), since the value of the angle η is small, Equation (B·44) cannot be satisfied for a sufficiently large N. As a result, it is difficult to sufficiently obtain the effect of decreasing partial coherence (the effect of increasing partial non - coherence).

[0429] Next, the characteristics when the imaging optical system is composed of a combination of a plurality of optical path changing elements (collimating lens 26 and condensing lens 98) arranged at spatially different positions (Fig. 51(b)) will be described. In this case, the focal length Fc of the optical path conversion element (collimating lens 26) arranged on the front side can be set to a value much smaller than SF (Fc << SF). The relational expression regarding the angle η at this time is η ≒ tan -1 (ι / Fc) …(B·45) Since Fc can be set sufficiently small (Fc << SF) in Equation (B·45), the angle η becomes large. Therefore, since a large value of the angle η can be substituted into Equation (B·43), a large optical path length difference δ can be obtained. Therefore, when a plurality of optical path changing elements arranged at spatially different positions are combined, Equation (B·44) holds for a sufficiently large N, and a large effect of decreasing partial coherence (the effect of increasing partial non - coherence) can be obtained.

[0430] The optical axis of the imaging optical system formed by combining a plurality of optical path changing elements (such as the collimating lens 26 and the condensing lens 98) is indicated by an alternate long and short dash line in Fig. 51(b). The intersection point of the extension line of this optical axis and the light emitting source 70 (for example, the tungsten filament 70) is represented by point α. The light emitting point in the light emitting source 70 that exists at the position farthest from this point α is defined as point β. Also, the distance between point α and point β is denoted as ι.

[0431] After being emitted from the above-mentioned point β and point α respectively, the optical path length difference δc between the irradiation lights 12 passing on the optical axis in the front-side arranged optical path conversion element (collimating lens 26) is δc = Fc{(cosη) -1 - 1} ≒ Fc·η 2 / 2 …(B·46) This is the case. Here, the angle η satisfies the formula (B·45).

[0432] Next, consider the irradiation light 12 that is emitted from the above-mentioned point β and passes on the optical axis in the rear-side arranged optical path conversion element (condensing lens 98). Here, the focal length of the rear-side arranged optical path conversion element (condensing lens 98) is represented by Fo. And as shown in Fig. 51(b), let the inclination angle from the optical axis in the traveling direction of this light be κ. The optical path length δo between the optical path until this light reaches the entrance of the optical fiber 100 after passing on the optical axis in the optical path conversion element (condensing lens 98) and the optical path passing on the optical axis is δo = Fo{(cosκ) -1 - 1} ≒ Fo·κ 2 / 2 …(B·47) This is the case.

[0433] Therefore, when the optical design is carried out so that the sum of the optical path length differences until reaching the entrance of the optical fiber 100 after being emitted from point α and point β respectively satisfies δc + δo ≧ N·l CL …(B·48) the reduction effect of partial coherence (the increase effect of partial non-coherence) is exerted. In the formula (B·48), the coherence distance l CLIt is given by formula (B·6) or formula (B·12). Also, the value of the natural number N must be 1 or greater, and preferably a value of 2 or greater or 4 or greater and as large as possible.

[0434] In the embodiment shown in FIG. 51, an optical fiber 100 is used as the photosynthesis unit (or light mixing unit) 102. However, as described above, since the core diameter ΔD of the generally available optical fiber 100 made of inorganic materials (such as anhydrous silica glass) is mostly 1.0 mm or less, it is necessary to reduce the light emission pattern from the light source 70 and form an image.

[0435] Also, when the imaging magnification is reduced, a large optical path occurs for the incident angle η of the irradiation light 12 to the entrance of the optical fiber 100. The maximum incident angle η that can enter the core region 142 in the optical fiber 100 is defined by the NA value (NA = sin η). And the NA value of a standard optical fiber 100 is relatively small, at 0.22. Therefore, when the imaging magnification at the entrance of the optical fiber 100 is reduced, a part of the irradiation light 12 that has passed through a large optical path of the incident angle η cannot enter the core region 142, resulting in a problem of a significant reduction in light utilization efficiency.

[0436] To solve the above problems, as shown in FIGS. 52 to 54, an optical guide or light pipe (Light Guide / Light Pipe) 250 may be used as the photosynthesis unit (or light mixing unit) 102. The optical guide (light pipe) 250 is a type of waveguide element described in FIG. 9 and represents a transparent optical element through which light can pass inside. That is, light (for example, irradiation light 12) enters from the front-end boundary 252 of the optical guide (pipe), passes through the inside while undergoing internal reflection (total internal reflection) at the side surface 254, and exits from the back-end boundary 256 of the optical guide (pipe).

[0437] Before entering the optical guide (light pipe) 250, lights that have traveled different paths (for example, between lights emitted from different light-emitting points α and β in the light source 70) pass through the inside of the optical guide (light pipe) 250 and mix (or are mixed or combined) with each other. If the structure is such that the light passing through the inside of this optical guide (light pipe) 250 (irradiation light 12) does not leak from the side surface 254 (total reflection is not blocked), the optical guide (light pipe) 250 can take any shape. As a specific example of the shape of this optical guide (light pipe) 250, it may take a prismatic shape or a cylindrical shape (or a shape close to a pyramid or a cone).

[0438] The refractive index n inside the optical guide (light pipe) 250 is always greater than the refractive index in air (in a vacuum). Therefore, the incident angle κ(η) of the irradiation light 12 at the front end face 252 of the optical guide (light pipe) allows any value within the range of 0 degrees ≤ κ ≤ 90 degrees (see Fig. 54(a)). Therefore, there is an effect of reducing the light loss when passing through the light incident surface (the front end face 252 of the optical guide (light pipe)) to the optical guide (light pipe) 250.

[0439] For example, light that is perpendicularly incident on a planar glass with a refractive index n of 1.5 causes about 4% reflection at the incident surface. Therefore, antireflection coatings (AR coatings (Antireflection Coatings)) may be applied to both the front end portion 252 and the rear end portion 256 of the optical guide (pipe) (controlling the reflectance to 1% or less, desirably 0.5% or less) to reduce the light loss when passing through the front end portion 252 and the rear end portion 256.

[0440] Furthermore, when using the optical guide (light pipe) 250 for light synthesis or mixing, the constraints on the imaging magnification (between the light source 70 and the front end face 252 of the optical guide (light pipe)) are reduced. This is because, for example, when using an optical guide (light pipe) 250 made of a transparent inorganic material (such as made of fused silica glass) and having a rectangular parallelepiped shape, the optical guide (light pipe) 250 can be easily created with arbitrary dimensions (the dimensional arbitrariness of the optical guide (light pipe) 250 is high). Therefore, there is also an effect of improving the degree of freedom in the design of the imaging optical system in the middle (using the optical path conversion element 210).

[0441] As an example of the specific shape of the above-mentioned optical guide (light pipe) 250, a quadrangular prism is shown in FIG. 54. Also, in FIGS. 52 and 53, the shape is an intermediate shape between the shape of a quadrangular prism and the shape obtained by cutting off and removing the tip of a quadrangular pyramid. However, it is not limited thereto, and for example, a hexagonal prism, a hexagonal pyramid (part thereof), or a triangular prism, a triangular pyramid (part thereof) may also be used.

[0442] Also, for the reasons explained at the end of Section 3.1, it is desirable to use an inorganic material for the material of this optical guide (light pipe) 250 instead of an organic material. Examples of such inorganic materials include optical glass, CaF2, MgF2, or LiF, KBr, etc.

[0443] In particular, a low-OH material that satisfies the condition that the amount of hydroxyl groups contained in the material of this optical guide (light pipe) 250 is "100 ppm or less" (desirably "1 ppm or less") is suitable. Specific examples include 'glass materials with less hydroxyl group incorporation and well-controlled production','silica glass without water', 'fused silica', etc.

[0444] As shown in FIG. 52, an imaging optical system is formed by the action of the optical path changing element 210 (such as the imaging lens 216 or the combination of the collimating lens 26 and the condenser lens 98). When a plurality of optical path changing elements (collimating lens 26 and condenser lens 98) are arranged at different positions as shown in FIG. 52(b), an optical property changing member (FIG. 9) may be arranged between them. As an example of the function of the optical property changing member, "generating a further optical path length difference using wavefront splitting" may be performed. Specifically, any method already described in Section 3.3 can be used. As an example, in FIG. 52(b), transparent semi-circular parallel plates 94-1 and 2 are arranged in the parallel light beam portion between the collimating lens 26 and the condenser lens 98.

[0445] Due to the function of the above imaging optical system, an imaging pattern with respect to the light emission pattern on the light source 70 (for example, the tungsten filament 50) is projected onto the front end face 252 of the light guide (pipe). The light that forms this projected image (imaging pattern) enters the light guide (light pipe) 250 (photosynthesis (mixing) unit 102) as it is and is emitted from the rear end face 256 of the light guide (pipe).

[0446] In FIG. 52, an example is described in which a reduced imaging pattern is projected (the imaging magnification is less than 1). However, it is not limited to this, and patterns with any imaging magnification may be projected onto the front end face 252 of the light guide (pipe). In this case, it is desirable that the area size of the front end face 252 of the light guide (pipe) is larger than the projected imaging pattern. Thereby, the utilization efficiency of the irradiation light 12 that enters the front end face 252 of the light guide (pipe) is increased.

[0447] In the embodiment shown in FIG. 52, the side surfaces 254-1 and 2 of the light guide (light pipe) 250 (photosynthesis (mixing) unit 102) have a slight inclination (taper) with respect to the optical axis. As a result, the area size of the rear end face 256 of the light guide (pipe) becomes smaller than the area size of the front end face 252. And the light density of the light (irradiation light 12) passing through the light guide (light pipe) 250 (photosynthesis (mixing) unit 102) is higher at the rear end face 256 than at the front end face 252.

[0448] As described above, the diameter ΔD of the core region 142 in a general optical fiber 100 is often around 0.6 mm. As described above, the side surfaces 254-1 and 2 may be inclined so that the area size of the rear end face 256 of the light guide (pipe) is set smaller than that. For example, consider the case where the light emitted from the rear end face 256 of the light guide (pipe) passes through the optical fiber 100. By appropriately changing the area size of the rear end face 256 using the inclined side surfaces 254-1 and 2, "improvement of the light utilization efficiency during the optical coupling between the light guide (light pipe) 250 and the optical fiber 100" (prevention of significant light loss at the optical joint) can be achieved.

[0449] In the example of the optical guide (light pipe) 250 shown in Fig. 52, the side surfaces 254-1 and 254-2 are each a plane with a slight inclination (taper). However, it is not limited to this, and only one of the four side surfaces 254 constituting the optical guide (light pipe) 250 may have a gradient. Furthermore, not only that, but a part of the side surfaces 254-1 and 2 may have a curved surface shape and be partially inclined. However, in this case, as will be described later, it is necessary to maintain a shape in which the light passing through the inside of the optical guide (light pipe) 250 is reflected (total reflection) by the side surfaces 254-1 and 2, or to have a structure in which the light is reflected by the side surfaces 254-1 and 2 (for example, forming a light reflection layer on the side surfaces 254-1 and 2 so that the light is internally reflected).

[0450] Also, in the embodiment of Fig. 52, the cross-sectional shape of the optical guide (light pipe) 250 (photosynthesis (mixing) unit 102) is square. However, it is not limited to this (for example, considering the optical coupling efficiency with the optical fiber 100), and the cross-sectional shape may be circular or elliptical.

[0451] By appropriately changing the region size between the front end face 252 and the rear end face 256 using the inclined side surfaces 254-1 and 2 in this way, an effect is produced that makes it easier to achieve consistency between "the light emitting part size of the light emitting source 70" and "the region size of the rear end face 256 required by the optical system arranged after photosynthesis (mixing)".

[0452] Note that it is not limited to the above, and the side surfaces 254-1 and 2 may be parallel to the optical axis (to make the region size between the front end face 252 and the rear end face 256 the same).

[0453] In Figs. 52 to 54, the description of the optical path after passing through the rear end portion 256 of the optical guide (pipe) is omitted. As described above, when the region size of the rear end face 256 of the optical guide (pipe) is reduced, the light after passing through the rear end portion 256 of the optical guide (pipe) can be treated as "diverging light from a pseudo point light source". And the light emitted from the rear end portion 256 of the optical guide (pipe) can be treated as "the irradiation light (first light) 12 emitted from the light source portion 2 in Fig. 1A".

[0454] Alternatively, as shown in Fig. 24A, a collimating lens 26 may be arranged immediately behind the rear end portion 256 of the optical guide (pipe) to make it in a substantially parallel light state, and parallel light irradiation may be performed on the object 10 as shown in Fig. 1B (or Fig. 21A).

[0455] Furthermore, as shown in Fig. 1C, an objective lens 25 may be arranged in the optical path of the substantially parallel light, and the object 10 may be irradiated in a substantially focused light state. As another example of this substantially focused light irradiation, a part of the optical systems in Figs. 7, 14E, and 20 may also be used.

[0456] That is, the above optical guide (light pipe) 250 may be arranged as the photosynthesis (mixing) unit 102 in the light source unit 2 shown in Figs. 1A to 1C. Further, an optical path changing element 210, which is a kind of optical property changing member, may be arranged (in front of the above photosynthesis (mixing) unit 102) in the light source unit 2 to generate an optical path length change 76 (Fig. 10) for a part of the optical path. Moreover, not limited thereto, any optical property changing member shown in Fig. 9 may be arranged in the light source unit 2 shown in Figs. 1A to 1C, and the functions described in Section 3.1 may be provided using Figs. 8A and 10(a)(b).

[0457] Moreover, the rear end portion 256 of the optical guide (pipe) may be optically joined to the optical fiber 100, and an optical system as shown in Fig. 24 may be arranged at the outlet of the optical fiber 100. Further, the rear end portion 256 of the optical guide (pipe) may be optically joined to the bundle-shaped optical fiber group 300, and an optical system as shown in Fig. 21C or Fig. 22 may be arranged at the outlet of the bundle-shaped optical fiber group 300.

[0458] In the system of this embodiment, as shown in the examples of FIGS. 14A, 14E, 16B, 18, 21A, 21C, 22, 24A, 24B, and 24C, an optical fiber 100, a pinhole, or a slit 130 may be installed in the optical path. Moreover, not limited thereto, when the area size of the rear end surface 256 is narrowed in the optical guide (light pipe) 250 (photosynthesis (mixing) unit 102), an optical effect substantially equivalent to that of installing a pinhole or a slit 130 is produced. And when these optical elements are installed in the optical path of "partially coherent light", it is said that the spatial coherency increases. As a result, the partial coherency of the irradiation light (first light) 12 or the detection light (second light) 16 increases, and the optical noise tends to increase easily.

[0459] In contrast, when the irradiation light 12 is passed through the optical guide (light pipe) 250 at a position close to the light source 70 (inside the light source unit 2 or near the emission position from the light source unit 2) as in the system of this embodiment, the light emitted from different light emission points in the light source 70 is combined or mixed inside the optical guide (light pipe) 250. In this way, the partial coherency of the irradiation light 12 is reduced (the partial non-coherency is increased) in advance at a position close to the light source 70 (inside the light source unit 2 or near the emission position from the light source unit 2). Then, even if an optical fiber 100, a pinhole, or a slit 130 is installed in the subsequent optical path, the partial coherency of the irradiation light 12 does not increase (the partial non-coherency does not decrease). By arranging the optical guide (light pipe) 250 inside the light source unit 2 or near the emission position from the light source unit 2 in this way, there is an effect of reducing the optical noise.

[0460] As shown in FIG. 52, when the front end face 252 of the light guide is disposed at the imaging position of the light emitting source 70, high light utilization efficiency with respect to the emitted light from the light emitting source 70 can be obtained. However, not limited thereto, the front end face 252 of the light guide may be disposed at a non-imaging position of the light emitting source 70. As a specific example, in FIG. 52(a), another optical element (such as other optical characteristic changing members described in FIG. 9) other than the imaging lens 216 may be disposed between the light emitting source 70 and the light guide (light pipe) 250, or no optical element may be disposed between the light emitting source 70 and the light guide (light pipe) 250. Also not limited thereto, a non-imaging optical system may be formed.

[0461] Another application example in the system of this embodiment is shown in FIG. 53. The differences from the prior art shown in FIG. 17 were described in section 3.7. In FIG. 17, since the light traveling directions after passing through the collimating lens 136 do not coincide with each other as α and β, the partial coherence does not decrease (the partial non-coherence does not increase) as it is.

[0462] On the other hand, in this application example, both lights that have exited the optical fibers 100-1 and 100-2 pass through the inside of the light guide (light pipe) 250. The two lights are combined or mixed with each other inside the light guide (light pipe) 250, and their light traveling directions coincide with each other. Therefore, also in the application example shown in FIG. 53, the inside of the light guide (light pipe) 250 functions as the light combining (mixing) unit 102.

[0463] In the description so far, the function of the light combining (mixing) unit 102 of the light guide (light pipe) 250 has been utilized. Here, FIG. 54 is used to explain the basic principle of having the function of the light combining (mixing) unit 102. It has already been explained that incident light having a large incident angle η cannot enter the core region 142 of the optical fiber 100. Therefore, when the optical fiber 100 is disposed in the optical path of (for example, the irradiation light 12), a large light amount loss at its entrance becomes a big problem. On the other hand, the reason why no light amount decrease occurs at the front end face 252 of the light guide (light pipe) is shown in FIG. 54(a).

[0464] Light incident in air (or in vacuum) at an incident angle κ is refracted at an angle of refraction ξ within a transparent medium with a refractive index n. The approximate formula showing the relationship between the incident angle κ and the angle of refraction ξ has already been explained by Equation (B·14). By the way, expressing Snell's law accurately without using approximation, sinκ = nsinξ …(B·49) is obtained.

[0465] In Equation (B·49), it is always necessary that "sinκ ≦ 1". And the maximum value of the angle of refraction ξ for which "sinκ = 1" holds is called the angle of total internal reflection. For example, when "n = 1.5", the angle of total internal reflection is "41.8 degrees" from Equation (B·49).

[0466] In Fig. 54(a), the irradiation light 12 traveling in air (or in vacuum) passes through the front end face 252 of the optical guide (pipe) and enters the inside of the optical guide (optical pipe) 250. Looking at this optical path in reverse. When the light passing through the inside of the optical guide (optical pipe) 250 reaches the front end face 252 of the optical guide (pipe) at an angle ξ, it is refracted to an angle κ and travels in air (or in vacuum). Here, when the angle reaching the front end face 252 of the optical guide (pipe) becomes larger than "41.8 degrees", this light is totally reflected at the front end face 252 of the optical guide (pipe) and cannot emerge into air (or in vacuum).

[0467] While there are restrictions on the angle of arrival at the interface within the refractive body, there are no restrictions on the angle of arrival (the angle of incidence κ) for the incident light (irradiation light 12) in air (or in a vacuum). Therefore, within the range of "0 degrees ≤ κ ≤ 90 degrees", the irradiation light 12 with any angle of incidence κ can pass through the front end face 252 of the optical guide (optical pipe). From the results of precise optical calculations, there is a slight light quantity loss due to minute light reflection when passing through the front end face 252 of the optical guide (pipe). However, by applying an antireflection coating (AR coating (Antireflection Coatings)) to the front end face 252 of the optical guide (optical pipe), the light quantity loss here can be significantly reduced. Therefore, when using the optical guide (optical pipe) 250 in the photosynthesis (mixing) unit 102 (see FIGS. 8A and 8B), an effect of obtaining a high light utilization efficiency of the light passing through the optical guide (optical pipe) 250 (irradiation light 12) can be achieved.

[0468] And the irradiation light 12 passing through the optical guide (optical pipe) 250 is reflected (total reflection) on the side face 254-1 inside the optical guide (optical pipe) 250. The reflection angle (total reflection angle) at this time is represented by φ. As shown in FIG. 54(a), when the side face 254-1 of the optical guide (optical pipe) 250 and the front end face 252 of the optical guide (pipe) are orthogonal, the relationship between the above refraction angle ξ and the reflection angle (total reflection angle) φ is ξ + φ = 90 degrees …(B·50) is given by.

[0469] The refraction angle ξ of the irradiation light 12 entering the optical guide (optical pipe) 250 at an arbitrary angle of incidence κ with respect to the front end face 252 of the optical guide (pipe) is always "41.8 degrees or less" as described above. Therefore, from equation (B·50), the angle φ is always "48.2 degrees or more". And the phenomenon of "φ ≥ 48.2 degrees" means, for the reasons described above, that "the irradiation light 12 passing through the optical guide (optical pipe) 250 is totally reflected on the side faces 254-1 and 2 inside the optical guide (optical pipe) 250, and there is no light loss during reflection". That is, when using the optical guide (optical pipe) 250 for the generation of the combined light (mixed light) 78 (see FIG. 10), an effect of being able to greatly reduce the light loss during photosynthesis (mixing) can be achieved.

[0470] As examples of optical property changing members used for generating synthetic light (mixed light) 78, usage examples of diffraction gratings 120 and 124 (FIGS. 12A and 14C), optical fibers 100 (FIGS. 14A, 24A, 24B, and 24C), phase conversion elements 102-2 and 212 (FIGS. 14B, 21A(b), 21C, and 22) and the like were described. By the way, when light passes through the above-described optical property changing members, some transmission light quantity loss occurs in any of the optical property changing members. Compared with these optical property changing members, a light guide (light pipe) 250 (which also belongs to the optical property changing members) has significantly less light loss during use.

[0471] The light guide (light pipe) 250 illustrated in FIG. 54 has a rectangular parallelepiped shape. In contrast, in the structures of the light guides (light pipes) 250 illustrated in FIGS. 52 and 53, at least a part of side surfaces 254-1 and 2 has a gradient. Further, a structure in which a part of side surfaces 254-1 and 2 has a curved surface shape and the gradient amount changes partially is also allowed. And in this case, the angle between the front end surface 252 or the rear end surface 256 of the light guide (pipe) and the side surfaces 254-1 and 2 is different from 90 degrees (a place may exist at least locally).

[0472] Assuming that the slope angle in the side surfaces 254-1 and 2 (at least locally) is μ , for the formula (B·50) ξ + φ + μ = 90 degrees …(B·51) the following relationship holds.

[0473] Substituting the maximum value that the refraction angle ξ can take ("41.8 degrees" when the refractive index n is "1.5") and "φ = 41.8 degrees" as the critical angle at which total reflection occurs on the side surfaces 254-1 and 2 into the formula (B·50), "μ = 6.4 degrees" is obtained. That is, in order for total reflection to occur on the side surfaces 254-1 and 2, it is necessary to make the slope angle μ on the side surfaces 254-1 and 2 "6.4 degrees or less".

[0474] When considering the angular errors of the front end face 252 and the rear end face 256 during the manufacture of the optical guide (optical pipe) 250 and the change in the refractive index n due to the change in the wavelength of the irradiation light 12, it is desirable to set the grazing angle μ on the side surfaces 254-1 and 2 of the optical guide (pipe) to "6 degrees or less" (preferably "5 degrees or less").

[0475] As a premise of the above calculation, it is assumed that "the surfaces of the side surfaces 254-1 and 2 of the optical guide (pipe) are exposed in the air (in a vacuum)". However, in this embodiment, it is not limited to the above conditions, and the grazing angle μ on the side surfaces 254-1 and 2 of the optical guide (pipe) may be set to, for example, "5 degrees or more". In this case, since the "total reflection condition on the side surfaces 254-1 and 2" is broken, instead, the surfaces of the side surfaces 254-1 and 2 of the optical guide (pipe) may be coated with a light reflection layer.

[0476] The situation where the irradiation light 12 that travels while repeating total reflection inside the optical guide (optical pipe) 250 is optically combined (mixed) is shown in Fig. 54(b). The ε point on the front end face 252 of the optical guide corresponds to the imaging point of the light emitting point α on the light source 70 (tungsten filament 50) in Fig. 52 or the exit port of the optical fiber 100-2 in Fig. 53. Similarly, the ζ point corresponds to the imaging point of the light emitting point β on the light source 70 (tungsten filament 50) or the exit port of the optical fiber 100-1. As shown in Fig. 54(b), in the vicinity of the ε point and the ζ point, the light of both passes through different optical paths.

[0477] However, at a point where the light has traveled a little inside the optical guide (optical pipe) 250, the optical path 260 of the light passing through the ε point and the optical path 270 of the light passing through the ζ point overlap with each other. And the region where both optical paths 260 and 270 overlap becomes the light mixing region 280, and the light of each other is combined (mixed). Further, while repeating total reflection on the side surfaces 254-1 and 2 inside the optical guide (optical pipe) 250, the combination (mixing) of the light of both progresses further. And at the time of passing (emission) through the rear end face 256 of the optical guide (pipe), it becomes the combined light (mixed light) 78 (shown in Fig. 8A or Fig. 8B, Fig. 10).

[0478] The diffraction gratings 120 and 124 shown in FIGS. 12A and 14C, or the phase conversion elements 102-2 and 212 described in FIGS. 14B, 21A(b), 21C, and 22, which are examples of optical property changing members used for generating the synthetic light (mixed light) 78, basically perform only one light synthesis (light mixing) operation.

[0479] In contrast, in the optical guide (light pipe) 250, multiple optical path superposition (i.e., light synthesis / light mixing) processes are performed every time total reflection occurs on the side surfaces 254-1 and 254-2. Therefore, the degree of mixing (synthesis) between the lights emitted from the light source 70 and passing through different optical paths is improved, and there is an effect of improving the reduction efficiency of partial coherence (the increase efficiency of partial incoherence).

[0480] 3.11 Method for Reducing Partial Coherence with Respect to Electromagnetic Waves Having a Longer Wavelength than Infrared Light and Application Examples In the system of this embodiment described in FIGS. 1A to 1C, the irradiation light (first light) 12 is irradiated into the object 10, and the characteristics and states inside the object 10 are measured using the detection light (second light) 16 obtained therefrom. Inside this object 10, the irradiation light (first light) 12 (and the detection light (second light) 16) repeats multiple light scatterings. When the irradiation light 12 or the detection light 16 is partially coherent light, as described later in Chapter 5, optical noise is generated in the detection light 16 and the penetration length of the irradiation light 12 into the object 10 decreases.

[0481] This phenomenon occurs not only in near-infrared light and infrared light, but also in electromagnetic waves with longer wavelengths. By the way, in order to enhance the directivity of electromagnetic waves in, for example, radar (Radio Detection and Ranging), a method of flattening the wave front of electromagnetic waves is generally used. However, in this method, the coherence of electromagnetic waves increases, so the penetration distance into the object 10 decreases. (When using electromagnetic waves of a single frequency in radar, it becomes coherence instead of partial coherence.) The experimental data using near-infrared light shown in Chapter 5 suggests that the same phenomenon occurs in electromagnetic waves with longer wavelengths. On the other hand, if the wave front of electromagnetic waves is disturbed to reduce the partial coherence (or coherence) of electromagnetic waves, a problem occurs in that the directivity significantly decreases.

[0482] As an application example of this embodiment, a method for generating electromagnetic waves with low (partial) coherence while ensuring sufficient directivity will be described. Each electromagnetic wave source / receiver unit 292 in Fig. 55(a) is composed of (not shown) an antenna common to transmission and reception of electromagnetic waves, a transmission circuit for generating electromagnetic waves, and a reception circuit (detection circuit) for electromagnetic waves. Then, electromagnetic waves 290-1 to -n with directivity emitted from different electromagnetic wave source / receiver units 292-1 to -n (the antennas therein), that is, electromagnetic waves passing through different paths, are spatially overlapped with each other to mix the electromagnetic waves. For this purpose, a plurality of independent electromagnetic wave source / receiver units 292 that individually emit electromagnetic waves 290 with directivity are arranged close to each other, and the radiation directions are made to coincide. Then, at a position sufficiently far from the electromagnetic wave source / receiver units 292-1 to -n, a mixed electromagnetic wave 294 with directivity is created.

[0483] The generation mechanism of the mixed electromagnetic wave 294 with the above-mentioned directivity will be described in detail below. The electromagnetic waves 290-1 to -n radiated from each electromagnetic wave source / receiver unit 292-1 to -n have directivity respectively. However, at positions sufficiently far from the electromagnetic wave source / receiver units 292-1 to -n, the electromagnetic waves 290-1 to -n each have a spatial spread (in a plane perpendicular to the propagation direction). Therefore, when a plurality of electromagnetic wave source / receiver units 292-1 to -n are densely arranged in a one-dimensional or two-dimensional direction, at a sufficiently far distance (the right side in Fig. 55(a)), the electromagnetic waves 290-1 to -n with spreads spatially overlap with each other. And in this overlapping part, the electromagnetic waves 290-1 to -n are mixed, and a mixed electromagnetic wave 294 with directivity is generated. Here, since each of the electromagnetic waves 290-1 to -n has directivity, the directivity characteristics do not change even after mixing.

[0484] As described in Section 3.1 using Fig. 10, when the optical path length is changed by 76 so as to satisfy the formula (B·44) for a part 74 of the light emitted from the same light source 70, no optical interference occurs between the part 74 and another part 72 of the light. The cause of this optical interference was explained in Section 2.2 using the Uncertainty Principle.

[0485] Based on the cause of the interference (between electromagnetic waves) of the light described above, no interference occurs between the electromagnetic waves 290-1 to -n radiated from different electromagnetic wave source / receiver units 292-1 to -n. Therefore, the mixed electromagnetic wave 294 with directivity generated by the above method has a low (partial) coherence (a high (partial) incoherence) despite maintaining high directivity. When using this mixed electromagnetic wave 294 with directivity, as will be described later in Chapter 5, the penetration distance into the object 10 increases. Therefore, there is an effect that it is possible to measure up to a deep region regarding the characteristics and states inside the object 10. Furthermore, since the interference noise between the multiple scattered lights 370 inside the object 10 is reduced, highly accurate characteristic detection is also possible.

[0486] Incidentally, not limited to the above application examples, regarding the electromagnetic waves in the frequency domain described in this Section 3.11 as well, the methods described in Sections 3.1 to 3.10 (combining (mixing) electromagnetic waves passing through different paths (optical paths), or combining (mixing) after changing a part of the optical path length in the electromagnetic wave) may be used.

[0487] Inside the electromagnetic wave generation source / reception units 292-1 to -n, at least one radar antenna is individually installed. As this radar antenna structure, for example, any structure such as a Yagi Antenna structure or a structure that parallelizes electromagnetic waves emitted spherically from a single point using a hemispherical, elliptical, or parabolic reflector (Parabola Antenna) may be used. The frequency band of the radio waves used in this embodiment suitable for the above antenna structure includes the low frequency band to the medium frequency band. Specifically, not only LF waves (Low Frequency Waves: long waves) in the range of 30 kHz to 300 kHz, but also MF waves (Middle Frequency Waves: medium waves) in the range of 300 kHz to 3 MHz, HF waves (High Frequency Waves: short waves) in the range of 3 MHz to 30 MHz, and VHF waves (Very High Frequency Waves: long waves) in the range of 30 MHz to 300 MHz may be targeted.

[0488] When an alternating current flows through a single wire, electromagnetic waves are emitted to the surroundings. Also, when electromagnetic waves pass through this wire, an induced current flows, enabling the detection of electromagnetic waves. Therefore, when connecting an electromagnetic wave generation transmission circuit and an electromagnetic wave reception circuit (detection circuit), the same radar antenna can serve as both a source of electromagnetic waves and a reception unit for electromagnetic waves.

[0489] Next, an application example of this embodiment using an electromagnetic wave (standing wave) generation source 292 capable of emitting microwaves used in a microwave oven or a radar is shown in Fig. 55(b). The frequency used in a microwave oven is standardized internationally at 2.45 GHz (wavelength is 12.2 cm). However, within the United States of America only, use at 915 MHz (wavelength is 32.8 cm) is permitted.

[0490] In order to enhance the directivity of the microwaves emitted from the magnetron electromagnetic wave sources 296-1 to -n, waveguide antennas 298-1 to -n are installed at the microwave outlets. Specific shape examples of these waveguide antennas 298-1 to -n are cylinders with a hollow interior in the shape of a rectangular parallelepiped or a circular cylinder (or a pyramid or a cone), and microwaves with enhanced directivity are radiated to the outside while repeatedly reflecting on the inner walls within this cavity.

[0491] And these waveguide antennas 298-1 to -n serve as the microwave radiation ports and can also be used as part of a receiver (microwave detector) for microwaves entering from the outside. When using the waveguide antennas 298-1 to -n as a microwave receiver in this way, (not shown in the figure) a preamplifier circuit and a signal processing circuit may be connected to one end of each of the waveguide antennas 298-1 to -n.

[0492] The interior of the magnetron electromagnetic wave source 296 may have a thermionic tube structure installed in a strong DC magnetic field. The cathode installed at the center of the cavity of the vessel is heated by a heater. Then, the thermoelectrons emitted from this cathode move through the vacuum toward the anode under the action of the applied electrical field. At this time, the thermoelectrons draw a cycloid curve under the influence of the external DC magnetic field while emitting microwaves.

[0493] The practical frequency range of this magnetron electromagnetic wave source 296 is said to be from 100 MHz to 200 GHz. Therefore, the "microwave" referred to in this embodiment is used in a broad sense concept indicating the high-frequency band side in the radio wave category. That is, it includes not only the SHF wave (Super High Frequency Wave: narrow sense microwave) in the range of 3 GHz to 30 GHz defined by the narrow sense microwave, but also a wider frequency range. That is, the VHF wave in the range of 30 MHz to 300 MHz, the UHF wave (Ultra High Frequency Wave) in the range of 300 MHz to 3 GHz, and the EHF wave (Extremely High Frequency Wave: millimeter wave) in the range of 30 GHz to 300 GHz are also included in the "broad sense microwave frequency region".

[0494] The microwaves radiated outside the waveguide antennas 298-1 to -n become electromagnetic waves 290-1 to -n with directivity respectively. Even for the electromagnetic waves 290-1 to -n with high directivity, as shown in Fig. 55(b), they spread in the plane perpendicular to the traveling direction at a distance from the waveguide antennas 298-1 to -n. Also, as shown in Fig. 55(b), a plurality of sets respectively composed of the magnetron electromagnetic wave source 296 and the waveguide antennas 298 are densely arranged in one direction or a plane direction. Then, at a distance from the waveguide antennas 298-1 to -n, the electromagnetic waves 290-1 to -n with directivity spatially overlap and are synthesized (mixed) with each other. The mixed electromagnetic wave 294 with directivity generated by being synthesized (mixed) in such a way becomes an electromagnetic wave with low (partial) coherence.

[0495] By the way, a phased array antenna in which the waveguide antennas 298-1 to -n with a rectangular (or square) cross-sectional shape of the cavity are arranged in a two-dimensional direction is known. This has a structure for optimizing the wavefronts of the microwaves radiated from all the waveguide antennas 298-1 to -n in order to enhance the directivity of the microwaves. When using this antenna, only the single magnetron electromagnetic wave generation unit 296 is used. Therefore, the coherence of the microwaves radiated from this antenna is very high.

[0496] The arrangement examples of the waveguide antennas 298-1 to -n are similar to each other, but the effect of suppressing coherence is basically different between the phased array antenna and the application example of the present embodiment shown in Fig. 55(b). That is, in the conventional phased array antenna that generates microwaves with high coherence using the single magnetron electromagnetic wave generation unit 296, the penetration distance into the object 10 is short, and the electromagnetic wave noise mixed into the detection signal is large. In contrast, when using the application example of the present embodiment that uses a plurality of magnetron electromagnetic wave generation sources 296-1 to -n independent of each other, the penetration distance into the object 10 becomes long, and there is an effect that the electromagnetic wave noise mixed into the detection signal can be significantly reduced.

[0497] The source of the "hybrid electromagnetic wave 294 having high directivity and low (partial) coherence (high (partial) non-coherence)" generated by the method of Fig. 55(a) or (b) will hereafter be referred to as the directive electromagnetic wave generation / reception unit 362. And inside this directive electromagnetic wave generation / reception unit 362, a plurality of combinations of the electromagnetic wave generation / reception units 292-1 to -n or the magnetron electromagnetic wave generation units 296-1 to -n and the waveguide antennas 298-1 to -n are arranged. Also, the directive electromagnetic wave generation / reception unit 362 is equipped with a function of receiving (detecting) external electromagnetic waves (or microwaves).

[0498] Heating food in a microwave oven utilizes the principle that the "moisture" in the food absorbs the energy of the microwaves and generates heat. The mechanism of absorbing the energy of the electromagnetic waves differs depending on the wavelength band of the electromagnetic waves used. As will be described later in Section 5.2 with reference to Fig. 27, when irradiated with visible light, the "bias of the electron orbit" that constitutes the molecule absorbs the energy. Also, when irradiated with near-infrared light, the energy is absorbed by the "group vibration" within the functional group containing hydrogen atoms. Further, when irradiated with infrared light having a longer wavelength, the constituent atoms within the molecule vibrate.

[0499] On the other hand, when the wavelength of the irradiated electromagnetic wave is increased, the intramolecular vibrational motion between constituent atoms cannot absorb the electromagnetic wave, and the energy is absorbed by the "rotation and translational motion of the entire molecule". By the way, it is important that this "rotation and translational motion of the entire molecule" is likely to occur not in a "solid" but in a "liquid". That is, it can be said that the electromagnetic waves in the frequency range described here (the range from 30 kHz to 300 GHz, or the range from 30 MHz to 300 GHz) are most absorbed by water molecules in the "liquid" state (compared to solids). That is, the energy of the electromagnetic waves of the above frequencies is absorbed much more by water molecules than by solids.

[0500] The frequency at which the absorption of electromagnetic wave energy is maximized due to the dielectric loss of water itself is said to be in the range of 20 GHz to 80 GHz (the maximum frequency varies with temperature). However, even if the frequency of the electromagnetic wave is changed significantly, the "electromagnetic wave energy absorption efficiency of water" does not change much. Therefore, even if the frequency of the electromagnetic wave used in a microwave oven is set to 2.45 GHz (or 915 MHz), sufficient absorption by water molecules occurs, enabling heating (of food). Furthermore, due to the same reason, electromagnetic waves in the range from 30 MHz (or 3 MHz) to 300 GHz can also cause energy absorption and heat generation by water molecules.

[0501] In the application example of this embodiment, the above phenomenon may be utilized for the "exploration of water sources and metalliferous deposits 386". Specifically, a directional mixed electromagnetic wave 294 is irradiated onto the exploration location. Then, the degree of interaction with the mixed electromagnetic wave 294 for each measurement region is compared.

[0502] If there is a water source 386 at the search location, the water source 386 absorbs the energy of the mixed electromagnetic wave 294. Since the absorption of electromagnetic waves (microwaves) is large in the water source 386, the amount of electromagnetic wave reflection (backscattering amount) within the water source 386 relatively decreases. When the directional electromagnetic wave generation / reception unit 362 examines the change in the amount of electromagnetic wave reflection (backscattering amount), it can be found that the amount of electromagnetic wave reflection (backscattering amount) within the water source 386 decreases. Also, when the water source 386 absorbs the energy of electromagnetic waves (microwaves), the temperature within the water source 386 rises. By examining this temperature rise, the search for the location of the water source 386 can also be carried out.

[0503] Also, the amount of electromagnetic wave reflection (scattering) in the metal ore deposit 386 is larger than in other regions. Therefore, a region with a larger amount of electromagnetic wave reflection (scattering) compared to other regions suggests the possibility of the existence of the metal ore deposit 386.

[0504] In recent years, it has been found that water exists on the lunar surface. Using the electricity obtained from sunlight by the solar cell panel 384, the water on the lunar surface can be electrolyzed to obtain oxygen molecules and hydrogen molecules. Rocket fuel can be made from the oxygen molecules and hydrogen molecules. Furthermore, if oxygen molecules are utilized, it becomes possible for organisms to inhabit the lunar surface. Also, if various metals can be extracted from the metal ore deposits buried inside the lunar surface, they can be used as materials for products such as buildings, mobile objects, and rockets heading to other planets on the lunar surface.

[0505] Hereinafter, as an example of the application example adaptation, a method for exploring resources within the lunar surface will be described. However, it is not limited to this, and the following method can be used to explore resources within the Earth or in extraterrestrial regions (such as asteroids, planets, satellites).

[0506] An example of the structure of a water source / metal ore deposit exploration device that can be used to search for the location of the water source or metal ore deposit 386 on the lunar surface (or to explore resources in extraterrestrial regions other than the moon) is shown in FIG. 56. A caterpillar (Caterpillar Tread) 372 similar to that of a tank is in direct contact with the lunar surface. Then, the moving wheels 374 rotate to move the caterpillar, and the water source / metal ore deposit exploration device moves on the lunar surface.

[0507] The central part of FIG. 56 shows the internal layout of the water source / metal ore exploration device. The directional electromagnetic wave generation / reception unit 362 with the internal structure shown in FIG. 55 radiates a hybrid electromagnetic wave 294 that is directional downward (i.e., toward the interior of the lunar subsurface or the center of an extraterrestrial region other than the moon), and is arranged to receive (detect) the hybrid electromagnetic wave that is reflected (backscattered) and returns downward (i.e., from the interior of the lunar subsurface or the center of an extraterrestrial region other than the moon).

[0508] Also, this directional electromagnetic wave generation / reception unit 362 is housed within the rotation mechanism 364 of the electromagnetic wave generation / reception unit and is structured to be tiltable in any direction. Along with the rotation of the rotation drive unit 366 of the electromagnetic wave generation / reception unit, the entire rotation mechanism 364 of the electromagnetic wave generation / reception unit rotates slightly in any direction. By utilizing this mechanism, the directional hybrid electromagnetic wave 294 can be radiated in any direction within the interior of the lunar subsurface. Similarly, the hybrid electromagnetic wave 294 that is scattered or reflected and returns from any direction within the interior of the lunar subsurface can be received (detected).

[0509] As shown in FIG. 56, a far-infrared spectrometer 376 and an infrared spectrometer 376 are also mounted inside the water source / metal ore exploration device. Here, the far-infrared spectrometer 376 itself does not have a light source and is structured to be able to measure the spectral characteristics (spectral spectrum) of the far-infrared light radiated from the lunar subsurface. On the other hand, there is an independent infrared light source within the infrared spectrometer 378. The infrared light radiated from this light source is irradiated toward the lunar surface or the air near the lunar surface. Then, the spectral characteristics (spectral spectrum) of the reflected light or scattered light on the lunar surface or in the air near the lunar surface are examined.

[0510] The electric power generated within the solar cell panel 384 installed on the upper surface of the water source / metal ore exploration device is stored in the battery 388, enabling nighttime activities. Also, the communication control unit 394 controls wireless communication with external devices via the antenna 396. And the in-exploration device control system 398 integrally controls and manages the operations of these respective parts.

[0511] FIG. 57 shows an example of a method for exploring the location of a water source and a metal deposit inside the lunar surface (or exploring resources in an extraterrestrial region other than the moon) using this water source / metal deposit exploration device. Here, an example of a water source location exploration method using only one water source / metal deposit exploration device is shown in FIG. 57(a). And an example of a water source location exploration method using a plurality of water source / metal deposit exploration devices is described in FIG. 57(b). In the application example of this embodiment, first, the possibility of the burial of the water source or the metal deposit 386 may be explored using the simple method of FIG. 57(a), and then the area with possibility may be investigated in detail by the method of FIG. 57(b).

[0512] In the simple exploration of FIG. 57(a), a mixed electromagnetic wave 294 with directivity is radiated from the directional electromagnetic wave generation / reception unit 362 downward directly below the water source / metal deposit exploration device. The radiated mixed electromagnetic wave 294 with directivity is reflected (backscattered) everywhere inside the ground surface 392 and retur...

Claims

1. A method for generating combined light using a light source and an optical path changing element, wherein the light source is a filament, a fluorescent light source or a semiconductor light emitting element, the light source has a first light emitting region and a second light emitting region different from each other, the first light is emitted from the first light emitting region, the second light is emitted from the second light emitting region, the light source emits the first light and the second light simultaneously, the optical path changing element changes the optical path of the first light and the optical path of the second light, the width of the wavelength range of the first light is represented by Δλ, and the center wavelength of the wavelength range of the first light is represented by λ ０ and the width of the wavelength range of the second light is represented by Δλ, and the center wavelength of the wavelength range of the second light is represented by λ ０ when represented by, the optical path length difference between the first light and the second light is made longer than λ ０ ２ / Δλ, the first light and the second light with the optical path length difference made longer than λ02 / Δλ are combined to generate combined light, A method for generating combined light, which photoelectrically converts the combined light or the combined light after passing through an object to detect a signal.

2. The optical path changing element is included in an imaging optical system for the light source, The imaging optical system controls the optical path length difference. The method for generating combined light according to Claim 1.

3. The widest width of the light emitting region in the light source is λ ０ ２ / Δλ or more. The method for generating combined light according to Claim 1 or Claim 2.

4. Using a phase conversion element that diffuses the traveling direction of light as the optical path changing element, the method for generating combined light according to Claim 1, Claim 2 or Claim 3, which changes the optical path of the first light and the optical path of the second light.

5. A method for using light emitted from a light source, The light emitting source is a filament, a fluorescent light source, or a semiconductor light emitting element, The light emitting source has a first light emitting region and a second light emitting region that are different from each other, The first light is emitted from the first light emitting region, The second light is emitted from the second light emitting region, The light emitting source emits the first light and the second light simultaneously, The optical paths of the first light and the second light are changed, The width of the wavelength range of the first light is represented by Δλ, and the central wavelength of the wavelength range of the first light is λ ０ is represented, the width of the wavelength range of the second light is represented by Δλ, and the central wavelength of the wavelength range of the second light is λ ０ is represented, the optical path length difference between the first light and the second light is λ ０ ２ is made longer than λ 0 2 / Δλ, The first light and the second light with the optical path length difference made longer than λ 0 2 / Δλ are combined to generate combined light, The combined light or the combined light after passing through the object is photoelectrically converted to generate a detection signal, A light utilization method that utilizes the detection signal.

6. The light utilization method according to claim 5, wherein at least one of the operation of the object and the measurement of the object is performed using the detection signal.

7. A lens is disposed in the optical path of the combined light obtained from a predetermined region in the object to form an imaging optical system for the predetermined region, The detection signal is generated at a position corresponding to the imaging position of the predetermined region or the confocal position of the predetermined region. The light utilization method according to claim 5 or claim 6.

8. The optical path of the first light and the optical path of the second light are included in an imaging optical system for the light emitting source, The imaging optical system for the light emitting source controls the optical path length difference. The light utilization method according to claim 5, claim 6, or claim 7.

9. The widest width of the light emitting region in the light emitting source is λ ０ ２ The method for utilizing light according to claim 5, claim 6, claim 7 or claim 8, wherein the length is λ ２ / Δλ or more.

10. A phase conversion element for diffusing the traveling direction of light is disposed in the middle of the optical path of the first light and in the middle of the optical path of the second light, The method for utilizing light according to claim 5, claim 6, claim 7, claim 8 or claim 9, wherein the phase conversion element changes the optical path of the first light and the optical path of the second light.

11. It includes a light source, an optical path changing element, and a light synthesizing unit, The light source is a filament, a fluorescent light source or a semiconductor light emitting element, The light source has a first light emitting region and a second light emitting region different from each other, The first light is emitted from the first light emitting region, The second light is emitted from the second light emitting region, The light source emits the first light and the second light simultaneously, The optical path changing element changes the optical path of the first light and the optical path of the second light, The width of the wavelength range of the first light is represented by Δλ, and the center wavelength of the wavelength range of the first light is represented by λ ２ ０ The width of the wavelength range of the second light is represented by Δλ, and the center wavelength of the wavelength range of the second light is represented by λ ０ ０ When represented by ０ , the optical path length difference between the first light and the second light is made longer than λ ０ ０ ２ / Δλ, The light synthesizing unit synthesizes the first light and the second light whose optical path length difference is made longer than λ ０ / Δλ to generate synthesized light, A light source unit that photoelectrically converts the synthesized light or the synthesized light after passing through an object to detect a signal.

12. An imaging method for irradiating an object with irradiation light and using detection light obtained from the object, A light source is constituted by a filament, a fluorescent light source or a semiconductor light emitting element, The light source has a first light emitting region and a second light emitting region different from each other, emitting the first light from the first light-emitting region, emitting the second light from the second light-emitting region, the light source emitting the first light and the second light simultaneously, changing the optical paths of the first light and the second light, representing the width of the wavelength range of the first light by Δλ and the central wavelength of the wavelength range of the first light by λ ０ representing the width of the wavelength range of the second light by Δλ and the central wavelength of the wavelength range of the second light by λ ０ when represented by, making the optical path length difference between the first light and the second light longer than λ ０ ２ / Δλ in the optical path from the light source to the object, combining the first light and the second light with the optical path length difference made longer than λ 0 2 / Δλ to generate the irradiation light, irradiating the object with the irradiation light, An imaging method in which a camera photoelectrically converts the detection light obtained from the object and detects a signal.

13. Arranging a lens in the optical path of the detection light obtained from a predetermined region in the object to form an imaging optical system for the predetermined region, The imaging method according to claim 12, wherein the camera detects the signal at an imaging position or a confocal position of the predetermined region.

14. The optical path of the first light and the optical path of the second light are included in an imaging optical system for the light source, The imaging method according to claim 12 or claim 13, wherein the imaging optical system for the light source controls the optical path length difference.

15. Arranging a phase conversion element that diffuses the traveling direction of light in the middle of the optical path of the first light and in the middle of the optical path of the second light, The imaging method according to claim 12, claim 13, or claim 14, wherein the phase conversion element changes the optical paths of the first light and the second light.

16. Composed of a light source unit and a detection unit, irradiating the object with the irradiation light emitted by the light source unit, a measuring device in which the detection unit photoelectrically converts the detection light obtained from the object to generate a detection signal, the light source unit includes a light emitting source, an optical path changing element, and a light combining unit, the light emitting source is a filament, a fluorescent light source, or a semiconductor light emitting element, the light emitting source has a first light emitting region and a second light emitting region that are different from each other, emitting first light from the first light emitting region, emitting second light from the second light emitting region, the light emitting source emits the first light and the second light simultaneously, the optical path changing element changes the optical path of the first light and the optical path of the second light, when the width of the wavelength range of the first light is represented by Δλ, the central wavelength of the wavelength range of the first light is represented by λ0, the width of the wavelength range of the second light is represented by Δλ, and the central wavelength of the wavelength range of the second light is represented by λ0, the optical path length difference between the first light and the second light is made longer than λ02 / Δλ, the light combining unit combines the first light and the second light whose optical path length difference is made longer than λ02 / Δλ to generate the irradiation light, a measuring device.

17. The detection light is obtained from a predetermined region within the object, an imaging optical system for the predetermined region using a lens is included in the detection unit, The measuring device according to claim 16, wherein the detection signal is generated from the detection light at a position corresponding to the imaging position of the predetermined region or the confocal position of the predetermined region.

18. The detection unit includes a camera or a spectroscope, The measuring device according to claim 16 or claim 17, wherein the camera or the spectroscope generates the detection signal.

19. The light source unit includes an imaging optical system for the light emitting source, the optical path changing element is included in the imaging optical system for the light emitting source, The measuring device according to claim 16, claim 17 or claim 18, wherein the imaging optical system for the light source controls the optical path length difference.

20. The measuring device according to claim 16, claim 17, claim 18 or claim 19, wherein the widest width of the light emitting region in the light source is λ02 / Δλ or more.

21. The measuring device according to claim 16, claim 17, claim 18, claim 19 or claim 20, wherein the optical path changing element is a phase conversion element that diffuses the traveling direction of light.

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