Optical measurement device and optical measurement method

Abstract

To provide an optical measuring device and an optical measuring method which are capable of protecting a photosensor.SOLUTION: A lighting device 200 irradiates a predetermined region 10 with measuring light SIN having a wavelength changing temporally. A light-receiving device 300 includes a photosensor 302 which detects diffused transmission light SOBJ of a target object OBJ positioned at the predetermined region 10. The light-receiving device 300 is configured so that a component Sθ radiated in a direction displaced from an optical axis OA2 of measuring light SIN out of diffused transmission light SOBJ of the target object OBJ is incident on the photosensor 302.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an optical measurement device.

Background Art

[0002] Spectral analysis is widely used for component analysis and inspection of objects. In spectral analysis, measurement light is irradiated onto an object, and the spectrum of the object light obtained as a result of the irradiation is measured. Then, based on the relationship between the spectrum of the object light and the spectrum of the measurement light, optical properties such as reflection characteristics (wavelength dependency) or transmission characteristics can be obtained.

[0003] Spectral analysis is classified into a transmission type that uses transmitted light of an object as object light and a reflection type that uses reflected light as object light. The reflection type is suitable for measuring objects with high reflectivity, but the optical information obtained is limited to that near the surface of the object. Therefore, in measurements with objects such as precision industrial products, specimens collected from animals and plants, substances ingested by humans into the body, liquids and gases produced in production plants, etc., sufficient accuracy cannot be claimed.

[0004] The transmission type can obtain optical properties including not only the surface but also deep parts of an object, and is therefore suitable for cases where objects are food and beverages (hereinafter collectively referred to as food and drink products). Patent Documents 1 and 2 disclose transmission type product inspection devices. This product inspection device includes an irradiation optical system that irradiates pulsed light onto the surface of a product (object to be inspected) and a light receiver that is provided on the back side of the product and receives the light that has passed through the product.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] As a result of studying a transmission type inspection apparatus, the present inventor has come to recognize the following problems. In a conventional inspection apparatus, when there is no object, the measurement light directly enters the light receiver. When inspecting products with low transmittance such as food and drink, in order to ensure a sufficient S / N ratio, it is necessary to increase the intensity of the measurement light. However, when there is no inspection object, very high-intensity measurement light enters the photosensor (photoelectric conversion element) in the light receiver, which may cause the photosensor to malfunction in some cases. Therefore, measures for protecting the photosensor are required.

[0007] As measures for solving this problem, (i) controlling the operation / stop of the light source in a time division manner in synchronization with the presence or absence of the inspection object, (ii) providing an optical shutter (or a light attenuator) and blocking (or attenuating) the measurement light in synchronization with the presence or absence of the inspection object, etc. can be considered. However, when it is desired to inspect a large number of products at high speed, control synchronized with the presence or absence of the inspection object becomes difficult. In addition, the addition of components such as an optical shutter causes an increase in cost or introduces new uncertainties into the inspection apparatus, which is not preferable.

[0008] The present disclosure has been made in view of such problems, and an exemplary object of one aspect thereof is to provide an optical measurement apparatus and an optical measurement method capable of protecting a photosensor.

Means for Solving the Problems

[0009] One aspect of the present disclosure relates to an optical measurement apparatus. The optical measurement apparatus includes an illumination device that irradiates a measurement light whose wavelength changes over time onto a predetermined region, and a light receiving device that includes a photosensor that detects diffused transmitted light of an object located in the predetermined region. The light receiving device is configured such that a component of the diffused transmitted light of the object that is radiated in a direction deviated from the optical axis of the measurement light enters the photosensor.

[0010] Another aspect of the present disclosure is an optical measurement method. This method includes generating measurement light whose wavelength changes over time, repeatedly irradiating a predetermined region with the measurement light having a constant intensity, conveying an object so as to pass through the predetermined region, and detecting diffused transmitted light of the object with an optical sensor. The detecting step is performed such that the amount of light received by the optical sensor when the object is in the predetermined region is greater than the amount of light received by the optical sensor when the object is not in the predetermined region.

[0011] In addition, combinations of the above components arbitrarily, and those obtained by mutually substituting the components and expressions of the present disclosure among methods, apparatuses, systems, etc. are also effective as aspects of the present disclosure.

Effects of the Invention

[0012] According to an aspect of the present disclosure, an optical sensor can be protected.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

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Figure 11

Embodiments for Carrying Out the Invention

[0014] (Overview of Embodiment) The overview of some exemplary embodiments of the present disclosure will be described. This overview is for the purpose of providing a basic understanding of the embodiments as a prelude to the detailed description to follow, and simplifies and describes some concepts of one or more embodiments. It does not limit the scope of the invention or the disclosure. Also, this overview is not an all-inclusive overview of all possible embodiments and does not limit essential components of the embodiments. For convenience, "one embodiment" may be used to refer to one embodiment (example or modification) or a plurality of embodiments (examples or modifications) disclosed in this specification.

[0015] A light measurement apparatus according to one embodiment includes an illumination device that irradiates a measurement light whose wavelength changes over time onto a predetermined region, and a light receiving device that includes a light sensor for detecting diffused transmitted light of an object located in the predetermined region. The light receiving device is configured such that a component of the diffused transmitted light of the object that is radiated in a direction deviated from the optical axis of the measurement light enters the light sensor. Note that "configured" includes not only cases where the configuration has characteristics, but also cases where both the configuration and the arrangement have characteristics, or cases where only the arrangement has characteristics.

[0016] According to this light measurement apparatus, when an object is present, the object light attenuated by the object enters the light sensor. When the object is not present, the measurement light does not enter the light sensor, or even if it enters, the intensity is extremely weak. Therefore, the light sensor can be protected. Also, regardless of the presence or absence of the object, the illumination device can be continuously operated, and a shutter or the like synchronized with the presence or absence of the object is not required.

[0017] In one embodiment, the light receiving device may further include a condensing optical system. This condensing optical system is perpendicular to the photosensor and has an optical axis passing through the center of the photosensor. The light receiving device may be arranged such that the optical axis of the condensing optical system passes through a predetermined region and is non-parallel to the optical axis of the measurement light. In this way, by devising the arrangement of the light receiving device, it is possible to prevent the measurement light from directly irradiating the photosensor when the object is not present.

[0018] In one embodiment, the optical axis of the measurement light may be perpendicular to the object, and the optical axis of the condensing optical system may be non-perpendicular to the object.

[0019] In one embodiment, the optical axis of the measurement light may be non-perpendicular to the object, and the optical axis of the condensing optical system may be perpendicular to the object.

[0020] In one embodiment, the optical axis of the measurement light may be non-perpendicular to the object, and the optical axis of the condensing optical system may be non-perpendicular to the object.

[0021] In one embodiment, when defining the optical axis of the light receiving device as a straight line passing through the center of its incident window and perpendicular to the incident window, the light receiving device may have the optical axis of the light receiving device parallel to the optical axis of the measurement light, and the optical axis of the light receiving device and the optical axis of the measurement light may be arranged to be separated. Thereby, by making the separation distance large to a certain extent, it is possible to prevent the measurement light from entering the incident window when the object is not in the predetermined region.

[0022] In one embodiment, the light receiving device may further include a condensing optical system and a mask that shields a component of the diffused transmitted light of the object radiated in the direction of the optical axis of the measurement light.

[0023] In one embodiment, the wavelength of the measurement light may change over time. In one embodiment, the measurement light may be pulsed light whose wavelength changes over time within one pulse.

[0024] A light measurement method according to an embodiment includes a step of repeatedly irradiating a measurement light with a constant intensity on a predetermined region, a step of conveying an object so as to pass through the predetermined region, and a step of detecting diffused transmitted light of the object by a light sensor. The detecting step is performed such that the amount of light received by the light sensor when the object is in the predetermined region is larger than the amount of light received by the light sensor when the object is not in the predetermined region.

[0025] (Embodiment) Hereinafter, the present disclosure will be described with reference to the drawings based on preferred embodiments. The same or equivalent components, members, and processes shown in each drawing are denoted by the same reference numerals, and redundant descriptions will be omitted as appropriate. Further, the embodiments are illustrative and not restrictive of the disclosure, and not all features and combinations thereof described in the embodiments are necessarily essential to the disclosure.

[0026] The dimensions (thickness, length, width, etc.) of each member shown in the drawings may be enlarged or reduced as appropriate for ease of understanding. Further, the dimensions of a plurality of members do not necessarily represent their size relationships, and even if a member A is drawn thicker than another member B on the drawing, member A may be thinner than member B.

[0027] FIG. 1 is a block diagram of a light measurement device 100 according to an embodiment. The light measurement device 100 is a spectrometer that measures the transmission spectrum of an object OBJ, and mainly includes an illumination device 200, a light receiving device 300, a conveyance device 400, and a processing device 500.

[0028] The conveyance device 400 conveys the object OBJ so as to cross a predetermined region 10. Preferably, the conveyance device 400 is a belt conveyor having an endless track or a stage, and operates such that a plurality of objects OBJ sequentially pass through the predetermined region 10.

[0029] The illumination device 200 irradiates the object OBJ existing in the predetermined region 10 with a measurement light (also referred to as incident light) S whose wavelength changes over time. This measurement light S IN is irradiated.IN is associated with time and wavelength in a one-to-one relationship. This measurement light S IN is said to "have wavelength uniqueness". The illumination device 200 may be configured using known techniques, for example, those described in Patent Documents 1 and 2 can be used.

[0030] FIG. 2 is a diagram showing the measurement light S IN In the upper part of FIG. 2, the intensity (time waveform) I IN (t) of the measurement light S IN is shown, and in the lower part, the time change of the wavelength λ of the measurement light S IN is shown.

[0031] In this example, the measurement light S IN is a single pulse, the main wavelength is λ1 at the leading edge, the main wavelength is λ2 at the trailing edge, and the wavelength changes over time between λ1 and λ2 within one pulse. In this example, the measurement light S IN is a positive chirp pulse (λ1>λ2) whose frequency increases with time, in other words, whose wavelength shortens with time. Note that the measurement light S IN may be a negative chirp pulse whose wavelength increases with time (λ1<λ2).

[0032] Returning to FIG. 1. The measurement light S IN passes through the object OBJ and is radiated as transmitted light (hereinafter also referred to as object light) S OBJ from the back surface. When the spectrum of the measurement light S IN is I IN (λ) and the wavelength dependence of the transmittance of the object light S OBJ is T(λ), the spectrum I OBJ (λ) of the object light S OBJ is represented by the formula. I OBJ (λ)=T(λ)×I IN (λ) …(1)

[0033] The object light S OBJ may include direct transmitted light and diffused transmitted light, but this embodiment is particularly suitable for spectroscopic measurement of an object OBJ in which diffused transmitted light is dominant. The direct transmitted light is the measurement light S INis radiated in the same direction as the optical axis OA2 of, while the object light S which is diffused transmitted light OBJ is the measurement light S IN is radiated not only in the direction of the optical axis OA2 but also widely in a direction different from it. For example, the diffused transmitted light is radiated with an intensity distribution of cosine characteristics when the direction of the optical axis OA2 is set to 0°.

[0034] The light receiving device 300 includes an optical sensor 302 that detects the diffused transmitted light of the object OBJ as the object light S OBJ As will be described later, the light receiving device 300 may include a condensing optical system etc. in addition to the optical sensor 302, but it is omitted in FIG. 1.

[0035] The optical sensor 302 is a photoelectric conversion element that converts an optical signal into an electrical signal, and examples include a photodiode, an avalanche photodiode, a phototransistor, a photomultiplier tube (photomultiplier) that utilizes the photoelectric effect, and a photoconductive element that utilizes a change in electrical resistance due to light irradiation.

[0036] The output of the optical sensor 302 is converted into a digital detection signal by an A / D converter and supplied to the processing device 500. The detection signal indicates the time waveform I OBJ of the object light S OBJ (t).

[0037] Based on the output signal of the light receiving device 300, the processing device 500 generates the spectrum I OBJ of the object light S OBJ (λ). Then, based on the spectrum I IN of the measurement light S IN (λ) and the spectrum I OBJ of the object light S OBJ (λ), the transmittance T(λ) of the object OBJ is calculated. T(λ)=I OBJ (λ) / I IN (λ) …(2)

[0038] On the side of the illumination device 200 rather than the object OBJ, a part of the measurement light S IN is branched into a separate path using a beam splitter etc., and the branched measurement light SIN Time waveform I IN (t) is measured with a light receiving device different from the light receiving device 300 (not shown in FIG. 1, corresponding to 810 in FIG. 11), and the measurement light S IN spectrum I IN (λ) may be obtained. Alternatively, when the measurement light S IN has high stability, the previously measured spectrum I IN (λ) can be retained and used.

[0039] FIG. 3 is a diagram for explaining the spectroscopy by the optical measurement device 100 of FIG. 1. As described above, since the measurement light S IN has a one-to-one correspondence between the time t and the wavelength λ, the waveform I IN (t) in the time domain can be converted into the spectrum I IN (λ) in the frequency domain.

[0040] This measurement light S IN generated object light S OBJ time waveform I OBJ (t) also has a one-to-one correspondence between the time t and the wavelength λ. Therefore, the processing device 500 can convert the waveform I OBJ of the object light S indicated by the output of the light receiving device 300 OBJ (t) into the spectrum I OBJ of the object light S OBJ (λ).

[0041] The processing device 500 can calculate the transmission spectrum T(λ) of the object OBJ based on the ratio I OBJ (λ) / I IN (λ) of the two spectra I OBJ (λ) and I IN (λ).

[0042] Assume that the relationship between the wavelength λ and the time t in the measurement light S IN is represented by a function λ = f(t). Most simply, the wavelength λ changes linearly with respect to the time t according to a linear function. The time waveform I OBJ of the object light S OBJ (t) at a certain time t xWhen decreasing, the transmission spectrum T(λ) means that the absorption spectrum is present at the wavelength λ x =f(t x ).

[0043] Note that the processing in the processing device 500 is not limited to this. The ratio T(t) = I OBJ (t) / I IN (t) of two time waveforms I OBJ (t) and I IN (t) is calculated, and then the variable t of this time waveform T(t) is converted to λ to calculate the transmission spectrum T(λ).

[0044] Returning to FIG. 1. The illumination device 200 can be continuously operated asynchronously with the transport device 400, and the pulsed measurement light S in FIG. 2 IN is repeatedly generated at a predetermined period. When the object OBJ does not exist in the predetermined region 10, the pulse of the measurement light S IN generated at that time propagates directly in the direction of the optical axis OA2 without being diffused by the object OBJ.

[0045] Suppose that the light receiving device 300 is arranged on the optical axis OA2 of the measurement light S IN . When the object OBJ does not exist on the optical axis OA2, high-intensity measurement light S IN will directly enter the photosensor 302. To avoid this, in the present embodiment, the light receiving device 300 is configured such that the component S OBJ of the diffused transmitted light (object light S IN ) of the object OBJ that is radiated in a direction deviated from the optical axis OA2 of the measurement light S θ (the deviation angle is θ) enters the photosensor 302.

[0046] Note that it is only necessary that the object light S OBJ in the direction of the optical axis OA2 does not enter the photosensor 302, and it may enter the incident aperture of the light receiving device 300. This point will be described later with reference to FIG. 4(b).

[0047] The above is the configuration of the optical measurement device 100. According to this optical measurement device 100, when the object OBJ exists in the predetermined region 10, the object light S attenuated by the object OBJ OBJ enters the photosensor 302. On the other hand, when the object OBJ does not exist, the measurement light S IN does not enter the photosensor 302, or even if it enters, the intensity becomes extremely weak. Thereby, the photosensor 302 can be protected from overinput. Also, regardless of the presence or absence of the object OBJ, the lighting device 200 can be continuously operated, and burst control of the lighting device 200 synchronized with the presence or absence of the object OBJ and additional components such as shutters become unnecessary.

[0048] The present invention is understood as the block diagram of FIG. 1, or extends to various devices and methods derived from the above description, and is not limited to a specific configuration. Hereinafter, in order to assist in understanding the essence and operation of the invention and to clarify them, rather than narrowing the scope of the present invention, more specific configuration examples and embodiments will be described.

[0049] A more specific configuration and layout of the light receiving device 300 will be described.

[0050] (Example 1) FIGS. 4(a) and (b) are diagrams showing the optical measurement device 100 according to Example 1. As shown in FIG. 4(a), the irradiation optical system 230 of the lighting device 200 emits the measurement light S IN in the direction of the optical axis OA2 and irradiates the predetermined region 10. FIG. 4(a) shows the light rays when the object OBJ does not exist in the predetermined region 10.

[0051] FIG. 4(b) shows a configuration example of the light receiving device 300. FIG. 4(b) shows light rays when the object OBJ exists. The light receiving device 300 includes a condenser optical system 310 in addition to the photosensor 302. The optical axis OA3 of the condenser optical system 310 coincides with the perpendicular line from the center of the photosensor 302. In this example, the condenser optical system 310 includes a first lens 314 and a second lens 316, which are coaxially arranged. The focal length of each of the first lens 314 and the second lens 316 may be determined based on the distance from the object OBJ and the distance from the photosensor 302.

[0052] The first lens 314 makes the diffused transmitted light from the object OBJ approach parallel light. The second lens 316 condenses the light emitted from the first lens 314. The photosensor 302 is arranged near the focal point of the second lens 316. The second lens 316 has a smaller aperture than the first lens 314. Therefore, among the incident light of the first lens 314, the component having a large angle with the optical axis OA3 does not enter the second lens 316 and is not condensed on the photosensor 302.

[0053] The light receiving device 300 is arranged such that the optical axis OA3 of the condenser optical system 310 passes through the predetermined region 10 and is non-parallel to the optical axis OA2 of the measurement light S IN The inclination angle θ formed by the optical axis OA3 of the condenser optical system 310 and the optical axis OA2 of the measurement light S IN is determined to be sufficiently larger than 0°.

[0054] As described above, the object light S in the direction of the optical axis OA2 (θ = 0°) OBJ does not need to enter the photosensor 302 and may enter the incident aperture of the light receiving device 300. In the configuration of FIG. 4(b), the aperture of the first lens 314 is regarded as the incident aperture, and the object light S in the direction of the optical axis OA2 OBJ enters the first lens 314, but the object light S in the direction of the optical axis OA2 OBJ becomes stray light and is not condensed on the photosensor 302. In order to prevent the incidence of stray light on the photosensor 302, a light shielding plate may be provided inside the light receiving device 300.

[0055] FIG. 5 is a diagram (simulation result) showing the relationship between the tilt angle θ and the relative detection intensity of the photosensor 302 in the light receiving device 300 according to Example 1. The relative detection intensity is the detection intensity normalized so as to be 1 when the tilt angle θ is 0°. Plot A shows the relative detection intensity when the object OBJ exists in the predetermined area 10, and Plot B shows the relative detection intensity when it does not exist.

[0056] When the object OBJ exists, even if the tilt angle θ is changed, the relative detection intensity hardly changes. On the other hand, when the object OBJ does not exist, as the tilt angle θ increases, the detection intensity decreases. In this example, when the tilt angle θ exceeds 25°, the relative intensity falls below 0.1, and when it further exceeds 27°, the relative detection intensity becomes <0.02 and decreases to the same order as the typical transmittance of the object OBJ. The maximum intensity of the measurement light S IN is I IN_MAX , the maximum transmittance of the object OBJ is η MAX , the relative detection intensity when the object OBJ is present is A(θ), the relative detection intensity when it is not present is B(θ), and the maximum rating of the photosensor 302 is I RATE_MAX , then I RATE_MAX >I IN_MAX ×η MAX ×A(θ) I RATE_MAX >I IN_MAX ×B(θ) If the tilt angle θ is selected so as to satisfy RATE_MAX , it is possible to prevent power exceeding the maximum rating I RATE_MAX from being incident on the photosensor 302 regardless of the presence or absence of the object OBJ.

[0057] Preferably, the tilt angle θ may be selected so as to satisfy I RATE_MAX >I IN_MAX ×η MAX ×A(θ)≧I IN_MAX ×B(θ). Assuming η MAX is 1%, 0.01×A(θ)≧B(θ) If θ is selected so as to satisfy OBJThe detection step may be performed such that the amount of light received (incident intensity) by the optical sensor 302 when the object OBJ is in the predetermined region 10 is greater than the amount of light received (incident intensity) by the optical sensor 302 when the object OBJ is not in the predetermined region 10.

[0058] Note that the design of the condensing optical system 310 is not limited to that in FIG. 4, and those skilled in the art can design various optical systems having the same effect, and such are also included in the scope of the present invention. For example, in FIG. 4, it is composed of two convex lenses, but it may be composed of a combination of a concave lens and a convex lens. Also, the number of lenses and lens groups is not particularly limited. Further, in this example, θ > 27° is a condition, but it goes without saying that the range of this inclination angle θ depends on the design of the condensing optical system 310 of the light receiving device 300.

[0059] (Example 2) FIG. 6 is a diagram showing the light receiving device 300 according to Example 2. The difference from Example 1 is that in Example 1, the optical axis OA2 of the irradiation optical system 230 was perpendicular to the object OBJ, and the optical axis OA3 of the light receiving device 300 was inclined with respect to the optical axis OA2 of the irradiation optical system 230, whereas in Example 2, the optical axis OA3 of the light receiving device 300 is perpendicular to the object OBJ, and the optical axis OA3 of the light receiving device 300 is inclined with respect to the optical axis OA2 of the irradiation optical system 230. Note that being perpendicular to the object OBJ includes being perpendicular to the surface or the back surface of the object OBJ when the surface or the back surface of the object OBJ is flat. Also, when the surface of the object OBJ is a curved surface, being perpendicular to the object OBJ includes being perpendicular to the surface on which the object OBJ is placed. The configuration of the light receiving device 300 may be the same as or different from that in FIG. 4. According to this configuration, the same effect as in Example 1 can be obtained.

[0060] (Example 3) FIG. 7 is a diagram showing the light receiving device 300 according to Embodiment 3. In Embodiment 3, both the optical axis OA2 of the illumination device 200 and the optical axis OA3 of the condensing optical system of the light receiving device 300 are non-perpendicular to the mounting surface of the object OBJ. The configuration of the light receiving device 300 may be the same as or different from that in FIG. 4. According to this configuration, the same effects as in Embodiment 1 and Embodiment 2 can be obtained.

[0061] (Embodiment 4) FIG. 8 is a diagram showing the light receiving device 300 according to Embodiment 4. The optical axis OA3 of the light receiving device 300 is defined as a straight line passing through the center of the incident window 320 of the light receiving device 300 and perpendicular to the incident window 320. The incident window 320 may be the frontmost optical member of the light receiving device 300. The configuration of the light receiving device 300 is not particularly limited, and the light receiving device 300 is configured such that the light incident on the incident window 320 enters an internal photosensor (not shown in FIG. 8). The diameter φ AP of the incident window 320 is such that the light incident thereon can enter an internal photosensor (not shown in FIG. 8).

[0062] The light receiving device 300 is such that the optical axis OA3 of the light receiving device 300 is substantially parallel to the optical axis OA2 of the measurement light S IN and the optical axis OA3 of the light receiving device 300 and the optical axis OA2 of the measurement light S IN are arranged apart from each other.

[0063] By increasing the separation distance D to a certain extent, when the object OBJ is not in the predetermined region 10, the measurement light S IN can be prevented from entering the incident window 320, and thus from entering the photosensor. The beam diameter of the measurement light S IN at the position of the incident window 320 is φ BM , and the diameter of the incident window 320 is φ AP . When this is the case, the following relationship should hold for the separation distance D: D > φ AP / 2 + φ BM / 2 should be satisfied.

[0064] (Embodiment 5) FIG. 9 is a diagram showing the light receiving device 300 according to Example 5. The light receiving device 300 includes an optical sensor 302, a condensing optical system 310, and a mask 330. The configuration of the condensing optical system 310 is not particularly limited, and for example, it may be configured in the same manner as in FIG. 4. The optical axis OA3 of the light receiving device 300 is the measurement light S IN is arranged to coincide with the optical axis OA2 (0° direction of the object light S OBJ ) of. The mask 330 blocks the components of the object light S OBJ incident on the condensing optical system 310 in the range of -Δθ to +Δθ. The position of the mask 330 is not limited, and it may be provided on the object OBJ side with respect to the condensing optical system 310, on the optical sensor 302 side, or inserted between them when the condensing optical system 310 includes a plurality of lenses.

[0065] According to this configuration, by appropriately designing the diameter φ MASK of the mask 330, when the object OBJ is not in the predetermined region 10, the measurement light S IN can be prevented from entering the optical sensor 302.

[0066] (Example 6) FIG. 10 is a diagram showing the light receiving device 300 according to Example 6. The light receiving device 300 includes a condensing optical system 310 and an optical sensor 302. In this Example 6, the optical axis OA3 of the condensing optical system 310 of the light receiving device 300 is parallel to the optical axis OA2 of the measurement light S IN . However, the optical sensor 302 is not arranged on the optical axis OA3 of the condensing optical system 310, but is arranged in the vicinity of the position where the light incident at an angle θ with respect to the condensing optical system 310 is condensed.

[0067] According to this configuration, among the object light S OBJ emitted from the object OBJ, the component S θ emitted in the θ direction can be detected by the optical sensor 302, and when the object OBJ is not in the predetermined region 10, the measurement light S IN in the 0° direction can be prevented from entering the optical sensor 302.

[0068] (Application) Next, the use of the optical measurement device 100 according to the embodiment will be described. The optical measurement device 100 can be used as an inspection device for products such as food and drink products in which powders are solidified into a solid state. FIG. 11 is a diagram showing an inspection device 800 which is one form of the optical measurement device 100. The inspection device 800 inspects a large number of products P such as food and drink products and determines whether they are good or bad. In the case of food and drink products in which powders are solidified into a solid state, their transmittance is on the order of 1 / 100 to 1 / 1000.

[0069] As described with respect to the optical measurement device 100, the inspection device 800 includes an illumination device 200, a light receiving device 300, a transport device 400, and a processing device 500. Further, the inspection device 800 includes a light receiving device 810, a beam damper 820, a digitizer 830, and a pump 840.

[0070] The illumination device 200 includes a light source 210, a pulse stretcher 220, and an irradiation optical system 230. The light source 210 generates coherent pulsed light having a broad continuous spectrum in a continuous spectrum of at least 10 nm, specifically, in the near-infrared region of 900 to 1300 nm. The light source 210 may be an SC (Super Continuum) light source including a pulsed laser and a non-linear element. As the pulsed laser, a mode-locked laser, a microchip laser, a fiber laser, or the like can be used. As the non-linear element, a non-linear fiber such as a photonic crystal fiber can be used.

[0071] The pulse stretcher 220 stretches the pulse width of the pulsed light generated by the light source 210 in a manner in which time and wavelength correspond one-to-one. The pulse stretcher 220 may be composed of a single wavelength dispersion fiber.

[0072] Alternatively, the pulse stretcher 220 may be composed of a wavelength demultiplexer that branches the pulsed light into a plurality of paths for each wavelength, a plurality of fibers (fiber bundles) that provide different delays for each of the plurality of paths, and a wavelength multiplexer that recombines the outputs of the plurality of fibers. The demultiplexer can be composed of a planar lightwave circuit (PLC), and specifically, it may be composed of an arrayed waveguide grating (AWG). The plurality of fibers constituting the fiber bundle have different lengths.

[0073] The transfer device 400 includes a holder 410. On the holder 410, a plurality of products P are placed by a mounter (not shown) on the upstream side (the left side in the figure). Although not limited thereto, the holder 410 may be a recess formed on a flat surface. The transfer device 400 moves the holder 410 in its movable direction. Hereinafter, among the surfaces of the holder 410, the surface on which the product P is placed is referred to as the front surface, and the opposite surface is referred to as the back surface.

[0074] The irradiation optical system 230 irradiates the extended pulse as measurement light S IN onto a predetermined region 10. The predetermined region 10 is defined at the passage location of the product P on the holder 410. The irradiation optical system 230 can be composed of a transmission optical system such as a lens, a reflection optical system such as a mirror, or a combination thereof. As the holder 410 moves, the predetermined region 10 will be traversed sequentially by a plurality of products P.

[0075] The light source 210 repeatedly generates pulsed light at a predetermined frequency (period). The operating frequency of the light source 210 may be determined according to the moving speed of the holder 410, that is, the transfer speed of the product P, so that a plurality of measurement lights S IN are irradiated onto the same product P while one product P exists in the predetermined region 10.

[0076] The operation of the light source 210 is independent of the operation of the holder 410, in other words, the position of the product P. Therefore, the measurement light S INEven when the product P is not present within the predetermined area 10, the predetermined area 10 is repeatedly irradiated.

[0077] The light receiving device 300 is provided on the back side of the holder 410. A through hole 412 is provided in the holder 410. This through hole 412 is formed to guide the diffused transmitted light (object light) S from the product P OBJ to the light receiving device 300 on the back side.

[0078] A pump 840 may be provided on the back side of the holder 410. The pump 840 constitutes a suction means. By making the back side of the holder 410 negative pressure, the product P will be attracted to the holder 410, and it is possible to prevent the product P from rolling or shifting on the holder 410 as the holder 410 is transported. On the other hand, when the product P does not get stuck inside the holder 410 and the product P is not present within the predetermined area 10, the measurement light S IN will pass through this through hole 412 and leak to the back side where the light receiving device 300 is present.

[0079] The configuration and arrangement of the light receiving device 300 are as described above. In the optical sensor 302 inside the light receiving device 300, when the product P is not present in the predetermined area 10, the measurement light S IN will not be incident. The light receiving device 300 measures the time waveform I OBJ (t) of the object light S OBJ . Also, on the optical axis OA2 of the measurement light S IN , a beam damper 820 is provided to prevent stray light.

[0080] The light receiving device 810 is provided to measure the spectrum of the measurement light S IN . The irradiation optical system 230 branches a part of the measurement light S IN as the reference light S REF to a separate arm using a beam splitter or the like. The light receiving device 810 measures the time waveform I REF of the reference light S branched to the separate arm REF (t). This time waveform I REF (t) is the measurement light S INTime waveform I IN is equivalent to (t).

[0081] The digitizer 830 includes an A / D converter and samples the outputs of the light receiving devices 300 and 810, namely the time waveforms I OBJ (t), I REF (t) at a predetermined sampling frequency to convert them into waveform data D OBJ (t), D IN (t) of digital signals. When using the light receiving devices 300 and 810 with digital outputs, the digitizer 830 can be omitted.

[0082] The processing device 500 processes the digital waveform data D OBJ (t) and D IN (t) to obtain the transmission characteristic (or absorption characteristic) T(λ) of the product P. The processing device 500 can be implemented as a combination of a general-purpose or dedicated computer including a processor, a memory, a storage medium such as a hard disk, and a software program. The processing of the processing device 500 is as described above.

[0083] The above is the configuration of the inspection device 800. According to this inspection device 800, when the product P does not exist in the predetermined region 10, the light receiving device 300 can be protected. At this time, the light source 210 of the lighting device 200 can be operated in a free-running manner asynchronously with the operation of the transport device 400, and shutter control synchronized with the operation of the transport device 400 is not required.

[0084] The embodiments merely show the principles and applications of the present invention. In the embodiments, many modifications and arrangement changes are allowed without departing from the idea of the present invention defined in the claims.

Explanation of Reference Numerals

[0085] OA2, OA3 Optical axes 10 Predetermined region OBJ Object 100 Optical measurement device 200 Lighting device 210 Light source 220 Pulse stretcher 230 Irradiation optical system 300 Light receiving device 302 Optical sensor 310 Condensing optical system 314 First lens 316 Second lens 320 Incident window 400 Conveying device 410 Holder 412 Through hole 500 Processing device 800 Inspection device S IN Measurement light S OBJ Object light 810 Light receiving device 820 Beam damper 830 Digitizer 840 Pump P Product

Claims

1. An illumination device that irradiates a coherent measurement light whose wavelength changes over time onto a predetermined area with one optical axis, A light receiving device including a light sensor that detects diffused transmitted light of an object located in the predetermined area, Comprising, The object is conveyed by a conveying device so as to pass through the predetermined area, The light receiving device is configured such that a component of the diffused transmitted light of the object that is radiated in a direction deviated from the optical axis of the measurement light enters the light sensor, The light receiving device, Further includes a condensing optical system that is perpendicular to the light sensor and has an optical axis passing through the center of the light sensor, The light receiving device is arranged such that the optical axis of the condensing optical system passes through the predetermined area and is non-parallel to the optical axis of the measurement light. A light measuring device characterized by this.

2. The optical axis of the measurement light is perpendicular to the object, The light measuring device according to claim 1, wherein the optical axis of the condensing optical system is non-perpendicular to the object.

3. The optical axis of the measurement light is non-perpendicular to the object, The light measuring device according to claim 1, wherein the optical axis of the condensing optical system is perpendicular to the object.

4. The optical axis of the measurement light is non-perpendicular to the object, The light measuring device according to claim 1, wherein the optical axis of the condensing optical system is non-perpendicular to the object.

5. The light receiving device, The light measuring device according to claim 1, further including a mask that shields a component of the diffused transmitted light of the object that is radiated in the direction of the optical axis of the measurement light.

6. An illumination device that irradiates a coherent measurement light whose wavelength changes over time onto a predetermined area with one optical axis, A light receiving device including a light sensor that detects diffused transmitted light of an object located in the predetermined area, Comprising, The object is conveyed by a conveying device so as to pass through the predetermined area, The light receiving device is configured such that a component of the diffused transmitted light of the object that is radiated in a direction deviated from the optical axis of the measurement light enters the light sensor, When defining the optical axis of the light receiving device as a straight line passing through the center of the incident window and perpendicular to the incident window, The light receiving device is arranged such that the optical axis of the light receiving device is parallel to and spaced apart from the optical axis of the measurement light. A light measuring device characterized by this.

7. The light measurement device according to any one of claims 1 to 6, characterized in that the measurement light is pulsed light whose wavelength changes over time within one pulse.

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