Spectrophotometer

Abstract

According to the present invention, light emitted from a measurement point of an object surface S is integrated into one parallel light flux by an objective lens 15, the integrated parallel light flux is split into a first light flux and a second light flux by a phase shifter 19, and the first light flux and the second light flux are emitted toward a light-receiving surface of a photodetector 21 while having an optical path length difference therebetween. . A light shielding plate 13 is disposed on a surface that is optically conjugated to the object surface with respect to the objective lens 15, and only light passing through a translucent part of the light shielding plate 13 moves toward the objective lens 15. The lateral length of the translucent part of the light shielding plate 13 and an interval between two adjacent translucent parts are set on the basis of the focal length of the objective lens, the distance from the phase shifter 19 to the light-receiving surface of the photodetector 21, the pixel pitch of the photodetector, the length of a pixel, and a predetermined wavelength included in a wavelength range of the light emitted from the measurement point.

Description

[Technical field]

[0001] The present invention relates to a spectroscopic measurement device. [Background technology]

[0002] A method is known in which a biological component (such as glucose or cholesterol in blood) is qualitatively and quantitatively measured by irradiating a test site of a living body with light and measuring the spectral characteristics of the object light, such as transmitted light, diffused light, and scattered light, emitted from the test site. As a method for measuring the spectral characteristics of the object light, there is a method in which the object light is made into a parallel beam by an objective lens, guided to a phase shifter, and split into two beams having an optical path length difference by the phase shifter, and the spectral characteristics are obtained from the intensity change of the interference light formed from these two beams with respect to the phase difference between these two beams. As a method for providing a phase difference between the two beams, a method is generally used in which the parallelized object light is reflected by two mirrors arranged side by side to cause interference between the two beams, and one of the two mirrors is moved in the optical axis direction. In this method, a moving mechanism for moving one of the mirrors is required, and in order to measure the intensity change of the interference light, time is required to move the mirror.

[0003] In response to this, Patent Document 1 describes a method that does not require a mirror moving mechanism and can obtain a change in the intensity of interference light all at once. The phase shifter disclosed in Patent Document 1 is composed of two mirrors (a reference mirror and an inclined mirror) arranged side by side and with different inclinations of the reflecting surfaces. A parallel light beam introduced into the phase shifter is reflected by the reflecting surfaces of the reference mirror and the inclined mirror, and is focused on the same straight line by the imaging optical system. Therefore, on this straight line (imaging straight line), a linear interference image is formed by the light reflected by the reference mirror (reference reflected light) and the light reflected by the inclined mirror (inclined reflected light). Here, since the inclinations of the reflecting surfaces of the reference mirror and the inclined mirror are different, a continuous optical path length difference according to the angle between the two reflecting surfaces occurs between the reference reflected light and the inclined reflected light on the imaging straight line. Therefore, an interferogram can be obtained by detecting the change in light intensity of the interference image along the imaging straight line. In addition, the spectral characteristics of the object light can be obtained by Fourier transforming this interferogram.

[0004] In the method described in Patent Document 1, the light amount distribution (interferogram) of the interference image in the imaging line is affected by differences in the diffraction angle due to the texture (surface condition) of the test site. In other words, since the light amount distribution in the imaging line differs due to differences in the refractive index distribution of the test site and the optical texture of the area through which the object light passes, such a light amount distribution is superimposed on the light amount distribution (interferogram) of the interference image that depends on the concentration of the biological component, making it impossible to accurately measure the concentration of the biological component.

[0005] Furthermore, in the case of spatially coherent light, no higher-order diffracted light is generated from a test area with almost no texture, and only zero-order light is generated. For example, when a test area is irradiated with Kohler illumination, the zero-order light from the light source reaches the objective lens as a parallel beam without being diffused or scattered in the test area with almost no texture, and is focused on the reflecting surface of the reference mirror or tilted mirror. In such a case, the object light cannot be divided, and the spectral characteristics cannot be obtained.

[0006] In response to this, a method has been proposed in which an image of the object light is first formed on a plane (conjugate image plane) optically conjugate to the object plane by a conjugate imaging optical system, and then an amplitude diffraction grating placed on this conjugate image plane imparts a spatial periodic change to the object light (Patent Document 2). The amplitude diffraction grating has rectangular light-transmitting and light-shielding parts alternately arranged in the light-focusing direction of the imaging optical system (direction perpendicular to the above-mentioned imaging straight line). For example, the light-transmitting parts are made up of openings whose length and width (length in the light-focusing direction and length along the imaging straight line) and intervals (period) are several tens to several hundreds of μm, and are also called multiple slits.

[0007] Even light from a test site with almost no texture is diffracted in a direction according to the wavelength of the light by passing through the multiple slits. Therefore, by guiding the diffracted light to a phase shifter via an objective lens, a linear interference image can be obtained, and the spectral characteristics of the light can be obtained from the change in light intensity of the interference image along the imaging line. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2012-058068 A [Patent Document 2] International Publication WO2014 / 054708 [Patent Document 3] JP 2016-142522 A Summary of the Invention [Problem to be solved by the invention]

[0009] By using multiple slits, it is possible to obtain an interferogram of light emitted from a test site regardless of the texture, but the use of multiple slits may actually reduce the clarity of the interferogram. The present inventors have repeatedly studied the relationship between the clarity of the interferogram and multiple slits and have found the design conditions for multiple slits necessary to increase the clarity of the interferogram (Patent Document 3).

[0010] Patent Document 3 describes that the clarity of the interferogram can be improved by appropriately setting the period of the light-transmitting parts of the multiple slits and the length of the light-transmitting parts in the focusing direction based on the pixel pitch of the photodetector used to detect the light intensity of the interference image and the optical magnification of the imaging optical system.

[0011] The detection sensitivity of a photodetector depends on the amount of light that reaches the photodetector, i.e., the size of the light-transmitting portion of the multiple slits. However, as described above, the length of the light-transmitting portion in the light-gathering direction is restricted by the clarity of the interferogram. Therefore, in order to increase the detection sensitivity of the photodetector, it is conceivable to increase the length in the interference direction (the direction along the imaging line). However, if the length of the light-transmitting portion in the interference direction is increased, object light traveling in various directions passes through the light-transmitting portion, which actually reduces the clarity of the interference.

[0012] An object of the present invention is to improve the detection sensitivity and interference visibility in a spectroscopic measurement device. [Means for solving the problem]

[0013] The first aspect of the spectroscopic measurement device according to the present invention, which is made to solve the above problems, is as follows: a) an integrating optical system that integrates light emitted from a measurement point on the object plane into a single parallel beam; b) a photodetector having a light receiving surface on which a plurality of pixels are arranged at predetermined intervals along a predetermined direction; c) a phase shifter that splits the parallel beam into a first beam and a second beam and provides an optical path length difference between the first beam and the second beam; d) an interference unit that causes the first light beam and the second light beam, to which an optical path length difference has been imparted by the phase shifter, to interfere on the light receiving surface to generate interference light; e) a light-shielding member having a plurality of light-transmitting portions arranged at predetermined intervals along the array direction of the pixels, the light-shielding member being disposed on the object plane or on a plane optically conjugate with the object plane with respect to the integrated optical system; f) determining the measurement point based on the intensity distribution of the interference light detected by the photodetector; The light emitted from The interferogram is obtained by Fourier transforming the interferogram. spectroscopy A processing unit for acquiring a spectrum; Equipped with The length of the light-transmitting portion of the light-shielding member in the arrangement direction and the spacing between two light-transmitting portions adjacent to each other in the arrangement direction have a predetermined relationship with the wavelength of light emitted from the measurement point, the distance from the integrated optical system to the phase shifter, the distance from the phase shifter to the light-receiving surface of the photodetector, the length of the pixels in the direction in which the pixels are arranged, and the difference in optical path length given to each of two pixels adjacent to each other in the arrangement direction.

[0014] A second aspect of the spectroscopic measurement device according to the present invention is a) an integrating optical system that integrates light emitted from a measurement point on the object plane into a single parallel beam; b) a phase shifter that splits the parallel light beam into two in a predetermined first axis direction to form a first light beam and a second light beam, and provides an optical path length difference between the first light beam and the second light beam that changes continuously along a second axis direction perpendicular to the first axis direction; c) an imaging optical system that condenses, in the first axis direction, the first light beam and the second light beam, to which an optical path length difference has been imparted by the phase shifter, on an image forming surface to form a linear interference image along the second axis direction; d) a photodetector having a light receiving surface on the image forming surface and having a plurality of pixels for detecting a light intensity distribution of the linear interference image; e) a light-shielding member having a plurality of light-transmitting portions arranged at predetermined intervals in the second axis direction, the light-shielding member being disposed on the object plane or on a plane optically conjugate with the object plane with respect to the integrated optical system; f) determining the measurement point based on the light intensity distribution of the linear interference image detected by the photodetector; The light emitted from The interferogram is obtained by Fourier transforming the interferogram. spectroscopy A processing unit for acquiring a spectrum; Equipped with When the focal length of the integrated optical system is f1, the focal length of the imaging optical system is f2, the interval between the pixels of the photodetector in the second axis direction is P, the difference in optical path length difference given to each of two pixels adjacent in the second axis direction is Δλ, a predetermined wavelength included in the wavelength range of light emitted from the measurement point is λc, and the length of the light-transmitting portion of the light-shielding member in the second axis direction and the interval between two light-transmitting portions adjacent in the second axis direction are both L, L is expressed by the following formula (1): L={(λc×f1) / (4×Δλ×f2)}×P (1) The present invention is characterized in that it is represented by the following formula:

[0015] A third aspect of the spectroscopic measurement device according to the present invention is a) an optical system for combining light emitted from multiple measurement points on an object plane into a single parallel beam; b) a photodetector having a plurality of pixels arranged on a light receiving surface; c) a phase shifter that splits the parallel light beam integrated by the integrated optical system into two in a predetermined first axis direction to form a first light beam and a second light beam, and emits the first light beam and the second light beam toward the light receiving surface while imparting an optical path length difference between the first light beam and the second light beam that changes continuously along a second axis direction perpendicular to the first axis direction, and causes the first light beam and the second light beam to be planarly incident on the light receiving surface such that at least a part of an incident area of ​​the first light beam and at least a part of an incident area of ​​the second light beam on the light receiving surface overlap; d) a light-shielding member having a plurality of light-transmitting portions arranged at predetermined intervals in the second axis direction, the light-shielding member being disposed on the object plane or on a plane optically conjugate with the object plane with respect to the integrated optical system; e) determining whether the measurement point is a light receiving surface on the basis of a light intensity distribution along the second axis direction in a region where the first light beam incidence region and the second light beam incidence region overlap with each other; The light emitted from The interferogram is obtained by Fourier transforming the interferogram. spectroscopy A processing unit for acquiring a spectrum; Equipped with When a focal length of the integrating optical system is f, a distance from the integrating optical system to the phase shifter is h1, a distance from the phase shifter to the light receiving surface is h2, an interval between the pixels in the second axis direction is P, a difference between optical path length differences given to each of two pixels adjacent in the second axis direction is Δλ, a predetermined wavelength included in the wavelength range of light emitted from the measurement point is λc, and a length in the second axis direction of the light transmitting portion of the light blocking member and an interval between two light transmitting portions adjacent in the second axis direction are both L, L is expressed by the following formula (2): L=[(λc×f) / {2×Δλ×(h1+h2)}]×P (2) The present invention is characterized in that it is represented by the following formula:

[0016] In the present invention, the integrated optical system can be composed of one objective lens (collimator lens), a condenser lens and an objective lens (collimator lens), or a condenser lens, an objective lens, and a pinhole arranged at the common focal position of both lenses. It is also possible to use a concave mirror as the integrated optical system. Furthermore, the light-shielding member only needs to be configured so that light emitted from the measurement point passes through the light-transmitting portion and does not pass through any portion other than the light-transmitting portion; for example, a plurality of openings can be formed in the light-shielding member, and these openings can be used as light-transmitting portions. The optical path length difference given to each of two pixels adjacent in the second axis direction refers to the optical path length difference between the first and second light beams forming the interference light detected by each pixel, and the difference in optical path length difference refers to the difference between the optical path length difference of the interference light detected by a pixel and the optical path length difference of the interference light detected by the adjacent pixel. In this case, the optical path length difference corresponding to each pixel may be an average value, a maximum value, or a minimum value.

[0017] In the second and third aspects of the present invention, the predetermined wavelength λc may be any wavelength included in the wavelength range of light emitted from the measurement point, and may be, for example, the central wavelength, the shortest wavelength, the longest wavelength, etc. Depending on the purpose of determining the spectral characteristics of the measurement point, for example, when the purpose is to determine the concentration or type of a certain component, the predetermined wavelength λc may be a wavelength specific to the certain component.

[0018] In the spectroscopic measurement device of the first aspect, light emitted from a measurement point is integrated into a parallel beam by an integrated optical system, and then introduced into a phase shifter, which splits the light into a first beam and a second beam. The first beam and the second beam are interfered on a light receiving surface of a photodetector by an interference section. At this time, since a predetermined optical path length difference is provided between the first beam and the second beam, an interference image of the first beam and the second beam is formed in a light collecting region on the light receiving surface. In addition, since a light-shielding member is disposed on the object plane or on a plane optically conjugate with the object plane with respect to the integrated optical system, an interference image is formed on the light-receiving surface by the light having passed through the light-transmitting portion. Therefore, the light intensity distribution of the interference image on the light-receiving surface is detected by a photodetector and processed by a processing portion to obtain an interferogram, and the spectral characteristics of the measurement point are obtained by Fourier transforming the interferogram.

[0019] In the spectroscopic measurement device of the second aspect, light emitted from a measurement point is integrated into a parallel beam by an integration optical system, and then introduced into a phase shifter, where the light is split into a first beam and a second beam. The first beam and the second beam are focused in the first axis direction by an imaging optical system, and imaged in a linear region along the second axis direction on an imaging surface. At this time, since a predetermined optical path length difference is provided between the first beam and the second beam, an interference image of the first beam and the second beam is formed in the linear region. In addition, since a light blocking member is disposed on the object plane or on a plane optically conjugate with the object plane with respect to the integrated optical system, an interference image by the light after passing through the light-transmitting portion is formed in a linear region along the second axis direction on the image forming plane. Since a plurality of pixels of a photodetector are disposed on the image forming plane, an interferogram is obtained by detecting the light intensity distribution of the interference image formed by the light that has passed through the light-transmitting portion with the photodetector and processing the detected light intensity distribution with a processing unit, and the spectral characteristic of the measurement point is obtained by Fourier transforming the interferogram.

[0020] In the spectroscopic measurement device of the third aspect, light emitted from a measurement point is integrated into a parallel beam by an integrated optical system, and then introduced into a phase shifter, where the light is split into a first beam and a second beam by the phase shifter, and the first beam and the second beam are made to be planarly incident on the light receiving surface such that at least a part of an incident area of ​​the first beam and at least a part of an incident area of ​​the second beam overlap on the light receiving surface. At this time, since a predetermined optical path difference is given between the first beam and the second beam, an interference image of the first beam and the second beam is formed in a region where the incident areas of both beams overlap (overlapping region). In addition, since a light-shielding member is disposed on the object plane or on a plane optically conjugate with the object plane with respect to the integrated optical system, an interference image is formed in the overlapping region on the light-receiving surface by the light having passed through the light-transmitting portion. Since a plurality of pixels of a photodetector are disposed on the light-receiving surface, the light intensity distribution in the overlapping region is detected by the photodetector, and an interferogram is obtained by processing the detected light intensity distribution in a processing portion, and the spectral characteristics of the measurement point are obtained by Fourier transforming the interferogram. Effect of the Invention

[0021] As described above, the spectroscopic measurement According to the device, a light-shielding member having a plurality of light-transmitting portions is disposed on an object plane or a plane optically conjugate with the object plane with respect to the integrated optical system, so that a clear interferogram can be obtained. Moreover, in the present invention, the length of the light-transmitting portions of the light-shielding member in the arrangement direction and the interval between two adjacent light-transmitting portions in the arrangement direction have a predetermined relationship with the wavelength of the light emitted from the measurement point, the distance from the integrated optical system to the phase shifter, the distance from the phase shifter to the light-receiving surface of the photodetector, the length of the pixels in the direction in which the pixels are arranged, and the difference in the optical path length difference given to each of two adjacent pixels in the arrangement direction, so that the light-shielding member can be easily designed. [Brief description of the drawings]

[0022] [Figure 1A]1 is a perspective view showing an overall configuration of a spectroscopic measurement device according to a first embodiment of the present invention. [Figure 1B] FIG. 1B is a top view of the spectroscopic measurement device shown in FIG. 1A. [Figure 1C] FIG. 1B is a side view of the spectroscopic measurement device shown in FIG. 1A. [Diagram 2] FIG. 2 is a diagram showing the photodetector as viewed from the light receiving surface side. [Diagram 3] A view of the light shielding plate from the objective lens side. [Figure 4A] This diagram shows how monochromatic light emitted from a measurement point on an object to be measured is combined into a parallel beam by the combining optical system, then split into a first beam and a second beam with an optical path length difference imparted by a phase shifter, and focused onto a linear area on the imaging plane. [Figure 4B] This diagram shows how monochromatic light emitted from different measurement points on the object to be measured is combined into a parallel beam by the combining optical system, then split into a first beam and a second beam with an optical path length difference imparted by a phase shifter, and focused onto a linear area on the image plane. [Diagram 5] 4 is a diagram showing a change in light intensity of an interference image formed on a light receiving surface. [Figure 6] FIG. 2 is a diagram showing the positional relationship between a conjugate plane, an objective lens, a phase shifter, an imaging lens, and a light receiving surface. [Figure 7] 13 is a graph showing a change in the amplitude of the light intensity of an interference image caused by increasing the length of a light-transmitting portion in the second axial direction. [Figure 8A] FIG. 13 shows the results of actual measurements of the change in intensity of the interference image of HeNe laser light when a light-shielding plate is placed on the conjugate plane, where (b) is an enlarged view of a portion of (a). [Figure 8B] FIG. 13 shows the results of an actual measurement, performed for comparison, of the change in intensity of the interference image of HeNe laser light when a light-shielding plate was placed on the conjugate plane, where (b) is an enlarged view of a portion of (a). [Figure 9A] This figure shows the results of actual measurements of the change in intensity of the interference image of white light (light source: metal halide lamp) when a light-shielding plate is placed on the conjugate plane, and (b) is a horizontal enlargement of the area enclosed in a rectangular frame in (a). [Figure 9B]FIG. 13 shows the results of actual measurements of the change in intensity of the interference image of white light (light source: metal halide lamp) when a light-shielding plate of the comparative example is placed on the conjugate plane, and (b) is a horizontal enlargement of the area enclosed in a rectangular frame in (a). [Figure 10] FIG. 4 is a diagram showing a schematic overall configuration of a spectroscopic measurement device according to a second embodiment of the present invention. [Figure 11] FIG. 4 is a view of the light shielding plate as viewed from the transmissive optical element side. [Figure 12] FIG. 3(a) to (d) are diagrams showing the configuration of a transmissive optical element, and FIG. 3(e) is a diagram showing how light that has passed through the transmissive optical element is incident on the light-receiving surface of a photodetector. [Figure 13] FIG. 2 is a diagram showing the positional relationship between an object plane, a transmissive optical element, and a light receiving surface. [Figure 14A] FIG. 11 is a schematic perspective view of a spectroscopic measurement device according to a third embodiment of the present invention. [Figure 14B] 4 is a diagram showing the positional relationship between the reflecting surface of a reference mirror and the reflecting surface of an inclined mirror; [Figure 15A] FIG. 13 is a diagram illustrating an amplitude division interference optical system that constitutes a spectroscopic measurement device according to a fourth embodiment of the present invention. [Figure 15B] FIG. 15B is a diagram showing a transmission-type equivalent optical system of the amplitude division interference optical system shown in FIG. 15A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Next, a specific embodiment of the spectroscopic measurement device according to the present invention will be described.

[0024] [First embodiment] 1A to 1C are respectively a perspective view, a top view, and a side view showing the configuration of a spectroscopic measurement device 1 of a first embodiment. This spectroscopic measurement device 1 is composed of a conjugate plane imaging optical system 100 and a transmission imaging type one-dimensional Fourier spectroscopic optical system 200 (hereinafter referred to as a "one-shot optical system 200"). The conjugate plane imaging optical system 100 forms an image of a measurement object (object plane) S on a plane optically conjugate with the object plane using a lens 11 (imaging lens, wide-angle lens, microscope objective lens, etc.) according to the field of view range and magnification, which are the observation conditions. This conjugate plane becomes the object plane of the one-shot optical system 200. A light shielding plate 13 (corresponding to the light shielding member of the present invention) is arranged on this conjugate plane.

[0025] The one-shot optical system 200 is an infinity corrected imaging optical system consisting of an objective lens (collimator lens) 15 and an imaging lens 17, in which a phase shifter 19 is disposed near the optical Fourier transform plane, and a photodetector 21 is disposed near the imaging plane of the imaging lens 17. The photodetector 21 is composed of a two-dimensional area sensor such as a CCD camera, a MOS type image sensor, an InGaAs camera, a microbolometer, or an MCT sensor, in which a plurality of pixels are two-dimensionally arranged on the imaging plane of the imaging lens 17. A detection signal from the photodetector 21 is processed by a processing unit 25.

[0026] The phase shifter 19 is composed of a first transmitting portion 191 and a second transmitting portion 192, which are transmissive optical members. The first transmitting portion 191 is made of a rectangular plate-like optical member of a constant thickness, with a light incident surface and a light exit surface parallel to each other. The second transmitting portion 192 is made of a light incident surface that is inclined with respect to the light incident surface of the first transmitting portion 191, and a light exit surface that is inclined with respect to the light incident surface of the first transmitting portion 191. light On the same plane as the exit surface light It is made of a rectangular plate-shaped optical member having an exit surface. The direction in which the first transmission portion 191 and the second transmission portion 192 are arranged (the vertical direction in FIG. 1A) corresponds to the first axis direction of the present invention, and the direction perpendicular to both the first axis direction and the optical axis of the objective lens 15 corresponds to the second axis direction of the present invention. In this embodiment, the second transmission portion 192 is configured so that the thickness at the center in the second axis direction is the same as the thickness of the first transmission portion 191, and the thickness gradually decreases from the center toward the front side in FIG. 1A and gradually increases toward the back side.

[0027] The imaging lens 17 is a plano-convex cylindrical lens. The surface of the imaging lens 17 facing the phase shifter 19 is a cylindrical convex surface that protrudes toward the phase shifter 19, and the surface facing the photodetector 21 is a flat surface that is parallel to the emission surface of the phase shifter 19.

[0028] Fig. 2 is a view of the photodetector 21 as viewed from the light receiving surface 21A side. As shown in Fig. 2, on the light receiving surface 21A of the photodetector 21, a plurality of pixels 211 are arranged at a predetermined pitch in the first axis direction and the second axis direction, respectively.

[0029] 3 is a view of the light-shielding plate 13 as viewed from the objective lens 15 side. The light-shielding plate 13 is composed of a plurality of light-transmitting portions 131 through which light (object light) emitted from the object surface can pass, and a light-shielding portion 132 which is a portion other than the light-transmitting portions 131 and through which the object light cannot pass. The light-transmitting portions 131 may be openings formed in the light-shielding plate 13, or the light-transmitting portions 131 may be formed by fitting a member such as glass having light-transmitting properties into the openings.

[0030] With the above configuration, in the spectroscopic measurement device 1 of this embodiment, light emitted from a measurement point on the object surface S is collected by the lens 11 on a conjugate plane relative to the objective lens 15, passes through the light-transmitting portion 131 of the light-shielding plate 13, and heads toward the objective lens 15. Then, the light is combined into a parallel beam by the objective lens 15, is split into two beams by the phase shifter 19, and is given a predetermined optical path length difference. Then, the light is collected by the imaging lens 17 on a linear region along the second axis direction of the light-receiving surface 21A of the photodetector 21 to form an interference image. The light intensity of the interference image formed on the light-receiving surface 21A is detected by the photodetector 21, so the processing unit 25 obtains an interferogram from the light intensity distribution of the interference image and performs a Fourier transform on the interferogram to obtain the spectrum of the measurement point.

[0031] 3, the light transmitting portions 131 are arranged at predetermined intervals in the first axis direction and the second axis direction. The present invention was made by finding conditions (design conditions) related to the length of each light transmitting portion 131 in the second axis direction and the distance between two adjacent light transmitting portions 131 for the light transmitting portions 131 arranged in a line in the second axis direction, and is characterized by the design conditions. The design conditions of the light transmitting portions 131 of the light blocking plate 13 will be described below.

[0032] 4A and 4B are optical path diagrams showing how light of a single wavelength (monochromatic light) emitted from multiple measurement points on the object plane S is collected at the conjugate plane 13C and then travels toward the objective lens (integrated optical system) 15. Note that, in reality, the light emitted from the multiple measurement points is multi-wavelength light, but for convenience of explanation, it will be described as monochromatic light. Fig. 4A is a light path diagram of a monochromatic light passing through point A where the optical axis of objective lens 15 intersects with conjugate plane 13C, and Fig. 4B is a light path diagram of a monochromatic light passing through point B separated in the second axial direction by distance L from point A. As shown in these figures, the monochromatic light is combined into a parallel light beam by objective lens 15, and then split by phase shifter 19 into two light beams having an optical path length difference, and is focused in a linear region on light receiving surface (imaging surface) 21A of photodetector 21 by imaging lens 17 (not shown in Figs. 4A and 4B).

[0033] The phase shifter 19 is disposed so that a line segment (optical path length difference=0) where the light incident surface of the first transmitting portion 191 and the light incident surface of the second transmitting portion 192 intersect coincides with the rear focal point of the objective lens 11. In other words, the phase shifter 19 is disposed on a so-called Fourier transform plane. When the wavefront of a light beam (first light beam) that is incident on the first transmitting portion 191 of the phase shifter 19 and then reaches the light receiving surface 21A is parallel to the light receiving surface 21A, the wavefront of a light beam (second light beam) that is incident on the second transmitting portion 192 and then reaches the light receiving surface 21A is inclined with respect to the light receiving surface 21A. At this time, among the first and second light beams that have reached the light receiving surface 21A, at a point (a point indicated by reference symbol 21Z in FIGS. 4A and 4B (referred to as zero point 21Z)) where the light that has traveled from point A and point B in a direction parallel to the optical axis of the objective lens 15 and entered the first transmission section 191 or the second transmission section 192 reaches the light receiving surface 21A, the phase difference between the first and second light beams is 0 (rad.), whereas in an area above the zero point 21Z, the second light beam is delayed in phase from the first light beam, and the amount of delay increases as it moves away from the zero point. On the other hand, in an area below the zero point, the second light beam is advanced in phase from the first light beam, and the amount of advance increases as it moves away from the zero point. Therefore, an interference image of the first and second light beams, whose phase difference changes continuously, is formed in a linear area on the light receiving surface 21A where the first and second light beams are condensed.

[0034] Fig. 5 shows the change in light intensity of the interference image formed on the light receiving surface 21A. In Fig. 5, the horizontal axis represents the position in the second axis direction on the object surface S, and the vertical axis represents the light intensity of the interference image. Here, the coordinate in the second axis direction on the light receiving surface 21A is defined as a phase θ (rad.) where the length of one period of the interference fringes of monochromatic light (wavelength λ) is 2π. In other words, the length (m) of one period of the interference fringes formed on the light receiving surface 21A is 2π (rad.), and the coordinate of the distance x (m) in the second axis direction from an arbitrary point on the light receiving surface 21A is θ (rad.), as defined by the following formula. θ = x / λ × 2π (3) For example, when an arbitrary position a(m) in the second axis direction on the light-receiving surface 21A has a coordinate θa (rad.), I(θa) represents the light intensity of the interference image at the coordinate θa (rad.), which is an arbitrary position a(m) in the second axis direction on the light-receiving surface 21A. Moreover, when converted into a distance on the light-receiving surface 21A, I(θa+Δθ) represents the light intensity of the interference image at a position x=Δθ / 2π×λ(m) away from the coordinate a(m).

[0035] As shown in FIG. 6, if the focal length of the objective lens 15 is f1 and the focal length of the imaging lens 17 is f2, the relationship between the distance L between points A and B on the object surface S and the distance L' between points A' and B' corresponding to points A and B on the light receiving surface 21A is expressed by the following formula (4). This ratio of L / L' is called the "conversion ratio to the conjugate surface". This is determined by various known spatial phase shift interference optical systems, but in this embodiment, it is determined by formula (4). Specifically, as shown in FIG. 4B, a light ray parallel to the principal axis between the conjugate surface 13C and the objective lens 15 passes through the rear focus of the objective lens 15. In other words, the distance L' on the light receiving surface 21A can be converted to the distance L on the conjugate surface 13C by the ratio of 2×f2 to f1. L / L'=f1 / (2×f2 ) (4)

[0036] Here, consider a case where the light shielding plate 13 is disposed on the conjugate plane 13C, and points A and B are located at both ends of the length L in the second axis direction of the light transmitting portion 131 of the light shielding plate 13. That is, points A and B are two points separated by a distance L on the conjugate plane 13C. This means that interference fringes are formed at positions shifted in the second axis direction by a distance L'=L×2×f2 / f1 on the light receiving surface 21A. In addition, since there are countless points between points A and B, monochromatic light also travels toward the objective lens 15 from these points, and interference images of these monochromatic lights are continuously formed on the light receiving surface 21A. As can be seen from FIG. 4A and FIG. 4B, the zero point Z of the interference image formed on the light receiving surface 21A according to the emission position of the monochromatic light moves according to the conversion ratio to the conjugate plane. That is, on the light receiving surface 21A, the interference images of the monochromatic light that has passed through the light transmitting portion 131 are formed with their zero points shifted little by little in the second axis direction. If the amount of deviation in this coordinate is Δθ, then the light intensity I(θa) of the interference image at position a, i.e., coordinate θa, is the integral of the graph (sine curve) of light intensity I(θ) shown in FIG. 5 from θa to θa+Δθ, and can be calculated using the following formula.

number

[0037] The above equation can be rearranged to obtain the following equation (5).

number

[0038] In formula (5), 2A×sin(Δθ / 2) represents the amplitude of the light intensity of the interference image, and A×Δθ represents the reference value (offset) of the light intensity. From formula (5), it can be seen that the amplitude of the light intensity of the interference image is maximum (2A) when the length Δθ of the light-transmitting portion 131 in the second axial direction is (2m+1)×π (m is an integer equal to or greater than 0), and is minimum (zero) when Δθ is 2n×π (n is an integer equal to or greater than 1). In other words, even if the length Δθ of the light-transmitting portion 131 in the second axial direction is increased, the amplitude of the light intensity of the interference image only changes periodically between 0 and 2A and does not exceed 2A, while the offset increases as the length Δθ of the light-transmitting portion 131 in the second axial direction increases (see FIG. 7). In other words, when the length Δθ of the light-transmitting section 131 in the second axial direction is increased, the light intensity of the interference image increases, but the amplitude of the light intensity merely fluctuates periodically between 0 and A×Δθ, and the ratio of the magnitude of the amplitude (the amount of change in light intensity) to the light intensity value of the interference image decreases, so that the clarity of the interferogram (interference clarity) actually decreases.

[0039] In contrast, when n light-transmitting sections 131, each having a length Δθ in the second axis direction, are arranged side by side at a distance Δθ in the second axis direction, n interference images are formed on light-receiving surface 21A by monochromatic light passing through each light-transmitting section 131. At this time, the light intensity of the interference images formed on light-receiving surface 21A is expressed by the following equation (6).

number

[0040] As can be seen from formula (6), when the width Δθ of light transmitting portion 131 in the second axial direction corresponds to π, the offset and the amplitude of the interference image increase according to the number of light transmitting portions 131, resulting in improved detection sensitivity and interference visibility. Therefore, when the wavelength included in the wavelength range of light emitted from the measurement point on object surface S is λc, half the length of the interference fringes that wavelength λc forms on light receiving surface 21A is set as distance L', and L obtained by the conversion ratio to the conjugate plane is set as the distance between light transmitting portions 131, and the number of light transmitting portions 131 is increased, thereby making it possible to improve the visibility and detection sensitivity of the interferogram.

[0041] If the pixel pitch of the photodetector 21 is P, and the difference between the optical path length difference imparted to a pixel by the phase shifter and the optical path length difference between that pixel and its adjacent pixel in the second axis direction is Δλ (for example, if the shortest wavelength of the wavelength band of light emitted from the measurement point is λmin, then Δλ=λmin / 4 can be determined), then the length L' on the light receiving surface 21A is expressed by the following equation (7). L'={(λc / 2) / Δλ}×P (7)

[0042] Using the above-mentioned equation (4) and equation (7) which express the relationship between distance L and distance L', and the conversion ratio to the conjugate plane determined by each optical system, the length in the second axial direction of the light-transmitting portion 131 of the light-shielding plate 13 and the distance L between adjacent light-transmitting portions 131 are expressed by the following equation (1). L=[λc / {(2×Δλ)×(2×f2 / f1)}]×P ={(λc×f1) / (4×Δλ×f2)}×P (1)

[0043] As described above, according to this embodiment, if the pixel pitch P of the photodetector 21, the difference Δλ in the optical path length difference between each of two pixels adjacent in the second axis direction, the wavelength λc included in the wavelength range emitted from the measurement point, and the focal lengths f1, f2 of the objective lens 15 and the imaging lens 17 are known, the length L in the second axis direction of each light-transmitting portion 131 of the light-shielding plate 13 and the spacing L in the second axis direction of the light-transmitting portions 131 can be designed based on these values, thereby improving the clarity of the interferogram. It is preferable that "L" is a value that satisfies the above formula (1). However, if setting "L" to the value obtained from formula (1) results in a small amount of light passing through the light-transmitting portion, "L" may be set to an odd-numbered value of the value obtained from formula (1). In addition, since the interval L is designed to match the single wavelength λc of interest, the interference visibility of the wavelength λc is improved most efficiently. In the case of spectroscopy, since light of multiple wavelengths is handled simultaneously, there are cases where it is desired to simultaneously improve the interference visibility of wavelengths other than the wavelength λc. In such cases, the light shielding plate 1 of 3 The wavelengths λc1 and λc2 to be focused on may be set differently for each different horizontal row of the coordinate in the first axis direction (see FIG. 3).

[0044] (Example) The intensity change of the interference image obtained when a light-shielding plate 13 having one to three light-transmitting portions (apertures) 131 designed to satisfy the above-mentioned formula (1) (specifically, a light-shielding plate 13 in which the distance L in the second axis direction of the light-transmitting portions 131 and the interval L are both 15.57 μm) is placed on the conjugate plane 13C of the above-mentioned spectroscopic measurement device was measured. This is because the focal lengths f1 and f2 are equal, the conversion ratio to the conjugate plane is 1 / 2, and the length of the interference fringes formed on the light-receiving surface 21A is 62.28 μm. , the inclination of the phase shifter in the interference optical system, etc. This is the case when the objective lens 15 is designed to have a wavelength of 633 nm. The results are shown in Figures 8A and 9A. Figure 8A shows the measurement results when monochromatic light (wavelength = 633 nm) emitted from a HeNe laser is incident on the objective lens 15, and Figure 9A shows the measurement results when white light emitted from a metal halide lamp is incident on the objective lens 15. Also, (b) of Figures 8A and 9A is an enlargement in the horizontal direction of the part enclosed by a rectangular frame in (a).

[0045] On the other hand, Fig. 8B and Fig. 9B are the results of an experiment conducted for comparison. In the comparative experiment, when a light-shielding plate having one light-transmitting portion with a distance L of 15.57 μm was placed at a predetermined position on the conjugate plane 13C, and when the light-shielding plate was placed at a position shifted from the predetermined position by 15.57 μm in the second axis direction, the intensity change of each interference image was measured. Fig. 8B shows the measurement result when monochromatic light (wavelength = 633 nm) emitted from a HeNe laser was incident on the objective lens 15, and Fig. 9B shows the measurement result when white light emitted from a metal halide lamp was incident on the objective lens 15. Moreover, Fig. 8B and Fig. 9B (b) are the enlarged views of the part surrounded by a rectangular frame in Fig. 8B (a) in the horizontal direction. Moreover, Fig. 8B (c) shows the sum of the intensity changes of the two interference images shown in Fig. 8B (a).

[0046] 8A and 9A show that the intensity changes of the interference light are all in phase when the number of light transmitting parts is 1 to 3. In addition, it was confirmed that the intensity and amplitude of the interference light when the number of light transmitting parts is 1 and when the number of light transmitting parts is 2 and 3 increases with the number of light transmitting parts, that is, the clarity of the interferogram improves.

[0047] In contrast, in Figures 8B and 9B, it can be seen that the intensity change of the interference light when the light-transmitting portion is located at a position shifted by 15.57 μm in the second axis direction is shifted in phase by π. The intensity change of the interference light when the length L of the light-transmitting portion in the second axis direction is 31.14 μm (= 15.57 μm × 2) is the sum of the intensity change indicated by the symbol (1) and the intensity change indicated by the symbol (2), which cancel each other out, and therefore has a smaller amplitude. This is also clear from (c) of Figure 8B.

[0048] [Second embodiment] 10 shows a schematic configuration of a spectroscopic measurement device of the second embodiment. The spectroscopic measurement device 1A includes a transmissive optical element 110, a photodetector 120 having a light receiving surface 121, and a processing unit 130 for processing a detection signal of the photodetector 120. The photodetector 120 is composed of a two-dimensional area sensor such as a CCD camera in which a plurality of pixels are arranged two-dimensionally. The transmissive optical element 110 has a light incident surface 111 and a light exit surface 112 on the back side thereof, and is disposed between the object surface S and the light receiving surface 121 such that the light incident surface 111 faces the side of the measurement target (object surface) S and the light exit surface 112 faces the light receiving surface 121 side of the photodetector 120. In this spectroscopic measurement device 1A, a light shielding plate 13A is disposed on the object surface S.

[0049] 11 shows the light shielding plate 13A as viewed from the transmissive optical element 110 side. As with the light shielding plate 13 of the first embodiment, the light shielding plate 13A is composed of a plurality of light-transmitting portions 131A through which light (object light) emitted from an object surface can pass, and a light shielding portion 132A, which is a portion other than the light-transmitting portions 131A and through which the object light cannot pass. The light-transmitting portions 131A are arranged in a matrix shape along the first axis direction and the second axis direction on the light shielding plate 13A. The light-transmitting portions 131A may be openings formed in the light shielding plate 13A, and the light-transmitting portions 131A may be formed by fitting a member such as glass having light-transmitting properties into the openings.

[0050] Fig. 12(a) is a view of the transmissive optical element 110 from the light exit surface 112 side, Fig. 12(b) is a cross-sectional view taken along line b-b' in Fig. 12(a), Fig. 12(c) is a cross-sectional view taken along line c-c' in Fig. 12(a) seen from the top of the paper, Fig. 12(d) is a cross-sectional view taken along line d-d' in Fig. 12(a) seen from the bottom of the paper, and Fig. 12(e) is a diagram showing how light exiting from the light exit surface 112 of the transmissive optical element 110 enters the light receiving surface 121. Here, the top, bottom, left, and right in Fig. 12(a) are taken to be the top, bottom, left, and right of the transmissive optical element 110.

[0051] 12(a) to 12(d), the transmissive optical element 110 is made of a circular optical element when viewed from the light incident surface 111 side (or the light exit surface 112 side), and the light incident surface 111 is configured to be substantially spherical and convex outward. On the other hand, the light exit surface 112 is made up of a first light exit surface 112A and a second light exit surface 112B that are planar and arranged side by side, and each of them is inclined downward and upward from a center line CL at the center of the light exit surface 112 in the vertical direction toward the light incident surface 111 side.

[0052] Also, while the first light emitting surface 112A is not inclined in the c-c' direction (i.e., left-right direction) in Fig. 12(a), the second light emitting surface 112B is inclined by an angle θ toward the light incident surface 111 from the symbol c to the symbol c' in Fig. 12(a). In other words, the second light emitting surface 112B is inclined toward the light incident surface 111 from the center line CL upward, and is also inclined toward the light incident surface 111 from the right side to the left side. For this reason, the first light emitting surface 112A and the second light emitting surface 112B are not configured symmetrically with respect to the center line CL.

[0053] With the above configuration, in the spectroscopic measurement device 1A of this embodiment, when a group of light rays (object light) such as scattered light and fluorescent light is generated from a measurement point SP located at a focal point of the transmissive optical element 110 by irradiating light from the light source 140 to the object surface S, the light passes through the light transmitting portion 131A of the light shielding plate 13A and then travels toward the transmissive optical element 110. Then, the object light incident on the light incident surface 111 of the transmissive optical element 110 becomes a parallel light beam (hereinafter referred to as "object light beam") and travels toward the light exit surface 112 of the transmissive optical element 110. In addition, when the object light is refracted and emitted from each of the first light exit surface 112A and the second light exit surface 112B, it is split into a first light beam and a second light beam, and each light beam is incident on the light receiving surface 121 of the photodetector 120. At this time, the traveling directions of the first and second light beams are determined according to the inclination angles of the first and second light exit surfaces 112A and 112B, the wavelength of the object light beam, and the refractive index difference between the transmissive optical element 110 and the outside (air).

[0054] Therefore, by appropriately selecting the material of the transmissive optical element 110, the angle φ (see FIG. 12(b)) between the first light emitting surface 112A and the second light emitting surface 112B, the distance h from the transmissive optical element 110 to the light receiving surface 121 of the photodetector 120, and the like, the first and second light beams emitted from the first and second light emitting surfaces 112A and 112B, respectively, can be made to enter the light receiving surface 121 so as to overlap with each other at least partially. In addition, since the second light emitting surface 112B is inclined at an angle θ (see FIG. 12(d)) with respect to the first light emitting surface 112A, an optical path length difference occurs between the first and second light beams, and an interference image of the first and second light beams is formed in the region where the first and second light beams overlap on the light receiving surface 121. Therefore, by detecting the light intensity distribution of this interference image with the photodetector 120, an interferogram of the measurement point SP can be obtained, and by Fourier transforming this interferogram in the processing unit 130, the spectroscopic characteristics of the measurement point SP can be obtained.

[0055] In this embodiment, the portion of the transmissive optical element 110 from the light incident surface 111 to the light exit surface 112 functions as an integrated optical system, and the light exit surface 112 functions as a phase shifter. When the first light beam and the second light beam are incident on the light receiving surface 121 in an overlapping manner, the inclination angle of the second light exit surface 112B with respect to the first light exit surface 112A can be designed based on optical conditions such as the measurement wavelength range and the wavelength resolution.

[0056] As shown in FIG. 13, if the distance from the transmissive optical element 110 to the object surface S (corresponding to the focal length of the integrated optical system) is f and the distance from the transmissive optical element 110 to the light receiving surface 121 of the photodetector 120 is h, then the conversion ratio to the conjugate surface, which is the relationship between the distance L between points A and B on the object surface S and the distance L' between points A' and B' corresponding to points A and B on the light receiving surface 121, is given by the following equation (8). L / L'=f / h (8)

[0057] The relationship between the pixel pitch P of the photodetector 120, the difference Δλ in the optical path length difference between two pixels adjacent in the second axis direction, and the length L' on the light receiving surface 121 is expressed by the following equation (7), as in the spectroscopic measurement device of the first embodiment. L'={(λc / 2) / Δλ}×P (7)

[0058] Therefore, from equations (7) and (8), in the spectroscopic measurement device 1A of the second embodiment, L can be calculated from the following equation (2). L={(λc×f) / (2×Δλ×h)}×P (2)

[0059] The distance h from the transmissive optical element 110 to the light receiving surface 121 of the photodetector 120 corresponds to the sum (h1+h2) of the distance h1 from the integrated optical system to the phase shifter and the distance h2 from the phase shifter to the light receiving surface of the photodetector in the present invention. In this embodiment, the transmissive optical element 110 has a configuration in which the integrated optical system and the phase shifter are integrated, and the distance from the integrated optical system to the phase shifter is "0". Therefore, the sum is equivalent to the distance from the transmissive optical element 110 to the light receiving surface 121, that is, the distance from the phase shifter to the light receiving surface. In this embodiment, the aperture width is determined in the same manner not only in the second axis direction but also in the first axis direction. The same value is used for the wavelength λc in the first axis direction and the second axis direction, but the difference Δλ between the optical path length differences of two pixels adjacent in the second axis direction is different, so the aperture width in the first axis direction and the aperture width in the second axis direction have different values.

[0060] [Third embodiment] 14A is a perspective view showing a spectroscopic measurement device 300 of the third embodiment. The spectroscopic measurement device 300 includes an objective lens (collimator lens) 310, a phase shifter 320 having a reference mirror 321 and an inclined mirror 322, an imaging lens (cylindrical lens) 330, a photodetector 340 having a light receiving surface at a position that is the imaging surface of the imaging lens 330, and a processing unit (not shown) that processes a detection signal of the photodetector 340. The photodetector 340 is composed of a two-dimensional area sensor such as a CCD camera in which a plurality of pixels are arranged two-dimensionally. Both the reference mirror 321 and the inclined mirror 322 have a planar reflection surface. In the spectroscopic measurement device 300, a light shielding plate 313 is arranged on the object surface S. The light shielding plate 313 has the same structure as the light shielding plate 13 of the first embodiment.

[0061] In the above-mentioned spectroscopic measurement device 300, when a light beam (object light) such as scattered light or fluorescent light is emitted from a measurement point on the object surface S by irradiating light from a light source (not shown), the object light passes through a light transmitting portion 314 of a light shielding plate 313 and then travels toward an objective lens 310. The object light incident on the objective lens 310 is integrated into one parallel light beam (object light beam) by passing through the objective lens 310, and is then introduced from an oblique direction to each of the reflecting surfaces of a reference mirror 321 and an inclined mirror 322 of a phase shifter 320. The object light beam introduced into each of the reflecting surfaces of the reference mirror 321 and the inclined mirror 322 is reflected at an angle (reflection angle) that is the same as the angle of incidence, and then travels toward an imaging lens 330.

[0062] FIG. 14B shows the positional relationship between the reflecting surface of the reference mirror 321 and the reflecting surface of the inclined mirror 322. In FIG. 14B, the orthogonal coordinate axes defining the reflecting surface of the reference mirror 321 are defined as the x-axis and the y-axis, and the axis perpendicular to the x-axis and the y-axis is defined as the z-axis. In this embodiment, the objective lens 310 and the reference mirror 321 are arranged so that the optical axis (incident axis) of the object light incident on the reflecting surface of the reference mirror 321 is parallel to the yz plane. In addition, the inclined mirror 322 is installed so that the reflecting surface of the reference mirror 321 is parallel to the reflecting surface of the inclined mirror 322 when the reference mirror 321 is rotated around the x-axis by a predetermined angle θx with respect to the x-axis defined as above. As a result, the reflecting surface of the inclined mirror 322 is inclined in the y-axis direction with respect to the reflecting surface of the reference mirror 321, and the optical incident angle of the object light beam with respect to each reflecting surface is different. Therefore, the direction of travel of the light reflected by the inclined mirror 322 (the inclined reflected light) is shifted by a predetermined angle in the y-axis direction relative to the direction of travel of the light reflected by the reference mirror 321 (the reference reflected light), and this shift angle results in a continuous optical path length difference between the reference reflected light and the inclined reflected light.

[0063] Therefore, the reference reflected light and the oblique reflected light that are incident on the imaging lens 330 and pass through the imaging lens 330 are focused on the light receiving surface of the photodetector 340 to form a linear interference image. The photodetector 340 measures the change in light intensity along the linear interference image to obtain an interferogram of the light emitted from the measurement point on the object surface S, and the spectroscopic characteristics can be obtained by Fourier transforming this interferogram.

[0064] The spectroscopic measurement device 300 and the spectroscopic measurement device 1 of the first embodiment differ in that the phase shifter is composed of a transmissive optical element or a reflective optical element, but the configurations of the imaging optical system that images two light beams to which an optical path length difference has been imparted on the light receiving surface of the photodetector, and the photodetector are almost the same. Therefore, in this embodiment, too, the light shielding plate 313 can be designed in the same manner as in the first embodiment, and by arranging such a light shielding plate 313 on the object plane S, the clarity of the interferogram can be improved.

[0065] [Fourth embodiment] There are various configurations of spatial phase shift interference optical systems, and the conversion ratio to the conjugate plane is determined according to the configuration of each optical system. Up to the third embodiment, an example of a wavefront division type interference optical system that divides the wavefront of the object light integrated into a parallel light beam by an integrated optical system (objective lens) into two, has been shown, but there is also a Michelson interferometer shown in Fig. 15A. The Michelson interferometer is one of the most orthodox interference optical systems, and is an amplitude division type interference optical system that converts a light beam generated from an object surface S into a parallel light beam by an objective lens 410 and then divides the parallel light beam into two by a half mirror 420 in terms of light amount.

[0066] The parallel light beam split into two by the half mirror 420 is incident on two mirrors 430 and 440. By tilting one of the mirrors 430 and 440, an interference fringe is formed on the imaging plane due to spatial phase shift interference. Since a plurality of pixels (not shown) of the light receiving device 450 are arranged on the imaging plane, the interference fringe can be observed from the detection result of the light receiving device 450. In FIG. 15A, the optical path length difference is 0 at a point on the imaging plane where the distance indicated by the symbol M0 and the distance indicated by the symbol M1 are the same. The intensity distribution of the interference fringe is an interferogram, and the spectral characteristics can be obtained by Fourier transforming the interferogram.

[0067] In this embodiment, a phase shifter is composed of the half mirror 420 and the mirrors 430 and 440. The half mirror 420 also functions as an interference section.

[0068] In the interference optical system having the above configuration, the interference visibility can be improved by arranging the light shielding plate 413 on the object surface S or on a surface conjugate with the object surface S with respect to the objective lens 410. FIG. 15A shows an example in which the light shielding plate 413 is arranged on the object surface S. In order to make it easier to understand the conversion ratio to the conjugate surface in the optical system of FIG. 15A, FIG. 15B shows a transmission type equivalent optical system. As shown in FIG. 15B, in the case of an optical system in which the distance from the objective lens 410 to the object surface S (i.e., the focal length of the objective lens 410) is equal to the distance M0 and the distance M1, the conversion ratio to the conjugate surface is expressed by the following formula (9). L / L'=M0 / M1 (9) [Explanation of symbols]

[0069] 1, 1A, 300...Spectrometer 100...Conjugate plane imaging optical system 21, 120, 340...Photodetector 21A, 121... Light receiving surface 211…pixels 13, 13A, 313, 413...light shielding plate 131, 131A, 314...Transparent part 132, 132A…shading part 15, 310…Objective lens 17...Imaging lens 19, 320...Phase shifter 191...1st transmission section 192…Second transparent section 110...Transmissive optical element 130... Processing section 13C…conjugate plane S…Object surface

Claims

1. a) an integrating optical system that integrates light emitted from a measurement point on the object plane into a single parallel beam; b) a phase shifter that splits the parallel light beam into two in a predetermined first axis direction to form a first light beam and a second light beam, and imparts an optical path length difference between the first light beam and the second light beam that changes continuously along a second axis direction perpendicular to the first axis direction; c) an imaging optical system that condenses, on an image plane, the first light beam and the second light beam, to which an optical path length difference has been imparted by the phase shifter, in the first axis direction to form a linear interference image along the second axis direction; d) a photodetector having a light receiving surface on the image forming surface and having a plurality of pixels for detecting a light intensity distribution of the linear interference image; e) a light-shielding member having a plurality of light-transmitting portions arranged at predetermined intervals in the second axis direction, the light-shielding member being disposed on the object surface or on a surface optically conjugate with the object surface with respect to the integrated optical system; f) a processing unit that obtains an interferogram of light emitted from the measurement point based on the light intensity distribution of the linear interference image detected by the photodetector, and obtains a spectrum by subjecting the interferogram to Fourier transformation; Equipped with When the focal length of the integrated optical system is f1, the focal length of the imaging optical system is f2, the interval between the pixels of the photodetector in the second axial direction is P, the difference between the optical path length differences given to each of two pixels adjacent in the second axial direction is Δλ, the predetermined wavelength included in the wavelength range of the light emitted from the measurement point is λc, and both the length in the second axial direction of the light transmitting portion of the light blocking member and the interval between the two light transmitting portions adjacent in the second axial direction are L, L is expressed by the following formula (1): L={(λc×f1) / (4×Δλ×f2)}×P...(1) A spectroscopic measuring device characterized by being represented by the formula:

2. a) an optical system for combining light emitted from multiple measurement points on an object plane into a single parallel beam; b) a photodetector having a plurality of pixels arranged on a light receiving surface; c) a phase shifter that splits the parallel light beam integrated by the integrated optical system into two in a predetermined first axial direction to form a first light beam and a second light beam, and emits the first light beam and the second light beam toward the light receiving surface while imparting an optical path length difference between the first light beam and the second light beam that changes continuously along a second axial direction perpendicular to the first axial direction, and causes the first light beam and the second light beam to be planarly incident on the light receiving surface such that at least a portion of an incident area of ​​the first light beam and at least a portion of an incident area of ​​the second light beam on the light receiving surface overlap; d) a light-shielding member having a plurality of light-transmitting portions arranged at predetermined intervals in the second axis direction, the light-shielding member being disposed on the object plane or on a plane optically conjugate with the object plane with respect to the integrated optical system; e) a processing unit that obtains an interferogram of light emitted from the measurement point based on a light intensity distribution along the second axis direction in a region on the light receiving surface where an incident region of the first light flux and an incident region of the second light flux overlap, and obtains a spectrum by performing a Fourier transform on the interferogram. Equipped with When a focal length of the integrated optical system is f, a distance from the integrated optical system to the phase shifter is h1, a distance from the phase shifter to the light receiving surface is h2, an interval between the pixels in the second axis direction is P, a difference between optical path length differences given to each of two pixels adjacent in the second axis direction is Δλ, a predetermined wavelength included in the wavelength range of light emitted from the measurement point is λc, and a length in the second axis direction of the light transmitting portion of the light blocking member and an interval between two light transmitting portions adjacent in the second axis direction are both L, L is expressed by the following formula (2): L=[(λc×f) / {2×Δλ×(h1+h2)}]×P... (2) A spectroscopic measuring device characterized by being represented by the formula:

3. 3. The spectroscopic measurement device according to claim 1, A spectroscopic measurement device, wherein the integrated optical system comprises a collimator lens.

4. 2. The spectroscopic measurement device according to claim 1, a second transmitting portion arranged in parallel with the first transmitting portion in the first axial direction and having a planar light introducing surface and a planar light extracting surface, and one of the light introducing surface and the light extracting surface of the first transmitting portion is inclined with respect to the light introducing surface or the light extracting surface of the second transmitting portion corresponding to the one surface.

5. 2. The spectroscopic measurement device according to claim 1, A spectroscopic measurement device, wherein the phase shifter comprises a first mirror having a planar light reflecting surface, and a second mirror arranged alongside the first mirror in the first axial direction and having a planar light reflecting surface, the light reflecting surface of the second mirror being inclined with respect to the light reflecting surface of the first mirror.

6. 3. The spectroscopic measurement device according to claim 2, the phase shifter includes a first transmission portion having a planar light introduction surface and a planar light output surface, and a second transmission portion having a planar light introduction surface and a planar light output surface, A spectroscopic measurement device configured such that the optical axis of a second light beam emitted from the light output surface of the second transmissive portion is inclined relative to the optical axis of a first light beam emitted from the light output surface of the first transmissive portion.

7. 3. The spectroscopic measurement device according to claim 2, the phase shifter has a planar first reflecting surface and a planar second reflecting surface arranged side by side such that the parallel light beam is incident on the first reflecting surface from an oblique direction, A spectroscopic measurement device characterized in that the first reflecting surface and the second reflecting surface are configured so that the angle of incidence of the parallel light beam to the first reflecting surface and the angle of incidence of the parallel light beam to the second reflecting surface, and the light incidence surface of the parallel light beam to the first reflecting surface and the light incidence surface of the parallel light beam to the second reflecting surface are all different.

Images