Thickness measuring device and thickness measuring method

Abstract

The present invention provides a thickness measuring device and a thickness measuring method capable of accurately measuring the thickness of a sample. The thickness measuring device comprises: a first light-transmitting member having a first reference surface; a second light-transmitting member disposed opposite to the first light-transmitting member and having a second reference surface; a first light-emitting unit irradiating a sample disposed between the first light-transmitting member and the second light-transmitting member with light from a light source via the first reference surface; a first light-receiving unit receiving reflected light from the first reference surface and receiving reflected light from the sample via the first reference surface; a second light-emitting unit irradiating the sample with light from the light source via the second reference surface; a second light-receiving unit receiving reflected light from the second reference surface and receiving reflected light from the sample via the second reference surface; and a spectrometer that spectrometers the reflected light received by the first light-receiving unit and the reflected light received by the second light-receiving unit.

Description

[0001] This application is a divisional application of a Chinese patent application filed on January 23, 2017, with application number "201710058139.5" and invention name "Thickness Measuring Device and Thickness Measuring Method". Technical Field

[0002] The present invention relates to a thickness measuring device and a thickness measuring method, and in particular to a thickness measuring device and a thickness measuring method for measuring the thickness of a sample by using reflected light. Background Art

[0003] In recent years, displacement measuring devices that use light to measure distance have been developed. For example, the following structure is disclosed in Japanese Patent Gazette No. 2009-270939 (Patent Document 1). That is, the optical displacement meter includes: a wide-band light source device, which is used to generate wide-band light as detection light for measurement; a focusing lens, which is used to focus the above detection light, and the emission side end face emitted to the measured object is a plane; a spectrometer, which separates the reflected light reflected by the above measurement object and the reflected light reflected by the above emission side end face incident on the above focusing lens, and finds the frequency of the wavelength distribution characteristic curve, thereby calculating the distance between the above measurement object and the above emission side end face. The above focusing lens is a lens that emits the above detection light whose irradiation point becomes wider as it moves away from the above emission side end face.

[0004] In addition, the following structure is disclosed in Japanese Patent Publication No. 2014-115242 (Patent Document 2). That is, the displacement measuring device includes: a point light source for emitting light having a diffused spectrum; an optical element for causing the light to produce axial chromatic aberration and focusing the light having the axial chromatic aberration on a measurement object; an opening for allowing the light focused on the measurement object among the light focused by the optical element to pass; and a measuring unit for obtaining the spectrum of the light passing through the opening and obtaining the distance between the optical element and the measurement object based on the peak wavelength of the spectrum. The measuring unit obtains the spectral reflection characteristics of the measurement object and uses the obtained spectral reflection characteristics to reduce the error caused by the spectral reflection characteristics in distance measurement and obtain the distance.

[0005] In addition, Japanese Patent Application Laid-Open No. 2010-121977 (Patent Document 3) discloses the following structure. That is, an optical displacement meter includes: a detection light generating unit for generating detection light; a reference plane that reflects a part of the detection light and allows another part of the detection light to pass toward the inspection object; a spectroscopic unit that spectroscopically separates interference light, the interference light being composed of reflected light reflected by the reference plane and reflected light reflected by the inspection object; a light intensity distribution generating unit that receives the spectroscopically separated interference light and generates a light intensity distribution related to the wave number of the interference light; a light intensity maximum point extracting unit that converts the light intensity distribution related to the wave number into a light intensity distribution related to the light intensity spatial frequency for the wave number, and repeatedly extracts the maximum point of the light intensity distribution related to the spatial frequency at a predetermined time interval; a phase determining unit that determines the phase of a frequency component corresponding to the spatial frequency of the maximum point of the light intensity distribution related to the wave number; and a displacement amount judging unit that judges the displacement amount of the inspection object based on the phase. The phase determination unit includes: a relative phase determination unit that determines the relative phase of the frequency component within a range of 360 degrees; an absolute phase calculation unit that combines the relative phase based on the determination result of the relative phase determination unit and the past determination result, and calculates the absolute phase; a phase reference update unit that updates the reference point of the absolute phase based on a reset instruction. The displacement determination unit determines the displacement based on the absolute phase.

[0006] Patent Document 1: Japanese Patent Application Publication No. 2009-270939

[0007] Patent Document 2: Japanese Patent Application Publication No. 2014-115242

[0008] Patent Document 3: Japanese Patent Application Publication No. 2010-121977

[0009] When the techniques described in Patent Documents 1 to 3 are used to measure the thickness of a sample, for example, a method of measuring the thickness of the sample based on the measurement results of the distance from the grounded sample and the distance from the grounded surface can be considered.

[0010] However, when the sample surface is uneven or the sample is deformed or bent, a gap will be generated between the contact surface side surface and the contact surface of the sample. In this case, it will be difficult to accurately measure the thickness of the sample. Summary of the invention

[0011] The present invention is proposed to solve the above problems, and its purpose is to provide a thickness measuring device and a thickness measuring method which can accurately measure the thickness of a sample.

[0012] Technical solutions to the problem

[0013] (1) To solve the above problems, a thickness measuring device according to one aspect of the present invention includes:

[0014] a first light-transmitting member having a first reference surface;

[0015] A second light-transmitting member, disposed opposite to the first light-transmitting member and having a second reference surface;

[0016] a first light projecting unit configured to irradiate light from a light source to a sample disposed between the first light-transmitting member and the second light-transmitting member via the first reference surface;

[0017] a first light receiving unit for receiving the reflected light from the first reference surface and receiving the reflected light from the sample via the first reference surface;

[0018] a second light projecting unit configured to irradiate light from a light source onto the sample via the second reference surface;

[0019] a second light receiving part, which receives the reflected light from the second reference surface, and receives the reflected light from the sample via the second reference surface;

[0020] A spectrometer is configured to split the reflected light received by the first light receiving unit and the reflected light received by the second light receiving unit.

[0021] In this way, by irradiating light to both sides of the sample through each reference surface, and making the reflected light from the two sides of the sample interfere with the reflected light from the corresponding reference surface and perform spectroscopic analysis, even if the sample surface is concave and convex or the sample is deformed or bent, the distance between the surfaces on both sides of the sample and the corresponding reference surface can be calculated based on the spectroscopic results. And, for example, the sample thickness can be accurately calculated based on the calculated distances and the distances between the reference surfaces. Thus, the sample thickness can be accurately measured.

[0022] (2) Preferably, the light splitting section includes a spectrometer, and the thickness measuring device further includes an optical system for guiding the light received by the first light receiving section and the light received by the second light receiving section to the spectrometer.

[0023] By adopting such an optical system structure, the number of expensive spectrometers can be reduced, thereby reducing the manufacturing cost of the thickness measurement device.

[0024] (3) Preferably, the axis of the light beam irradiated from the first light projecting part to the sample via the first reference surface, the axis of the light beam irradiated from the second light projecting part to the sample via the second reference surface, the axis of the light beam reflected from the first reference surface and the axis of the light beam reflected from the sample received by the first light receiving part, and the axis of the light beam reflected from the second reference surface and the axis of the light beam reflected from the sample received by the second light receiving part are along each other.

[0025] According to this configuration, even when the reference surfaces are arranged non-parallel or the sample is not arranged parallel to the reference surface, the thickness of the sample can be accurately measured.

[0026] (4) Preferably, the spectroscopic unit includes a spectroscope; the thickness measuring device further includes an optical system for guiding the light received by the first light receiving unit and the light received by the second light receiving unit to the spectroscope. The optical distance of the path of the reflected light propagating from the sample via the first reference surface, the first light receiving unit, and the optical system to the spectroscope is set to be the same as the optical distance of the path of the reflected light propagating from the sample via the second reference surface, the second light receiving unit, and the optical system to the spectroscope.

[0027] According to such a structure, since the time required for the light reflected from the surfaces on both sides of the sample to reach the spectrometer can be almost the same, the reflected light reflected from each surface at almost the same timing can be split by the spectrometer. Thus, even if the sample moves, the sample thickness can be accurately measured using a simple structure.

[0028] (5) Preferably, the thickness measuring device further comprises a calculation unit, which calculates the distance between the first reference plane and the sample, i.e., the first distance, and the distance between the second reference plane and the sample, i.e., the second distance, based on the spectral result of the spectroscopic unit, and the calculation unit calculates the thickness of the sample by subtracting the first distance and the second distance from the distance between the first reference plane and the second reference plane.

[0029] In this way, by calculating the sample thickness based on the measurement results related to the sample external space, that is, each distance, the sample thickness can be calculated even if the sample is an opaque material. In addition, the sample thickness can be easily calculated without identifying the physical properties of the sample such as the refractive index.

[0030] (6) To solve the above problems, a thickness measurement method according to one aspect of the present invention is a thickness measurement method using a thickness measurement device, wherein the thickness measurement device comprises:

[0031] a first light-transmitting member having a first reference surface,

[0032] A second light-transmitting member is disposed opposite to the first light-transmitting member and has a second reference surface.

[0033] a first light projecting unit configured to irradiate light from a light source to a sample disposed between the first light-transmitting member and the second light-transmitting member via the first reference surface;

[0034] a first light receiving unit that receives the reflected light from the first reference surface and receives the reflected light from the sample via the first reference surface,

[0035] a second light projecting unit configured to irradiate light from a light source onto the sample via the second reference surface;

[0036] a second light receiving unit that receives the reflected light from the second reference surface and receives the reflected light from the sample via the second reference surface,

[0037] a spectrometer for splitting the reflected light received by the first light receiving unit and the reflected light received by the second light receiving unit,

[0038] The thickness measurement method comprises:

[0039] a step of calculating a first distance between the first reference surface and the sample and a second distance between the second reference surface and the sample based on the spectroscopic result of the spectroscopic unit,

[0040] A step of calculating the thickness of the sample by subtracting the first distance and the second distance from the distance between the first reference surface and the second reference surface, that is, the inter-surface distance.

[0041] In this way, by irradiating light to both sides of the sample through each reference surface, and making the reflected light from the two side surfaces of the sample interfere with the reflected light from the corresponding reference surface and perform spectroscopic structure, even if there are bumps on the sample surface or the sample is deformed or bent, the distance between the surface on both sides of the sample and the corresponding reference surface can be calculated based on the spectroscopic results. And, the sample thickness can be accurately calculated based on the calculated distances and the distances between the reference surfaces. Thus, the sample thickness can be accurately calculated. In addition, the thickness of the sample is calculated based on the measurement results of the external space of the sample, that is, each distance, so that even if the sample is an opaque material, the thickness of the sample can be calculated. In addition, the thickness of the sample can be easily calculated without identifying the physical properties of the sample such as the refractive index.

[0042] (7) Preferably, in a state where the sample is not provided, light from a light source is irradiated from the first light projecting unit to the second reference surface via the first reference surface, reflected light from the first reference surface is received by the first light receiving unit, and reflected light from the second reference surface is received by the first light receiving unit via the first reference surface, and the thickness measurement method further includes: in a state where the sample is not provided, a step of calculating the distance between the surfaces based on a spectroscopic result of the spectroscopic unit spectroscopically analyzing the reflected light received by the first light receiving unit.

[0043] According to this structure, the surface distance can be calculated using the same method as the method for calculating the first distance and the second distance, so the surface distance can be calculated with the same degree of high calculation accuracy as the calculation accuracy of the first distance and the second distance. Thus, for example, the sample thickness can be calculated more accurately than when the surface distance is calculated using other methods with poor accuracy.

[0044] According to the present invention, the thickness of a sample can be accurately measured. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a diagram showing the structure of a thickness measuring device according to an embodiment of the present invention.

[0046] Figure 2 This is a diagram showing an enlarged view of the periphery of a probe of the thickness measuring device according to the embodiment of the present invention.

[0047] Figure 3 This is a diagram for explaining the function of a fiber junction of the thickness measuring device according to the embodiment of the present invention.

[0048] Figure 4 This is a diagram showing an example of a power spectrum generated in the calculation unit of the thickness measurement device according to the embodiment of the present invention.

[0049] Figure 5 This is a diagram showing an example of a power spectrum generated in the calculation unit of the thickness measurement device according to the embodiment of the present invention.

[0050] Figure 6 This is a flowchart defining an example of the procedure of a measurement method using the thickness measurement device according to the embodiment of the present invention.

[0051] Figure 7 It is a diagram showing a comparative example of a probe.

[0052] Description of Reference Numerals

[0053] 1.2 Probe 3 Spectrometer

[0054] 4 Light source 5 Optical system

[0055] 6 Operation unit 31, 32, 33, 34 Optical fiber

[0056] 35 optical fiber connector 36 joint

[0057] 41 optical splitter 42 data generating unit

[0058] 51, 52 lens system 55, 56, 57, 58 lens

[0059] 61, 62 transparent substrate 65, 66, 67, 68 surface

[0060] 70 Reference axis 71, 72 Projection beam

[0061] 73, 74, 75, 76 reflected beam 77, 78 end face

[0062] 81, 82 surface 91 probe

[0063] 92 working table 93 specimen

[0064] 94 surface 101 thickness measuring device

[0065] 151 samples DETAILED DESCRIPTION

[0066] Hereinafter, the embodiments of the present invention will be described with reference to the accompanying drawings. In addition, the same or equivalent parts in the accompanying drawings are denoted by the same reference numerals and their repeated description is omitted. In addition, at least a part of the embodiments described below may be arbitrarily combined.

[0067] Figure 1 It is a diagram showing the structure of a thickness measuring device according to an embodiment of the present invention. Figure 2 This is a diagram showing an enlarged view of the periphery of a probe of the thickness measuring device according to the embodiment of the present invention.

[0068] Reference Figure 1 and Figure 2 , the thickness measuring device 101 includes probes 1, 2, a spectrometer 3, a light source 4, an optical system 5, and a computing unit 6. Probe 1 includes a lens system 51 and a light-transmitting substrate (first light-transmitting component) 61. The lens system 51 includes a lens 55 and a lens (a first light-projecting unit and a first light-receiving unit) 57. The light-transmitting substrate 61 has a surface (a first reference surface) 65 and a surface 67. Probe 2 includes a lens system 52 and a light-transmitting substrate (a second light-transmitting component) 62. The lens system 52 includes a lens 56 and a lens (a second light-projecting unit and a second light-receiving unit) 58. The light-transmitting substrate 62 has a surface (a second reference surface) 66 and a surface 68. The spectrometer 3 includes a spectrometer 41 and a data generating unit 42. The optical system 5 includes optical fibers 31, 32, 33, 34 and an optical fiber connector 35.

[0069] The light source 4 in the thickness measurement device 101 is, for example, a laser that outputs light with a wide bandwidth. The light source 4 is an LED (Light-Emitting Diode) or an incandescent lamp.

[0070] The optical system 5 guides light output from the light source 4 to the probes 1 and 2 . More specifically, the optical fiber 34 of the optical system 5 receives light from the light source 4 at an input end optically coupled to the light source 4 , and transmits the received light to the optical fiber connector 35 .

[0071] Figure 3 This is a diagram for explaining the function of the optical fiber connector of the thickness measuring device according to the embodiment of the present invention.

[0072] Reference Figure 3 The optical fiber connector 35 distributes the light received from the optical fiber 34 to the optical fibers 31 and 32 .

[0073] Refer again Figure 1 and Figure 2 The optical fiber 31 transmits the light from the light source 4 distributed by the optical fiber connector 35 to the lens system 51 of the probe 1. In addition, the optical fiber 32 transmits the light from the light source 4 distributed by the optical fiber connector 35 to the lens system 52 of the probe 2.

[0074] In the thickness measuring device 101, for example, the axis of the projected light beam 71 of light irradiated from the lens 57 to the sample 151 via the surface 65, the axis of the projected light beam 72 of light irradiated from the lens 58 to the sample 151 via the surface 66, the axis of the reflected light beam 73 of the reflected light from the surface 65 received by the lens 57 and the axis of the reflected light beam 75 of the reflected light from the sample 151 received by the lens 57, and the axis of the reflected light beam 74 of the reflected light from the surface 66 received by the lens 58 and the axis of the reflected light beam 76 of the reflected light from the sample 151 received by the lens 58 are along each other. Here, when the light beam is a parallel light beam, the axis of the light beam is the axis along the light rays included in the parallel light beam, and when the light beam is a divergent light beam or a focused light beam, the axis of the light beam is the symmetry axis of a cone having side surfaces along the light rays included in the divergent light beam or the focused light beam.

[0075] More specifically, in the lens system 51 , the lenses 55 and 57 are, for example, cylindrical convex lenses, and are disposed so that their optical axes are along each other. Here, a virtual axis along the optical axes of the lenses 55 and 57 is defined as a reference axis 70 .

[0076] The lens 57 serves as a first light projecting unit, and irradiates the light from the light source 4 toward the sample 151 located between the light-transmitting substrate 61 and the light-transmitting substrate 62 via the surface 65 .

[0077] The sample 151 is placed on a workbench (not shown) and can be moved between the light-transmitting substrate 61 and the light-transmitting substrate 62 along a plane parallel to the surfaces 65 and 66. Here, a portion of the sample 151 is located between the light-transmitting substrate 61 and the light-transmitting substrate 62. Alternatively, the entire sample 151 may be located between the light-transmitting substrate 61 and the light-transmitting substrate 62.

[0078] The lens 55 is placed opposite to the end face 77 of the optical fiber 31 optically coupled thereto, receives the light beam 71 having the optical axis of the lens 55 as the axis of the light beam from the end face 77, and converts the light beam from the divergent light beam into a parallel light beam. Therefore, the axis of the light beam 71 is along the reference axis 70.

[0079] Lens 57 is disposed between lens 55 and light-transmitting substrate 61 , and converts projection beam 71 from lens 55 into a focusing beam, thereby focusing light from light source 4 via surface 65 on a surface facing surface 65 , that is, near surface 81 of sample 151 .

[0080] The light-transmitting substrate 61 and the light-transmitting substrate 62 are disposed opposite to each other. Specifically, the light-transmitting substrate 61 and the light-transmitting substrate 62 are disposed facing each other. More specifically, the light-transmitting substrate 61 and the light-transmitting substrate 62 are disposed so that the surface 65 as the first reference surface and the surface 66 as the second reference surface face each other.

[0081] In addition, the light-transmitting substrate 61 and the light-transmitting substrate 62 are not limited to being arranged in a structure in which the surface 65 and the surface 66 face each other, but may also be arranged to face each other.

[0082] The light-transmitting substrate 61 and the light-transmitting substrate 62 are, for example, parallel planar substrates, and are transparent or translucent in the frequency band of the light output by the light source 4. More specifically, the surface 65 and the surface 67 of the light-transmitting substrate 61 are, for example, planes and parallel to each other. The light-transmitting substrate 61 is arranged so that the normal line of the surface 65 is along the reference axis 70 and the surface 65 and the surface 67 are respectively opposite to the surface 81 of the sample 151 and the lens 57.

[0083] Surface 66 and surface 68 of transparent substrate 62 are, for example, planes and parallel to each other. Transparent substrate 62 is disposed such that the normal line of surface 66 is along reference axis 70 and surfaces 66 and 68 face surface 82 of sample 151 and lens 58, respectively.

[0084] In addition, the surface 65 and the surface 67 may not be parallel to each other. In addition, the surface 66 and the surface 68 may not be parallel to each other. In addition, the thickness measurement device 101 may be a structure having a light-transmitting member having a shape other than a plate shape instead of the light-transmitting substrate 61 and the light-transmitting substrate 62.

[0085] The lens 57 of the lens system 51 serves as a first light receiving unit, receives the reflected light from the surface 65 of the light-transmitting substrate 61 , and receives the reflected light from the sample 151 via the surface 65 .

[0086] More specifically, surface 65 is the interface between light-transmitting substrate 61 and the air layer, and therefore reflects light from lens 57. Surface 81 of sample 151 is the interface between sample 151 and the air layer, and therefore reflects light received from lens 57 via light-transmitting substrate 61.

[0087] Lens 57 receives reflected light beam 75 , which is a beam with the optical axis of lens 57 as an axis, among the light beams reflected by sample 151 , through surface 65 , and converts the reflected light beam 75 from a divergent beam to a parallel beam.

[0088] In addition, lens 57 receives a light beam having an axis of the optical axis of lens 57, i.e., reflected light beam 73, among the light beams reflected by surface 65, and converts the light beam from a divergent light beam into a parallel light beam. Thus, the axis of reflected light beam 73 is along reference axis 70. In this example, the distance between surface 65 and surface 81 is shorter than the distance between lens 57 and surface 81, and thus reflected light beam 73 is converted almost into a parallel light beam by lens 57.

[0089] Lens 55 converts the reflected light beam 75 from lens 57 into a focused light beam, thereby focusing the reflected light from sample 151 via surface 65 on end face 77 of optical fiber 31, and converts the reflected light beam 73 from lens 57 into a focused light beam, thereby focusing the reflected light from surface 65 on end face 77.

[0090] On the one hand, in the lens system 52 , the lenses 56 and 58 are, for example, cylindrical convex lenses, and are arranged with their respective optical axes along the reference axis 70 .

[0091] The lens 58 serves as a second light projecting unit, and irradiates the sample 151 with the light from the light source 4 via the surface 66 .

[0092] More specifically, the lens 56 is disposed opposite to the end face 78 of the optical fiber 32 optically coupled thereto, receives the light beam having the optical axis of the lens 56 as the axis, i.e., the projection light beam 72, among the light beams from the end face 78, and converts the light beams from divergent to parallel. Thus, the axis of the projection light beam 72 is along the reference axis 70.

[0093] Lens 58 is disposed between lens 56 and light-transmitting substrate 62 , and converts projection beam 72 from lens 56 into a focused beam, thereby focusing light from light source 4 via surface 66 on a surface facing surface 66 , that is, near surface 82 of sample 151 .

[0094] The lens 58 of the lens system 52 serves as a second light receiving unit, receives the reflected light from the surface 66 of the light-transmitting substrate 62 , and receives the reflected light from the sample 151 via the surface 66 .

[0095] More specifically, surface 66 is the interface between light-transmitting substrate 62 and the air layer, and therefore reflects light from lens 58. Surface 82 of sample 151 is the interface between sample 151 and the air layer, and therefore reflects light received from lens 58 via light-transmitting substrate 62.

[0096] Lens 58 receives reflected light beam 76 , which is a beam with the optical axis of lens 58 as its axis, among the light beams reflected by sample 151 , through surface 66 , and converts the reflected light beam 76 from a divergent beam to a parallel beam.

[0097] In addition, lens 58 receives a light beam having an axis of the optical axis of lens 58, i.e., reflected light beam 74, among the light beams reflected by surface 66, and converts the light beam from a divergent light beam into a parallel light beam. Thus, the axis of reflected light beam 74 is along reference axis 70. In this example, the distance between surface 66 and surface 82 is shorter than the distance between lens 58 and surface 82, and thus reflected light beam 74 is converted almost into a parallel light beam by lens 58.

[0098] Lens 56 converts the reflected light beam 76 from lens 58 into a focused light beam, thereby focusing the reflected light from sample 151 via surface 66 on end face 78 of optical fiber 32, and converts the reflected light beam 74 from lens 58 into a focused light beam, thereby focusing the reflected light from surface 66 on end face 78.

[0099] The optical system 5 guides the light received by the lens 57 and the light received by the lens 58 to the spectrometer 41 of the spectroscopic unit 3 , for example.

[0100] More specifically, the optical fiber 31 of the optical system 5 transmits the reflected light received from the lens 55 to the optical fiber connector 35. The optical fiber 32 transmits the reflected light received from the lens 56 to the optical fiber connector 35.

[0101] Refer again Figure 3 The optical fiber connector 35 mixes the reflected light received from the optical fibers 31 and 32 in the coupling portion 36 , and outputs the mixed reflected light to the optical fiber 33 .

[0102] Refer again Figure 1 The optical fiber 33 transmits the reflected lights mixed by the optical fiber connector 35 to the spectrometer 41 of the spectrometer 3 .

[0103] For example, in the thickness measuring device 101 , the optical distance of the path of reflected light propagating from the sample 151 via the surface 65 , the lens 57 , and the optical system 5 to the spectrometer 41 is set to be the same as the optical distance of the path of reflected light propagating from the sample 151 via the surface 66 , the lens 58 , and the optical system 5 to the spectrometer 41 .

[0104] In other words, in the thickness measuring device 101, the optical distance of the path of the reflected light propagating from the sample 151 via the surface 65, the lens 57 and the optical system 5 to the spectrometer 41 is set to be approximately the same as the optical distance of the path of the reflected light propagating from the sample 151 via the surface 66, the lens 58 and the optical system 5 to the spectrometer 41.

[0105] More specifically, in thickness measurement device 101 , when the distance between surface 65 and surface 81 and the distance between surface 66 and surface 82 are substantially the same, the sizes of probes 1 and 2 and the lengths of optical fibers 31 and 32 are set as follows.

[0106] That is, the dimensions of the probes 1 and 2 and the lengths of the optical fibers 31 and 32 are set so that light propagates from the surface 81 through the surface 65, the lenses 57 and 55, and the optical fiber 31 to the joint 36 of the optical fiber connector 35 (see Figure 3 ) is approximately the same as the time required for light to propagate from surface 82 through surface 66, lenses 58, 56, and optical fiber 32 to the coupling portion 36 of the optical fiber connector 35.

[0107] In this example, the distance between the surface 65 and the end face 77 of the optical fiber 31 is set to be approximately the same as the distance between the surface 66 and the end face 78 of the optical fiber 32, and the length from the end face 77 of the optical fiber 31 to the coupling portion 36 of the optical fiber connector 35 is set to be approximately the same as the length from the end face 78 of the optical fiber 32 to the coupling portion 36.

[0108] The spectroscopic unit 3 separates the reflected light received by the lens 57 and the reflected light received by the lens 58 .

[0109] More specifically, the spectrometer 41 of the spectroscopic unit 3 is provided with a diffraction grating and a one-dimensional image sensor, and each reflected light transmitted by the optical fiber 33 is diffracted by the diffraction grating and irradiated to the one-dimensional image sensor.

[0110] The one-dimensional image sensor photoelectrically converts each reflected light diffracted by the diffraction grating, thereby accumulating charges corresponding to the intensity of each wavelength of each reflected light.

[0111] The data generation unit 42 acquires the charge for each wavelength accumulated in the one-dimensional image sensor at a predetermined gate time, thereby generating a signal indicating the intensity of each wavelength, and outputs the generated signal to the calculation unit 6 according to, for example, the RS232C communication standard or the Ethernet (registered trademark) communication standard.

[0112] When the calculation unit 6 receives a signal from the data generation unit 42 , it converts the intensity of each wavelength indicated by the received signal into the reflectivity of each wavelength.

[0113] More specifically, for example, in a state where light is blocked from entering the spectrometer 41 , the calculation unit 6 stores the intensity of each wavelength indicated by the signal received from the data generation unit 42 as reference spectrum data.

[0114] In addition, for example, when a reference object such as an aluminum plate is set between the transparent substrate 61 and the transparent substrate 62 instead of the sample 151, the operation unit 6 will subtract each wavelength intensity included in the benchmark spectral data from each wavelength intensity represented by the signal received from the data generation unit 42, and maintain it as reference spectral data.

[0115] When the sample 151 is set between the transparent substrate 61 and the transparent substrate 62, the calculation unit 6 subtracts the intensity of each wavelength included in the benchmark spectrum data from each wavelength intensity represented by the signal received from the data generation unit 42, and then divides it by the intensity of each wavelength included in the reference spectrum data, thereby generating reflection spectrum data containing the reflectivity of each wavelength.

[0116] Figure 4 : is a diagram showing an example of a power spectrum generated in the computing unit of the thickness measuring device according to the embodiment of the present invention. Figure 4 In the figure, the vertical axis represents the power spectrum intensity and the horizontal axis represents the thickness.

[0117] Reference Figure 2 and Figure 4 The calculation unit 6 calculates, for example, the distance d1 between the surface 65 and the sample 151 and the distance d2 between the surface 66 and the sample 151 based on the spectroscopic result of the spectroscopic unit 3 .

[0118] More specifically, the calculation unit 6 calculates a power spectrum representing the power spectrum intensity for each spatial frequency by Fourier transforming the generated reflection spectrum data. Furthermore, the calculation unit 6 generates Figure 4 The power spectrum is shown.

[0119] The calculation unit 6 calculates the distance d1 based on the position of the peak P1, which is based on the interference of the reflected light from the surface 81 and the reflected light from the surface 65. In addition, the calculation unit 6 calculates the distance d2 based on the position of the peak P2, which is based on the interference of the reflected light from the surface 82 and the reflected light from the surface 66. In this example, the calculation unit 6 calculates the distances d1 and d2 as 168.3 micrometers and 625.4 micrometers, respectively.

[0120] Figure 5 : is a diagram showing an example of a power spectrum generated in the computing unit of the thickness measuring device according to the embodiment of the present invention. Figure 5 In the figure, the vertical axis represents the power spectrum intensity and the horizontal axis represents the thickness.

[0121] Reference Figure 2 and Figure 5 The calculation unit 6 calculates the thickness of the sample 151 by, for example, subtracting the distances d1 and d2 from the distance da between the surface 65 and the surface 66 , that is, the inter-surface distance.

[0122] For example, the surface distance da is obtained by the following method. That is, in a state where the sample 151 is not provided between the light-transmitting substrate 61 and the light-transmitting substrate 62, light from the light source 4 is irradiated from the lens 57 to the surface 66 via the surface 65, the reflected light from the surface 65 is received by the lens 57, and the reflected light from the surface 66 is received by the lens 57 via the surface 65, the light from the light source 4 is irradiated from the lens 58 to the surface 65 via the surface 66, the reflected light from the surface 66 is received by the lens 58, and the reflected light from the surface 65 is received by the lens 58 via the surface 66.

[0123] In this state, the calculation unit 6 performs Fourier transform on the intensity of each wavelength represented by the signal received from the data generation unit 42, thereby calculating the power spectrum intensity of each spatial frequency, that is, the power spectrum. In addition, the calculation unit 6 converts the spatial frequency into thickness to generate Figure 5 The power spectrum is shown.

[0124] The calculation unit 6 calculates the surface distance da based on the position of the peak Pa, for example, in the above state, based on the interference of the reflected light from the surface 65 toward the lens 57, the reflected light from the surface 66 toward the lens 57 via the surface 65, the reflected light from the surface 66 toward the lens 58, and the reflected light from the surface 65 toward the lens 58 via the surface 66. In this example, the calculation unit 6 calculates the surface distance da as 2800.0 micrometers. Therefore, the calculation unit 6 calculates the thickness of the sample 151 as 2006.3 micrometers by calculating (2800.0-168.3-625.4).

[0125] In addition, in the thickness measuring device 101, although the calculation unit 6 is a structure that calculates the surface distance da using the above method, it is not limited to this. The calculation unit 6 may also be a structure that retains the surface distance da obtained by other methods such as mechanical measurement methods in advance. In this case, the calculation unit 6 calculates the thickness of the sample 151 using the retained surface distance da.

[0126] [Measurement method]

[0127] Figure 6 This is a flowchart that defines an example of the procedure of a measurement method using the thickness measurement device according to the embodiment of the present invention.

[0128] Reference Figure 6 First, the thickness measuring device 101 obtains the spectroscopic result after the spectroscopic unit 3 performs spectroscopic analysis on the reflected light received by the lens 57 and the reflected light received by the lens 58 without the sample 151. Specifically, the thickness measuring device 101 obtains Figure 5 The power spectrum shown (step S102).

[0129] Next, the thickness measuring device 101 calculates the surface distance da based on the obtained spectroscopic result. Figure 5 The inter-surface distance da is calculated based on the peak Pa position of the power spectrum shown (step S104).

[0130] Next, the measurer places the sample 151 between the light-transmitting substrate 61 and the light-transmitting substrate 62 (step S106 ).

[0131] Next, the thickness measuring device 101 obtains the spectroscopic result of the spectrometer 3 when the sample 151 is provided. Specifically, Figure 4 The power spectrum shown (step S108).

[0132] Next, the thickness measuring device 101 calculates the distances d1 and d2 based on the spectroscopic result of the spectroscopic unit 3 while the sample 151 is provided. Figure 4 The distances d1 and d2 are calculated based on the positions of the peaks P1 and P2 of the power spectrum shown (step S110 ).

[0133] Next, the thickness measurement device 101 subtracts the distances d1 and d2 from the inter-surface distance da, thereby calculating the thickness of the sample 151 (step S112).

[0134] In addition, the order of the above steps S102 to S104 and steps S106 to S110 is not limited to the above example, and the order may be reversed.

[0135] In addition, the thickness measurement device 101 calculates the surface distance da in the above steps S102 and S104, but the present invention is not limited thereto. As described above, when the thickness measurement device 101 holds the surface distance da in advance, the surface distance da may not be calculated.

[0136] In addition, in the above step S102, when the thickness measuring device 101 irradiates light from both lenses 57 and 58, the spectroscopic result after the spectroscopic unit 3 spectrally spectrally irradiates the reflected light received by lens 57 and the reflected light received by lens 58 is obtained, but the present invention is not limited thereto. In the above step S102, when the thickness measuring device 101 irradiates light from either lens 57 or lens 58, the spectroscopic result of the reflected light received by the corresponding lens is obtained.

[0137] In addition, in the thickness measuring device according to the embodiment of the present invention, the spectroscopic unit 3 has a structure including one spectrometer 41, but is not limited thereto. The spectroscopic unit 3 may also have a structure including two spectrometers 41. In this case, the two spectrometers 41 respectively spectrometer the reflected light received by the lens 57 and the reflected light received by the lens 58. The calculation unit 6 calculates the distances d1 and d2 based on the spectroscopic results of the two spectrometers 41.

[0138] In addition, the thickness measuring device of the embodiment of the present invention has a structure having one light source 4, but is not limited thereto. The thickness measuring device 101 may also have a structure having two light sources 4. In this case, the lens 57 irradiates the light from the light source 4 on one side to the sample 151 via the surface 65. The lens 58 irradiates the light from the light source 4 on the other side to the sample 151 via the surface 66.

[0139] In addition, in the thickness measuring device according to the embodiment of the present invention, the first light projecting unit and the first light receiving unit are formed integrally, but the present invention is not limited thereto. In the thickness measuring device 101, the first light projecting unit and the first light receiving unit may be provided separately.

[0140] Specifically, the thickness measuring device 101 may have a structure including the lens 57 functioning as the first light projecting unit and another lens functioning as the first light receiving unit, or may have a structure including the lens 57 functioning as the first light receiving unit and another lens functioning as the first light projecting unit.

[0141] That is, the axis of the projected light beam 71 of light irradiated from the lens 57 via the surface 65 to the sample 151, the axis of the projected light beam 72 of light irradiated from the lens 58 via the surface 66 to the sample 151, the axis of the reflected light beam 73 of the reflected light from the surface 65 received by the lens 57 and the axis of the reflected light beam 75 of the reflected light from the sample 151, and the axis of the reflected light beam 74 of the reflected light from the surface 66 received by the lens 58 and the axis of the reflected light beam 76 of the reflected light from the sample 151 are along one another.

[0142] In addition, the thickness measuring device 101 may also be Figure 1 A semi-transparent mirror is provided between the light-transmitting substrate 61 and the lens 57, thereby having a structure with the lens 57 functioning as a first light-projecting unit and another lens functioning as a first light-receiving unit receiving the reflected light reflected by the semi-transparent mirror. Alternatively, a structure may be provided with another lens functioning as a first light-projecting unit for irradiating the light from the light source 4 to the sample 151 via the semi-transparent mirror and the surface 65, and the lens 57 functioning as a first light-receiving unit. In these structures, the axes of the projected light beam 71 and the reflected light beams 73 and 75 can be made to be along the surface 65 and the surface 81.

[0143] Similarly, in the thickness measuring device according to the embodiment of the present invention, although the second light projecting unit and the second light receiving unit are formed integrally, the present invention is not limited thereto. In the thickness measuring device 101, the second light projecting unit and the second light receiving unit may be provided separately.

[0144] Specifically, the thickness measuring device 101 may have a structure including the lens 58 functioning as the second light projecting unit and another lens functioning as the second light receiving unit, or may have a structure including the lens 58 functioning as the second light receiving unit and another lens functioning as the second light projecting unit.

[0145] In addition, the thickness measuring device 101 may also be Figure 1 A semi-transparent mirror is provided between the light-transmitting substrate 62 and the lens 58, thereby having a structure including the lens 58 functioning as a second light-projecting unit and another lens functioning as a second light-receiving unit receiving the reflected light reflected by the semi-transparent mirror. Alternatively, a structure including another lens functioning as a second light-projecting unit for irradiating the light from the light source 4 to the sample 151 via the semi-transparent mirror and the surface 66 and the lens 58 functioning as a second light-receiving unit may be adopted. In these structures, the axes of the projected light beam 72 and the reflected light beams 74 and 76 can be made to be along the surface 66 and the surface 82.

[0146] In addition, in the thickness measuring device of the embodiment of the present invention, the surface of the transparent substrate 61 facing the sample 151, that is, the surface 65, is used as the first reference surface, but the present invention is not limited thereto. In the thickness measuring device 101, the surface of the transparent substrate 61 on the opposite side to the sample 151, that is, the surface 67, can also be used as the first reference surface.

[0147] In addition, in the thickness measuring device of the embodiment of the present invention, the surface of the transparent substrate 62 facing the sample 151, that is, the surface 66, is used as the second reference surface, but the present invention is not limited thereto. In the thickness measuring device 101, the surface of the transparent substrate 62 on the opposite side to the sample 151, that is, the surface 68, can also be used as the second reference surface.

[0148] The thickness measuring device of the present embodiment includes the light source 4, the optical system 5 and the computing unit 6, but is not limited thereto. At least one of the light source 4, the optical system 5 and the computing unit 6 may be disposed outside the thickness measuring device 101.

[0149] In the thickness measurement device according to the embodiment of the present invention, the spectroscopic unit 3 includes the data generating unit 42 , but the present invention is not limited thereto. The data generating unit 42 may be provided outside the thickness measurement device 101 .

[0150] However, when the techniques described in Patent Documents 1 to 3 are used to measure the sample thickness, for example, a method of measuring the sample thickness based on the measurement results of the distance from the sample and the measurement results of the distance from the contact surface can be considered.

[0151] However, when the sample surface is uneven or the sample is deformed or bent, a gap will be generated between the contact surface side surface and the contact surface of the sample. In this case, it will be difficult to accurately measure the thickness of the sample.

[0152] Figure 7 : is a diagram showing a comparative example of a probe. Figure 7 For example, when the thickness of a sample 93 placed on a workbench 92 is measured using the light projected and received by the probe 91, the distance dw obtained by subtracting the distance ds between the surface 94 and the sample 93 from the distance dg between the surface 94 as a reference surface and the contact surface of the workbench 92 is measured as the thickness of the sample 93. Figure 7 As shown, since the surface of the sample 93 has irregularities, even if the correct thickness of the sample 93 is d, dw is calculated as the thickness of the sample 93.

[0153] In this regard, in the thickness measuring device according to the embodiment of the present invention, the light-transmitting substrate 61 has a surface 65. The light-transmitting substrate 62 is disposed opposite to the light-transmitting substrate 61 and has a surface 66. The lens 57 irradiates the light from the light source 4 to the sample 151 located between the light-transmitting substrate 61 and the light-transmitting substrate 62 via the surface 65. The lens 57 receives the reflected light from the surface 65, and receives the reflected light from the light-receiving sample 151 via the surface 65. The lens 58 irradiates the light from the light source 4 to the sample 151 via the surface 66. The lens 58 receives the reflected light from the surface 66, and receives the reflected light from the sample 151 via the surface 66. Furthermore, the spectroscopic unit 3 spectroscopically separates the reflected light received by the lens 57 and the reflected light received by the lens 58.

[0154] In this way, by irradiating light to both sides of the sample 151 through the surfaces 65 and 66, the reflected light from the surfaces 81 and 82 on both sides of the sample 151 interferes with the reflected light from the surfaces 65 and 66 and performs spectral separation. Therefore, even if the surfaces 81 and 82 of the sample 151 are uneven or the sample 151 is deformed or bent, the distances d1 and d2 between the surfaces 81 and 82 on both sides of the sample 151 and the surfaces 65 and 66 can be calculated based on the spectral results. And, for example, the thickness of the sample 151 can be accurately calculated based on the calculated distances d1 and d2 and the inter-surface distance da between the surfaces 65 and 66. Therefore, the thickness of the sample can be accurately measured.

[0155] In the thickness measuring device according to the embodiment of the present invention, the spectroscopic unit 3 includes one spectroscope 41 . The optical system 5 guides the light received by the lens 57 and the light received by the lens 58 to the spectroscope 41 .

[0156] By using such a structure of the optical system 5 , the number of expensive beam splitters 41 can be reduced, and thus the manufacturing cost of the thickness measurement device 101 can be reduced.

[0157] In addition, in the thickness measuring device of the embodiment of the present invention, the axis of the projected light beam 71 of light irradiated from the lens 57 via the surface 65 to the sample 151, the axis of the projected light beam 72 of light irradiated from the lens 58 via the surface 66 to the sample 151, the axis of the reflected light beam 73 of the reflected light from the surface 65 received by the lens 57 and the axis of the reflected light beam 75 of the reflected light from the sample 151, and the axis of the reflected light beam 74 of the reflected light from the surface 66 received by the lens 58 and the axis of the reflected light beam 76 of the reflected light from the sample 151 are along each other.

[0158] According to such a configuration, even when the surfaces 65 and 66 are arranged non-parallel to each other or the sample 151 is not provided parallel to the surfaces 65 and 66 , the sample thickness can be accurately measured.

[0159] For example, Figure 2As shown in FIG. 1 , when the sample 151 moves along the reference axis 70 at a speed v in a direction approaching the surface 65, the following problem may occur. That is, when the difference between the time T1 required for the reflected light from the surface 81 to reach the spectrometer 41 and the time T2 required for the reflected light from the surface 82 to reach the spectrometer 41, that is, (T1-T2) is ΔT, the distance that the sample 151 approaches the surface 65 during the time ΔT is only v×ΔT. Therefore, the calculation unit 6 calculates the distance d2 based on the reflected light from the surface 82 and the reflected light from the surface 66, and calculates the distance (d1+v×ΔT) based on the reflected light from the surface 81 and the reflected light from the surface 65. That is, in the thickness measurement device 101, it is difficult to accurately calculate the thickness of the sample 151.

[0160] In addition, for example, the following method can be considered. That is, a first spectrometer for splitting the reflected light received by the lens 57 and a second spectrometer for splitting the reflected light received by the lens 58 are prepared, and the time for the first spectrometer to split the reflected light is delayed by ΔT compared with the time for the second spectrometer to split the reflected light, thereby accurately calculating the thickness of the sample 151. However, since the control of the splitting time of each spectrometer is complicated, it is not preferred.

[0161] In this regard, in the thickness measuring device according to the embodiment of the present invention, the spectroscopic unit 3 includes a spectroscope 41. The optical system 5 guides the light received by the lens 57 and the light received by the lens 58 to the spectroscope 41. Furthermore, the optical distance of the path of the reflected light propagating from the sample 151 via the surface 65, the lens 57, and the optical system 5 to the spectroscope 41 is set to be the same as the optical distance of the path of the reflected light propagating from the sample 151 via the surface 66, the lens 58, and the optical system 5 to the spectroscope 41.

[0162] With this structure, since the time required for the light reflected from the surfaces 81 and 82 on both sides of the sample 151 to reach the spectrometer 41 can be made almost the same, the reflected light reflected from the surfaces 81 and 82 at almost the same time can be split by the spectrometer 41. Thus, even if the sample 151 moves, the thickness of the sample 151 can be accurately measured with a simple structure.

[0163] In the thickness measuring device according to the embodiment of the present invention, the calculation unit 6 calculates the distance d1 between the surface 65 and the sample 151 and the distance d2 between the surface 66 and the sample 151 based on the spectroscopic result of the spectroscopic unit 3. The calculation unit 6 calculates the thickness of the sample 151 by subtracting the distances d1 and d2 from the inter-surface distance da between the surface 65 and the surface 66.

[0164] In this way, by calculating the thickness of the sample 151 based on the measurement result of the external space of the sample 151, that is, each distance, the thickness of the sample 151 can be calculated even if the sample 151 is an opaque substance. In addition, the thickness of the sample 151 can be easily calculated without identifying the physical property values ​​of the sample 151 such as the refractive index.

[0165] In addition, the thickness measurement method of the embodiment of the present invention is a thickness measurement method using a thickness measuring device 101, and the thickness measurement method includes: a step of measuring the distance d1 between the surface 65 and the sample 151, and the distance d2 between the surface 66 and the sample 151 based on the spectroscopic result of the spectrometer 3; and a step of calculating the thickness of the sample 151 by subtracting the distances d1 and d2 from the inter-surface distance da between the surface 65 and the surface 66.

[0166] In this way, by irradiating light to both sides of the sample 151 through the surfaces 65 and 66, and making the reflected light from the surfaces 81 and 82 on both sides of the sample 151 interfere with the reflected light from the surfaces 65 and 66 and performing the spectroscopic structure, even if the surfaces 81 and 82 of the sample 151 are uneven or the sample 151 is deformed or bent, the distances d1 and d2 between the surfaces 81 and 82 on both sides of the sample 151 and the surfaces 65 and 66 can be calculated based on the spectroscopic results. Moreover, the thickness of the sample 151 can be accurately calculated based on the calculated distances d1 and d2 and the inter-surface distance da between the surface 65 and the surface 66. Thus, the thickness of the sample can be accurately calculated. In addition, the thickness of the sample 151 is calculated based on the measurement results for the external space of the sample 151, that is, each distance, so that even if the sample 151 is an opaque substance, the thickness of the sample 151 can be calculated. In addition, the thickness of the sample 151 can be easily calculated without identifying the physical property values ​​such as the refractive index of the sample 151.

[0167] In addition, in the thickness measuring device according to the embodiment of the present invention, in a state where the sample 151 is not provided, light from the light source 4 is irradiated from the lens 57 to the surface 66 via the surface 65, and the reflected light from the surface 65 is received by the lens 57, and the reflected light from the surface 66 is received by the lens 57 via the surface 65. Moreover, the thickness measuring method according to the embodiment of the present invention further includes a step of calculating the surface distance da based on the spectroscopic result after the spectroscopic unit 3 spectroscopically splits the reflected light received by the lens 57 in a state where the sample 151 is not provided.

[0168] With this structure, the surface distance da can be calculated using the same method as the distance d1 and d2, so the surface distance da can be calculated with the same high calculation accuracy as the distance d1 and d2. Thus, for example, the thickness of the sample 151 can be calculated more accurately than when the surface distance da is calculated using other methods with lower accuracy.

[0169] The above embodiments are to be understood as illustrative in all aspects and not restrictive. The scope of the present invention is indicated by the claims rather than the above description, and includes all modifications within the meaning and scope equivalent to the claims.

Claims

1. A thickness measuring device, wherein: have: A first light-transmitting member having a first reference surface; A second light-transmitting member, disposed opposite to the first light-transmitting member, and having a second reference surface; a first light projecting unit configured to irradiate light from a light source through the first reference surface to a sample disposed between the first light-transmitting member and the second light-transmitting member; a first light receiving unit, receiving the reflected light from the first reference surface, and receiving the reflected light from the sample via the first reference surface; a second light projecting unit, irradiating light from a light source to the sample via the second reference surface; a second light receiving part, receiving the reflected light from the second reference surface, and receiving the reflected light from the sample via the second reference surface; a spectrometer that splits the reflected light received by the first light receiving unit and the reflected light received by the second light receiving unit, The light splitting unit includes a light splitter, The thickness measuring device further includes an optical system for mixing the light received by the first light receiving unit and transmitted by the first optical fiber and the light received by the second light receiving unit and transmitted by the second optical fiber, and guiding the light to the beam splitter via a third optical fiber.

2. The thickness measuring device according to claim 1, wherein: The axis of the light beam irradiated from the first light projecting part to the sample via the first reference surface, the axis of the light beam irradiated from the second light projecting part to the sample via the second reference surface, the axis of the light beam reflected from the first reference surface and the axis of the light beam reflected from the sample received by the first light receiving part, and the axis of the light beam reflected from the second reference surface and the axis of the light beam reflected from the sample received by the second light receiving part are along each other.

3. The thickness measuring device according to claim 1 or 2, wherein: The thickness measuring device further includes a calculation unit that calculates a first distance between the first reference surface and the sample and a second distance between the second reference surface and the sample based on the spectroscopic result of the spectroscopic unit. The calculation unit calculates the thickness of the sample by subtracting the first distance and the second distance from the distance between the first reference surface and the second reference surface.

4. A thickness measurement method, which is a method of measuring thickness using a thickness measuring device, The thickness measuring device comprises: The first light-transmitting member has a first reference surface, A second light-transmitting member is disposed opposite to the first light-transmitting member and has a second reference surface. a first light projecting unit irradiating light from a light source through the first reference surface to a sample disposed between the first light-transmitting member and the second light-transmitting member; a first light receiving unit that receives the reflected light from the first reference surface and receives the reflected light from the sample via the first reference surface; The second light projecting unit irradiates the sample with light from a light source via the second reference surface. a second light receiving unit that receives the reflected light from the second reference surface and receives the reflected light from the sample via the second reference surface; a light splitting unit for splitting the reflected light received by the first light receiving unit and the reflected light received by the second light receiving unit; The thickness measurement method comprises: a step of calculating a first distance between the first reference surface and the sample and a second distance between the second reference surface and the sample based on the spectroscopic result of the spectroscopic unit, a step of calculating the thickness of the sample by subtracting the first distance and the second distance from the distance between the first reference surface and the second reference surface, that is, the inter-surface distance, In the step of calculating the first distance and the second distance, the first distance and the second distance are calculated based on the spectroscopic results of mixing the reflected light received by the first light receiving part and transmitted by the first optical fiber and the reflected light received by the second light receiving part and transmitted by the second optical fiber and transmitting the reflected light to a spectrometer in the spectrometer via a third optical fiber.

5. The thickness measurement method according to claim 4, wherein: In a state where the sample is not provided, light from a light source is irradiated from the first light projecting unit to the second reference surface via the first reference surface, reflected light from the first reference surface is received by the first light receiving unit, and reflected light from the second reference surface is received by the first light receiving unit via the first reference surface, The thickness measurement method further comprises, A step of calculating the inter-surface distance based on a spectroscopic result of the spectroscopic unit spectroscopically analyzing the reflected light received by the first light receiving unit in a state where the sample is not provided.

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