Optical interference device

Abstract

To enlarge a measurement range in a depth direction, using Fabry-Perot etalon, and identify the number of times of repeated reflection by a single camera.SOLUTION: An optical interference device 1A is provided that has: a camera 100A; a BS 110; a BS 120; a lens 170; a FP 150; a grating 160; generation means 182; and identification means 184A. The BS 110, BS 120, lens 170, and grating 160 consist of a Mach-Zehnder optical system, and the FP 150 is provided in an optical path ranging from the BS 110 to the grating 160. The camera 100A is configured to receive first return light R1 from a measurement object OB, and second return light R2 from the grating 160. The generation means 182 is configured to generate a two-dimensional image representing an interference fringe generating by the first return light R1 and second return light R2. The identification means 184A is configured to identify the number of times of repeated reflection by the FP 150 in the second return light R2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to optical interference devices. [Background technology]

[0002] One example of a measurement technique for measuring the unevenness of the surface of a measurement object is a technique that uses a Mach-Zehnder optical system (see, for example, Patent Document 1). In this type of measurement technique, light emitted from a light source is separated into measurement light and reference light that are irradiated onto the measurement object, and the measurement light and reference light reflected by the measurement object are combined to form a combined light (interference light), thereby measuring the interference fringes of the combined light, thereby measuring the surface shape of the measurement object. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-099239 Summary of the Invention [Problem to be solved by the invention]

[0004] In surface measurement techniques using Mach-Zehnder optics, placing a Fabry-Perot etalon in the optical path of a reference beam can be considered to expand the measurement range in the depth direction, such as the normal direction of the surface. A Fabry-Perot etalon is an optical element consisting of two reflective planes arranged opposite each other. In a Fabry-Perot etalon, optical interference occurs due to repeated reflections between the opposing reflective surfaces, and only light with wavelengths that satisfy a predetermined interference condition is transmitted. By placing a Fabry-Perot etalon in the optical path of a reference beam, a reference beam with a phase delay equal to the number of repeated reflections is generated for each repeated reflection. If the thickness (optical length) of the Fabry-Perot etalon is less than the basic measurement range of a grating, multiple reference beams with different phase delays interfere with the reflected measurement beam from the measurement object, resulting in a continuous repetition of the basic measurement range. The depth measurement range can be expanded by simultaneously measuring multiple interference fringes with a camera.

[0005] When a Fabry-Perot etalon is placed in the reference light path, it is necessary to determine which of the interference fringes in the interference fringes created by multiple repeated reflections in the Fabry-Perot etalon corresponds to the number of repeated reflections. This is because the number of repeated reflections (order) corresponds to the depth of the depression on the surface of the object being measured. In principle, it is also possible to generate images of the interference fringes for each wavelength using multiple cameras and calculate the order of the reference light repetition resulting from the interference signal by analyzing the multiple images. However, in an embodiment where multiple cameras are used to generate images of the interference fringes for each wavelength, the signal strength per camera decreases, resulting in a deterioration in the S / N ratio. The S / N ratio refers to the ratio of signal to noise. Therefore, it is desirable to be able to determine the number of repeated reflections using a single camera, but no technology has been available to date that enables this.

[0006] The present invention aims to provide a technique for measuring surfaces using a Mach-Zehnder optical system, which uses a Fabry-Perot etalon to expand the depth measurement range and enables the number of repeated reflections to be determined using a single camera. [Means for solving the problem]

[0007] An optical interference device according to a first aspect of the present invention includes a light receiving means, first and second beam splitters, a lens, a Fabry-Perot etalon, a grating, a generating means, and an identifying means. Light emitted from a light source is incident on the first beam splitter. The lens focuses the measurement light, which is the first light split by the first beam splitter, onto a measurement object. Reference light, which is the second light split by the first beam splitter and is different from the first light, is incident on the Fabry-Perot etalon. The reference light emitted from the Fabry-Perot etalon is guided to the grating. The second beam splitter is provided between the first beam splitter and the lens. The second beam splitter guides the first light to the lens and also guides the first return light from the measurement object to the light receiving means. The second beam splitter also guides the second return light from the grating to the light receiving means. The generating means generates a two-dimensional image representing interference fringes generated by the first return light and the second return light received by the light receiving means, and the identifying means identifies the number of repeated reflections by the Fabry-Perot etalon of the second return light that generates the interference fringes, based on the thickness of the interference fringes represented in the two-dimensional image generated by the generating means.

[0008] An optical interference device according to a second aspect of the present invention includes a light receiving means, first and second beam splitters, a lens, a Fabry-Perot etalon, a grating, a generating means, and an identifying means. The light receiving means separates the received light into two or more predetermined wavelength bands. Light emitted from a light source is incident on the first beam splitter. The lens focuses the measurement light, which is the first light split by the first beam splitter, onto a measurement object. Reference light, which is the second light split by the first beam splitter and is different from the first light, is incident on the Fabry-Perot etalon. The reference light emitted from the Fabry-Perot etalon is guided to the grating. The second beam splitter is provided between the first beam splitter and the lens. The second beam splitter guides the first light to the lens and guides first return light from the measurement object to the light receiving means. The second beam splitter guides the second return light from the grating to the light receiving means. The generating means generates a two-dimensional image representing interference fringes generated by the first return light and the second return light received by the light receiving means. When two or more interference fringe sets exist in the depth direction of the measurement object in the two-dimensional image generated by the generating means, the identifying means identifies the number of repeated reflections by the Fabry-Perot etalon of the second return light that generates the interference fringe set, based on the spacing between the interference fringes that make up the interference fringe set.

[0009] In the optical interference device of the second aspect, the light receiving means may include a filter that transmits or reflects light in two or more predetermined wavelength bands, and a monochrome camera arranged after the filter.

[0010] In the optical interference device of the second aspect, the light receiving means may include a color camera that separates the received light into at least three wavelength bands.

[0011] In the optical interference device of each of the above aspects, the beam shape of the measurement light immediately before it is incident on the measurement object may be linear. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram showing an example of the configuration of an optical interference device 1A according to a first embodiment of the present invention. [Figure 2] FIG. 10 is a diagram showing an example of the output timing of the reference light L2 from the FP 150 when no dispersion is applied. [Figure 3] 10 is a diagram showing an example of the output timing of the reference light L2 from the FP 150 in this embodiment. FIG. [Figure 4] 1A and 1B are diagrams showing examples of actual surface conditions of a measurement object OB. [Figure 5] FIG. 10 is a diagram showing an example of a discrimination result based on interference fringes when no dispersion is applied. [Figure 6] 10A and 10B are diagrams showing examples of interference fringes captured by a camera 100A in this embodiment. [Figure 7] FIG. 10 is a diagram showing an example of the configuration of an optical interference device 1B according to a second embodiment of the present invention. [Figure 8] FIG. 10 is a diagram showing an example of interference fringes captured by a camera 100A. [Figure 9] FIG. 10 is a diagram showing an example of the configuration of an optical interference device 1C according to a third embodiment of the present invention. [Figure 10] FIG. 10 is a diagram showing an example of wavelength sensitivity of each of R, G, and B pixels in a camera 100C. [Figure 11] 10A and 10B are diagrams showing examples of interference fringes captured by a camera 100C. DETAILED DESCRIPTION OF THE INVENTION

[0013] Although various technically preferable limitations are applied to each of the embodiments described below, the embodiments of the present invention are not limited to the following embodiments.

[0014] A. First embodiment FIG. 1 is a diagram illustrating an example of the configuration of an optical interference device 1A according to a first embodiment of the present invention. The optical interference device 1A is a device for measuring the unevenness of the surface of a measurement object OB. In addition to the optical interference device 1A, FIG. 1 also illustrates a light source SC and a measurement object OB. As shown in FIG. 1, the optical interference device 1A includes a camera 100A, a beam splitter (abbreviated as BS in FIG. 1, and the same applies hereinafter in this specification) 110, BSs 120 and 130, a mirror 140, a Fabry-Perot etalon (abbreviated as FP in FIG. 1, and the same applies hereinafter in this specification) 150, a grating 160, a processing device 180A, a relay lens 190, a relay lens 200, and a lens 210. In this embodiment, the axis normal to the surface of the measurement object OB, whose unevenness is to be measured by the optical interference device 1A, is referred to as the Z-axis. One of two axes perpendicular to the Z-axis is referred to as the X-axis, and the other is referred to as the Y-axis.

[0015] In the optical interference device 1A, a Mach-Zehnder optical system is configured by BSs 110, 120, and 130, a mirror 140, and a grating 160. Each of BSs 110, 120, and 130 is a polarizing beam splitter. The reason for using polarizing beam splitters as BSs 110, 120, and 130 is that it is easy to adjust the intensity of transmitted light and reflected light at each.

[0016] As shown in Fig. 1, light L emitted from a light source SC is incident on the BS 110. In a preferred embodiment, the light source SC is a coherent, broadband, and high-intensity pulsed light source produced by applying a nonlinear effect to the light emitted from an ultrashort pulse laser. Its wavelength range preferably covers red, green, and blue light. The BS 110 splits the incident light L into a measurement light L1 and a reference light L2. The BS 110 is an example of a first beam splitter in the present disclosure. The measurement light L1 is an example of a first light in the present disclosure. The reference light L2 is an example of a second light, i.e., a second light different from the first light, in the present disclosure.

[0017] The reference light L2 is reflected by the mirror 140 and then enters the FP150. The reference light L2 that entered the FP150 is reflected multiple times within the FP150 and then exits from the FP150. In this embodiment, the thickness of the FP150 (the optical length of one round trip of the reference light L2 within the FP150) is equal to or less than the basic measurement range of the depth of a depression along the Z axis on the surface of the measurement object OB. The reference light L2 that exits from the FP150 is guided by the BS130 and then enters the grating (diffraction grating) 160. In this embodiment, dispersion is imparted to the FP150 so that the output timing of the reference light L2 that exits from the FP150 differs for each color, i.e., so that the phase delay differs for each wavelength.

[0018] FIG. 2 is a diagram showing an example of the output timing of reference light L2 that is output after making N (in FIG. 2, N=1 to 4) round trips within FP150 when no dispersion is applied. Time T in FIG. 2 is the time required for reference light L2 to make one round trip within FP150. In FIG. 2, hatching that slopes downward to the right represents the output spectrum of blue light, hatching that stretches horizontally represents the output spectrum of green light, hatching that stretches vertically represents the output spectrum of yellow light, and hatching that slopes upward to the right represents the output spectrum of red light (the same applies to FIG. 3, which will be described later). As shown in FIG. 2, when no dispersion is applied, the blue, green, yellow, and red light contained in reference light L2 are output at the same timing.

[0019] 3 is a diagram showing an example of the output timing of the reference light L2 emitted from the FP 150 in this embodiment. In this embodiment, dispersion is imparted to the FP 150, so a phase delay occurs for each wavelength in the reference light L2 for each round trip. As is clear from FIG. 3, if the number of round trips is the same, the output timing of yellow, green, and blue light is delayed in this order relative to red light, and the greater the number of round trips, the greater the delay Δ between the output of the red light and the output of the blue light.

[0020] The grating 160 has a plurality of sawtooth grooves on its incident surface for the reference light L2. FIG. 1 illustrates one of these grooves. In this embodiment, the depth d of this groove is the basic measurement range for the depth of a depression along the Z axis on the surface of the measurement object OB. The grating 160 reflects the incident reference light L2. The reflected light R2 of the reference light L2 by the grating 160 is guided by the BS 130, relay lens 190, and relay lens 200 before entering the BS 120. The reflected light R2 is an example of the second return light in this disclosure. Hereinafter, the reflected light R2 will also be referred to as the second return light R2.

[0021] As shown in FIG. 1, the BS 120 is provided between the BS 110 and the lens 170. The BS 120 guides the measurement light L1 to the lens 170 and also guides the reflected light R1 of the measurement light L1 by the measurement object OB to the camera 100A. The reflected light R1 of the measurement light L1 by the measurement object OB is an example of the first returned light in the present disclosure. Hereinafter, the reflected light R1 will also be referred to as the first returned light R1. The BS 120 also guides the reflected light R2 to the camera 100A. The BS 120 is an example of the second beam splitter in the present disclosure.

[0022] The lens 170 is a cylindrical lens that focuses the incident measurement light L1 linearly along the X-axis. In this embodiment, the surface irregularities of the measurement object OB are measured using linear measurement light L1 that is approximately 20 mm long and approximately 10 microns wide along the X-axis. Because the surface irregularities of the measurement object OB are measured using linear measurement light L1 that is linear along the X-axis, scanning in the X-axis direction is unnecessary in this embodiment; only scanning in the Y-axis direction is required. The linear measurement light L1 emitted from the lens 170 is focused by the lens 210 and then irradiated onto the surface of the measurement object OB. Reflected light R1 of the measurement light L1 by the measurement object OB is guided by the lens 210, the lens 170, and the BS 120 and enters the camera 100A.

[0023] The camera 100A is a monochrome camera. The camera 100A outputs an image signal GM representing the light received from the first return light R1 and the second return light R2, i.e., an image signal GM representing a monochrome image of interference fringes generated by the first return light R1 and the second return light R2, to the processing device 180A. The camera 100A is an example of a light receiving means in the present disclosure.

[0024] The processing device 180A includes a processor, such as a CPU (Central Processing Unit), i.e., a computer. The processing device 180A may include one computer or multiple computers. The processing device 180A functions as the generating means 182 and the identifying means 184A by operating in accordance with a program stored in a storage device not shown in FIG. 1. In other words, the generating means 182 and the identifying means 184A in FIG. 1 are software modules realized by operating a computer in accordance with a program. The processing device 180A and the storage device may be part of a personal computer.

[0025] The generating means 182 generates a two-dimensional image, i.e., a monochrome two-dimensional image, based on the image signal GM, representing interference fringes caused by the first return light R1 and the second return light R2. Hereinafter, each bright portion of the interference fringes caused by the first return light R1 and the second return light R2 will be referred to as a bright line, and each dark portion will be referred to as a dark line. Bright lines and dark lines appear alternately in the interference fringes.

[0026] The identifying means 184A identifies the number of repeated reflections by FP150 of the second return light R2 that causes the interference fringes (i.e., the number of round trips of the reference light L2 within FP150) based on the thickness of the interference fringes, i.e., the thickness of the bright or dark lines, shown in the two-dimensional image generated by the generating means 182. The reason why the number of repeated reflections by FP150 can be identified based on the thickness of the interference fringes is as follows.

[0027] In the reference light L2, the phase of each wavelength (color of light) differs for each number of repeated reflections, and therefore, in the interference fringes generated by the interference between the first return light R1 and the second return light R2, color bleeding occurs according to the number of repeated reflections. As described above, in this embodiment, the camera 100A that captures these interference fringes is a monochrome camera. Therefore, color bleeding according to the number of repeated reflections appears as differences in the thickness of the interference fringes in the image captured by the camera 100A. This is why the number of repeated reflections by the FP 150 can be determined based on the thickness of the interference fringes.

[0028] Here, let us consider a case where the measurement range in the Z-axis direction is expanded to the tenth order by providing FP 150, but dispersion is not provided to FP 150. In this case, as shown in Figure 2 above, the output timing of each color of light is the same for the reference light L2 for each number of reflections, and the color bleeding described above does not occur. Figure 4 shows an example of the actual surface condition of a measurement object OB. In this example, a recess RE (···P1-P2-P3-P4-P5-P6···) is formed on the surface of the measurement object OB. That is, the wall surface of the recess RE is inclined with respect to the depth direction (Z-axis direction, in other words, the direction parallel to the direction in which the measurement light is incident on the measurement object OB) between P2 and P3, but is parallel to the depth direction between P4 and P5 (in other words, the hole is cut vertically). Figure 5 conceptually shows the interference fringes obtained when measuring this measurement object OB without applying dispersion to the FP150. In Figure 5, the interference fringes corresponding to the section between P4 and P5 appear as multiple overlapping fringes due to the expanded measurement range. As a result, the depth of the recess RE between P4 and P5 cannot be accurately determined from the interference fringes.

[0029] FIG. 6 is a schematic diagram of interference fringes obtained when measuring the object OB shown in FIG. 4 with dispersion applied to FP150. As shown in the figure, the number of repeated reflections is reflected as differences in the thickness of the interference fringes. That is, in the region on the image corresponding to P2-P6, the interference fringes are thicker (wider; in other words, the lines appear blurred) than in other areas. More specifically, in the region on the image corresponding to P2-P3, the interference fringes gradually become thicker, while in the regions on the image corresponding to P1-P2, P3-P4, and P5-P6 (indicated by F0, F1, and F2 in the figure), the thickness of the interference fringes is constant. Based on the thickness of the interference fringes (in other words, the degree of line blurring), the number of repeated reflections can be determined, and the shape of the hole (for example, information including the depth of the recess RE in this example, the distance in the Z-axis direction) can be correctly determined. As described above, the optical interference device 1A of this embodiment makes it possible to expand the depth measurement range using a Fabry-Perot etalon in a surface measurement technique using a Mach-Zehnder optical system, and to determine the number of repeated reflections with a single camera.

[0030] B. Second embodiment Fig. 7 is a diagram showing an example of the configuration of an optical interference device 1B according to a second embodiment of the present invention. In Fig. 7, the same components as those in Fig. 1 are assigned the same reference numerals. As is clear from a comparison of Fig. 7 with Fig. 1, the configuration of the optical interference device 1B differs from the configuration of the optical interference device 1A in the following two points.

[0031] The first difference is that a filter 220 is provided between the camera 100A and the BS 120. The filter 220 is a color filter that transmits light in two separate wavelength bands (in this embodiment, a wavelength band of 500 nm±10 nm and a wavelength band of 700 nm±10 nm). In this embodiment, the filter 220 and the camera 100A form a light receiving means that separates the received light into two or more predetermined wavelength bands. Instead of the filter 220, a color filter that reflects light in two or more predetermined wavelength bands may be used, and the light reflected by the color filter may be guided to the camera 100A to form a light receiving means that separates the received light into two or more predetermined wavelength bands.

[0032] The second difference is that the processing device 180B replaces the processing device 180A. The processing device 180B is identical to the processing device 180A in functioning as the generating unit 182, but differs from the processing device 180A in functioning as the identifying unit 184B instead of the identifying unit 184A. The identifying unit 184B is similar to the identifying unit 184A in that it identifies the number of repeated reflections by the FP150 based on the interference fringes between the first return light R1 and the second return light R2. The identifying unit 184B differs from the identifying unit 184A in that, when two or more interference fringe sets exist in the depth direction of the measurement object OB in the two-dimensional image generated by the generating unit 182, the identifying unit 184B identifies the number of repeated reflections based on the spacing between the interference fringes that make up the interference fringe set. When two or more interference fringe sets exist in the Z-axis direction, the reason why the number of repeated reflections can be identified based on the spacing between the interference fringes that make up the interference fringe set is as follows.

[0033] In this embodiment, dispersion is also imparted to the FP 150, so that a phase delay occurs for each wavelength in the reference light L2 after each reflection, as shown in FIG. 3 . Because the phase of each wavelength in the reference light L2 differs with each reflection, color fringes corresponding to the number of reflections occur in the interference fringes generated by the interference between the first return light R1 and the second return light R2. In this embodiment, a filter 220 is disposed in front of the camera 100A, so that interference fringes of two wavelength bands transmitted through the filter 220 in the color fringes are observed in pairs as shown in FIG. 8 (in the figure, F1R and F1L form a pair of interference fringes, and F2R and F2L form a pair of interference fringes). In other words, there are two Z-axis values ​​corresponding to a certain position on the X-axis. The fringe spacing of the two wavelength bands in the set of interference fringes differs depending on the number of reflections. This is the reason why, when there are two or more sets of interference fringes in the Z-axis direction, the number of repeated reflections can be determined based on the spacing between the interference fringes that make up the set of interference fringes.

[0034] As described above, the optical interference device 1B of this embodiment also makes it possible to expand the depth measurement range by using a Fabry-Perot etalon in a surface measurement technique using a Mach-Zehnder optical system, and to identify the number of repeated reflections with a single camera.

[0035] C. Third embodiment FIG. 9 is a diagram illustrating an example of the configuration of an optical interference device 1C according to a third embodiment of the present invention. In FIG. 9, the same components as those in FIG. 7 are denoted by the same reference numerals. Comparing FIG. 9 with FIG. 7, the configuration of the optical interference device 1C differs from the configuration of the optical interference device 1B in the following two points. The first difference is that the optical interference device 1C does not include a filter 220. The second difference is that the camera 100A is replaced with a camera 100C. The camera 100C differs from the camera 100A in that it is a color camera that outputs image signals GC of red, green, and blue, i.e., separates the received light into at least three wavelength bands. Similar to the filter 220 and the camera 100A in the second embodiment, the camera 100C serves as a light receiving means that separates the received light into two or more predetermined wavelength bands.

[0036] In this embodiment, the identifying unit 184B identifies the number of repeated reflections based on the difference in the intervals between interference fringes in two predetermined colors out of red, green, and blue. For example, if the camera 100C is a Bayer pattern camera in which the wavelength sensitivities of the R (red), G (green), and B (blue) pixels are as shown in Fig. 10(A), or if the camera 100C is a prism camera in which the wavelength sensitivities of the R, G, and B pixels are as shown in Fig. 10(B), wavelengths near the sensitivity boundaries of each color are used, and therefore the identifying unit 184B may be made to identify the number of repeated reflections based on the difference in the intervals between interference fringes in each of red and blue. Fig. 11 is a diagram showing an example of interference fringes captured by camera 100C. In the example shown in Fig. 11, the dashed-dotted lines represent interference fringes of red light, the solid lines represent interference fringes of green light, and the dotted lines represent interference fringes of blue light. As shown in Fig. 11, in the interference fringes captured by camera 100C, the positions of the red and blue interference fringes relative to the green light interference fringe are different from each other, and the distance between the blue light interference fringe and the red light interference fringe varies depending on the number of repeated reflections.

[0037] As described above, the optical interference device 1C of this embodiment also enables the use of a Fabry-Perot etalon to expand the depth measurement range and to determine the number of repeated reflections with a single camera in a surface measurement technique using a Mach-Zehnder optical system. Note that although the number of repeated reflections is determined based on the spacing between interference fringes in two predetermined colors, the measurement of the distance in the Z-axis direction may be performed based on one of the colors R, G, and B to mitigate the effects of color bleeding.

[0038] D. Deformation The above-described embodiments may be modified as follows. (1) In each of the above embodiments, the Fabry-Perot etalon 150 may be replaced with a plurality of Fabry-Perot etalons arranged in series (for example, two Fabry-Perot etalons arranged in series). Due to limitations in the machining accuracy of the reflecting surface of the Fabry-Perot etalon, the envelope of the spectrum of the output light does not have a very clean waveform. However, by arranging a plurality of Fabry-Perot etalons in series, the influence caused by limitations in the machining accuracy can be alleviated.

[0039] (2) In the first embodiment, the generating means 182 and the identifying means 184A are software modules, but either or both of the generating means 182 and the identifying means 184A may be hardware modules such as ASICs. Even if either or both of the generating means 182 and the identifying means 184A are hardware modules, the same effects as in the first embodiment can be achieved. The identifying means 184B in the second embodiment may also be a hardware module.

[0040] (3) In the above embodiments, the beam shape of the measurement light L1 immediately before it is incident on the measurement object OB is linear. However, if scanning is performed in the Y-axis direction in addition to the X-axis direction, the beam shape of the measurement light L1 does not have to be linear. [Explanation of symbols]

[0041] 1A, 1B, 1C...optical interference device, 100A...camera, 110, 120, 130...beam splitter, 140...mirror, 150...Fabry-Perot etalon, 160...grating, 170...lens, 180A, 180B...processing device, 182...generating means, 184A, 184B...identifying means, 190, 200,...relay lens, 210...lens, 220...filter.

Claims

1. Light receiving means; a first beam splitter onto which the light emitted from the light source is incident; a lens that focuses the measurement light, which is the first light split by the first beam splitter, onto a measurement object; a Fabry-Perot etalon on which a reference light, which is a second light different from the first light split by the first beam splitter, is incident; a grating through which the reference light emitted from the Fabry-Perot etalon is guided; a second beam splitter provided between the first beam splitter and the lens, which guides the first light to the lens, guides first return light from the object to the light receiving means, and guides second return light from the grating to the light receiving means; a generating means for generating a two-dimensional image representing interference fringes generated by the first return light and the second return light received by the light receiving means; an identification means for identifying the number of times that the second return light, which generates the interference fringes, is repeatedly reflected by the Fabry-Perot etalon based on the thickness of the interference fringes displayed in the two-dimensional image; An optical interference device having:

2. a light receiving means for separating the received light into two or more predetermined wavelength bands; a first beam splitter onto which the light emitted from the light source is incident; a lens that focuses the measurement light, which is the first light split by the first beam splitter, onto a measurement object; a Fabry-Perot etalon on which a reference light, which is a second light different from the first light split by the first beam splitter, is incident; a grating through which the reference light emitted from the Fabry-Perot etalon is guided; a second beam splitter provided between the first beam splitter and the lens, which guides the first light to the lens, guides first return light from the object to the light receiving means, and guides second return light from the grating to the light receiving means; a generating means for generating a two-dimensional image representing interference fringes generated by the first return light and the second return light received by the light receiving means; an identification means for identifying the number of times that the second return light, which generates an interference fringe set, is repeatedly reflected by the Fabry-Perot etalon based on the interval between the interference fringes constituting the interference fringe set when two or more interference fringe sets exist in the depth direction of the measurement object in the two-dimensional image; An optical interference device having:

3. The light receiving means includes a filter that transmits or reflects light in two or more predetermined wavelength bands, and a monochrome camera arranged after the filter. The optical interference device according to claim 2 .

4. The light receiving means includes a color camera that separates the received light into at least three wavelength bands. The optical interference device according to claim 2 .

5. The beam shape of the measurement light immediately before being incident on the measurement object is linear.

5. The optical interference device according to claim 1.

Images