displacement measuring device

Abstract

A displacement measuring device is provided. The displacement measuring device has: a light source that generates broadband light source light; a first interferometer that causes the light source light to branch and be incident on a reference surface (reference side mirror) and a measurement surface (workpiece), and causes reference light and measurement light to superimpose to generate interference light; a second interferometer that causes the interference light to branch and be incident on a first reflection surface (first mirror) and a second reflection surface (second mirror), and causes first reflection light and second reflection light to superimpose to generate spread light that spreads in a prescribed spread direction and in which a difference in optical path length changes along the spread direction; an image sensor that detects the spread light; and a calculation device that measures displacement of the measurement surface based on displacement of a peak position of an interference signal in an image detected by the image sensor.

Description

Technical Field

[0001] This invention relates to a displacement measuring device. Background Technology

[0002] A displacement measuring device using an interferometer with broadband light as the light source is known. Such displacement measuring devices are known in time-domain mode, spectral region mode, and wavelength scanning mode.

[0003] In the time-domain method, the optical path length is mechanically changed in a part of the optical path in the interferometer, and interference fringes generated near the position where the difference between the optical path lengths of the reference light and the measurement light is zero are detected, and the displacement of the object being measured is measured (see reference 1 (Japanese Patent Publication No. 2017-524138) etc.).

[0004] In the spectral region method, broadband light such as white light is used as the light source and is interfered with by an interferometer. The interference light is split and the frequency characteristics of the light intensity are obtained. The peak position of the interference signal corresponding to the wavelength is detected (see reference 2 (Japanese Patent Application Publication No. 2017-38997) etc.).

[0005] In the wavelength scanning method, the wavelength of the light source is scanned continuously in the interferometer within a short time, and the displacement of the object is detected based on the frequency characteristics and phase of the light intensity change produced by the interference light (see reference 3 (Japanese Patent Application Publication No. 2021-189112) etc.).

[0006] Each of the aforementioned time-domain method, spectral region method, and wavelength scanning method has the following characteristics.

[0007] In the time-domain method, the measurement range is relatively wide and high precision can be obtained. However, on the other hand, mechanical actions are required to change the optical path length. Due to this action, the measurement time is longer, and the mechanism for precisely changing the optical path length becomes a reason for high cost.

[0008] In the spectral region method, no mechanical action is required and high precision can be obtained, but the measurement range is narrow, for example, about 2~3mm, and the spectrometer and other components become the reason for the high cost.

[0009] Wavelength scanning methods do not require mechanical action and can have a relatively wide measurement range, such as over 1 meter. However, variable wavelength lasers are expensive and easily affected by temperature, making it difficult to achieve high precision.

[0010] Thus, existing methods cannot simultaneously meet the requirements of no mechanical movement, high precision, wide measurement range, and low cost.

[0011] In one aspect, the object of the present invention is to provide a displacement measuring device that can simultaneously meet the conditions of no mechanical movement, high precision, wide measuring range and low cost.

[0012] One aspect of the displacement detector includes: a light source that generates broadband light; a first interferometer that branches the light source and incident it onto a reference surface and a measurement surface, and superimposes reference light reflected from the reference surface and measurement light reflected from the measurement surface to generate interference light; a second interferometer that branches the interference light and incident it onto a first reflecting surface and a second reflecting surface, and superimposes first reflected light reflected from the first reflecting surface and second reflected light reflected from the second reflecting surface to generate extended light that diffuses in a predetermined extension direction and whose optical path length difference changes along the extension direction; an image sensor that detects the extended light; and a computing device that determines the displacement of the measurement surface based on the displacement of the peak position of the interference signal in the image detected by the image sensor.

[0013] According to the present invention, a displacement detector can be provided that simultaneously satisfies the conditions of no mechanical movement, high precision, wide measurement range and low cost. Attached Figure Description

[0014] Figure 1 This is a configuration diagram showing the structure of the first embodiment of the present invention.

[0015] Figure 2 This is a schematic diagram illustrating the optical path length difference of the mirror-based extended light in the first embodiment.

[0016] Figure 3 This is a schematic diagram illustrating the displacement measurement of the first embodiment.

[0017] Figure 4 This is a schematic diagram illustrating the displacement measurement of the first embodiment.

[0018] Figure 5 This is a configuration diagram illustrating the structure of the second embodiment of the present invention.

[0019] Figure 6 This is a perspective view showing the multi-stage tilting mirror of the second embodiment.

[0020] Figure 7 This is a schematic diagram illustrating the displacement measurement of the second embodiment.

[0021] Figure 8 This is a schematic diagram illustrating the displacement measurement of the second embodiment.

[0022] Figure 9 This is a schematic diagram illustrating the displacement measurement of the second embodiment.

[0023] Figure 10 This is a configuration diagram showing the structure of the third embodiment of the present invention.

[0024] Figure 11 This is a perspective view showing the multi-stage tilting mirror of the third embodiment.

[0025] Figure 12 This is a perspective view showing the aperture of the third embodiment.

[0026] Figure 13 This is a perspective view showing other apertures of the third embodiment.

[0027] Figure 14 This is a configuration diagram showing the structure of the fourth embodiment of the present invention.

[0028] Figure 15 This is a perspective view showing the cylindrical lens array of the fourth embodiment.

[0029] Figure 16 This is a configuration diagram illustrating the structure of the fifth embodiment of the present invention.

[0030] Figure 17 This is a configuration diagram showing the structure of the sixth embodiment of the present invention.

[0031] Figure 18 This is a schematic diagram illustrating the displacement measurement of the sixth embodiment.

[0032] Figure 19 This is a configuration diagram showing the structure of the seventh embodiment of the present invention.

[0033] Figure 20 This is a configuration diagram showing the structure of the eighth embodiment of the present invention. Detailed Implementation

[0034] [First Implementation]

[0035] exist Figures 1 to 4 The figures show the displacement measuring device 1 according to the first embodiment of the present invention.

[0036] exist Figure 1 In the process, the displacement measuring device 1 measures the displacement d9 of the workpiece 9. The displacement measuring device 1 includes a light source 2, an image sensor 3, a computing device 4, a first interferometer 10, and a second interferometer 20.

[0037] Light source 2 is a light source device that generates broadband light source L11, such as white light.

[0038] Image sensor 3 is a one-dimensional or two-dimensional solid-state imaging element that uses a CCD (charge-coupled device) image sensor or the like.

[0039] The arithmetic unit 4 is composed of a computer system that performs actions based on a prescribed action program, and is capable of processing the detection images of the image sensor 3 and calculating the displacement of the workpiece 9.

[0040] The first interferometer 10 includes an incident-side lens 11, a beam splitter 12, a reference-side mirror 13 serving as a reference surface, and an exit-side lens 16. The surface of the workpiece 9, the object of measurement, is set as the measurement surface.

[0041] In the first interferometer 10, the light source L11 from the light source 2 is incident on the incident side lens 11. The light source L11 that passes through the incident side lens 11 is split into the reference light L12 and the measurement light L14 by the beam splitter 12.

[0042] The reference light L12 is reflected by the reference side mirror 13, and the reflected reference light L13 returns to the beam splitter 12.

[0043] The measuring light L14 is reflected by the surface (measuring surface) of the workpiece 9, and the reflected measuring light L15 returns to the beam splitter 12.

[0044] The reference light L13 returning to the beam splitter 12 is superimposed with the measurement light L15 to form the interference light L16, which is then emitted from the exit lens 16 to the second interferometer 20.

[0045] The second interferometer 20 includes an incident-side lens 21, a beam splitter 22, a first mirror 23 serving as a first reflecting surface, a second mirror 25 serving as a second reflecting surface, and an exit-side lens 26.

[0046] In the second interferometer 20, the interference light L21 (L16) from the first interferometer 10 is incident on the incident-side lens 21. The interference light L21 that passes through the incident-side lens 21 becomes a beam with a specified optical path width, is incident on the beam splitter 22 and splits into a first branch light L22 and a second branch light L24.

[0047] The first branch light L22 is reflected by the first mirror 23, and the reflected light L23 returns to the beam splitter 22.

[0048] The second branch light L24 is reflected by the second mirror 25, and the reflected second light L25 returns to the beam splitter 22.

[0049] In the second interferometer 20, the first mirror 23 and the second mirror 25 are configured as tilting mirrors that are tilted relative to the incident optical axes of the first branch light L22 and the second branch light L24.

[0050] First shot, 23 Figure 1 The middle left end Figure 1The right end of the first mirror 23 is shifted upwards from the center in the diagram. The surface of the first mirror 23 is tilted at an angle θA relative to the plane orthogonal to the incident optical axis of the first branch light L22, and the displacement of the left end in the diagram is set as a distance dA. Through this tilting of the first mirror 23, the first reflected light L23, having a defined optical path width... Figure 1 The components on the left side relative to Figure 1 The optical path length difference opdA of the component at the right end is a distance of 2dA. In the region between each end, from Figure 1 From the right end to the left end, the optical path length difference opdA continuously changes from a distance of 0 to a distance of 2dA. Furthermore, Figure 1 The optical path length difference opdA at the left end of the middle is strictly speaking the distance dA[1+cos(2θA)], but since θA is small enough, it can be approximated as the distance 2dA.

[0051] Second shot 25 Figure 1 middle and lower side Figure 1 The upper middle end is shifted to the left in the diagram, and the surface of the second mirror 25 is tilted at an angle θB relative to the plane orthogonal to the incident optical axis of the second branch light L24, with the displacement at the lower end of the diagram set as a distance dB. Through this tilting of the second mirror 25, the second reflected light L25, having a defined optical path width... Figure 1 The composition of the middle and lower ends relative to Figure 1 The optical path length difference between the components at the upper and middle ends is 2 dB, and in the region between each end, from Figure 1 From the upper middle end to the lower end, the optical path length difference (opdB) continuously varies from 0 to 2dB. Furthermore, Figure 1 The optical path length difference opdB at the lower end is strictly speaking the distance dB[1+cos(2θB)], but since θB is small enough, it can be approximated as the distance 2dB.

[0052] The first reflected light L23 and the second reflected light L25, which return to the beam splitter 22, are emitted from the exit-side lens 26 as the first reflected light L26 and the second reflected light L27 to the image sensor 3.

[0053] The first reflected light L23 and the second reflected light L25 are offset from the optical axes of the original first branch light L22 and the second branch light L24, respectively. The first reflected light L26 and the second reflected light L27 emitted from the beam splitter 22 will not superimpose. The first reflected light L26 and the second reflected light L27 superimpose when incident on the surface of the image sensor 3, generating an extended light L28 with a predetermined optical path width in the extension direction E. The extended light L28 diffuses in the predetermined extension direction E, and the optical path length difference opdC changes along the extension direction E.

[0054] Here, the travel directions of the first reflected light L26 and the second reflected light L27 are tilted by 2θA and 2θB respectively due to the tilt angles θA and θB of the first mirror 23 and the second mirror 25, compared to the travel directions of the reflected light when the first mirror 23 and the second mirror 25 are not tilted. Therefore, in Figure 2 In the process, the first reflected light L26 and the second reflected light L27, which are generated by superposition to form the extended light L28, have a maximum optical path length difference of 2dA and 2dB on both sides of the extension direction E due to the tilt angles 2θA and 2θB of their respective travel directions. Therefore, the extended light L28 formed by superposition generates an optical path length difference opdC equivalent to the optical path length difference opdA + opdB. From one end of the extension direction E to the other, the optical path length difference opdC continuously changes from a distance of 0 to a distance of 2dA + 2dB. At a point a distance x from one end of the extension direction E, the optical path length difference opdC of the extended light L28 becomes a distance dCx (0 ≤ x ≤ 0). <dCx<2dA+2dB)。

[0055] Furthermore, the tilt angles θA and θB of the first mirror 23 and the second mirror 25, as well as the distances 2dA and 2dB that constitute the optical path length differences opdA and opdB, can be set to the same values. Alternatively, the first mirror 23 and the second mirror 25 can be tilted, but only one of them can be tilted. In this case, the optical path length difference opdC in the extended light L28 is the optical path length difference (either of the optical path length differences opdA and opdB) of the tilted mirror.

[0056] As described above, the interference light L21 incident on the second interferometer 20 is the interference light L16 emitted from the first interferometer 10. The interference light L16 contains an interference signal with an optical path length difference of twice (reciprocating amount) the displacement d9 of the measurement surface of the first interferometer 10, i.e., the surface of the workpiece 9.

[0057] In the extended light L28, interference fringes are generated when the optical path length difference opdC is twice the displacement d9 of the surface of workpiece 9. At this time, the optical path length difference opdC is the distance dCx = 2d9, which can determine a point at a distance x from one end in the extension direction E.

[0058] exist Figure 3 In the extended light L28 detected by image sensor 3, the interference signal peaks appear at most three times. Figure 3 The vertical axis of the graph represents the light signal intensity i of the image sensor 3, and the horizontal axis represents the distance x from the reference position in the extension direction E.

[0059] In the case of three peaks, the first peak p1 that appears in the center is the peak of the interference signal that appears at the position where the optical path length difference opdC of the second interferometer 20 is zero, and it always appears at the same position regardless of the displacement d9 of the workpiece 9.

[0060] The second peak p2 and the third peak p3 appear at positions symmetrical to the left and right of the first peak p1 at the center. The second peak p2 and the third peak p3 appear at positions where the total optical path length difference between the optical path length difference of the first interferometer 10 (equivalent to the displacement d9 of the workpiece 9) and the optical path length difference opdC of the second interferometer 20 is zero.

[0061] The distance xp between the first peak p1 and the second peak p2, and the distance between the first peak p1 and the third peak p3, are both proportional to the difference in optical path length of the first interferometer 10, i.e., the displacement d9 of the workpiece 9. Therefore, the displacement d9 of the workpiece 9 can be calculated by measuring either one, for example, the distance xp between the first peak p1 and the second peak p2.

[0062] The position of the first peak p1 detected by the image sensor 3 can be selected by the relative positional relationship between the first mirror 23 and the second mirror 25, and by the adjustment of the image sensor 3 or the computing device 4.

[0063] like Figure 4 As shown, during measurement, the position of the first peak p1 can be made close to the end of the detection area of ​​the image sensor 3, and both the first peak p1 and the second peak p2 can be displayed. With this setting, even if the distance between the second peak p2 and the first peak p1 increases, the second peak p2 can still be captured within the detection range of the image sensor 3, thereby expanding the measurement range of the displacement d9 of the workpiece 9.

[0064] According to this embodiment, the following effects can be obtained.

[0065] In the present embodiment, the displacement measuring device 1 includes: a light source 2 that generates broadband light source light L11; a first interferometer 10 that branches the light source light L11 and makes it incident on a reference surface (reference-side mirror 13) and a measurement surface (the surface of the workpiece 9), and superimposes the reference light L13 reflected by the reference surface and the measurement light L15 reflected by the measurement surface to generate interference light L16; a second interferometer 20 that branches the interference light L21 (L16) and makes it incident on a first reflection surface (first mirror 23) and a second reflection surface (second mirror 25), and superimposes the first reflected light L23 reflected by the first reflection surface and the second reflected light L25 reflected by the second reflection surface to generate extended light L28 that diffuses in a specified expansion direction E and whose optical path length difference opdC changes along the expansion direction E; an image sensor 3 that detects the extended light L28; and an arithmetic unit 4 that measures the displacement d9 of the measurement surface (the surface of the workpiece 9) based on the displacement of the peak positions (first peak p1 and second peak p2) of the interference signal in the image detected by the image sensor 3.

[0066] In this structure, the interference light L16 (L21) from the first interferometer 10 is passed through the second interferometer 20. For the optical path length difference opdC of the second interferometer 20 generated in the extended light L28, an interference signal peak is generated at a position where the optical path length difference opdC is equal to twice the displacement d9 of the workpiece 9, and this interference peak is detected as the interference peak on the image of the extended light L28.

[0067] Specifically, the extended light L28 diffuses in the expansion direction E and the distance dCx (0 < dCx < 2dA + 2dB) of the optical path length difference opdC changes along the expansion direction E, whereby an interference signal peak is generated at a point x where dCx - 2d9 = 0. In an image that diffuses along the expansion direction E (refer to Figure 3 ), interference peaks (first peak p1 and second peak p2) corresponding to the optical path length difference opdC and the displacement d9 can be reflected in the extended light L28, and the displacement d9 of the workpiece 9 as the measurement surface can be measured with high precision based on the distance between the interference peaks on the image.

[0068] In this structure, since the interference peaks (first peak p1 and second peak p2) on the image of the extended light L28 are measured, it is possible to perform the measurement at once even for a signal that continuously changes along the expansion direction E, and mechanical operations and measurement times like those of the existing time-domain method are not required. Also, in the second interferometer 20, by expanding the change in the distance dCx of the optical path length difference opdC along the expansion direction E of the extended light L28, the measurement range can also be expanded.

[0069] In this structure, the displacement d9 of the workpiece 9, which serves as the measurement surface, is determined based on the distance xp between the interference peaks (first peak p1 and second peak p2) of the extended light L28 on the image. Therefore, even if there are errors such as temperature changes, high-precision measurement can be performed stably.

[0070] The positions of the first peak p1 and the second peak p2 detected by the image sensor 3 are set by adjusting the relative positions of the first mirror 23 and the second mirror 25, and by adjusting the image sensor 3 or the computing device 4.

[0071] Here, when the displacement measuring device 1 is affected by temperature changes, the positions of the first peak p1 and the second peak p2 detected by the image sensor 3 may change. When measuring using only the position information of a single interference peak, such as the first peak p1 or the second peak p2, these positional changes may become errors, leading to a decrease in measurement accuracy. However, in the displacement measuring device 1 of this embodiment, the distance xp, i.e., the relative displacement of the two interference peaks (the first peak p1 and the second peak p2), is used. Therefore, even if each peak changes due to temperature, the error is canceled out when calculating the distance xp, enabling consistently high-precision measurements.

[0072] In this embodiment, the second interferometer 20 has a beam splitter 22 that branches the interference light L21 and incident it onto the first reflecting surface (first mirror 23) and the second reflecting surface (second mirror 25). The first reflected light L23, L26 and the second reflected light L25, L27 are incident onto the image sensor 3 via the beam splitter 22, and at least one of the first reflecting surface (first mirror 23) and the second reflecting surface (second mirror 25) is a tilting mirror that is tilted relative to the incident light axial extension direction E.

[0073] In this structure, the first interferometer 10 and the second interferometer 20 can be implemented using a Tervamann-Green type interferometer. Moreover, by setting one or both of the first reflecting surface (first mirror 23) and the second reflecting surface (second mirror 25) as tilted mirrors, optical path length differences opdA and opdB along the incident optical axis direction can be formed in each reflecting surface along the tilt direction, and extended light L28 that diffuses in a specified extension direction E and whose optical path length difference opdC changes along the extension direction E can be generated.

[0074] [Second Implementation]

[0075] exist Figures 5 to 9 The figures show a displacement measuring device 1A according to a second embodiment of the present invention.

[0076] This embodiment differs from a portion of the structure of the first embodiment described above. In the following description, the description of the common structures will be omitted, and the different structures will be described.

[0077] exist Figure 5 In the process, the displacement measuring device 1A measures the displacement d9 of the workpiece 9. The displacement measuring device 1A includes a light source 2, an image sensor 3, a computing device 4, a first interferometer 10, and a second interferometer 20A.

[0078] In the aforementioned first embodiment, a tilted first mirror 23 (see reference 20) is used as the first reflecting surface of the second interferometer 20. Figure 1 In contrast, in the second interferometer 20A of this embodiment, a multi-level tilting mirror 23A is used as the first reflecting surface.

[0079] Furthermore, regarding the second mirror 25, which serves as the second reflecting surface of the second interferometer 20A, for the sake of simplicity, in the following description, it is set to angle θB=0, i.e., no tilt, and the optical path length difference is set to opdC=opdA.

[0080] exist Figure 6 In the above, the multi-level tilt mirror 23A is a tilt mirror with high flatness formed by cutting a part of the rectangular substrate 230 to form stepped tilt surfaces 231 to 234 and then precisely grinding the surface of each step.

[0081] Each inclined surface 231-234 is inclined at an angle θA relative to a virtual reference surface 239 that has been shifted a predetermined distance from the back surface of the substrate 230. This inclination causes the distance from the surface of each inclined surface 231-234 to the reference surface 239 to increase from one end (left side of the figure) to the other end (right side of the figure), becoming the distance dA with the largest change. Furthermore, the inclined surfaces 231-234 are staggered in a step-like manner at intervals of distance dA.

[0082] Such a multi-stage tilting mirror 23A is arranged with the reference plane 239 orthogonal to the incident optical axis of the first branch light L22. Thus, the tilting surfaces 231 to 234 are respectively equivalent to the tilting mirrors of the first mirror 23 in the first embodiment described above.

[0083] Here, since the distance dA, which represents the largest change in the angle of each tilting mirror, is the same as the distance dA of the offset, by virtually joining the tilting mirrors sequentially, the change in the incident optical axis direction of the first branch light L22 can be expanded from the distance dA of each surface to a distance of 4dA corresponding to all four surfaces. That is, regarding the change in the incident optical axis direction of the first branch light L22, if the left end of the diagram of tilting surface 231 is set to 0, then the right end of the diagram of tilting surface 231 is the distance dA. The left end of the diagram of tilting surface 232 is the same distance dA as the right end of the diagram of tilting surface 231, and the right end of the diagram of tilting surface 232 is the distance 2dA. By accumulating in the same way, the right end of the diagram of tilting surface 234 is the distance 4dA.

[0084] Therefore, when the first branch light L22 is incident on the multi-stage tilt mirror 23A, the optical path length can be varied from 0 to a maximum distance of 8dA (twice the maximum value of 4dA of the change in the direction of the incident optical axis) depending on the incident position of the whole obtained by combining the tilt surfaces 231 to 234.

[0085] Return to Figure 5 The first reflected light L26 from the multi-level tilting mirror 23A is incident on the image sensor 3 and superimposed with the second reflected light L27 from the second mirror 25 to form an extended light L28. At this time, if the image sensor 3 is set as a two-dimensional image sensor, the fourth-level extended light L28 corresponding to the fourth-level first reflected light L26 reflected by the tilting surfaces 231~234 is detected on the image.

[0086] like Figures 7 to 9 As shown, in image sensor 3, fourth-order extended light L28 reflected by inclined surfaces 231-234 is detected.

[0087] That is, the tilting surfaces 231-234 of the multi-level tilting mirror 23A are arranged in directions intersecting the incident optical axis of each tilting direction and the first branch light L22. Therefore, the first reflected light L26 incident on the image sensor 3 from the tilting surfaces 231-234 becomes a four-level band extending in the tilting direction of the tilting surfaces 231-234 and parallel to each other. On the other hand, since the second reflected light L27 is uniformly distributed on the entire surface of the image sensor 3, the extended light L28 generated in the overlapping area also exhibits a four-level band based on the first reflected light L26.

[0088] As described above, the optical path length changes from a maximum of 0 to a distance of 8dA by sequentially joining the inclined surfaces 231 to 234. Therefore, regarding the optical path length difference opdC of the extended light L28, by sequentially joining the four levels of extended light L28 detected by the image sensor 3 and bringing the first peak p1 close to the left end (position 0) in the figure, the optical path length difference opdC can be expanded from a maximum of 0 to a distance of 8dA.

[0089] exist Figure 7 In the process, when the optical path length difference opdC of the extended light L28 is in the range of 0~2dA, the peaks of the interference signal (the first peak p1 and the second peak p2) appear at the top of the extended light L28.

[0090] When the optical path length difference opdC of the extended light L28 is in the range of more than 2dA and less than 4dA, the second peak p2 appears in the second stage of the extended light L28.

[0091] Therefore, similar to the first embodiment described above, the displacement d9 of the workpiece 9 can be calculated by measuring the distance xp between the first peak p1 and the second peak p2.

[0092] exist Figure 8 In the process, when the optical path length difference opdC of the extended light L28 exceeds the distance 2dA, the first peak p1 remains unchanged in the same position, but the second peak p2 appears in the second stage of the extended light L28.

[0093] exist Figure 8 In this process, the distance from the first peak p1 of the uppermost stage of the extended light L28 to the point where the optical path length difference opdC becomes 2dA is denoted as xp1, and the distance from the point where the optical path length difference opdC of the second stage of the extended light L28 becomes 2dA to the second peak p2 is denoted as xp2. At this point, the distance from the first peak p1 to the second peak p2 can be calculated as xp = xp1 + xp2, and the displacement d9 of the workpiece 9 can be calculated based on the obtained distance xp.

[0094] Similarly, when the optical path length difference opdC of the extended light L28 exceeds a distance of 4dA, the first peak p1 remains in the same position, but the second peak p2 appears in the third stage of the extended light L28.

[0095] Furthermore, when the optical path length difference opdC of the extended light L28 exceeds a distance of 6dA, the first peak p1 remains unchanged in the same position, but the second peak p2 appears in the fourth order of the extended light L28.

[0096] exist Figure 9 In this process, the distance from the first peak p1 in the uppermost extended light L28 to the point where the optical path length difference opdC becomes 2dA is defined as xp1; the distance from the point where the optical path length difference opdC of the second stage of the extended light L28 becomes 2dA to the point where it becomes 4dA is defined as xp2; the distance from the point where the optical path length difference opdC of the third stage of the extended light L28 becomes 4dA to the point where it becomes 6dA is defined as xp3; and the distance from the point where the optical path length difference opdC of the fourth stage of the extended light L28 becomes 6dA to the second peak p2 is defined as xp4. At this point, the distance from the first peak p1 to the second peak p2 can be calculated as xp = xp1 + xp2 + xp3 + xp4, and the displacement d9 of the workpiece 9 can be calculated based on the obtained distance xp.

[0097] Therefore, even if the peak position of the interference signal detected in the extended light L28 (from the first peak p1 to the second peak p2) is far away and cannot be covered by a single tilting mirror (tilted surfaces 231~234), it is possible to detect it by combining multiple levels, thereby expanding the measurement range of the extended light L28.

[0098] Furthermore, in the above description, for the sake of simplicity, the second mirror 25, which serves as the second reflecting surface of the second interferometer 20A, was described as having an angle θB = 0, i.e., no tilt. However, the second mirror 25 can also be tilted at an angle θB, similar to the first embodiment. In this case, in the multi-stage tilt mirror 23A, the tilt surfaces 231 to 234 are staggered in a step-like manner at intervals of distance dA. In contrast, by changing this distance dA to dA + dB, the optical path length difference opdC of the second interferometer 20A can be changed from a maximum of 0 to a distance of 8(dA + dB).

[0099] According to this embodiment, the same effects as the first embodiment described above can be obtained, and the following effects can be obtained.

[0100] In this embodiment, the tilting mirror is a multi-stage tilting mirror 23A in which multiple tilting mirrors (tilting surfaces 231~234) are arranged in a direction that intersects the incident optical axis and the extension direction (tilting direction), and the multiple tilting mirrors are staggered with each other in the direction of the incident optical axis.

[0101] In this structure, by staggering the tilt mirrors (tilt surfaces 231~234) of each level in the optical axis direction, the optical path length difference opdC in the optical axis direction of the multi-level tilt mirror 23A as a whole can be expanded, and a wide measurement range that cannot be obtained by a single tilt mirror can be achieved.

[0102] [Third Implementation Method]

[0103] exist Figures 10 to 13 The figures show the displacement measuring device 1B according to the third embodiment of the present invention.

[0104] This embodiment differs from a portion of the structure of the first embodiment described above. In the following description, the description of the common structures will be omitted, and the different structures will be described.

[0105] exist Figure 10 In the process, the displacement measuring device 1B measures the displacement d9 of the workpiece 9. The displacement measuring device 1B includes a light source 2, an image sensor 3, a computing device 4, a first interferometer 10, and a second interferometer 20B.

[0106] In the aforementioned first embodiment, a tilted first mirror 23 (see reference 20) is used as the first reflecting surface of the second interferometer 20. Figure 1 In contrast, in the second interferometer 20B of this embodiment, a multi-level tilting mirror 23B is used as the first reflecting surface. Furthermore, the second reflecting surface of the second interferometer 20B in this embodiment is also, in the same way as in the first embodiment described above, a tilted second mirror 25.

[0107] exist Figure 11In the above, the multi-level tilt mirror 23B is a tilt mirror with high flatness formed by cutting a part of the rectangular substrate 230 to form stepped tilt surfaces 231 to 238 and then precisely grinding the surface of each step.

[0108] The aforementioned second embodiment of the multi-stage tilting mirror 23A (see reference) Figure 6 The first embodiment has four levels of tilting mirrors (tilt surfaces 231-234). In contrast, the second embodiment has an increased number of levels in its multi-level tilting mirror 23B, with eight levels of tilting mirrors (tilt surfaces 231-238). Apart from the increased number of levels, the structure of the second embodiment's multi-level tilting mirror 23B is the same as that of the second embodiment's multi-level tilting mirror 23A.

[0109] Return to Figure 10 In the displacement measuring device 1B, the multi-stage tilt mirror 23B has a tilt mirror with more stages than the displacement measuring device 1A of the second embodiment, thereby further expanding the measurement range.

[0110] Here, with the number of tilting mirrors increased as in the multi-stage tilting mirror 23B, the diffraction effect of the reflected light from each stage of the tilting mirror becomes significant, sometimes resulting in poor imaging when projected onto the image sensor 3. To prevent this, in the displacement measuring device 1B, a beam splitter is arranged between the image sensor 3 and the beam splitter 22. Figure 12 That kind of double-hole method or Figure 13 The aperture stop 27B is a slit-type aperture.

[0111] exist Figure 12 In the image sensor 3, the aperture stop 27B has two circular holes 271 arranged along the expansion direction E. The first reflected light L26 and the second reflected light L27 pass through the respective circular holes 271 and are incident on the image sensor 3 in a confined state.

[0112] exist Figure 13 In the image sensor 3, the aperture stop 27B has a slit 272 extending along the expansion direction E. The first reflected light L26 and the second reflected light L27 pass through the slit 272 and are incident on the image sensor 3 in a confined state, respectively.

[0113] According to this embodiment, the same effects as the first and second embodiments described above can be obtained, and the following effects can be obtained.

[0114] In this embodiment, an aperture stop 27B for limiting the first reflected light L26 and the second reflected light L27 is disposed between the image sensor 3 and the beam splitter 22.

[0115] In this structure, by blocking the diffracted light caused by the construction of the multi-level tilting mirror 23B, a high depth of focus can be achieved, so that the reflected light from the multi-level tilting mirror 23B, which is deep in the optical axis direction, can be well imaged, thereby achieving a larger measurement range.

[0116] [Fourth Implementation Method]

[0117] exist Figure 14 and Figure 15 The displacement measuring device 1C according to the fourth embodiment of the present invention is shown in the figure.

[0118] This embodiment differs from a portion of the structure of the first embodiment described above. In the following description, the description of the common structures will be omitted, and the different structures will be described.

[0119] exist Figure 14 In the process, the displacement measuring device 1C measures the displacement d9 of the workpiece 9. The displacement measuring device 1C includes a light source 2, an image sensor 3, a computing device 4, a first interferometer 10, and a second interferometer 20C.

[0120] In the aforementioned first embodiment, a tilted first mirror 23 (see reference 20) is used as the first reflecting surface of the second interferometer 20. Figure 1 In contrast, in the second interferometer 20C of this embodiment, a multi-level tilting mirror 23A (the same as in the aforementioned second embodiment) is used as the first reflecting surface. Furthermore, the second reflecting surface of the second interferometer 20C in this embodiment is also, in the same way as in the aforementioned first embodiment, a tilted second mirror 25.

[0121] Furthermore, in the displacement measuring device 1C, a cylindrical lens array 28C is provided between the image sensor 3 and the beam splitter 22.

[0122] exist Figure 15 In the image sensor 3, the cylindrical lens array 28C is formed by arranging four cylindrical lenses 281 in parallel along the expansion direction E. Each cylindrical lens 281 can converge the first reflected light L26 from the four-stage tilting mirrors (tilted surfaces 231~234) of the multi-stage tilting mirror 23A and expand it together with the second reflected light L27 from the second mirror 25 into four linear expanded light L28 extending along the expansion direction E on the surface of the image sensor 3.

[0123] By having such a cylindrical lens array 28C, the amount of light per unit area received by the image sensor 3 can be increased, thereby improving the light intensity of the extended light L28.

[0124] According to this embodiment, the same effects as the first and second embodiments described above can be obtained, and the following effects can be obtained.

[0125] In this embodiment, a cylindrical lens 281 (cylindrical lens array 28C) is provided that continuously converges incident light (first reflected light L26 and second reflected light L27) incident on the image sensor 3 in the extension direction E to the image sensor 3.

[0126] In this structure, by using a cylindrical lens 281 that is designed to converge the incident light (first reflected light L26 and second reflected light L27) when it is illuminated by the image sensor 3 to increase the light intensity and is continuous in the expansion direction E, it is possible to ensure that the extended light L28 has the characteristics of spreading in the specified expansion direction E required for measurement and that the optical path length difference opdC changes along the expansion direction E.

[0127] [Fifth Implementation Method]

[0128] exist Figure 16 The displacement measuring device 1D according to the fifth embodiment of the present invention is shown in the figure.

[0129] This embodiment differs from a portion of the structure of the first embodiment described above. In the following description, the description of the common structures will be omitted, and the different structures will be described.

[0130] exist Figure 16 In the process, the displacement measuring device 1D measures the displacement d9 of the workpiece 9. The displacement measuring device 1D includes a light source 2, an image sensor 3, a computing device 4, a first interferometer 10, and a second interferometer 20D.

[0131] In the aforementioned first embodiment, as the first and second reflecting surfaces of the second interferometer 20, a first mirror 23 and a second mirror 25, which are approximately orthogonal but slightly tilted to the first branch light L22 and the second branch light L24 from the beam splitter 22, are used to return the first reflected light L23 and the second reflected light L25 to the beam splitter 22, thereby setting the second interferometer 20 as a Tervamann-Green type interferometer (see...). Figure 1 ).

[0132] In contrast, the second interferometer 20D in this embodiment is a two-path branch unidirectional interferometer similar to the Mach-Zehnder type. However, in the Mach-Zehnder type, the beams from the two optical paths are superimposed in a beam splitter located before the image sensor, but the second interferometer 20D in this embodiment does not have a beam splitter and the beams are superimposed in the image sensor 3.

[0133] That is, in the second interferometer 20D of this embodiment, the first mirror 23D and the second mirror 25D are tilted significantly relative to the first branch light L22 and the second branch light L24, so that the first reflected light L23 and the second reflected light L25 are emitted to the side opposite to the beam splitter 22 and superimposed in the image sensor 3 to generate the extended light L28.

[0134] In this second interferometer 20D, by appropriately setting the tilt angles of the first mirror 23D and the second mirror 25D, the first reflected light L23 and the second reflected light L25 incident on the image sensor 3 are made into beams that diffuse in the expansion direction E. Here, the optical path lengths of the first reflected light L23 and the second reflected light L25 are the same. On the other hand, the incident angle of the first reflected light L23 onto the image sensor 3 and the incident angle of the second reflected light L25 onto the image sensor 3 are set to be different angles.

[0135] By superimposing the first reflected light L23 with the second reflected light L25, the extended light L28, similar to that in the first embodiment described above, is generated. Regarding the extended light L28, the interference signal is measured as described in the first embodiment above (see [reference]). Figure 3 It can measure the displacement d9 of the workpiece 9, which is the object of measurement.

[0136] Therefore, the displacement measuring device 1D according to this embodiment can also achieve the same effect as the first embodiment described above, and can also achieve the following effects.

[0137] In this embodiment, the second interferometer 20D has a beam splitter 22 that branches the interference light L21 and incident it onto the first reflecting surface (first mirror 23D) and the second reflecting surface (second mirror 25D). The first reflected light L23 and the second reflected light L25 are incident onto the image sensor 3 without passing through the beam splitter 22, and the incident angle of the first reflected light L23 onto the image sensor 3 is different from that of the second reflected light L25 onto the image sensor 3.

[0138] In this structure, it can be achieved by setting the first interferometer 10 as a Tervamann-Green interferometer and the second interferometer 20D as a two-path branch unidirectional interferometer similar to the Mach-Zehnder type. The two-path branch unidirectional interferometer has a simpler optical path than the Tervamann-Green interferometer, thus reducing the loss of light reaching the image sensor 3.

[0139] In the second interferometer 20D, the incident angles of the first reflected light L23 and the second reflected light L25 relative to the image sensor 3 are set to different angles, thereby enabling the spread light L28 generated on the surface of the image sensor 3 to generate a continuous optical path length difference opdC. At this time, by forming the image sensor 3 to be longer in the spreading direction E, the optical path length difference opdC of the spread light L28 can be increased, thus expanding the measurement range. Furthermore, by using a one-dimensional sensor extending along the spreading direction E as the image sensor 3, the measurement operation can be further accelerated.

[0140] [Sixth Implementation Method]

[0141] exist Figure 17 and Figure 18 The displacement measuring device 1E according to the sixth embodiment of the present invention is shown in the figure.

[0142] This embodiment differs from a portion of the structure described in the fifth embodiment. In the following description, the common structures will be omitted, and the different structures will be described.

[0143] exist Figure 17 In the process, the displacement measuring device 1E measures the displacement d9 of the workpiece 9. The displacement measuring device 1E includes a light source 2, an image sensor 3, a computing device 4, a first interferometer 10, and a second interferometer 20E.

[0144] The second interferometer 20E of this embodiment has the same characteristics as the second interferometer 20D of the fifth embodiment described above (refer to...). Figure 16 The same structure. However, in this embodiment, the second mirror 25E is located further away from the beam splitter 22 than the second mirror 25D in the fifth embodiment, and the optical path length of the second reflected light L25 is extended.

[0145] In the displacement measuring device 1E of this embodiment, as described in the displacement measuring device 1D of the fifth embodiment described above, the displacement d9 of the workpiece 9 to be measured can be measured by measuring the interference signal of the extended light L28 received by the image sensor 3 in the same way as the displacement measuring device 1 of the first embodiment described above.

[0146] Furthermore, in the displacement measuring device 1E of this embodiment, the position of the second mirror 25E is changed to extend the optical path of the second reflected light L25, thereby enabling the projection position of the extended light L28 received by the image sensor 3 to shift.

[0147] exist Figure 18 As shown above, sometimes the displacement d9 of workpiece 9 is large, and the interval of the interference signal in the extended light L28 obtained by the displacement measuring device 1D of the fifth embodiment becomes wider, thus failing to converge within the width range of the image sensor 3. In the displacement measuring device 1E of this embodiment, by shifting the projection position of the extended light L28 on the image sensor 3, such as... Figure 18 As shown in the lower part, even when the interval between the interference signals (the distance xp between the first peak p1 and the second peak p2) is wide, it is possible to detect them all at once by the image sensor 3.

[0148] In this embodiment, the optical path length from the beam splitter 22 to the image sensor 3 via the first reflecting surface (first mirror 23D) of the second interferometer 20E is different from the optical path length from the beam splitter 22 to the image sensor 3 via the second reflecting surface (second mirror 25E).

[0149] In this structure, by adjusting the configuration of the first reflecting surface (first mirror 23D) and the second reflecting surface (second mirror 25E) (changing the position of the second mirror 25E), a difference in the optical path length of the reflected light from each reflecting surface can be generated, and the peak of the interference fringes appearing in the extended light L28 received by the image sensor 3 can be shifted in the extension direction E (the extension direction of the image sensor 3). For example, by moving the reference interference signal peak (first peak p1) representing the optical path length difference opdC of the second interferometer 20 being zero to the end of the light-receiving area, a longer optical path length difference measurement width can be generated, thus expanding the measurement range.

[0150] [Seventh Implementation Method]

[0151] exist Figure 19 The displacement measuring device 1F of the seventh embodiment of the present invention is shown in the figure.

[0152] This embodiment differs from a portion of the structure described in the fifth embodiment. In the following description, the common structures will be omitted, and the different structures will be described.

[0153] exist Figure 19 In the process, the displacement measuring device 1F measures the displacement d9 of the workpiece 9. The displacement measuring device 1F includes a light source 2, an image sensor 3, a computing device 4, a first interferometer 10, and a second interferometer 20F.

[0154] The second interferometer 20F of this embodiment has the same characteristics as the second interferometer 20E of the sixth embodiment described above (see reference). Figure 17 The same structure. Furthermore, in this embodiment, a cylindrical lens 28F is provided along the light-receiving surface of the image sensor 3.

[0155] According to this embodiment, the same effects as the aforementioned fifth and sixth embodiments can be obtained, and the following effects can also be obtained.

[0156] In this embodiment, a cylindrical lens 28F is provided that continuously converges incident light (first reflected light L23 and second reflected light L25) incident on the image sensor 3 in the extended direction E to the image sensor 3.

[0157] In this structure, by using a cylindrical lens 28F that is designed to converge the incident light (first reflected light L23 and second reflected light L25) when it is illuminated by the image sensor 3 to increase the light intensity and is continuous in the expansion direction E, it is possible to ensure that the extended light L28 has the characteristics of spreading in the specified expansion direction E required for measurement and that the optical path length difference opdC changes along the expansion direction E.

[0158] [Eighth Implementation Method]

[0159] exist Figure 20 The displacement measuring device 1G of the eighth embodiment of the present invention is shown in the figure.

[0160] This embodiment differs from the second embodiment described above in some structural aspects. In the following description, the common structures will be omitted, and the different structures will be described.

[0161] exist Figure 20 In this embodiment, the displacement measuring device 1G measures the displacement d9 of the workpiece 9. The displacement measuring device 1G includes a light source 2, an image sensor 3, a computing device 4, a first interferometer 10G, and a second interferometer 20A. The light source 2, the image sensor 3, the computing device 4, and the second interferometer 20A are the same as those in the second embodiment described above.

[0162] In the displacement measuring device 1G of this embodiment, the paths from the light source 2 to the first interferometer 10G and from the first interferometer 10G to the image sensor 3 are composed of optical fibers 31, 32, 33 and coupler 34.

[0163] The first interferometer 10G includes an incident-side lens 11, a beam splitter 12, and a reference-side mirror 13 serving as a reference surface. The surface of the workpiece 9, which is the object of measurement, is set as the measurement surface.

[0164] In the first interferometer 10G, the light source L11 from the light source 2 is incident on the incident side lens 11 through the optical fibers 31 and 32. The light source L11 that passes through the incident side lens 11 is split into the reference light L12 and the measurement light L14 by the beam splitter 12.

[0165] The reference light L12 is reflected by the reference side mirror 13, and the reflected reference light L13 returns to the beam splitter 12.

[0166] The measuring light L14 is reflected by the surface (measuring surface) of the workpiece 9, and the reflected measuring light L15 returns to the beam splitter 12.

[0167] The reference light L13 and the measurement light L15 that return to the beam splitter 12 are superimposed to become the interference light L16, which passes through the incident side lens 11 again and is then emitted through the optical fibers 32 and 33 to the second interferometer 20A.

[0168] As described in the second embodiment, the emitted interference light L16 is detected by the image sensor 3 as extended light L28 by the second interferometer 20A, and the displacement d9 of the workpiece 9 is measured.

[0169] In this embodiment, the entrance of the light source L11 of the first interferometer 10G and the exit of the interference light L16 are common. The paths from the light source 2 to the light source L11 of the first interferometer 10G (fibers 31 and 32) and the paths from the first interferometer 10G to the interference light L16 of the second interferometer 20A (fibers 32 and 33) are respectively composed of optical fibers 31, 32, and 33, and the portions of each fiber closest to the first interferometer 10G (fiber 32) are combined into one.

[0170] In this structure, the first interferometer 10G and the workpiece 9 can be positioned separately from the light source 2 and the second interferometer 20A, thereby miniaturizing the detector including the first interferometer 10G, and making it easy to insert the detector even when the workpiece 9 is in a narrow gap.

[0171] [Postscript]

[0172] The following notes are also disclosed regarding the aforementioned implementation methods.

[0173] (Postscript 1)

[0174] A displacement measuring device, comprising:

[0175] A light source that generates broadband light.

[0176] The first interferometer branches the light source light and directs it onto a reference surface and a measurement surface, and superimposes the reference light reflected from the reference surface and the measurement light reflected from the measurement surface to generate interference light;

[0177] The second interferometer branches the interference light and then incident it onto the first and second reflecting surfaces, and superimposes the first reflected light reflected by the first reflecting surface and the second reflected light reflected by the second reflecting surface to generate extended light that diffuses in a predetermined extension direction and whose optical path length difference changes along the extension direction.

[0178] An image sensor that detects the extended light; and

[0179] The computing device determines the displacement of the measurement surface based on the displacement of the peak position of the interference signal in the image detected by the image sensor.

[0180] In this structure, the interference light from the first interferometer generates interference fringes with phases varying according to wavelength, depending on the displacement of the measurement surface. Therefore, in the time domain, interference fringes appear only near locations where the optical path length difference is zero; at other locations, the interference fringes of different wavelengths cancel each other out, resulting in no observable interference fringes. However, if the interference fringes are decomposed according to each wavelength, they can be observed. In existing spectral region methods, a beam splitter is used to spread the interference light by each wavelength to detect the interference fringes.

[0181] In this structure, interference light from a first interferometer is passed through a second interferometer. For the optical path length difference generated in the extended light based on the second interferometer, an interference signal peak is generated at a position where this optical path length difference is equal to twice the workpiece displacement. This interference peak is detected as the interference peak of the extended light in the image. Specifically, the extended light diffuses in the extension direction, and the optical path length difference changes along the extension direction. This allows the interference peak corresponding to the optical path length difference of the extended light to be reflected in the image diffused along the extension direction, enabling high-precision measurement of the displacement of the measurement surface based on the interference peak in the image.

[0182] In its construction, since the interference peak of the extended light on the image is measured, even signals that change continuously along the extension direction can be measured in a single step, eliminating the need for mechanical actions and measurement time required by existing time-domain methods. Furthermore, in the second interferometer, the measurement range can be expanded by amplifying the change in the optical path length difference along the extension direction of the extended light.

[0183] In this structure, the displacement of the measurement surface is determined based on the distance between the interference peaks of the extended light on the image. Therefore, even with errors such as temperature variations, stable and high-precision measurements can be performed. Specifically, if the components of the displacement measuring device are affected by temperature changes, the positions of the interference peaks detected by the image sensor may change. If only the position information of a single interference peak is used for measurement, these positional variations may become errors, leading to a decrease in measurement accuracy. However, in this structure, since the distance, i.e., the relative displacement of two interference peaks, is used, even if the peaks change due to temperature, the errors in calculating the distance cancel each other out, ensuring consistently stable and high-precision measurements.

[0184] (Postscript 2)

[0185] According to the displacement measuring device described in Appendix 1, wherein,

[0186] The second interferometer has a beam splitter that branches the interference light before it is incident on the first and second reflecting surfaces.

[0187] The first reflected light and the second reflected light are incident on the image sensor via the beam splitter.

[0188] Furthermore, at least one of the first reflecting surface and the second reflecting surface is a tilted mirror that is tilted relative to the incident light axis in the expansion direction.

[0189] In this structure, the first and second interferometers can be implemented using a Tervamann-Green interferometer. Furthermore, by setting one or both of the first and second reflecting surfaces as tilting mirrors, a difference in the optical path length along the incident optical axis can be formed along the tilting direction, thereby generating extended light that diffuses in a predetermined extension direction and whose optical path length difference changes along the extension direction.

[0190] (Note 3)

[0191] According to the displacement measuring device described in Appendix 2, wherein,

[0192] The tilting mirror is a multi-stage tilting mirror arranged in a direction intersecting the incident optical axis and the expansion direction, and the multiple tilting mirrors are staggered relative to each other in the direction of the incident optical axis.

[0193] In this structure, by staggering the tilt mirrors of each level in the optical axis direction, the optical path length difference in the optical axis direction of the entire multi-level tilt mirror can be expanded, and a wider measurement range that cannot be obtained by a single tilt mirror can be achieved.

[0194] (Postscript 4)

[0195] According to the displacement measuring device described in Appendix 3, wherein...

[0196] An aperture stop is disposed between the image sensor and the beam splitter to limit the first reflected light and the second reflected light.

[0197] In this structure, by blocking the diffracted light caused by the construction of the multi-level tilting mirrors, a high focal depth can be achieved, which enables the reflected light from the multi-level tilting mirrors that are deep in the optical axis direction to be well imaged, thereby achieving a larger measurement range.

[0198] (Note 5)

[0199] According to the displacement measuring device described in Appendix 2, wherein,

[0200] The image sensor is equipped with a cylindrical lens that is continuous in the extended direction and converges incident light incident on the image sensor onto the image sensor.

[0201] In this structure, by using a cylindrical lens that is designed to converge the incident light when it is illuminated by the image sensor to increase the light intensity and is continuous in the expansion direction, it is possible to ensure the characteristics of the expanded light, such as diffusion in the specified expansion direction required for measurement and the change of the optical path length difference along the expansion direction.

[0202] (Note 6)

[0203] According to the displacement measuring device described in Appendix 1, wherein,

[0204] The second interferometer has a beam splitter that branches the interference light before it is incident on the first and second reflecting surfaces.

[0205] The first reflected light and the second reflected light are incident on the image sensor without passing through the beam splitter.

[0206] Furthermore, the incident angle of the first reflected light onto the image sensor is different from the incident angle of the second reflected light onto the image sensor.

[0207] This structure can be achieved by setting the first interferometer as a Terwaiman-Green interferometer and the second interferometer as a two-path branch unidirectional interferometer similar to the Mach-Zehnder type. The two-path branch unidirectional interferometer has a simpler optical path than the Terwaiman-Green interferometer, thus reducing the amount of light lost reaching the image sensor.

[0208] In the second interferometer, by setting the incident angles of the first reflected light and the second reflected light relative to the image sensor to different angles, a continuous optical path length difference can be generated in the extended light produced on the surface of the image sensor. At this time, by forming the image sensor to be longer in the extended direction, the optical path length difference of the extended light can be increased, thereby expanding the measurement range. Furthermore, if a one-dimensional sensor extending in the extended direction is used as the image sensor, the measurement operation can be further accelerated.

[0209] (Note 7)

[0210] According to the displacement measuring device described in Appendix 6, wherein,

[0211] The optical path length from the beam splitter through the first reflective surface to the image sensor is different from the optical path length from the beam splitter through the second reflective surface to the image sensor.

[0212] In this structure, by adjusting the configuration of the first and second reflecting surfaces, a difference in the optical path length of the reflected light from each reflecting surface can be created, causing the peak of the interference fringes appearing in the extended light received by the image sensor to shift in the extension direction (the extension direction of the image sensor). For example, by moving the reference interference signal peak representing the zero optical path length difference of the second interferometer to the end of the light-receiving area, a longer optical path length difference can be generated, thereby expanding the measurement range.

[0213] (Note 8)

[0214] According to the displacement measuring device described in Appendix 6, wherein,

[0215] The image sensor is equipped with a cylindrical lens that is continuous in the extended direction and converges incident light incident on the image sensor onto the image sensor.

[0216] In this structure, by using a cylindrical lens that is designed to converge the incident light when it is illuminated by the image sensor to increase the light intensity and is continuous in the expansion direction, it is possible to ensure the characteristics of the expanded light, such as diffusion in the specified expansion direction required for measurement and the change of the optical path length difference along the expansion direction.

[0217] (Note 9)

[0218] According to the displacement measuring device described in Appendix 1, wherein,

[0219] The light source inlet and the interference light outlet of the first interferometer are common.

[0220] The paths of the light from the light source to the first interferometer and the paths of the interference light from the first interferometer to the second interferometer are each made of optical fibers, and the portions of the optical fibers closest to the first interferometer are combined into one.

[0221] In this structure, the first interferometer and the workpiece can be positioned separately from the light source and the second interferometer, thereby miniaturizing the detector including the first interferometer, and making it easy to insert the detector even when the workpiece is in a narrow gap.

Claims

1. A displacement measuring device, comprising: A light source that generates broadband light. The first interferometer branches the light source light and directs it onto a reference surface and a measurement surface, and superimposes the reference light reflected from the reference surface and the measurement light reflected from the measurement surface to generate interference light; The second interferometer branches the interference light and then incident it onto the first and second reflecting surfaces, and superimposes the first reflected light reflected by the first reflecting surface and the second reflected light reflected by the second reflecting surface to generate extended light that diffuses in a predetermined extension direction and whose optical path length difference changes along the extension direction. An image sensor that detects the extended light; as well as The computing device determines the displacement of the measurement surface based on the displacement of the peak position of the interference signal in the image detected by the image sensor.

2. The displacement measuring device according to claim 1, wherein, The second interferometer has a beam splitter that branches the interference light before it is incident on the first and second reflecting surfaces. The first reflected light and the second reflected light are incident on the image sensor via the beam splitter. Furthermore, at least one of the first reflecting surface and the second reflecting surface is a tilted mirror that is tilted relative to the incident light axis in the expansion direction.

3. The displacement measuring device according to claim 2, wherein, The tilting mirror is a multi-stage tilting mirror arranged in a direction intersecting the incident optical axis and the expansion direction, and the multiple tilting mirrors are staggered relative to each other in the direction of the incident optical axis.

4. The displacement measuring device according to claim 3, wherein, An aperture stop is disposed between the image sensor and the beam splitter to limit the first reflected light and the second reflected light.

5. The displacement measuring device according to claim 2, wherein, The image sensor is equipped with a cylindrical lens that is continuous in the extended direction and converges incident light incident on the image sensor onto the image sensor.

6. The displacement measuring device according to claim 1, wherein, The second interferometer has a beam splitter that branches the interference light before it is incident on the first and second reflecting surfaces. The first reflected light and the second reflected light are incident on the image sensor without passing through the beam splitter. Furthermore, the incident angle of the first reflected light onto the image sensor is different from the incident angle of the second reflected light onto the image sensor.

7. The displacement measuring device according to claim 6, wherein, The optical path length from the beam splitter through the first reflective surface to the image sensor is different from the optical path length from the beam splitter through the second reflective surface to the image sensor.

8. The displacement measuring device according to claim 6, wherein, The image sensor is equipped with a cylindrical lens that is continuous in the extended direction and converges incident light incident on the image sensor onto the image sensor.

9. The displacement measuring device according to claim 1, wherein, The light source inlet and the interference light outlet of the first interferometer are common. The paths of the light from the light source to the first interferometer and the paths of the interference light from the first interferometer to the second interferometer are each made of optical fibers, and the portions of the optical fibers closest to the first interferometer are combined into one.

Images