Measuring device, measuring method, and method for manufacturing optical system

Abstract

To provide a measuring device capable of measuring eccentricity of an inspection object optical system with high accuracy.SOLUTION: A measuring device 1 which measures eccentricity of an inspection object optical system on the basis of a wavefront acquired for each measurement target surface among a plurality of inspection object surfaces of the inspection object optical system, comprises: a first light source 11 that illuminates a chart including an index surface provided with an index; an objective lens 55 that guides index light emitted from the chart to the inspection object optical system; a first imaging element 90 that receives the index light reflected by the inspection object surface of the inspection object optical system; an interferometer that has a second light source 10 and a second imaging element 95, divides light from the second light source 10 into inspection object light and reference light, and receives, by the second imaging element 95, the reference light and measurement light being the inspection object light reflected at a measurement target surface via the objective lens 55 to acquire a wavefront of the measurement light; and reduction means 300 that reduces intensity of a signal of light reflected at surfaces other than the measurement target surface among the inspection object light reflected at the plurality of inspection object surfaces and received by the second imaging element 95.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a measurement technique for measuring the decentration of a test surface in an optical system. [Background technology]

[0002] The optical performance of an optical system composed of multiple optical elements is affected by the accuracy of the placement of each optical element. To determine whether each optical element is placed in the desired position, a technique for measuring the decentering of the test surface of each optical element is known.

[0003] Patent Document 1 discloses an apparatus for measuring the decentration of a test surface in a test optical system having multiple test surfaces. The apparatus disclosed in Patent Document 1 projects an index light onto the apparent spherical center position of each of the multiple test surfaces. Next, the test optical system and the projection optical system are moved relatively to each other according to the position of an image formed by the projected index light reflected by the test surface. Then, the decentration of the test surface is measured based on the amount of relative movement between the test optical system and the projection optical system. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-164267 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the measurement device disclosed in Patent Document 1, the image formed by the reflected light from the measurement target surface may become unclear due to the influence of the reflected light from the measurement target surface other than the measurement target surface, and as a result, it is not possible to measure the decentering of the measurement target optical system with high accuracy.

[0006] An object of the present invention is to provide a measurement apparatus capable of measuring the decentering of an optical system to be measured with high precision. [Means for solving the problem]

[0007] An eccentricity measurement device as one aspect of the present invention is a measurement device that measures the eccentricity of a test optical system based on a wavefront acquired for each measurement target surface among a plurality of test surfaces in the test optical system, and is characterized by including a first light source that illuminates a chart including an index surface on which an index is provided, an objective lens that guides the index light emitted from the chart to the test optical system, a first imaging element that receives the index light reflected by the test surface of the test optical system, a second light source, and a second imaging element, and is characterized by having an interferometer that divides light from the second light source into test light and reference light, and receives the reference light and the measurement light, which is the test light reflected by the measurement target surface via the objective lens, at the second imaging element, thereby acquiring the wavefront of the measurement light, and a reduction means that reduces the signal intensity of light reflected at places other than the measurement target surface among the test light reflected by the plurality of test surfaces and received by the second imaging element. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a measurement apparatus that can measure the decentering of an optical system to be measured with high precision. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating a configuration of a measurement device according to a first embodiment. [Figure 2] 3A and 3B are diagrams showing a chart, an image-forming surface chart, and an image captured by an image sensor in the first embodiment. [Figure 3] 3 is a flowchart showing a measurement method according to the first embodiment. [Figure 4] FIG. 10 is a diagram illustrating a configuration of a measurement device according to a second embodiment. [Figure 5] 10 is a flowchart showing a measurement method according to a second embodiment. [Figure 6] FIG. 10 is a diagram illustrating a configuration of a measurement device according to a third embodiment. [Figure 7] FIG. 10 is a diagram illustrating the configuration of a measurement device according to a fourth embodiment. [Figure 8]10 is a flowchart illustrating a method for manufacturing an optical system using the measurement device of each embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Note that the drawings may be drawn at a scale different from the actual scale for convenience. In addition, the same reference numerals are used to designate the same components in the drawings, and redundant explanations will be omitted.

[0011] [Example 1] Fig. 1 shows the configuration of a measurement device 1 according to Example 1. Fig. 2 shows a schematic diagram of a chart, an image-forming surface chart, and an image captured by an image sensor in Example 1.

[0012] The measurement device 1 includes an illumination light source (first light source) 11, a chart 40, an objective lens 55, a first image sensor 90, a stage (adjustment means) 150, a low-coherence interferometer 400, and a computer (computation means) 100. The test optical system 60 is an optical system configured by combining multiple lenses, and the measurement device 1 measures the decentration of multiple test surfaces (number of surfaces: N) of the test optical system 60.

[0013] The first light source 11 emits illumination light 290 to illuminate the transmissive chart 40. In this embodiment, the first light source is configured by, for example, a halogen lamp or an LED (Light Emitting Diode). The calculation means may be a processor within the measurement device 1, an external device, or another storage medium. The first image sensor 90 (and an image sensor 95, described later) is, for example, a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal-Oxide Semiconductor) sensor.

[0014] Fig. 2(A) is a schematic diagram of the chart 40 in this embodiment. The chart 40 includes an index surface on which indices are provided. The white areas in Fig. 2(A) indicate areas through which light passes. If the position of the white circle is taken as the origin of the chart 40, the pattern (white triangles) formed on the chart 40 in this embodiment is asymmetric with respect to the origin.

[0015] Using a chart 40 with an asymmetric pattern with respect to the origin, as shown in FIG. 2A, is preferable because it makes it easy to determine whether the origin of the chart image formed by the index light 250 is at the center of curvature of the test surface or on the surface of the test surface. For example, when the chart shown in FIG. 2A is used, when the chart image is formed at the surface position of the test surface, an image like that shown in FIG. 2E (inverted with respect to the origin compared to FIG. 2D) is observed. Furthermore, in step S30 (described later), when the objective lens 55 is positioned near the design position, the index light may be focused on a surface of the test surface other than the surface to be measured, resulting in multiple chart images being observed on the image sensor 90. Even in such cases, using a chart 40 with an asymmetric pattern is preferable because it makes it easy to determine the reflected light from the surface to be measured.

[0016] In this embodiment, a chart having the shape shown in Fig. 2(A) was used as the chart 40, but the shape is not limited to this. The shape of the light-transmitting area may also be any shape; for example, a cross, a circle, a square, etc. may be arranged instead of a triangle.

[0017] The chart 40 emits divergent light (index light) 250. The patterns (white circles and white triangles in FIG. 2(A)) formed on the chart 40 are close to each other (for example, at a distance of 1 mm or less), and therefore are depicted in FIG. 1 as light diverging from a single point.

[0018] The index light 250 passes through the beam splitter 35, becomes parallel light by the collimator lens 50, passes through the beam splitter 36 and the beam splitter 30, is collected by the objective lens 55, and enters the optical system 60 to be tested. The objective lens 55 is installed on a stage 150 that moves in the X, Y, and Z directions in FIG. 1, and can adjust the position of the chart image (real image or virtual image) formed by the index light 250. The position of the stage 150 is managed by the computer 100.

[0019] Note that the method for adjusting the relative positions of the objective lens 55 and the test optical system 60 is not limited to this. For example, the objective lens 55 may be fixed, and the test optical system 60 may be placed on a stage, and the position of the test optical system 60 may be adjusted. Also, both the objective lens 55 and the test optical system 60 may have adjustment means. Furthermore, all optical elements other than the test optical system 60, including the objective lens 55, may be placed on a stage, and the relative positions of the objective lens 55 and the test optical system 60 may be adjusted by moving their positions together.

[0020] During measurement, the origin (X, Y, Z) of the chart image formed by the index light 250 is brought close to the apparent center of curvature (Xc, Yc, Zc) of the kth (k = 1, 2, . . . , N) test surface (measurement target surface 60k) in the test optical system 60. As a result, the index light 250 is reflected from the measurement target surface 60k and travels backward along an optical path similar to the incident optical path. That is, the index light 250 reflected from the measurement target surface 60k passes through the objective lens 55, beam splitter 30, beam splitter 36, and collimator lens 50, and reaches the beam splitter 35. A portion of the index light 250 is reflected by the beam splitter 35 and enters the imaging surface chart 80. At this time, the image of the chart 40 is formed on the imaging surface chart 80. The imaging lens 52 also forms the image on the imaging surface chart 80 onto the first image sensor 90. The first image sensor 90 captures an image of the chart 40. The image obtained by the first image sensor 90 is sent to the computer 100. Note that the index light 250 reflected by a test surface other than the measurement target surface 60k travels backward as light with a different degree of convergence and divergence compared to the incident light, and therefore does not form an image on the first image sensor 90.

[0021] In this embodiment, the imaging surface chart 80 has a reference line (broken line) drawn on it, as shown in FIG. 2(B). Therefore, the first image sensor 90 simultaneously captures an image of the chart and an image of the reference line. The imaging surface chart 80 is not limited to this, and a chart of any shape can achieve the same effect. The reference line may be drawn directly on the display that displays the image obtained by the first image sensor 90, or may be overlaid on the image data.

[0022] FIG. 2(C) is a schematic diagram of an image captured by the first imaging element 90 when the position of the origin (X, Y, Z) of the chart image and the position of the apparent center of curvature (Xc, Yc, Zc) of the measurement target surface 60k are X≠Xc, Y≠Yc, and Z=Zc. FIG. 2(D) is a schematic diagram of an image captured by the first imaging element 90 when X=Xc, Y=Yc, and Z=Zc. FIG. 2(D) is the same as the image observed when a plane mirror is placed between the collimator lens 50 and the objective lens 55 so as to be parallel to the XY plane and the index light 250 is reflected by the plane mirror. The position of the image at this time is referred to as the reference position in this embodiment. For simplicity of explanation, FIGS. 2(C) and 2(D) show an example in which the vertical and horizontal orientations are aligned with those of the pattern arrangement in FIG. 2(A). The arrangement and orientation of the pattern are not limited to this, and an image that is inverted vertically and horizontally may be obtained depending on the orientation of the first imaging element 90 and the signal processing in the computer 100.

[0023] The low-coherence interferometer 400 in this embodiment is a Twyman-Green interferometer that includes a low-coherence light source (second light source) 10, a fiber 20, collimator lenses 51 and 54, an aperture 110, beam splitters 30 and 36, an objective lens 55, a reference mirror 70, a reference stage (adjustment means) 160, a condenser lens 53, a spatial filter 300, and a second image sensor 95. The spatial filter 300 is, for example, a pinhole or an aperture, and corresponds to the reduction means in this embodiment.

[0024] The measurement device 1 of this embodiment has an aperture 110 between the collimator lens 51 and the beam splitter 36. By narrowing the beam of low-coherence light 200 using the aperture 110 to reduce the irradiation area on the measurement target surface 60k, the position of the objective lens 55 can be adjusted with high precision even in the case of an aspherical surface on which there are multiple apparent spherical center positions on the measurement target surface 60k. This is because reducing the irradiation area using the aperture 110 allows an aspherical surface to be considered as a spherical surface. The index light 250 needs to have a relatively high spatial frequency (a large beam of light including peripheral light) to form a chart image, but the low-coherence light 200 may have a low spatial frequency (a beam of light smaller than the beam of the index light) as long as it is able to form interference fringes.

[0025] In this embodiment, the diaphragm 110 is placed between the collimator lens 51 and the beam splitter 36, but this is not limitative. The diaphragm 110 may be placed anywhere before irradiation onto the measurement target surface 60k. For example, it may be placed between the beam splitter 30 and the objective lens 55. In addition to the method of placing the diaphragm, the irradiation area can be made smaller by changing the NA of the collimator lens 51 so that it is larger than the NA of the fiber 20. This configuration also provides the same effect.

[0026] The second light source 10 is a broadband light source such as an LED or an SLD (Super Luminescent Diode). Alternatively, a semiconductor laser with a relatively short coherence length may be used. The low-coherence light 200 emitted from the second light source 10 is emitted through a fiber 20, converted into parallel light by a collimator lens 51, transmitted through an aperture 110, and then reflected by a beam splitter 36. The low-coherence light 200 reflected by the beam splitter 36 propagates in the same direction as the index light 250 and is split by the beam splitter 30 into reflected light (reference light) 200r and transmitted light (test light) 200s.

[0027] The reference light 200r reflected by the beam splitter 30 is reflected by a reference mirror 70 arranged on the reference stage 160 and returns to the beam splitter 30. The reference stage 160 moves in the direction of the arrow (Y direction) in FIG. 1, and can change the optical path length (reference optical path length) of the reference light 200r. Note that the position of the reference stage 160 in this embodiment is managed by the computer 100.

[0028] An ND filter or the like that adjusts the intensity of the reference light 200r may be disposed between the beam splitter 30 and the reference mirror 70. The reference mirror 70 may be a metal mirror with high reflectivity, or a glass surface with reflectivity similar to that of the test surface. A portion of the reference light 200r passes through the beam splitter 30, is collected by the collecting lens 53, passes through the spatial filter 300, and then diverges. The collimator lens 54 converts the light into parallel light and the light enters the second image sensor 95.

[0029] The test light 200s transmitted through the beam splitter 30 is focused by the objective lens 55 and enters the test optical system 60. As with the index light 250, when the position of the apparent focusing point of the test light 200s coincides with the position of the apparent center of curvature of the measurement target surface 60k, the test light 200s is reflected by the measurement target surface 60k and travels backward along an optical path similar to the incident optical path. The test light (measurement light) 200s reflected by the measurement target surface 60k is converted into parallel light by the objective lens 55 and reaches the beam splitter 30. A portion of the test light (measurement light) 200s is reflected by the beam splitter 30, focused by the condenser lens 53, transmitted through the spatial filter 300, and then diverges. The collimator lens 54 converts the parallel light into parallel light and enters the second image sensor 95.

[0030] On the other hand, unwanted light, which is test light reflected by a test surface other than the measurement target surface 60k, travels backward as light with a different degree of convergence and divergence than the incident light. The unwanted light passes through the objective lens 55, is partially reflected by the beam splitter 30, and is guided to the spatial filter 300 via the condenser lens 53. However, because the unwanted light has a different degree of convergence and divergence from the measurement light 200s, it does not form an image at the position of the spatial filter 300. As a result, the spatial filter 300 can reduce the unwanted light incident on the second image sensor 95.

[0031] The second imaging element 95 receives the measurement light 200s and the reference light 200r. The measurement light 200s and the reference light 200r interfere with each other and form interference fringes before entering the second imaging element 95. A signal obtained from the light received by the second imaging element 95 is sent to the computer 100. At this time, the second imaging element 95 converts the received light into a signal through processing such as photoelectric conversion. The computer (computing means) 100 calculates a wavefront based on the signal (interference signal) of the measurement light 200s and the reference light 200r obtained by the second imaging element 95, and determines the eccentricity based on the position of the objective lens 55 (stage 150) and the calculated wavefront.

[0032] In the interferometer of this embodiment, interference fringes are formed by making the optical path lengths of the measurement light and the reference light approximately equal to each other using the reference stage 160. On the other hand, the optical path lengths of the test light reflected from a test surface other than the measurement target surface 60k are not approximately equal to the optical path lengths of the reference light, and therefore, no interference fringes are formed even when the light beams are combined.

[0033] In conventional measurement devices using the autocollimation method, the position of the image formed by the reflected light (measurement light) from the measurement target surface is acquired, and the decentering of the measurement target surface is calculated from that position. However, when there are many test surfaces or when a lens with a large decentering is present inside the test optical system, the image may become blurred due to the effects of aberration and vignetting.

[0034] Furthermore, because reflected light from test surfaces other than the surface being measured (unwanted light) also enters the imaging element, the image formed by the measurement light may be difficult to distinguish due to background noise caused by the unwanted light, which can reduce the accuracy of eccentricity measurement.

[0035] Therefore, the measurement device 1 according to this embodiment reduces reflected light from other than the measurement target surface that is incident on the second image sensor by a reduction unit (spatial filter 300). With this configuration, it is possible to measure the decentering of the test surface in the test optical system with high accuracy.

[0036] Next, the measurement method in this embodiment will be described with reference to Fig. 3. Fig. 3 is a flowchart showing the decentration measurement method for the test optical system in the first embodiment.

[0037] First, in step S10, a measurement target surface 60k (the kth test surface) is selected from a plurality of test surfaces (number of surfaces: N). The measurement target surfaces may be selected in order from the first surface to the Nth surface of the test optical system (in order of optical path length), or in order of the distance from the apparent center of curvature position. Alternatively, they may be selected in random order.

[0038] In step S20, the design position of the objective lens 55 and the design position of the reference stage 160 on the measurement target surface are acquired. The design position of the objective lens 55 is the X, Y, and Z positions (calculated values) of the objective lens 55 when the position of the origin of the chart image and the apparent center of curvature of the measurement target surface 60k coincide with each other. These values are calculated by paraxial calculation or ray tracing using the design values of the test optical system 60. The design position of the reference stage 160 is the position of the reference stage 160 when the optical path length of the test light reflected on the measurement target surface 60k and the reference optical path length are equal, and is calculated based on the design values of the test optical system 60.

[0039] In step S30, the position of the objective lens 55 is adjusted by the stage 150 so that an image of the chart 40 is formed at a reference position on the first imaging element 90. It is preferable to record the adjustment amount (or position information) of the objective lens 55 by the first adjustment means at this time as a first adjustment amount. In this step, first, the objective lens 55 is placed near the design position (initial position), and the position of the objective lens 55 in the Z direction is adjusted so that an image of the chart 40 is formed on the first imaging element 90.

[0040] If the measurement target surface 60k is decentered, the chart image observed will be displaced from the reference position, as shown in Figure 2(C). Therefore, the X and Y positions of the objective lens 55 are adjusted by the adjustment means (stage 150) so that the image observed by the first image sensor 90 is formed at the reference position (as shown in Figure 2(D)). This adjustment in step S30 corresponds to the first adjustment (coarse adjustment) of the objective lens 55.

[0041] In step S40, in the low-coherence interferometer 400, the reference stage 160 scans the reference optical path length, and interference fringes are obtained due to interference between the measurement light 200s and the reference light 200r.

[0042] In step S50, a wavefront is calculated based on the interference fringes (interference signal), and the position of the objective lens 55 is adjusted based on the wavefront. The adjustment amount (or position information) of the objective lens 55 by the second adjustment means at this time is recorded as a second adjustment amount. The wavefront can be calculated using, for example, a phase shift method. The X and Y positions of the objective lens 55 can be adjusted based on the tilt component of the wavefront. Furthermore, the Z position of the objective lens 55 can be adjusted based on the defocus component of the wavefront.

[0043] In this embodiment, as an example, the wavefront tilt component and defocus component are adjusted to be the wavefront tilt component (reference amount) and defocus component (reference amount) obtained when a mirror parallel to the XY plane is inserted between the beam splitter 30 and the objective lens 55. However, it is not necessary to adjust them to be exactly the same as the reference amount; it is sufficient to adjust them to be within the range of the reference amount ±λ / 2. This adjustment in step S50 corresponds to a fine adjustment (second adjustment) of the objective lens 55.

[0044] In step S60, an adjustment amount for the position of the objective lens is acquired. The adjustment amount for the position of the objective lens is an amount equivalent to the first adjustment amount acquired in step S30 and the second adjustment amount acquired in step S50, or the sum of the first adjustment amount and the second adjustment amount, or information on the final position of the objective lens 55.

[0045] In step S70, it is determined whether or not the adjustment amount of the objective lens position relative to each test surface has been acquired. If it has been acquired, the process proceeds to step S80, and if it has not been acquired, the process returns to step S10.

[0046] In step S80, the decentering of each test surface is calculated based on the adjustment amount of the objective lens 55 for each test surface. In this embodiment, the decentering is calculated in order (in order of optical path length) from the first surface to the Nth surface of the test optical system. The relative position between the objective lens 55 and the test optical system 60 is determined from the adjustment amount of the objective lens 55, and the decentering of the test surface 60k can be calculated by paraxial calculation or ray tracing from the objective lens 55 to the test surface 60k. Note that when calculating the decentering of the kth surface, the decentering from the first surface to the k-1th surface is required, so it is preferable to calculate the decentering in order starting from the first surface.

[0047] In this embodiment, the lighting of the first light source 11 and the second light source 10 is separated in time. This configuration is preferable because it does not require processing such as image processing to separate the signal based on the received reflected light.

[0048] In this embodiment, the first light source 10, objective lens 55, and first image sensor 90 for acquiring the chart image are not essential, and the effects of the present invention can be achieved by the interferometer and the reduction means. Similarly, the reduction means is not essential, and the decentering of the test optical system can be measured with high accuracy by using the configuration for acquiring the chart image and the interferometer.

[0049] In a conventional measurement device that calculates the eccentricity of a measurement target surface from a wavefront obtained by a low-coherence interferometer, when measuring an optical system including a highly decentered test surface, the optical path of the reflected light is significantly tilted, resulting in dense interference fringes, making it difficult to accurately obtain the wavefront. Furthermore, background noise caused by reflected light from test surfaces other than the measurement target surface also contributes to a decrease in accuracy. Therefore, the adjustment means in the measurement device 1 according to this embodiment adjusts the relative position of the objective lens 55 and the test optical system 60 so that a chart image is formed at a reference position on the first image sensor 90 (step S30). This adjustment reduces the tilt of the optical path of the reflected light, thereby obtaining less dense interference fringes. Furthermore, this adjustment allows the measurement light 200 to pass through the spatial filter 300, thereby separating unwanted light from the measurement light 200. By sufficiently reducing background noise, the position of the objective lens 55 can be accurately adjusted based on the wavefront. As a result, the accuracy of eccentricity measurement can be improved.

[0050] [Example 2] FIG. 4 shows the configuration of a measurement device 2 according to the second embodiment.

[0051] The measurement device 2 includes a light source 12, a chart 41, an objective lens 55, a first image sensor 90, a stage (adjustment means) 151, a low-coherence interferometer 400, and a computer (computation means) 100. The light source 12 in this embodiment differs from that in the first embodiment in that it functions as a first light source and a second light source.

[0052] The light source 12 emits illumination light 290, which illuminates a transmissive chart 41 via a condenser lens 56. The chart 41 in this embodiment is a chart (pinhole) with only a white circle (origin) and no white triangular portion as shown in FIG. 2A. The chart 41 emits divergent light (index light 250 and low-coherence light 200).

[0053] The index light 250 passes through the beam splitter 35 , is converted into parallel light by the collimator lens 50 , passes through the beam splitters 31 and 30 , is condensed by the objective lens 55 , and enters the optical system 60 to be tested.

[0054] The stage 151 is driven in the X, Y, and Z directions. The test optical system 60 is placed on the stage 151. The stage 151 adjusts the position of the test optical system 60 relative to the position of the image of the chart formed by the index light 250. The position of the stage 151 is managed by the computer 100.

[0055] During measurement, the position (X, Y, Z) of the origin of the chart image formed by the index light 250 is brought close to the position (Xc, Yc, Zc) of the apparent center of curvature of the kth (k=1, 2, . . . , N) test surface (measurement target surface 60k) in the test optical system 60. As a result, the index light 250 is reflected by the measurement target surface 60k and travels backward along an optical path similar to the incident optical path. The index light 250 reflected by the measurement target surface 60k passes through the objective lens 55, beam splitter 30, beam splitter 31, collimator lens 50, beam splitter 35, image plane chart 80, and imaging lens 52 and enters the first image sensor 90.

[0056] The low-coherence interferometer 400 in this embodiment is a Twyman-Green interferometer comprising a light source 12, a collimator lens 50, a beam splitter 30, a beam splitter 31, an objective lens 55, a reference mirror 70, a reference stage (changing means) 160, and second image sensors 95 and 96. In this interferometer, the optical path length from the beam splitter 30 to the second image sensor 95 is approximately equal to the optical path length from the beam splitter 30 to the second image sensor 96. The shape of the wavefront changes depending on the propagation distance (optical path length) from the beam splitter 30 to the second image sensor. In this embodiment, the above-described configuration is used so that the wavefront shapes at the second image sensors 95 and 96 are approximately equal.

[0057] The low-coherence light 200 passes through the beam splitter 35, is converted into parallel light by the collimator lens 50, passes through the beam splitter 31, and is split by the beam splitter 30 into reflected light (reference light) 200s and transmitted light (test light) 200r.

[0058] The reference light 200r reflected by the beam splitter 30 is reflected by a reference mirror 70 arranged on the reference stage 160 and returns to the beam splitter 30. A portion of the reference light 200r, namely, light 200r1, passes through the beam splitter 30 and enters a second image sensor 95. A portion of the reference light 200r, namely, light 200r2, is reflected by the beam splitter 30 and beam splitter 31 and enters another second image sensor 96. The position of the reference stage 160 is managed by the computer 100.

[0059] The test light 200s transmitted through the beam splitter 30 is focused by the objective lens 55 and enters the test optical system 60. As with the index light 250, when the position of the apparent focusing point of the test light 200s coincides with the position of the apparent center of curvature of the measurement target surface 60k, the test light 200s is reflected by the measurement target surface 60k and travels backward along an optical path similar to the incident optical path. The test light (measurement light) 200s reflected by the measurement target surface 60k is converted into parallel light by the objective lens 55 and reaches the beam splitter 30. A portion of the measurement light 200s, light 200s1, is reflected by the beam splitter 30 and enters the second image sensor 95. A portion of the measurement light 200s, light 200s2, is transmitted through the beam splitter 30, reflected by the beam splitter 31, and enters another second image sensor 96.

[0060] It is preferable that the sum of the intensities of the test light 200s1 and the reference light 200r1 incident on the second image sensor 95 and the sum of the intensities of the test light 200s2 and the reference light 200r2 incident on the second image sensor 96 are adjusted in advance to have the same signal intensity A(x, y). Note that the signal intensity may be adjusted by changing the exposure time or gain of each image sensor, or by inserting an ND filter in front of the image sensor.

[0061] The measurement light 200s1 and the reference light 200r1 are incident on the second image sensor 95 while forming interference fringes (first interference fringes). A first signal I1(x, y) obtained based on the light received by the second image sensor 95 is sent to the computer 100. The first signal I1(x, y) is expressed using the following equation (1) using the amplitude B(x, y) of the interference fringes, the wavefront Φ(x, y), and the intensity N(x, y) of the test light (unwanted light) reflected from a test surface other than the measurement target surface 60k. I1(x,y)=A(x,y)+B(x,y)cos(Φ(x,y))+N(x,y) ···(1)

[0062] Similarly, the measurement light 200s2 and the reference light 200r2 are incident on the second image sensor 95 while forming interference fringes (second interference fringes). A second signal I2(x,y) obtained based on the light received by the second image sensor 95 is sent to the computer 100. The second signal I2(x,y) is expressed by the following equation (2) using the amplitude B(x,y) of the interference fringes, the wavefront Φ(x,y), and the intensity N(x,y) of the test light (unwanted light) reflected by a test surface other than the measurement target surface 60k. The phase of the second signal I2(x,y) is inverted with respect to the first signal I1(x,y). I2(x,y)=A(x,y)+B(x,y)cos(Φ(x,y)+π)+N(x,y) ···(2)

[0063] The reduction means in this embodiment reduces the influence of unwanted light by calculating a differential interference signal D(x,y) from a first signal I1(x,y) expressed by equation (1) and a second signal I2(x,y) expressed by equation (2). The differential interference signal D(x,y) is expressed by the following equation (3). D(x,y)=2B(x,y)cos(Φ(x,y)) ···(3)

[0064] By adopting such a configuration, it is possible to reduce background noise of interference fringes, thereby improving the accuracy of eccentricity measurement. Note that the reduction means in this embodiment is executed by arithmetic processing by the computer 100.

[0065] It should be noted that the reduction means in this embodiment is not limited to this, and may be configured by a circuit (not shown) for communicating signals between the second imaging elements 95, 96 and the computer 100, or by a CPU or arithmetic device separate from the computer 100.

[0066] Furthermore, the reduction means of this embodiment may be configured in combination with the reduction means (spatial filter) of embodiment 1. By arranging a condenser lens, a spatial filter, and a collimator lens in front of each of the second image sensors 95 and 96 in the measurement device 2 according to this embodiment, the reduction means of embodiment 1 can be combined.

[0067] Combining the reduction means using arithmetic processing in this embodiment with separation of unwanted light using a spatial filter is preferable because it is possible to further reduce the influence of unwanted light.

[0068] FIG. 5 is a flowchart showing a method for measuring the eccentricity of the optical system to be measured in the second embodiment.

[0069] First, in step S11, the designed position of the optical system 60 to be measured and the designed position of the reference stage 160 on each surface to be measured are acquired.

[0070] In step S21, a measurement target surface 60k (the k-th test surface) is selected from a plurality of test surfaces (number of surfaces: N).

[0071] In step S31, the position of the test optical system 60 is adjusted by the stage 151 so that an image of the chart 40 is formed at a reference position on the first image sensor 90. It is preferable to record the adjustment amount (or position information) of the test optical system 60 by the first adjustment means at this time as the first adjustment amount.

[0072] In step S41, the reference stage 160 in the low-coherence interferometer 400 scans the reference optical path length to obtain interference fringes.

[0073] In step S51, a wavefront is calculated from the interference fringes. In this embodiment, unlike the first embodiment, the second adjustment (fine adjustment) of the test optical system 60 by the second adjustment means based on the wavefront is not performed, and the wavefront is obtained from the interference fringes.

[0074] In step S61, it is confirmed whether the first adjustment amount and wavefront for each test surface have been acquired. If completed, the process proceeds to step S71, and if not completed, the process returns to step S21.

[0075] In step S71, the decentering of each test surface is calculated from the first adjustment amount and wavefront of each test surface. In step S71 in this embodiment, an amount equivalent to the second adjustment amount in Example 1 is calculated by paraxial calculation or ray tracing using the relative position between the objective lens 55 and the test optical system 60 when the wavefront of the test surface 60k is acquired and the wavefront at that time. Then, the decentering of the test surface 60k is calculated based on the first adjustment amount and the second adjustment amount.

[0076] In the measurement device 2 according to this embodiment, the reduction means executes a process of calculating the difference between the interference fringes I0(x, y) and I1(x, y) formed by reflection from or transmission through the beam splitter 30. With this configuration, it is possible to reduce the background noise of the interference fringes, and to measure the decentering of the test surface in the test optical system with high accuracy.

[0077] Furthermore, in the measurement method according to this embodiment, the relative position of the test optical system 60 with respect to the objective lens 55 is adjusted (coarse adjustment) so that the chart image is formed at the reference position on the first image sensor 90, and then interference fringes are acquired by the low-coherence interferometer. With this configuration, it is possible to acquire sparse interference fringes. As a result, it is possible to calculate the wavefront with high accuracy, and it is possible to improve the measurement accuracy of the eccentricity acquired based on the wavefront.

[0078] [Example 3] FIG. 6 shows the configuration of a measurement device 3 according to the third embodiment.

[0079] The measurement device 3 includes a light source 12, a chart 40, an objective lens 55, an image sensor 99, a stage (adjustment means) 150, a low-coherence interferometer 400, and a computer (computation means) 100. The light source 12 in this embodiment functions as a first light source and a second light source, similar to embodiment 2. The image sensor 99 in this embodiment differs from embodiment 1 in that it functions as a first image sensor and a second image sensor depending on the optical system inserted by an exchange means 550, which will be described later.

[0080] Furthermore, the measurement device 3 has an optical system 500A that includes an image-forming surface chart 80 and an imaging lens 52 and is used to acquire a chart image, an optical system 500B that includes a spatial filter 300 and a collimator lens 54 and is used to acquire interference fringes, and an exchange means 550. The optical system (chart image acquisition optical system) 500A and the optical system (interference fringe acquisition optical system) 500B are configured to be exchangeable. The exchange means 550 is configured with a stage or the like, and inserts 500A into the optical path when acquiring a chart image, and 500B into the optical path when acquiring interference fringes.

[0081] The index light 250 passes through the beam splitter 35 , is converted into parallel light by the collimator lens 50 , passes through the beam splitter 30 , is condensed by the objective lens 55 , and enters the optical system 60 to be tested.

[0082] The position (X, Y, Z) of the origin of the chart image formed by the index light 250 is brought closer to the position (Xc, Yc, Zc) of the apparent center of curvature of the kth (k=1, 2, . . . , N) test surface (measurement target surface 60k) in the test optical system 60. As a result, the index light 250 is reflected by the measurement target surface 60k and travels backward along an optical path similar to the incident optical path. The index light 250 reflected by the measurement target surface 60k passes through the objective lens 55, the beam splitter 30, the collimator lens 50, the beam splitter 35, and the optical system 500A and enters the image sensor 99 (first image sensor).

[0083] The low-coherence interferometer 400 in this embodiment is a Twyman-Green interferometer that includes a light source 12, a collimator lens 50, a beam splitter 30, an objective lens 55, a reference mirror 70, a reference stage (changing means) 160, an optical system 500B, and an image sensor 99 (second image sensor).

[0084] The low-coherence light 200 passes through the beam splitter 35, is converted into parallel light by the collimator lens 50, and is split by the beam splitter 30 into reflected light (reference light) 200s and transmitted light (test light) 200r.

[0085] The reference light 200r reflected by the beam splitter 30 is reflected by a reference mirror 70 arranged on the reference stage 160 and returns to the beam splitter 30. A portion of the reference light 200r is reflected by the beam splitter 30, collected by the collimator lens 50, reflected by the beam splitter 35, and guided to a spatial filter (reduction means) 300 of the optical system 500B. The reference light 200r transmitted through the spatial filter 300 diverges, is converted into parallel light by the collimator lens 54, and enters the image sensor 99.

[0086] The test light 200s transmitted through the beam splitter 30 is focused by the objective lens 55 and enters the test optical system 60. As with the index light 250, when the position of the apparent focusing point of the test light 200s coincides with the position of the apparent center of curvature of the measurement target surface 60k, the test light 200s is reflected by the measurement target surface 60k and travels backward along an optical path similar to the incident optical path. The test light (measurement light) 200s reflected by the measurement target surface 60k is converted into parallel light by the objective lens 55 and reaches the beam splitter 30. A portion of the measurement light 200s transmits through the beam splitter 30, is collected by the collimator lens 50, is reflected by the beam splitter 35, and is collected on the spatial filter 300 of the optical system 500B. A portion of the measurement light 200s transmitted through the spatial filter 300 diverges, is converted into parallel light by the collimator lens 54, and enters the image sensor 99. The reduction means in this embodiment is a spatial filter 300, which reduces the unwanted light incident on the second image sensor 95 by using the difference in the degree of convergence and divergence between the unwanted light and the measuring light 200s.

[0087] The measurement light 200s and the reference light 200r form interference fringes, which are received by the image sensor 99. A signal obtained based on the light received by the image sensor 99 is sent to the computer 100.

[0088] In the measurement device 3 according to this embodiment, unnecessary light is blocked by a reduction means (spatial filter 300). With this configuration, the decentering of the test surface in the test optical system can be measured with high accuracy.

[0089] Furthermore, after adjusting (roughly adjusting) the objective lens 55 so that the chart image is formed at the reference position on the first image sensor 90, interference fringes are acquired by the low-coherence interferometer. This makes it easy to acquire sparse interference fringes. As a result, eccentricity can be calculated using a wavefront obtained based on sparse interference fringes, thereby achieving highly accurate eccentricity measurement.

[0090] [Example 4] FIG. 7 shows the configuration of a measurement device 4 according to the fourth embodiment.

[0091] The measurement device 4 includes a light source 12, a chart 41, an objective lens 55, a first image sensor 90, a stage (adjustment means) 150, a low-coherence interferometer 400, and a computer (computation means) 100. The light source 12 in this embodiment functions as a first light source and a second light source, similarly to the second and third embodiments.

[0092] The index light 250 is converted into parallel light by the collimator lens 50, passes through the beam splitter 30, is collected by the objective lens 55, passes through the beam splitter 32, and enters the test optical system 60. The test optical system 60 is placed on a stage (adjustment means) 151 that moves in the X, Y, and Z directions, and the relative position between the position of the chart image formed by the index light 250 and the position of the test optical system 60 can be adjusted. The position of the stage 151 is managed by the computer 100.

[0093] When the index light 250 reflected by the measurement object surface 60k forms a virtual image of the chart 41 at negative infinity on the Z axis, the index light 250 becomes parallel light and is emitted from the test optical system 60. The index light 250 reflected by the measurement object surface 60k is reflected by the beam splitter 32, passes through the beam splitter 33, is collected by the imaging lens 52, and enters the first image sensor 90. The image obtained by the first image sensor 90 is sent to the computer 100.

[0094] The low-coherence interferometer 400 in this embodiment is a Mach-Zehnder interferometer including a light source 12, a collimator lens 50, beam splitters 30 to 33, an objective lens 55, a reference mirror 70, a reference stage (adjustment means) 160, and a second image sensor 95. By placing the second image sensor 95 on a stage 170 that moves in the Z direction, it is possible to adjust the position at which the interference light between the measurement light 200s and the reference light 200r is incident. The position of the stage 170 is managed by a computer 100.

[0095] The low-coherence light 200 is collimated by the collimator lens 50 and split by the beam splitter 30 into reflected light (reference light) 200s and transmitted light (test light) 200r.

[0096] The reference light 200r reflected by the beam splitter 30 passes through the beam splitter 31, is reflected by the reference mirror 70 arranged on the reference stage 160, and returns to the beam splitter 31. Thereafter, the reference light 200r is reflected by the beam splitter 31, passes through the beam splitter 33, and enters the second image sensor 95.

[0097] The test light 200s transmitted through the beam splitter 30 is collected by the objective lens 55, transmitted through the beam splitter 32, and enters the test optical system 60 (guided to the measurement target surface 60k). The test light (measurement light) 200s reflected by the measurement target surface 60k becomes parallel light, similar to the index light 250, and is emitted from the test optical system 60. The parallel light is reflected by the beam splitter 32 and the beam splitter 33, and enters the second image sensor 95.

[0098] On the other hand, test light (unwanted light) reflected at a location other than the measurement target surface 60k converges or diverges, exits the test optical system 60, and also enters the second image sensor 95 as convergent or divergent light. In this embodiment, the position of the second image sensor 95 is adjusted by the stage (reduction means) 170 to minimize the influence of the unwanted light, and the second image sensor 95 receives the interference light between the measurement light 200s and the reference light 200r to obtain interference fringes. A signal obtained based on the light received by the second image sensor 95 is sent to the computer 100.

[0099] With this configuration, the effect of background noise can be reduced by adjusting the position of the second image sensor 95 using the reduction means (stage 170). As a result, a highly accurate wavefront can be acquired, and the measurement accuracy of eccentricity can be improved.

[0100] Furthermore, in the measurement method according to this embodiment, the relative positions of the objective lens 55 and the test optical system 60 are adjusted (coarsely adjusted) so that the chart image is formed at the reference position on the first image sensor 90, and then interference fringes are acquired by the low-coherence interferometer. This configuration makes it possible to acquire sparse interference fringes. As a result, the wavefront can be calculated with high accuracy, and the measurement accuracy of the eccentricity acquired based on the wavefront can be improved.

[0101] [Example 5] FIG. 8 shows a flowchart of a method for manufacturing an optical system according to this embodiment.

[0102] The result of decentering measured using any one of the measuring devices 1 to 4 described in the first to fourth embodiments can be fed back to the manufacturing method of the optical system (test optical system 60).

[0103] First, in step S101, the manufacturer assembles an optical system using a plurality of optical elements (lenses, etc.), and adjusts the position of each optical element.

[0104] Next, in step S102, the manufacturer evaluates the accuracy and performance of the assembled and adjusted optical system. If the evaluation results do not satisfy the criteria, the process proceeds to step S103, where an analysis is performed to determine the reasons why the criteria were not met. One of the subjects of analysis is the decentering of the optical element. Any of measuring devices 1 to 4 can be used to measure this decentering. On the other hand, if the evaluation results satisfy the criteria, the manufacture of the optical system using this manufacturing method is terminated.

[0105] The results of the decentering measurement can be utilized not only for the NG factor analysis in step S103 but also for the position adjustment of the optical element in step S101. That is, the decentering of multiple optical elements in the optical system can be measured using any of the measuring devices 1 to 4, and the position adjustment of the optical elements can be performed using the results.

[0106] Although the preferred embodiments and examples of the present invention have been described above, the present invention is not limited to these embodiments and examples, and various combinations, modifications, and changes are possible within the scope of the gist of the present invention.

[0107] An embodiment of the present invention includes the following configuration.

[0108] [Configuration 1] 1. A measurement apparatus that measures decentering of a test optical system based on a wavefront acquired for each measurement target surface among a plurality of test surfaces in the test optical system, comprising: a first light source that illuminates a chart including an index surface on which an index is provided; an objective lens that guides the index light emitted from the chart to the optical system to be tested; a first image sensor that receives the index light reflected from a test surface of the test optical system; an interferometer including a second light source and a second image sensor, which splits light from the second light source into test light and reference light, and receives the reference light and the measurement light, which is the test light reflected by the measurement target surface via the objective lens, at the second image sensor, thereby acquiring a wavefront of the measurement light; and a reduction unit that reduces the intensity of a signal of light reflected by a surface other than the surface to be measured, out of the test light reflected by the plurality of test surfaces and received by the second imaging element.

[0109] [Configuration 2] 2. The measuring device according to configuration 1, wherein the reducing means is a spatial filter.

[0110] [Configuration 3] 3. The measuring device according to configuration 2, wherein the spatial filter is a pinhole.

[0111] [Configuration 4] 4. The measuring device according to any one of configurations 1 to 3, wherein the reduction means adjusts the position of the second imaging element.

[0112] [Configuration 5] the interferometer includes a beam splitter; The measurement device according to any one of configurations 1 to 4, wherein the reduction means acquires a first signal obtained by receiving the reference light and the measurement light reflected by the beam splitter, and a second signal obtained by receiving the reference light and the measurement light transmitted through the beam splitter, and acquires the wavefront based on a difference between the first signal and the second signal.

[0113] [Configuration 6] 6. The measuring device according to any one of configurations 1 to 5, wherein the reducing means reduces the intensity of the signal of the light reflected at a surface other than the measurement target surface to be smaller than the intensity of the signal of the measurement light.

[0114] [Configuration 7] The measurement device according to any one of configurations 1 to 6, further comprising a first adjustment means for adjusting the relative position of the objective lens and the test optical system based on the position of an image formed by the index light received by the first image sensor.

[0115] [Configuration 8] The measurement device according to configuration 7, wherein the eccentricity of the measurement target surface is measured based on the wavefront and a first adjustment amount obtained when the relative position is adjusted by the first adjustment means.

[0116] [Configuration 9] a second adjusting means for adjusting the tilt component of the wavefront; The measurement device according to configuration 8, wherein the eccentricity of the measurement target surface is measured based on a second adjustment amount obtained when the relative position is adjusted by the second adjustment means and the first adjustment amount.

[0117] [Configuration 10] 10. The measurement device according to any one of configurations 1 to 9, wherein the interferometer has a change unit that changes the optical path length of the reference light.

[0118] [Configuration 11] 11. The measurement device according to any one of configurations 1 to 10, further comprising a stop in an optical path from the second light source to the objective lens.

[0119] [Configuration 12] 1. A measurement apparatus that measures decentering of a test optical system based on a wavefront acquired for each measurement target surface among a plurality of test surfaces in the test optical system, comprising: an interferometer including a light source and an image sensor, which splits light from the light source into test light and reference light, and receives the reference light and the measurement light, which is the test light reflected by the measurement target surface via an objective lens, with the image sensor to acquire a wavefront of the measurement light; a reduction unit that reduces the intensity of a signal of light reflected by a surface other than the surface to be measured, out of the test light reflected by the plurality of test surfaces and received by the image sensor.

[0120] [Configuration 13] 1. A measurement apparatus that measures decentering of a test optical system based on a wavefront acquired for each measurement target surface among a plurality of test surfaces in the test optical system, comprising: a first light source that illuminates a chart including an index surface on which an index is provided; an objective lens that guides the index light emitted from the chart to the optical system to be tested; a first image sensor that receives the index light reflected from a test surface of the test optical system; a measurement device including a second light source and a second image sensor, and an interferometer that splits light from the second light source into test light and reference light, and receives the reference light and measurement light, which is the test light reflected by the measurement target surface via the objective lens, at the second image sensor, to obtain a wavefront of the measurement light.

[0121] [Method 1] A measurement method for measuring decentering of a test optical system based on a wavefront acquired for each measurement target surface among a plurality of test surfaces in the test optical system, comprising: an illumination step of illuminating a chart including an index surface on which an index is provided; an imaging step of causing the index light emitted from the chart to enter an optical system to be tested via an objective lens, causing the index light to enter the optical system to be tested, and receiving the index light reflected by the plurality of test surfaces of the optical system to be tested with a first image sensor; an acquisition step of splitting the light emitted from the second light source into test light and reference light, receiving the reference light and the measurement light, which is the test light that has passed through the objective lens and been reflected by the measurement target surface, with a second image sensor, and acquiring a wavefront of the measurement light; A measurement method characterized in that, in the acquisition step, the intensity of a signal of light reflected by areas other than the measurement target surface is reduced from the test light reflected by the multiple test surfaces and received by the second imaging element.

[0122] [Method 2] measuring the decentering of the test optical system using the decentering measurement method described in Method 1; and adjusting the test optical system using the measurement result of decentering of the test optical system. [Explanation of symbols]

[0123] 10 Second light source 11 1st light source 55 Objective Lens 90 First image sensor 95 Second imaging element 100 calculation means 300 Reduction Measures 400 Low Coherence Interferometer

Claims

1. 1. A measurement apparatus that measures decentering of a test optical system based on a wavefront acquired for each measurement target surface among a plurality of test surfaces in the test optical system, comprising: a first light source that illuminates a chart including an index surface on which an index is provided; an objective lens that guides the index light emitted from the chart to the optical system to be tested; a first image sensor that receives the index light reflected from a test surface of the test optical system; an interferometer including a second light source and a second image sensor, which splits light from the second light source into test light and reference light, and receives the reference light and the measurement light, which is the test light reflected by the measurement target surface via the objective lens, at the second image sensor, thereby acquiring a wavefront of the measurement light; a reduction unit that reduces the intensity of a signal of light reflected by a surface other than the surface to be measured, out of the test light reflected by the plurality of test surfaces and received by the second imaging element.

2. 2. The measurement apparatus according to claim 1, wherein the reducing means is a spatial filter.

3. 3. The measurement apparatus according to claim 2, wherein the spatial filter is a pinhole.

4. The measuring device according to claim 1 , wherein the reducing means adjusts the position of the second image pickup element.

5. the interferometer includes a beam splitter; The measurement device according to claim 1, characterized in that the reduction means acquires a first signal obtained by receiving the reference light and the measurement light reflected by the beam splitter, and a second signal obtained by receiving the reference light and the measurement light transmitted through the beam splitter, and acquires the wavefront based on the difference between the first signal and the second signal.

6. 6. The measurement apparatus according to claim 1, wherein the reducing means reduces the intensity of the signal of the light reflected from a surface other than the measurement target surface to be smaller than the intensity of the signal of the measurement light.

7. 6. The measurement device according to claim 1, further comprising a first adjustment means for adjusting the relative position between the objective lens and the optical system to be measured based on the position of an image formed by the index light received by the first imaging element.

8. 8. The measurement device according to claim 7, wherein the eccentricity of the measurement target surface is measured based on the wavefront and a first adjustment amount obtained when the relative position is adjusted by the first adjustment means.

9. a second adjusting means for adjusting the tilt component of the wavefront; 9. The measurement device according to claim 8, wherein the eccentricity of the measurement target surface is measured based on a second adjustment amount obtained when the relative position is adjusted by the second adjustment means and the first adjustment amount.

10. 6. The measurement apparatus according to claim 1, wherein the interferometer comprises a changer for changing the optical path length of the reference light.

11. 6. The measurement device according to claim 1, further comprising a stop in an optical path from the second light source to the objective lens.

12. 1. A measurement apparatus that measures decentering of a test optical system based on a wavefront acquired for each measurement target surface among a plurality of test surfaces in the test optical system, comprising: an interferometer including a light source and an image sensor, which splits light from the light source into test light and reference light, and receives the reference light and the measurement light, which is the test light reflected by the measurement target surface via an objective lens, with the image sensor to acquire a wavefront of the measurement light; a reduction unit that reduces the intensity of a signal of light reflected by a surface other than the surface to be measured, out of the test light reflected by the plurality of test surfaces and received by the image sensor.

13. 1. A measurement apparatus that measures decentering of a test optical system based on a wavefront acquired for each measurement target surface among a plurality of test surfaces in the test optical system, comprising: a first light source that illuminates a chart including an index surface on which an index is provided; an objective lens that guides the index light emitted from the chart to the optical system to be tested; a first image sensor that receives the index light reflected from a test surface of the test optical system; a measurement device including a second light source and a second image sensor, and an interferometer that splits light from the second light source into test light and reference light, and acquires a wavefront of the measurement light by receiving the reference light and the measurement light, which is the test light reflected by the measurement target surface via the objective lens, with the second image sensor.

14. A measurement method for measuring decentering of a test optical system based on a wavefront acquired for each measurement target surface among a plurality of test surfaces in the test optical system, comprising: an illumination step of illuminating a chart including an index surface on which an index is provided; an imaging step of causing the index light emitted from the chart to enter a test optical system via an objective lens, causing the index light to enter the test optical system, and receiving the index light reflected by the plurality of test surfaces of the test optical system with a first image sensor; an acquisition step of splitting the light emitted from the second light source into test light and reference light, receiving the reference light and the measurement light, which is the test light that has passed through the objective lens and been reflected by the measurement target surface, with a second image sensor, and acquiring a wavefront of the measurement light; A measurement method characterized in that, in the acquisition step, the intensity of the signal of light reflected by areas other than the measurement target surface is reduced from the test light reflected by the multiple test surfaces and received by the second imaging element.

15. measuring the eccentricity of the test optical system using the eccentricity measurement method according to claim 14; and adjusting the test optical system using the measurement result of decentering of the test optical system.

Images