Measurement method, measurement device, program, and storage medium

Abstract

To provide a phase measurement method that can measure a variety of amounts of phase shift with a simple configuration.SOLUTION: A phase measurement method includes: a changing step of changing an illumination area of a specimen illuminated with illumination light; a first correction step of correcting the propagation direction of the illumination light through the illumination area or the position of a photodetector in association with the change of the illumination area; an acquisition step of acquiring, with the photodetector, the light intensity distribution of the illumination light passing through the illumination area; and a calculation step of calculating the amount of phase shift of the illumination light caused by the specimen from the light intensity distribution and the amount of the correction performed in the first correction step. The calculation step includes a second correction step of correcting the phase of the illumination light based on the amount of the correction.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a phase measurement method, a phase measurement device, a program, and a storage medium for estimating a phase change of light caused by an object to be measured. [Background technology]

[0002] In recent years, the emergence of advanced astronomical telescopes using goggle-type optical systems and off-axis optical systems, such as those used in AR and VR, has led to an increased demand for optical elements using aspherical and free-form surfaces. Knowing the surface shapes and transmission characteristics of these optical elements is important for ensuring product performance, but it is difficult to measure these shapes using phase measurement methods such as interferometers.

[0003] Non-Patent Document 1 discloses a phase measurement method that applies ptychography technology. The technology described in Non-Patent Document 1 sequentially changes the area that is illuminated on the test surface, and obtains the light intensity distribution through that area. By performing optimization calculations on the multiple obtained light intensity distributions, the amount of phase change of light caused by the test object is estimated. The method described in Non-Patent Document 1 enables measurement to be achieved with a simpler optical system than an interferometer or the like. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Aaron M. Michalko, and James R. Fienup, “Development of a concave freeform surface measurement using transverse translation-diverse phase retrieval”, Optical Engineering Vol.59, pp.064101, June 2020, USA [Non-patent document 2] Gregory R. Brady, Manuel Guizar-Sicairos, and James R. Fienup, “Optical wavefront measurement using phase retrieval with transverse translation diversity”, Optics express Vol.17, pp.624, January 2009, USA Summary of the Invention [Problem to be solved by the invention]

[0005] However, the method disclosed in Non-Patent Document 1 has limitations on the shape of the test object that can be measured. Depending on the characteristics and shape of the test object, the propagation direction of light changes significantly depending on the illumination position. Therefore, light that passes through a certain area reaches the image sensor, but light that passes through another area propagates in a direction different from that of the image sensor. If light does not reach the image sensor, it is impossible to know the phase information in that area.

[0006] The present invention provides a phase measurement method that can measure a variety of phase change amounts with a simple configuration. [Means for solving the problem]

[0007] As one aspect of the present invention Plan The measurement method includes a changing step of changing an illumination area of ​​an object illuminated by illumination light, a first correction step of correcting the propagation direction of the illumination light passing through the illumination area or the position of a photodetector in accordance with the change of the illumination area, an acquisition step of acquiring a light intensity distribution of the illumination light passing through the illumination area by the photodetector, and a measurement step of comparing the light intensity distribution and the first correction step. in Correction amount Based on and a calculation step of calculating a phase change amount of the illumination light caused by the object to be measured, wherein the calculation step includes a second correction step of correcting the phase of the illumination light based on the correction amount.

[0008] Other objects and features of the present invention will be described in the following embodiments. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a phase measurement method, a phase measurement device, a program, and a storage medium that are capable of measuring various phase change amounts with a simple configuration. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a phase measurement device using ptychography. [Figure 2] 10 is a flowchart illustrating a phase measurement method according to each embodiment. [Figure 3] FIG. 1 is a diagram illustrating a phase measurement device according to a first embodiment. [Figure 4] FIG. 4 is a diagram showing the amount of rotation in the first embodiment. [Figure 5] FIG. 10 is a diagram illustrating a phase measurement device according to a second embodiment. [Figure 6] FIG. 10 is a diagram showing the amount of rotation in the second embodiment. [Figure 7] FIG. 10 is a diagram illustrating another phase measurement device according to the second embodiment. [Figure 8] FIG. 10 is a diagram illustrating a phase measurement device according to a third embodiment. [Figure 9] FIG. 10 is a diagram showing the amount of movement in the third embodiment. [Figure 10] FIG. 10 is a schematic diagram of a phase measurement device according to another embodiment. [Figure 11] FIG. 10 is a schematic diagram of a phase measurement device according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to designate the same components, and redundant explanations will be omitted.

[0012] FIG. 1(a) is a schematic diagram of a phase measurement device 100 using ptychography. After an illumination area is limited by an aperture 102, illumination light 101 passes through a half mirror 103 and illuminates a test object 104. The light reflected by the test object 104 is then reflected by the half mirror 103 and enters an image sensor (photodetector) 105. The image sensor 105 detects the light that has passed through the illumination area and acquires the light intensity distribution on the surface of the image sensor 105. The aperture 102 is moved by a driver 106 controlled by a computer (controller) 107. The movement of the aperture 102 changes the illumination area that illuminates the test object 104. The aperture 102 and the driver 106 constitute a change unit for changing the illumination area. By repeatedly moving the aperture 102 and acquiring the light intensity distribution, the light intensity distribution of the light that has passed through each illumination area can be acquired. The acquired light intensity distribution is stored in the computer 107 or a data storage device (not shown). The computer 107 estimates the spatial distribution of the amount of phase change of the light caused by reflection by performing post-processing based on the acquired light intensity distribution and the position of the aperture 102. The post-processing may be performed by the computer 107 or by a separate arithmetic device. Alternatively, the post-processing may be performed by a arithmetic device present on a cloud via a network.

[0013] The method for calculating the phase in the phase measurement device 100 is described below. For simplicity, the illumination light is assumed to be monochromatic. The object to be measured is assumed to be the spatial distribution W(x, y) of the phase change amount of light caused by reflection on the test object 104. Hereinafter, this spatial distribution W(x, y) will be referred to as the phase change amount. With x and y as Cartesian coordinates perpendicular to the optical axis, the amplitude transmittance distribution of the aperture 102 is assumed to be Ap(x, y). As an example, if the aperture 102 is assumed to be a circular aperture with a radius r, Ap(x, y) is given by equation (1).

[0014]

number

[0015] The complex amplitude of the incident light is E 0 (x, y), and the position where the center of the opening 102 is placed by the j-th movement by the driving unit 106 is (x j, yj ), the complex amplitude E of the light immediately after passing through the aperture 102 is p j (x, y) is given by equation (2).

[0016]

number

[0017] j takes a value from 1 to N (a natural number), and N is the total number of positions where the apertures 102 are placed. The light transmitted through the apertures 102 propagates to the test object 104. The distance from the apertures 102 to the test object 104 is L. i Then, the complex amplitude E of the light reaching the test object 104 is in j (x, y) is given by equation (3).

[0018]

number

[0019] JPEG0007757196000004.jpg96

[0020] is the operator that indicates the propagation of light, JPEG0007757196000005.jpg1038

[0021] indicates that light expressed by the function f is propagated over a distance L. The calculation method for light propagation can be selected appropriately depending on the optical arrangement. In a typical configuration, the illumination wavelength λ is in the visible range and the propagation distance L is several mm to several tens of cm, so the Fresnel diffraction formula is suitable from the perspective of calculation scale and calculation accuracy.

[0022] The light that reaches the test object 104 is reflected by the surface (test surface) of the test object 104. For simplicity, the reflectance of the test surface is assumed to be 1 over the entire area. When the shape of the test surface is H(x, y), the amount of phase change W(x, y) of light due to reflection is given by equation (4).

[0023]

number

[0024] k is the wave number of light. From equations (3) and (4), the complex amplitude E of the light reflected from the test surface is out j (x, y) is given by equation (5).

[0025]

number

[0026] i is an imaginary unit. The light reflected from the test surface propagates to the image sensor 105. The distance from the test surface to the image sensor 105 is L. d Then, the complex amplitude E of light on the image sensor 105 surface is d j (x, y) is given by equation (6).

[0027]

number

[0028] Light intensity distribution I acquired by the image sensor 105 j (x, y) is the square of the absolute value of the complex amplitude on the surface of the image sensor 105, and is expressed by equation (7).

[0029]

number

[0030] Light intensity distribution I j (x, y) is acquired by changing the position of the aperture 102 N times. One method for calculating the phase change amount W(x, y) from the acquired N light intensity distributions is optimization. Optimization is a calculation method in which the variables to be estimated (optimization variables) are successively changed so that the value of the objective function F is minimized. The objective function F is the degree to which the optimization variables in each iterative optimization step reproduce the measurement result. For example, the objective function F can be set as follows: measj The light intensity distribution I is calculated from (x, y) and the estimated phase change amount W using equations (1) to (7). est j There is a sum of squared differences with (x,y;W).

[0031]

number

[0032] Other examples include the sum of squared differences of the absolute values ​​of complex amplitudes. The objective function F can be selected appropriately depending on the problem. A method for estimating the phase change amount W(x, y) using optimization is described in Non-Patent Document 2, so its description will be omitted here.

[0033] The light intensity distribution I measured by the above method meas j From (x, y), it is possible to estimate the amount of phase change W(x, y) of light caused by the test object 104. However, depending on the shape of the test object 104, it may not be possible to estimate the amount of phase change W(x, y). This problem is illustrated using Figure 1(b). Figure 1(a) shows a case where the test surface is concave and the focal position of the test surface and the position of the image sensor 105 are approximately the same. In this case, reflected light propagates toward the image sensor 105 regardless of the position of the aperture 102. On the other hand, when the test surface is convex as shown in Figure 1(b), light reflected in the peripheral region of the test surface propagates outward and does not enter the image sensor 105. In other words, it is not possible to measure the amount of phase change W(x, y) in the peripheral region of the test surface.

[0034] For simplicity of explanation, the above comparison was made between the reflections from convex and concave surfaces, assuming that the illumination light 101 was parallel light, but this problem can be easily generalized. When the illumination position of the test object 104 is changed, the propagation direction of the light reflected by or transmitted through the test object 104 changes depending on the shape and refractive index distribution of the test object 104. Therefore, except in special cases, the light that passes through the test object 104 propagates in a direction different from the direction of the image sensor 105. To measure an arbitrary shape H(x, y), i.e., an arbitrary phase change amount W(x, y), the propagation direction of the light or the position of the image sensor 105 must be corrected according to each illumination area.

[0035] In each embodiment, the optical arrangement of the phase measurement device 100 is corrected in accordance with the movement of the aperture 102 so that light reflected by or transmitted through the test object 104 is incident on the image sensor 105. To guide the light that has passed through the test object 104 to the image sensor 105, the propagation direction of the illumination light or the light immediately after being reflected by or transmitted through the test object 104 may be corrected, or the image sensor 105 may be moved to the location where the light propagates. The propagation direction of light can be corrected by changing the positions and angles of various optical elements. For example, the propagation direction of light can be corrected by changing the angle of incidence of the illumination light 101, the installation angle of the test object 104, the angle of the half mirror 103, or the like. As long as the light can be guided to the image sensor 105, the elements that perform the correction are not limited to specific ones. The propagation direction of light can also be corrected by adding an element capable of controlling the propagation direction of light, such as a spatial phase modulator or a DMD (Digital Micromirror Device), to the optical path. The amount of correction when making these corrections, that is, the amount of driving of the elements, is determined by the geometric arrangement of the phase measurement device 100 and the optical characteristics of the test object 104, such as the surface shape H(x, y) and refractive index distribution of the test object 104.

[0036] Although light can be guided to the image sensor 105 by correcting the optical arrangement of the phase measurement device 100, this alone is not enough to properly calculate the phase change amount W(x, y). As shown in equations (1) to (8), the phase change amount W(x, y) is calculated from the N acquired light intensity distributions using a mathematical formula based on the optical arrangement and an optimization calculation, so when the optical arrangement is corrected, the series of mathematical formulas used in the calculation also need to be corrected.

[0037] In each embodiment, the phase of the complex amplitude of light can be changed (corrected) to correct the propagation direction of light or the position of the image sensor 105. Since the propagation direction of light is determined by the phase gradient of the complex amplitude, when the propagation direction of light is corrected, the phase gradient can be corrected. Phase correction targets the complex amplitude of light on the element where the propagation direction of light is changed, or the complex amplitude of light at the destination from there. Alternatively, it also targets the complex amplitude of light for which a correspondence relationship is derived by changing a mathematical formula. If the phase of the complex amplitude of light to be corrected is Φ(x, y), phase correction corresponds to calculating equation (9).

[0038]

number

[0039] where c x,j and c y,j is a constant determined from the correction amount of the optical arrangement of the phase measurement device 100 at the time of the j-th image capture. Due to the nature of multiplication of exponential functions, this correction is equivalent to multiplying a function representing the complex amplitude of light by equation (10).

[0040]

number

[0041] Because light changes its distribution as it propagates through space, it is not limited to simply correcting the phase tilt. The change in the formula is not limited to the specific changes defined in Equation (9) or Equation (10), but more generally, it is to correct the phase of the complex amplitude. The amount of phase correction in this case corresponds to the correction of the optical arrangement described above, and is therefore determined from the correction amount of the optical arrangement.

[0042] The phase measurement method of each embodiment will be described below with reference to Fig. 2. Fig. 2 is a flowchart showing the phase estimation method of each embodiment.

[0043] In step S 1 , the driving unit 106 moves the position of the opening 102 based on instructions from the computer 107 .

[0044] In step S2, the light propagation direction or the position of the image sensor 105 is corrected based on instructions from the computer 107. The computer 107 also stores or records the corrected sensor and the amount of correction.

[0045] In step S3, the computer 107 acquires the light intensity distribution on the image sensor 105 acquired by the image sensor 105.

[0046] In step S4, the computer 107 determines whether the number of times the processes from step S1 to step S3 have been executed reaches a predetermined number. If the number of times has reached the predetermined number, the flow proceeds to step S5; if not, the flow returns to step S1.

[0047] By performing the processes from step S1 to step S4, it is possible to obtain a plurality of light intensity distributions through different illumination areas.

[0048] In step S5, the computer 107 estimates the phase change amount W(x, y) from the multiple light intensity distributions acquired in steps S1 to S3, the position of the aperture 102, and the correction amount of the optical arrangement. In step S501, the phase of the complex amplitude of the light is corrected based on the correction amount of the optical arrangement performed in step S2. In step S502, the phase change amount W(x, y) is estimated using the corrected complex amplitude.

[0049] Each embodiment can be mathematically modeled and therefore can be implemented as a software function of a computer system. Here, the software function of the computer system includes programming (programs) including executable code. The software code can be executed on a general-purpose computer. During operation of the software code, the code or associated data is stored within a general-purpose computer platform. However, in other cases, the software is stored elsewhere or loaded into a suitable general-purpose computer system. Thus, the software code can be held in at least one machine-readable medium (storage medium) as one or more modules. Example 1 A phase measurement method in the first embodiment will be described below. Fig. 3 is a schematic diagram of a phase measurement device 300 in the first embodiment. The phase measurement device 300 in the first embodiment has a rotation mechanism (correction mechanism) 110 that tilts the test object 104 to change the angle of the test object 104. When illuminating the peripheral area of ​​the test object 104, the test object 104 is tilted so that reflected light is incident on the image sensor 105. A method for determining the rotation angle θ at this time will be described with reference to Fig. 4.

[0050] In Fig. 4, for ease of explanation, the image sensor 105 is shown at a position where it is reflected by a half mirror. Also, to make it easier to understand the signs of each variable, the object 104 is shown as a concave surface. The direction in which reflected light propagates is the center position x of each illumination area. j It is determined by the inclination of the test surface at position x j The angle that the tangent at makes with the horizontal plane is φ j Then, φ j The relation between the surface shape H(x) and the surface shape H(x) is given by Equation (11).

[0051]

number

[0052] The sign of the angle is positive in the counterclockwise direction on the paper, and the sign of the coordinate x is positive to the right on the paper. The reflected light is in the opposite direction to the incident light and is 2φ j The distance from the object 104 to the image sensor 105 is L d and the position x j The angle between the line connecting the center of the image sensor 105 and the center line of the incident light is φ j0 Then, from the geometric arrangement, φ j0 is determined by equation (12).

[0053]

number

[0054] The test object 104 is rotated by θ j When rotated, the propagation direction of the reflected light changes by 2θ j Therefore, the condition for making the reflected light incident on the image sensor 105 is given by equation (13).

[0055]

number

[0056] In FIG. 4, the test object 104 is rotating clockwise, so θ j Note that the value of is negative. Using equations (11) and (13), the relationship in equation (14) can be obtained.

[0057]

number

[0058] Using the relational expression (14), the rotation angle θ of the test object 104 in the j-th image capture is calculated. j is determined, and θ jBy rotating the test object 104 by only this amount, the reflected light can be guided to the image sensor 105.

[0059] Here, the surface shape H(x) is a measurement target and cannot be known in advance. j To determine this, an approximate value (approximate shape of the surface shape H(x)) determined from design values ​​or the like may be used as the surface shape H(x).

[0060] If the design value cannot be used, the position of the reflected light on the surface of the image sensor 105 can be obtained while slightly moving the aperture 102, and feedback can be applied to the rotation mechanism 110 for each minute movement. d and the rotation amount Δθ of the test object 104 are expressed by the following equation (15).

[0061]

number

[0062] The rotation mechanism 110 can be fed back using the relational expression (15). j The total amount of rotation of the rotation mechanism 110 until the rotation reaches θ j However, since minute driving is required, the measurement time may increase. More preferably, θ is determined by using an approximate value such as a design value. j It is a good way to determine this.

[0063] As described above, the light can be guided to the image sensor 105. However, since the angle of the test object 104 is changed, the mathematical formula used for the calculation must also be corrected. By rotating the test object 104, the direction in which the reflected light propagates changes by 2θ j This can be expressed mathematically as the complex amplitude E of the reflected light. out j (x) by equation (16).

[0064]

number

[0065] Furthermore, the amount of phase shift W(x) of light due to reflection on the test surface also changes due to rotation. j The phase change amount W''(x) caused by the tilt is expressed by equation (17) using the surface shape H(x).

[0066]

number

[0067] In this way, the magnitude of the phase change amount W''(x) is j Therefore, the complex amplitude E of the reflected light after the test object 104 is rotated changes based on the out j (x) is expressed as equation (18) from equations (5), (16), and (17).

[0068]

number

[0069] By performing optimization calculations using the formulas modified as above, the amount of phase change W(x) can be estimated. Example 2 A phase measurement method in the second embodiment will be described below. FIG. 5 is a schematic diagram of a phase measurement device 500 in the second embodiment. The phase measurement device 500 in the second embodiment has a rotation mechanism (correction mechanism) 204 that changes the angle of the illumination light 101 (the angle at which the illumination light 101 is incident on the test object 104). The illumination light 101 is emitted from an illumination unit 201. The illumination unit 201 has a light source 202, a collimator lens 203, and an aperture 102. The drive unit 106 and the rotation mechanism 204 control the position and angle of the illumination unit 201 based on instructions from the computer 107. In step S1 of the flowchart shown in FIG. 2, the illumination unit 201 is moved by the drive unit 106 to change the illumination area of ​​the test object 104. Subsequently, in step S2, the illumination unit 201 is rotated by the rotation mechanism 204 to correct the propagation direction of the light so that the reflected light is directed toward the image sensor 105. The amount of rotation θ at this time is j is determined by equation (19) from the geometric diagram shown in FIG.

[0070]

number

[0071] In FIG. 6, the lighting unit 201 is rotating clockwise, so θ j Note that the value of φ is negative. j0 , φ j , θ j can be calculated using approximate values ​​such as design values, as in the first embodiment.

[0072] Since the illumination area changes due to the rotation of the illumination unit 201 in step S2, steps S1 and S2 are repeated as necessary. Alternatively, the amount of movement of the illumination unit 201 in step S1 is determined taking into consideration the change in the illumination area in step S2. Alternatively, x in equation (2) j By correcting the above, the amount of deviation of the illumination area may be taken into consideration during calculation.

[0073] In this way, the light can be guided to the image sensor 105. However, since the angle of the illumination light 101 is changed, the mathematical formula used for the calculation must also be corrected. In this embodiment, parallel light having an angle θj is incident on the aperture 102, so the complex amplitude E 0 (x) is expressed as equation (20).

[0074]

number

[0075] Since the light transmitted through the aperture 102 is also approximately parallel light, the complex amplitude E in j (x) can be approximated by equation (21).

[0076]

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[0077] As in the first embodiment, the amount of phase change of the light due to reflection caused by the tilt of the illumination light 101 is W″(x). Therefore, using equations (5), (17), and (21), the reflected light E immediately after being reflected from the test surface can be calculated as follows: out j Rewriting (x) gives equation (22).

[0078]

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[0079] Equation (22) has a form in which the phase gradient is corrected, similar to equation (18), and shows that the same effect as in the first embodiment can be obtained.

[0080] By performing optimization calculations using the formulas modified as above, the amount of phase change W(x) can be estimated.

[0081] Although an approximation formula is used in equation (21), a term for correcting the phase gradient can be obtained in the same way even if light propagation is calculated as Fresnel diffraction.

[0082] In this embodiment, a configuration in which the illumination unit 201 is rotated has been exemplified, but the method of setting an angle to the illumination light 101 is not limited to this. For example, instead of using a rotation mechanism 204 that rotates the illumination unit 201, the angle of the illumination light 101 can also be changed by moving the light source 202 with a drive unit 205 as shown in FIG. Example 3 A phase measurement method in the third embodiment will be described below. Fig. 8 is a schematic diagram of a phase measurement device 800 in the third embodiment. The phase measurement device 800 in the third embodiment has a drive mechanism (correction mechanism) 301 that moves the image sensor 105 to change the position of the image sensor 105. In step S2 of the flowchart shown in Fig. 2, the drive mechanism 301 moves the image sensor 105 in accordance with the propagation direction of the reflected light based on an instruction from the computer 107. The amount of movement Δx at this time is j is determined by equation (23) from the geometric diagram shown in FIG.

[0083]

number

[0084] Therefore, the image sensor 105 is moved by Δx j By moving the object by this distance, the light intensity distribution of the reflected light can be obtained.

[0085] In this embodiment, since the position of the image sensor 105 is changed, it is necessary to correct the formula used in the calculation in accordance with the movement of the image sensor 105. j The light intensity distribution I meas j (x) is the actual light intensity distribution I j (x) to Δx j is shifted by 1, and is expressed by equation (24).

[0086]

number

[0087] Therefore, in the estimation calculation of the phase change amount W(x), I est j Calculate (x) and subtract this from Δx j After shifting the value by , the objective function F expressed by equation (25) is calculated.

[0088]

number

[0089] However, depending on the surface shape, Δx j Since is larger than the spread of the light intensity distribution on the surface of the image sensor 105, it is necessary to expand the calculation area to calculate equation (25). Expanding the calculation area is undesirable because it increases the calculation time. Therefore, equation (25) is rewritten as follows. The propagation operator is set as follows, assuming that light propagation is Fresnel diffraction. JPEG0007757196000028.jpg96

[0090] If we write it down, we get Δx from equation (6). j The complex amplitude E of light on the image sensor 105 surface shifted by d j (x-Δx j ) becomes equation (26).

[0091]

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[0092] By making a simple change to equation (26), equation (27) is obtained.

[0093]

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[0094] Equation (27) is the propagation operator JPEG0007757196000031.jpg107

[0095] Rewriting it using, we get equation (28).

[0096]

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[0097] operator JPEG0007757196000033.jpg107

[0098] The phase part that appears before disappears during imaging and can be ignored. Therefore, the only change required in the formula for calculation is E out j (x) by equation (29) which represents phase modulation.

[0099]

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[0100] Furthermore, from equation (5), equation (30) can be obtained.

[0101]

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[0102] From equation (30), the movement of the image sensor 105 can be treated in the same way as correcting the phase gradient. In other words, equation (30) has a form in which the phase gradient is corrected in the same way as equation (18), and shows that the same effect as in the first embodiment can be obtained.

[0103] By performing optimization calculations using the formulas modified as above, the amount of phase change W(x) can be estimated.

[0104] The above-described Examples 1 to 3 can be combined as appropriate. That is, the light intensity distribution can be acquired by changing at least one of the angle at which the illumination light 101 is incident on the test object 104, the angle of the test object 104, and the position of the image sensor 105. [Other Examples] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention.

[0105] In each of the above embodiments, various elements are driven to correct the propagation direction of light so that light passing through each illumination area of ​​the test object 104 reaches the image sensor 105, or the position of the image sensor 105 is corrected. In addition, the mathematical formula corresponding to these corrections is corrected before the phase change amount W is estimated. The mathematical formula correction can be achieved by multiplying the complex amplitude of light by a complex function that imparts a phase change, or by correcting the phase gradient. The amount of correction for the phase gradient is determined based on the amount of correction for the optical arrangement. The methods for correcting the optical arrangement and the methods for correcting the mathematical formula shown in each of the above embodiments are merely examples, and can be modified within the spirit and scope of the present invention.

[0106] In the above embodiments, the measurement target is the amount of phase change W of light caused by reflection on the test object 104, but the measurement target is not limited to this. If the amount of phase change W of light caused by reflection is obtained, the shape distribution H of the test surface can be obtained by equation (4). Alternatively, the surface shape can be calculated even if the optimization variable is H. In other words, the method described in each embodiment also functions as a shape measurement method.

[0107] 10, for example, the phase change amount W of light transmitted through the test object 104, i.e., the transmitted wavefront, can be obtained. That is, the methods described in each embodiment also function as a transmitted wavefront measurement method. Furthermore, if the measurement object is a lens, a concave mirror, or the like, the method also functions as an aberration measurement method that calculates the amount of aberration by reformulating the phase change amount W due to transmission or reflection as a difference amount from an ideal amount. In either case, the basis of the measurement amount obtained is the phase change amount W of light caused by the test object 104, and physical quantities converted from the phase change amount W are included in the measurement objects of the methods described in each embodiment. Furthermore, the light measured by the image sensor 105 is not limited to either reflected light or transmitted light from the test object 104.

[0108] In the above embodiments, for simplicity of explanation, detailed drive errors and changes in other values ​​accompanying drive are ignored. For example, in embodiment 1, when the test object 104 is tilted, the tilt changes the illumination position on the test object 104 and the distance from the aperture 102 to the test object 104. It is necessary to modify and implement a series of mathematical formulas to correct these changes. Therefore, the mathematical formulas exemplified in each embodiment are not uniquely determined for implementing the present invention, but may be modified as appropriate within the scope of the present invention.

[0109] In the above embodiments, the illumination light 101 is assumed to be parallel light for ease of explanation, but the form of the illumination light 101 is not limited to this. As shown in FIG. 11, the illumination light 101 may be configured by cutting out a part of a spherical wave emitted from a point light source 401. Alternatively, the illumination light 101 may be a part of a convergent wave formed by a lens. Depending on the form of the illumination light 101, the complex amplitude E 0 The present invention works if (x, y) is changed appropriately. Also, it is possible to eliminate the half mirror 103 as shown in FIG.

[0110] In the above embodiments, the aperture 102 was used as an example of a method for limiting the illumination area, but the method for limiting the illumination area is not limited to this. The present invention will work with any method that can limit the illumination range of the test surface and change the position of the illumination area. For example, because the light emitted from the end face of an optical fiber has a limited spread, the illumination range can be limited without installing a special aperture member. It is possible to change the position and illumination angle of the illumination area by changing the position or orientation of the fiber. Furthermore, because the light emitted from a semiconductor laser also has a limited spread, it is possible to limit and move the illumination area without using an aperture member.

[0111] The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that realizes one or more functions. [Explanation of symbols]

[0112] Modification methods 102,106 Photodetector 105 Control unit 107 Correction mechanism 110,204,301

Claims

1. a changing step of changing an illumination area of ​​the object illuminated by the illumination light; a first correction step of correcting a propagation direction of the illumination light passing through the illumination area or a position of a photodetector in accordance with a change in the illumination area; an acquisition step of acquiring a light intensity distribution of the illumination light passing through the illumination area by the photodetector; a calculation step of calculating a phase change amount of the illumination light caused by the object to be measured based on the light intensity distribution and the correction amount in the first correction step, The measurement method according to claim 1, wherein the calculation step includes a second correction step of correcting the phase of the illumination light based on the correction amount.

2. The measurement method described in Claim 1, characterized in that in the second correction step, the phase of the illumination light used in the calculation step is corrected based on the correction amount.

3. 3. The measurement method according to claim 2, wherein an optimization calculation is performed in the calculation step.

4. 4. The measurement method according to claim 1, wherein in the second correction step, a phase of a function representing a complex amplitude of the illumination light that illuminates the illumination area or the illumination light that has passed through the illumination area is corrected based on the correction amount.

5. 5. The measurement method according to claim 4, wherein in the second correction step, a phase gradient of the function is corrected based on the correction amount.

6. A measurement method described in any one of claims 1 to 5, characterized in that the amount of phase change changes based on the correction amount.

7. 7. The measurement method according to claim 1, wherein in the first correction step, at least one of an angle at which the illumination light is incident on the test object, an angle of the test object, or a position of the photodetector is changed.

8. 8. The measurement method according to claim 1, wherein the correction amount is determined based on an approximate shape of a surface of the object to be measured.

9. a changing means for changing an illumination area of ​​the object illuminated by the illumination light; a photodetector for acquiring a light intensity distribution of the illumination light passing through the illumination area; a correction mechanism that corrects a propagation direction of the illumination light passing through the illumination area or a position of the photodetector in accordance with a change in the illumination area; a control unit that calculates a phase change amount of the illumination light caused by the object to be measured based on the light intensity distribution and a correction amount of the correction mechanism, The control unit corrects the phase of the illumination light based on the correction amount.

10. A program for causing a computer to execute the measurement method according to any one of claims 1 to 8.

11. A computer-readable storage medium storing the program according to claim 10.

12. a changing step of changing an illumination area of ​​the object illuminated by the illumination light; a first correction step of correcting a propagation direction of the illumination light reflected from the illumination area or a position of a photodetector in accordance with a change in the illumination area; an acquiring step of acquiring a light intensity distribution of the illumination light reflected from the illumination area by the photodetector; a calculation step of calculating a surface shape of the object to be measured based on the light intensity distribution and the correction amount in the first correction step, The shape measurement method according to claim 1, wherein the calculation step includes a second correction step of correcting the phase of the illumination light based on the correction amount.

13. a changing step of changing an illumination area of ​​the object illuminated by the illumination light; a first correction step of correcting a propagation direction of the illumination light passing through the illumination area or a position of a photodetector in accordance with a change in the illumination area; an acquisition step of acquiring a light intensity distribution of the illumination light passing through the illumination area by the photodetector; a calculation step of calculating an amount of aberration of the object to be measured based on the light intensity distribution and the amount of correction in the first correction step, 10. The aberration measuring method according to claim 9, wherein the calculation step includes a second correction step of correcting the phase of the illumination light based on the correction amount.

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