MEASUREMENT METHOD, MEASUREMENT APPARATUS, 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 a test object.

Background Art

[0002] In recent years, goggle-type optical systems represented by AR and VR, and advanced astronomical telescopes using off-axis optical systems have emerged, and the demand for optical elements using aspherical and free-form surfaces has been increasing. Knowing the surface shape and transmission characteristics of these optical elements is important for ensuring the performance of products. However, it is difficult to measure these shapes using phase measurement methods such as interferometers.

[0003] In Non-Patent Document 1, a phase measurement method applying the Tychography technique is disclosed. In the technique described in Non-Patent Document 1, the region illuminating the test surface is sequentially changed, and the intensity distribution of light passing through that region is acquired. By performing an optimization operation on the acquired plurality of light intensity distributions, the amount of phase change of light caused by the test object is estimated. According to the method according to Non-Patent Document 1, measurement can be realized with a simpler optical system compared to an interferometer or the like.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Non-Patent Document 2

[0005] However, the method disclosed in Non-Patent Document 1 has limitations on the shape of the object that can be measured. Depending on the characteristics and shape of the object, the direction of light propagation can change significantly depending on the illumination position. As a result, light passing through one region may reach the image sensor, while light passing through another region may propagate in a different direction from the image sensor. If light does not reach the image sensor, it is not possible to obtain phase information in that region.

[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] A phase measurement method as one aspect of the present invention comprises: a modification step of changing the illumination area of ​​an object to be 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 the photodetector in accordance with the change in the illumination area; an acquisition step of obtaining the light intensity distribution of the illumination light passing through the illumination area using the photodetector; and a calculation step of calculating the amount of phase change of the illumination light caused by the object to be examined from the light intensity distribution and the correction amount of the correction performed in the first correction step, 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 are described in the following embodiments. [Effects of the Invention]

[0009] According to the present invention, a phase measurement method, a phase measurement device, a program, and a storage medium can be provided that enable the measurement of various phase change amounts with a simple configuration. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram of a phase measurement device using ptychography. [Figure 2] This flowchart shows the phase measurement method for each embodiment. [Figure 3] This is a diagram showing the phase measurement device of Example 1. [Figure 4] This figure shows the amount of rotation in Example 1. [Figure 5] This figure shows the phase measurement device of Example 2. [Figure 6] This figure shows the amount of rotation in Example 2. [Figure 7] This figure shows another phase measurement device from Example 2. [Figure 8] This figure shows the phase measurement device of Example 3. [Figure 9] This figure shows the amount of movement in Example 3. [Figure 10] This is a schematic diagram of a phase measurement device according to another embodiment. [Figure 11] This is a schematic diagram of a phase measurement device according to another embodiment. [Modes for carrying out the invention]

[0011] The embodiments of the present invention will be described in detail below with reference to the drawings. In each figure, the same reference numeral is used for identical components, and redundant explanations are omitted.

[0012] Figure 1(a) is a schematic diagram of a phase measurement device 100 using ptychography. Illumination light 101 is limited to an illumination area by an aperture 102, then passes through a half mirror 103 to illuminate the object under test 104. Light reflected from the object under test 104 is reflected by the half mirror 103 and then incident on 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 drive unit 106 controlled by a computer (control unit) 107. Moving the aperture 102 changes the illumination area that illuminates the object under test 104. The aperture 102 and the drive unit 106 constitute a means for changing the illumination area. By repeating the movement of the aperture 102 and the acquisition of 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 holding device (not shown). Computer 107 estimates the spatial distribution of the phase change of light caused by reflection by performing post-processing based on the acquired light intensity distribution and the position of aperture 102. The post-processing may be performed by computer 107, by another computing device, or by a computing device located on the 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 of measurement is the spatial distribution W(x,y) of the phase change amount of light due to reflection from the object under test 104. Hereafter, this spatial distribution W(x,y) will be referred to as the phase change amount. Let x and y be orthogonal coordinates perpendicular to the optical axis, and let Ap(x,y) be the amplitude transmittance distribution of the aperture 102. As an example, if we assume that the aperture 102 is a circular aperture with radius r, then Ap(x,y) is given by equation (1).

[0014]

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

[0016]

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[0017] j takes values ​​from 1 to N (a natural number), where N is the total number of positions where the aperture 102 can be placed. Light transmitted through aperture 102 propagates to the object 104. The distance from aperture 102 to object 104 is L. i Therefore, the complex amplitude E of the light that reached the object 104 is in j (x,y) is given by equation (3).

[0018]

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[0019] JPEG2023115859000005.jpg96

[0020] This is an operator that shows the propagation of light. JPEG2023115859000006.jpg1038

[0021] This shows that light represented by function f propagates over a distance L. The method for calculating light propagation can be appropriately selected depending on the optical configuration. In a typical configuration, the illumination wavelength λ is in the visible range and the propagation distance L is from a few millimeters to several tens of centimeters, so the Fresnel diffraction equation is suitable from the viewpoint of calculation scale and accuracy.

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

[0023]

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[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 out j (x, y) is given by equation (5).

[0025]

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

[0027]

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

[0029]

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[0030] The light intensity distribution I j (x, y) is obtained by changing the position of the aperture 102 N times. As a method for calculating the phase change amount W(x, y) from the N acquired light intensity distributions, for example, there is optimization. Optimization is an operation method in which the variable to be estimated (optimization variable) is sequentially changed so that the value of the objective function F becomes the smallest. The objective function F is the degree to which the optimization variable in each iteration step of the optimization reproduces the measurement result. For example, as the objective function F, as shown in equation (8), the measured light intensity distribution I measj The light intensity distribution I is calculated from the estimated phase change W (x,y) using equations (1) to (7). est j There is a sum of squared differences between (x, y; W) and (x, y; W).

[0031]

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

[0033] The light intensity distribution I measured by the method described above meas j The amount of phase change W(x,y) of light caused by the object 104 can be estimated from (x,y). However, depending on the shape of the 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 the case where the surface under test is concave and the focal position of the surface under test and the position of the image sensor 105 are approximately the same. In this case, the reflected light propagates toward the image sensor 105 regardless of the position of the aperture 102. On the other hand, as shown in Figure 1(b), when the surface under test is convex, the light reflected in the peripheral region of the surface under test propagates outward and does not enter the image sensor 105. In other words, the amount of phase change W(x,y) in the peripheral region of the surface under test cannot be measured.

[0034] In the above explanation, for the sake of simplicity, the illumination light 101 was assumed to be parallel light, and the reflection by convex and concave surfaces was compared. However, this problem can be easily generalized. When the illumination position of the object under test 104 is changed, the propagation direction of the light reflected or transmitted by the object under test 104 changes according to the shape and refractive index distribution of the object under test 104. Therefore, except in special cases, the light that has passed through the object under test 104 propagates in a direction different from the direction of the image sensor 105. In order to measure an arbitrary shape H(x,y), that is, an arbitrary phase change 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 as the aperture 102 moves in order to direct the light reflected or transmitted by the object under test 104 into the image sensor 105. To guide the light that has passed through the object under test 104 to the image sensor 105, the propagation direction of the illumination light or the light immediately after it has been reflected or transmitted by the object under test 104 can be corrected, or the image sensor 105 can be moved to a location where the light is propagating. Correction of the light propagation direction can be achieved by changing the position and angle of various optical elements. For example, the light propagation direction can be corrected by changing the incident angle of the illumination light 101, the installation angle of the object under test 104, the angle of the half mirror 103, etc. Once the light is guided to the image sensor 105, the elements to be corrected are not limited to specific ones. Furthermore, correction of the light propagation direction can also be achieved by adding elements that can control the light propagation direction, such as a spatial phase modulator or a DMD (Digital Micromirror Device), to the optical path. The amount of correction used when performing these corrections, i.e., the amount of element drive, is determined by the geometric arrangement of the phase measuring device 100 and the optical characteristics of the object under test 104, such as the surface shape H(x,y) and refractive index distribution of the object under test 104.

[0036] By correcting the optical arrangement of the phase measurement device 100, light can be guided to the image sensor 105, but this alone is not sufficient 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 acquired N light intensity distributions using mathematical formulas and optimization calculations based on the optical arrangement. Therefore, 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 the light can be changed (corrected) to correct the direction of light propagation or the position of the image sensor 105. Since the direction of light propagation is determined by the slope of the phase of the complex amplitude, if the direction of light propagation is corrected, the slope of the phase can be corrected. Phase correction applies to the complex amplitude of the light on the element where the direction of light propagation has been changed, or to the complex amplitude of the light at the destination after propagation from there. Alternatively, it also includes the complex amplitude of the light whose correspondence can be derived by changing the mathematical formula. If the phase of the complex amplitude of the light to be corrected is Φ(x,y), then phase correction is equivalent to performing the calculation in equation (9).

[0038]

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

[0040]

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[0041] Because light changes its distribution as it propagates through space, simply correcting the phase tilt is not always sufficient. The changes in the formulas are not limited to the specific changes defined in equations (9) and (10), but more generally, they involve correcting the phase of the complex amplitude. The amount of phase correction in this case corresponds to the correction of the optical configuration mentioned earlier, and is therefore determined from the amount of correction for the optical configuration.

[0042] The phase measurement methods for each embodiment will be described below with reference to Figure 2. Figure 2 is a flowchart showing the phase estimation methods for each embodiment.

[0043] In step S1, the drive unit 106 moves the position of the opening 102 based on instructions from the computer 107.

[0044] In step S2, the direction of light propagation or the position of the image sensor 105 is corrected based on instructions from the computer 107. The computer 107 also retains 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 that the image sensor 105 has acquired.

[0046] In step S4, the computer 107 determines whether the number of times the processes from steps S1 to S3 have been executed has reached a predetermined number. If the predetermined number has been reached, the flow proceeds to step S5; otherwise, the flow returns to step S1.

[0047] By performing the processes from step S1 to step S4, multiple light intensity distributions across different illumination regions can be obtained.

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

[0049] Each embodiment can be mathematically modeled and therefore implemented as a software function of a computer system. Here, the software function of a computer system includes programming (programs) containing executable code. The software code is executable on a general-purpose computer. During the operation of the software code, the code, or associated data, is stored within the 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 as one or more modules in at least one machine-readable medium (storage medium). (Example 1) The phase measurement method in Example 1 will be described below. Figure 3 is a schematic diagram of the phase measurement device 300 in Example 1. The phase measurement device 300 in Example 1 has a rotation mechanism (correction mechanism) 110 that tilts the object under test 104 and changes the angle of the object under test 104. When illuminating the area surrounding the object under test 104, the object under test 104 is tilted so that reflected light is incident on the image sensor 105. The method for determining the rotation angle θ at this time will be explained using Figure 4.

[0050] In Figure 4, the image sensor 105 is shown in a position where it is reflected by a half-mirror for ease of explanation. Also, the object under test 104 is concave to make the signs of each variable easier to understand. The direction in which reflected light propagates is the center position x of each illumination region. j Determined by the inclination of the surface being examined. Position x j The angle that the tangent line makes with the horizontal plane is φ. j Therefore, φ j The relationship between the surface shape H(x) and the surface shape is given by equation (11).

[0051]

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[0052] The sign of the angle is considered positive when counterclockwise relative to the plane of the paper, and the sign of the coordinate x is considered positive to the right of the plane of the paper. The reflected light is in the opposite direction to the incident light and has an angle of incidence and 2φ. j It propagates in a direction with an angle. The distance from the object 104 to the image sensor 105 is L. d Let position x j The angle that the straight line connecting the center of the image sensor 105 makes with the center line of the incident light ray is φ j0 Therefore, from the geometric arrangement, φ j0 This is determined by equation (12).

[0053]

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

[0055]

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[0056] In Figure 4, the object 104 is rotating clockwise, so θ j Note that the value of is negative. Using equation (13) from equation (11), we can obtain the relationship in equation (14).

[0057]

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[0058] Using the relationship in equation (14), the rotation angle θ of the object 104 in the j-th image is determined. j Determine θ at each imaging stage. jBy simply rotating the object 104 under test, the reflected light can be guided to the image sensor 105.

[0059] Here, the surface shape H(x) is the object of measurement and therefore cannot be known in advance. Therefore, a correction amount θ is used. j To determine this, an approximate value (rough shape of surface shape H(x)) determined from design values, etc., can be used as the surface shape H(x).

[0060] If the design value is unavailable, the position of the reflected light on the surface of the image sensor 105 can be obtained by making small movements of the aperture 102, and feedback can be applied to the rotation mechanism 110 with each small movement. From the geometric arrangement, the amount of movement of the reflected light δx can be obtained. d The relationship between the rotation amount δθ of the object 104 and the object is given by equation (15).

[0061]

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[0062] The relationship in equation (15) can be used to provide feedback to the rotation mechanism 110. The opening 102 will be at the target position x j The total amount of rotation of the rotating mechanism 110 until it reaches θ j This allows us to determine θ. However, this may increase the measurement time because it requires minute drive. More preferably, we can use approximate values ​​such as design values ​​to determine θ. j The method for making that decision is good.

[0063] As described above, light can be guided to the image sensor 105, but since the angle of the object under test 104 has been changed, the mathematical formulas used in the calculation also need to be corrected. By rotating the object under test 104, the direction in which the reflected light propagates is 2θ j It changes by only that much. If we write this mathematically, it is the complex amplitude E of the reflected light. out j This involves multiplying (x) by equation (16).

[0064]

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

[0066]

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[0067] Thus, the magnitude of the phase change W''(x) is the correction amount θ j It changes based on this. Therefore, the complex amplitude E of the reflected light after rotating the object 104 is determined. out j (x) is obtained from equations (5), (16), and (17) as equation (18).

[0068]

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[0069] By performing optimization calculations using the modified formula described above, the phase change amount W(x) can be estimated. (Example 2) The phase measurement method in Example 2 will be described below. Figure 5 is a schematic diagram of the phase measurement device 500 in Example 2. The phase measurement device 500 in Example 2 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 object under test 104). The illumination light 101 is emitted from the 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 Figure 2, the illumination area of ​​the object under test 104 is changed by moving the illumination unit 201 with the drive unit 106. Subsequently, in step S2, the direction of light propagation is corrected so that the reflected light is directed toward the image sensor 105 by rotating the illumination unit 201 with the rotation mechanism 204. The amount of rotation θ at this time j This is determined by equation (19) from the geometric diagram shown in Figure 6.

[0070]

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[0071] Here, in Figure 6, the lighting unit 201 is rotating clockwise, so θ j Note that the value of φ will be negative. j0 , φ j , θ j This can be calculated using approximate values ​​such as design values, similar to Example 1.

[0072] Since the lighting area changes due to the rotation of the lighting unit 201 in step S2, steps S1 and S2 are repeated as needed. Alternatively, the amount of movement of the lighting unit 201 in step S1 is determined after considering the change in the lighting area in step S2. Or, x in equation (2) j By modifying this, the amount of displacement in the illumination area can be taken into account during calculation.

[0073] As described above, light can be guided to the image sensor 105, but since the angle of the illumination light 101 is changed, the formula used in the calculation also needs to be corrected. In this embodiment, parallel light with an angle θj is incident on the aperture 102, so the complex amplitude E of the illumination light 101 0 (x) is given by equation (20).

[0074]

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[0075] Since the light transmitted through aperture 102 is also approximately parallel light, the complex amplitude E of the light directly in front of the object 104 in j (x) can be approximated by equation (21).

[0076]

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[0077] Also, similar to Example 1, the phase change of light due to reflection is W''(x) due to the tilt of the illumination light 101. Therefore, using equations (5), (17), and (21), the reflected light E immediately after reflection from the surface under test can be expressed. out j Rewriting (x) gives equation (22).

[0078]

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[0079] Equation (22) is similar to equation (18) in that the phase slope is corrected, indicating that the same effect as in Example 1 can be obtained.

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

[0081] Although an approximation formula was used in equation (21), a term that corrects the phase slope can be similarly obtained by calculating the light propagation as Fresnel diffraction.

[0082] In this embodiment, a configuration in which the lighting unit 201 is rotated is illustrated, but the method of angling the illumination light 101 is not limited to this. For example, instead of the rotation mechanism 204 that rotates the lighting unit 201, the angle of the illumination light 101 can also be changed by moving the light source 202 with the drive unit 205, as shown in Figure 7. (Example 3) The phase measurement method in Example 3 will be described below. Figure 8 is a schematic diagram of the phase measurement device 800 in Example 3. The phase measurement device 800 in Example 3 has a drive mechanism (correction mechanism) 301 that moves the image sensor 105 to change its position. In step S2 of the flowchart shown in Figure 2, the drive mechanism 301 moves the image sensor 105 according to the propagation direction of reflected light based on instructions from the computer 107. The amount of movement at this time is Δx j This is determined by equation (23) from the geometric diagram shown in Figure 9.

[0083]

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[0084] Therefore, the image sensor 105 moves Δx in accordance with the movement of the aperture 102. j By moving only a short distance, it is possible to obtain the light intensity distribution of the reflected light.

[0085] In this embodiment, the position of the image sensor 105 is changed, so the mathematical formula used in the calculation also needs to be corrected according to the movement of the image sensor 105. j Because it only moved, the acquired light intensity distribution I meas j (x) is the actual light intensity distribution I j (x) Δx j This is the result of shifting by only one digit, and is expressed by equation (24).

[0086]

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[0087] Therefore, in the estimation calculation of the phase change amount W(x), I est j Calculate (x) and use this as Δx j After shifting by that amount, calculate the objective function F expressed by equation (25).

[0088]

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[0089] However, depending on the surface shape, Δx j Since this is larger than the spread of the light intensity distribution on the surface of the image sensor 105, it is necessary to expand the computation domain to calculate equation (25). Expanding the computation domain leads to an increase in computation time, which is undesirable. Therefore, equation (25) is rewritten as follows: Taking light propagation as Fresnel diffraction, the propagation operator JPEG2023115859000029.jpg96

[0090] If we write it out, from equation (6) Δx j The complex amplitude E of light on the image sensor 105 surface, which has been shifted by only that much. d j (x-Δx j ) becomes equation (26).

[0091]

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[0092] By making a simple modification to equation (26), we obtain equation (27).

[0093]

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[0094] Equation (27) is the propagation operator JPEG2023115859000032.jpg107

[0095] By rewriting it using this, we obtain equation (28).

[0096]

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[0097] operator JPEG2023115859000034.jpg107

[0098] The phase portion that appeared before it disappears during imaging and can be ignored. Therefore, the change in the formula required during calculation is E out j This involves multiplying (x) by equation (29), which represents phase modulation.

[0099]

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

[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 tilt. In other words, equation (30) is in the same form as equation (18) in that the phase tilt is corrected, indicating that the same effect as in Example 1 can be obtained.

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

[0104] The above embodiments 1 to 3 can be combined as appropriate. In other words, the light intensity distribution can be obtained by changing at least one of the angles at which the illumination light 101 is incident on the object 104, the angle of the object 104, or the position of the image sensor 105. [Other examples] Although 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 its gist.

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

[0106] In the above embodiments, the measurement target was the amount of phase change W of light due to reflection from the object 104, but the measurement target is not limited to this. If the amount of phase change W of light due to reflection is obtained, the shape distribution H of the surface under test can be obtained by equation (4). Alternatively, the surface shape can also be calculated by setting the optimization variable to H. In other words, the methods used in each embodiment also function as shape measurement methods.

[0107] Furthermore, by using the configuration shown in Figure 10, for example, it is possible to obtain the phase change amount W of light transmitted through the object 104, i.e., the transmitted wavefront. In other words, the methods described in each embodiment also function as transmitted wavefront measurement methods. Moreover, if the object to be measured is a lens or a concave mirror, it also functions as an aberration measurement method that calculates the amount of aberration by re-formulating the phase change amount W due to transmission or reflection as a difference from an ideal amount. In any case, the basis of the measured quantity obtained is the phase change amount W of light caused by the object 104, and the physical quantity converted from this phase change amount W is included in the measurement target of the methods in each embodiment described above. Also, the light measured by the image sensor 105 is not limited to either reflected light or transmitted light from the object 104.

[0108] In each of the above embodiments, for the sake of simplicity, detailed driving errors and changes in other values ​​associated with driving are ignored. For example, if the object under test 104 is tilted in Embodiment 1, the illumination position of the object under test 104 and the distance from the aperture 102 to the object under test 104 will change due to the tilt. It is necessary to modify a series of mathematical formulas to correct for these changes as well. Therefore, the mathematical formulas exemplified in each embodiment are not uniquely determined for carrying out the present invention, but can be modified as appropriate within the scope of the spirit of the present invention.

[0109] In the embodiments described above, the illumination light 101 was 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 Figure 11, it may be a configuration in which a portion of a spherical wave emitted from a point light source 401 is extracted. Alternatively, it may be a portion of a converged wave formed by a lens. The complex amplitude E of the illumination light 101 depends on the form of the illumination light 101. 0 The present invention will function by appropriately changing (x,y). Furthermore, as shown in Figure 11, it is also possible to eliminate the half-mirror 103.

[0110] In the embodiments described above, an 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 function as long as it is a method that can limit the illumination range of the surface under test and change the position of the illumination area. For example, since the spread of light emitted from the end face of an optical fiber is limited, the illumination range can be limited without installing any special aperture material. The position and illumination angle of the illumination area can be changed by changing the position or orientation of the fiber. Also, since the spread of light emitted from a semiconductor laser is limited, it is possible to limit and move the illumination area without using an aperture material.

[0111] The present invention can also be realized by supplying a program that implements one or more of the functions of each of the above embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be realized by a circuit (e.g., an ASIC) that implements 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 light detector; a calculation step of calculating an amount of phase change of the illumination light caused by the object 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 a 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 amount of correction.

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 change unit changes 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 an amount of phase change of the illumination light caused by the object based on the light intensity distribution and a correction amount of the correction mechanism, The control unit corrects a phase of the illumination light based on the amount of correction.

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; acquiring a light intensity distribution of the illumination light reflected from the illumination area by the light detector; 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 measuring method according to claim 1, wherein the calculation step includes a second correction step of correcting a 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 light detector; a calculation step of calculating an amount of aberration of the object based on the light intensity distribution and the correction amount in the first correction step, 4. The aberration measuring method according to claim 1, wherein the calculation step includes a second correction step of correcting a phase of the illumination light based on the correction amount.

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