JP7757196B2 - Measurement method, measurement device, program, and storage medium - Google Patents

Description

The present invention relates to a phase measurement method, a phase measurement device, a program, and a storage medium for estimating the phase change of light caused by a test object.

In recent years, advanced astronomical telescopes using goggle-type optical systems and off-axis optical systems, such as those used in AR and VR, have emerged, increasing demand for optical elements using aspherical and free-form surfaces. Knowing the surface shape 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.

Non-Patent Document 1 discloses a phase measurement method that applies ptychography technology. The technology described in Non-Patent Document 1 involves sequentially changing the area illuminated on the test surface and obtaining the light intensity distribution through that area. Optimization calculations are performed on the multiple obtained light intensity distributions to estimate the amount of phase change in light caused by the test object. The method described in Non-Patent Document 1 enables measurement to be achieved using a simpler optical system than interferometers, etc.

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 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

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

The present invention provides a phase measurement method that can measure a variety of phase changes with a simple configuration.

A measurement method as one aspect of the present invention includes a change step of changing an illumination area of a test 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 using the photodetector; and a calculation step of calculating a phase change amount of the illumination light caused by the test object based on the light intensity distribution and a correction amount 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.

Other objects and features of the present invention are described in the following embodiments.

The present invention provides a phase measurement method, a phase measurement device, a program, and a storage medium that can measure a variety of phase changes with a simple configuration.

FIG. 1 is a schematic diagram of a phase measurement device using ptychography. 10 is a flowchart illustrating a phase measurement method according to each embodiment. FIG. 1 is a diagram illustrating a phase measurement device according to a first embodiment. FIG. 10 is a diagram showing the amount of rotation in the first embodiment. FIG. 10 is a diagram illustrating a phase measurement device according to a second embodiment. FIG. 10 is a diagram showing the amount of rotation in the second embodiment. FIG. 10 is a diagram illustrating another phase measurement device according to the second embodiment. FIG. 10 is a diagram illustrating a phase measurement device according to a third embodiment. FIG. 11 is a diagram showing the amount of movement in the third embodiment. FIG. 10 is a schematic diagram of a phase measurement device according to another embodiment. FIG. 10 is a schematic diagram of a phase measurement device according to another embodiment.

Embodiments of the present invention will now be described in detail with reference to the drawings. In each drawing, identical components will be assigned the same reference numbers, and duplicate descriptions will be omitted.

Figure 1(a) is a schematic diagram of a phase measurement device 100 using ptychography. After the illumination area is limited by the 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 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 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 driver 106 constitute a change means for changing the illumination area. By repeatedly moving the aperture 102 and acquiring the light intensity distribution, the light intensity distribution of 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 performs post-processing based on the acquired light intensity distribution and the position of the aperture 102 to estimate the spatial distribution of the amount of phase change in light caused by reflection. The post-processing may be performed by the computer 107, or by a separate computing device. Alternatively, the post-processing may be performed by a computing device located on the cloud via a network.

The method for calculating the phase in the phase measurement device 100 is explained below. For simplicity, the illumination light is assumed to be monochromatic. The object to be measured is 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 defined as 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 expressed by equation (1).

If the complex amplitude of the incident light is E ⁰ (x, y) and the position at which the center of the aperture 102 is placed by the jth movement by the driving unit 106 is (x _j, y _j ), the complex amplitude ^Ep _j (x, y) of the light immediately after passing through the aperture 102 is given by equation (2).

j takes a value from 1 to N (a natural number), where N is the total number of positions at which the apertures 102 are placed. The light that has passed through the apertures 102 propagates to the test object 104. If the distance from the apertures 102 to the test object 104 is _Li , the complex amplitude E ⁱⁿ _j (x, y) of the light that has reached the test object 104 is given by Equation (3).

is the operator that indicates the propagation of light,

Indicates that light represented by the function f is propagated over a distance L. The method of calculating 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.

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 across 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).

From equations (3) and (4), the complex amplitude E ^out _j (x, y) of the light reflected from the test surface is given by equation (5).

where i is an imaginary unit. The light reflected from the test surface propagates to the image sensor 105. If the distance from the test surface to the image sensor 105 is _Ld , the complex amplitude E ^d _j (x, y) of the light on the surface of the image sensor 105 is given by Equation (6).

The light intensity distribution I _j (x, y) acquired by the image sensor 105 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).

The light intensity distribution I _j (x, y) is acquired by changing the position of the aperture 102 N times. Optimization, for example, is a method for calculating the phase change amount W(x, y) from the acquired N light intensity distributions. Optimization is a calculation method in which variables to be estimated (optimization variables) are sequentially changed so that the value of an 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 may be the sum of squared differences between the measured light intensity distribution I ^meas _j (x, y) and the light intensity distribution I ^est _j (x, y; W) calculated by equations (1) to (7) from the estimated phase change amount W, as shown in equation (8).

Other methods 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 explanation will be omitted here.

The above-described method makes it possible to estimate the phase change amount W(x, y) of light caused by the test object 104 from the measured light intensity distribution I ^meas _j (x, y). However, depending on the shape of the test object 104, it may be impossible to estimate the phase change amount W(x, y). This problem is illustrated using FIG. 1( b). FIG. 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 approximately coincide. 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 FIG. 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 phase change amount W(x, y) in the peripheral region of the test surface.

For simplicity's sake, the above comparison was made between reflections from convex and concave surfaces using parallel illumination light 101, but this problem can easily be generalized. When the illumination position of the test object 104 is changed, the propagation direction of 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, 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 light or the position of the image sensor 105 must be corrected for each illumination area.

In each embodiment, the optical arrangement of the phase measurement device 100 is corrected as the aperture 102 moves 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 can be corrected, or the image sensor 105 can 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, etc. As long as the light can be guided to the image sensor 105, the elements that are corrected are not limited to specific ones. Correction of the light propagation direction can also be achieved by adding an element capable of controlling the light propagation direction, such as a spatial phase modulator or DMD (Digital Micromirror Device), to the optical path. The amount of correction when making these corrections, i.e., the amount of element drive, 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.

Although correcting the optical arrangement of the phase measurement device 100 allows light to be guided to the image sensor 105, this alone does not allow for the appropriate calculation of 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 formula based on the optical arrangement and an optimization calculation. Therefore, when the optical arrangement is corrected, the series of formulas used in the calculation must also be corrected.

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. Because the propagation direction of light is determined by the phase gradient of the complex amplitude, if 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 is equivalent to calculating equation (9).

Here, c _x,j and c _y,j are constants determined from the correction amount of the optical arrangement of the phase measurement device 100 at the j-th imaging time. 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).

Since light changes its distribution as it propagates through space, it is not simply a matter of correcting the phase tilt. The change to the formula is not limited to the specific changes defined by equations (9) and (10), but more generally involves correcting the phase of the complex amplitude. The amount of phase correction in this case corresponds to the optical arrangement correction described above, and is therefore determined from the amount of correction for the optical arrangement.

The phase measurement method of each embodiment will be explained below with reference to Figure 2. Figure 2 is a flowchart showing the phase estimation method of each embodiment.

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

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 retains or records the corrected sensor and the amount of correction.

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

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

By performing steps S1 to S4, multiple light intensity distributions through different illumination areas can be obtained.

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 amount of correction for the optical arrangement. In step S501, the phase of the complex amplitude of the light is corrected based on the amount of correction for the optical arrangement performed in step S2. In step S502, the corrected complex amplitude is used to estimate the phase change amount W(x, y).

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 Example 1 will be described below. Fig. 3 is a schematic diagram of a 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 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 in this case will be described with reference to Fig. 4.

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 test object 104 is assumed to be concave. The direction in which the reflected light propagates is determined by the inclination of the test surface at the center position _xj of each illumination area. If the angle that the tangent at position _xj makes with the horizontal plane is _φj , then the relationship between _φj and the surface shape H(x) is expressed by Equation (11).

The sign of the angle is positive in the counterclockwise direction relative to the plane of the paper, and the sign of the coordinate x is positive to the right of the plane of the paper. The reflected light propagates in a direction opposite to the incident light, forming an angle of _2φj with the incident angle. If the distance from the test object 104 to the image sensor 105 is _Ld , and the angle between the line connecting the position _xj and the center of the image sensor 105 and the center line of the incident light is _φj0 , then _φj0 can be determined from the geometric arrangement by equation (12).

When the test object 104 is rotated by _θj , the propagation direction of the reflected light changes _{by 2θj} , and therefore the condition for making the reflected light incident on the image sensor 105 is given by equation (13).

4, it should be noted that the value of _θj is negative because the test object 104 is rotating clockwise. The relational expression of expression (14) can be obtained by using expressions (11) and (13).

The rotation angle θ _j of the test object 104 in the j-th image capture is determined using the relational expression (14), and the reflected light can be guided to the image sensor 105 by rotating the test object 104 by θ _j at each image capture.

Here, the surface shape H(x) is a measurement target and cannot be known in advance, so the correction amount _θj can be determined by using an approximate value (the approximate shape of the surface shape H(x)) determined from the design value or the like as the surface shape H(x).

If the design value is not available, 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 provided to the rotation mechanism 110 for each minute movement. From the geometrical arrangement, the relational expression between the movement amount δx _d of the reflected light and the rotation amount δθ of the test object 104 is given by Equation (15).

Feedback can be applied to the rotation mechanism 110 using the relational expression (15). _θj can be determined from the total amount of rotation of the rotation mechanism 110 until the aperture 102 reaches the target position _xj . However, since minute driving is required, the measurement time may increase. More preferably, _θj is determined using an approximate value such as a design value.

In this way, the light can be guided to the image sensor 105, but 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 propagation direction of the reflected light changes by _2θj . This can be expressed mathematically by multiplying the complex amplitude E ^out _j (x) of the reflected light by formula (16).

Furthermore, the amount of phase change W(x) of light caused by reflection on the test surface also changes due to rotation. The amount of phase change W″(x) caused by the surface tilting by _θj is expressed by equation (17) using the surface shape H(x).

In this way, the magnitude of the phase change amount W''(x) changes based on the correction amount _θj . Therefore, the complex amplitude ^Eoutj (x) of the reflected light after rotating the test object 104 is expressed by equation ( ₁₈ ) from equations (5), (16), and (17).

By performing optimization calculations using the formulas modified as above, the phase change amount 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 drive unit 106 moves the illumination unit 201 to change the illumination area of the test object 104. Subsequently, in step S2, the rotation mechanism 204 rotates the illumination unit 201 to correct the propagation direction of the light so that the reflected light is directed toward the image sensor 105. The amount of rotation _θj at this time is determined by equation (19) from the geometric diagram shown in FIG.

6, the lighting unit 201 is rotating clockwise, so the value of _θj is negative. _φj0 , _φj , and _θj can be calculated using approximate values such as design values, as in the first embodiment.

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, the amount of deviation of the illumination area may be taken into consideration during calculation by correcting _xj in equation (2).

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

Since the light transmitted through the aperture 102 is also approximately parallel light, the complex amplitude E ⁱⁿ _j (x) of the light just before the test object 104 can be approximated by equation (21).

Furthermore, similarly to the first embodiment, the amount of phase change of light due to reflection caused by tilting the illumination light 101 is W''(x). Therefore, by using equations (5), (17), and (21), the reflected light E ^out _j (x) immediately after reflection from the test surface can be rewritten as equation (22).

Equation (22) has a form in which the phase gradient is corrected, similar to equation (18), and shows that the same effect as in Example 1 can be obtained.

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

Equation (21) uses an approximate formula, but a term that corrects the phase tilt can be obtained in the same way by calculating light propagation as Fresnel diffraction.

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 _Δxj at this time is determined by equation (23) from the geometric diagram shown in Fig. 9.

Therefore, if the image sensor 105 is moved by _Δxj in response to the movement of the aperture 102, the light intensity distribution of the reflected light can be obtained.

In this embodiment, the position of the image sensor 105 is changed, and therefore the formula used for calculation needs to be corrected in accordance with the movement of the image sensor 105. Because the image sensor 105 has moved by _Δxj , the acquired light intensity distribution I ^measj (x) is the actual light intensity distribution _{I j (} x) shifted by _Δxj , and is expressed by equation (24).

Therefore, in the estimation calculation of the phase change amount W(x), I ^est _j (x) is calculated from the estimated value of W(x), and after shifting this by Δx _j , the objective function F expressed by equation (25) is calculated.

However, depending on the surface shape, _Δxj may become larger than the spread of the light intensity distribution on the surface of the image sensor 105, so 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 to

If we write this down, the complex amplitude E ^d _j (x−Δx _j ) of light on the surface of the image sensor 105 shifted by Δx _j from equation (6) becomes equation (26).

By making a simple change to equation (26), we obtain equation (27).

Equation (27) is transformed into the propagation operator

Rewriting this using equation (28) gives us equation (28).

operator

The phase part that appears before can be ignored because it disappears during imaging. Therefore, the only change to the formula required for calculation is to multiply E ^out _j (x) by formula (29) that represents phase modulation.

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

Equation (30) shows that the movement of the image sensor 105 can be treated as the same as correcting the phase tilt. In other words, equation (30) corrects the phase tilt in the same way as equation (18), and shows that the same effect as in Example 1 can be obtained.

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

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.

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 an estimated calculation of the phase change amount W is performed. The mathematical formula correction can be achieved by multiplying the complex amplitude of the light by a complex function that imparts a phase change, or by correcting the phase gradient. The amount of phase gradient correction 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.

In the above examples, the measurement target was 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 using equation (4). Alternatively, the surface shape can be calculated using H as the optimization variable. In other words, the method described in each example also functions as a shape measurement method.

Furthermore, for example, with the configuration shown in FIG. 10, it is also possible to obtain the phase change W of light transmitted through the test object 104, i.e., the transmitted wavefront. In other words, the methods described in each embodiment also function as a transmitted wavefront measurement method. Furthermore, if the measurement object is a lens or concave mirror, they also function as an aberration measurement method that calculates the amount of aberration by reformulating the phase change W due to transmission or reflection as a difference from an ideal amount. In either case, the basis of the measurement amount obtained is the phase change W of light caused by the test object 104, and the physical quantity converted from this phase change W is included in the measurement objects of the methods in each of the above embodiments. Furthermore, the light measured by the image sensor 105 is not limited to either reflected light or transmitted light from the test object 104.

In the above examples, for simplicity of explanation, detailed drive errors and changes in other values associated with drive are ignored. For example, if the test object 104 is tilted in Example 1, the tilt will change the illumination position on the test object 104 and the distance from the opening 102 to the test object 104. It is necessary to modify and implement a series of formulas to correct for these changes. For this reason, the formulas exemplified in each example are not uniquely determined for implementing the present invention, but may be modified as appropriate within the scope of the spirit of the present invention.

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 a portion of a spherical wave extracted from a point light source 401. Alternatively, the illumination light 101 may be a portion of a convergent wave formed by a lens. The present invention functions as long as the complex amplitude E ⁰ (x, y) of the illumination light 101 is appropriately changed depending on the form of the illumination light 101. Furthermore, it is also possible to eliminate the half mirror 103 as shown in FIG. 11 .

In the above examples, the aperture 102 was used as an example of a method for limiting the illumination area, but this is not the only method for limiting the illumination area. The present invention will work with any method that limits the illumination range of the test surface and allows the position of the illumination area to be changed. For example, because the light emitted from the end face of an optical fiber has a limited spread, it is possible to limit the illumination range 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.

The present invention can also be realized by supplying a program that realizes one or more of the functions of each of the above embodiments to a system or device via a network or storage medium, and 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 realizes one or more functions.

Change means 102, 106
Photodetector 105
Control unit 107
Correction mechanism 110, 204, 301

Claims (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 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 according to claim 1, wherein in the second correction step, a phase of the illumination light used in the calculation step is corrected based on the correction amount. 3. The measurement method according to claim 2, wherein an optimization calculation is performed in the calculation step . 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. 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. The measurement method according to claim 1, wherein the phase change amount is changed based on the correction amount . 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. 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. 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. A program for causing a computer to execute the measurement method according to any one of claims 1 to 8. A computer-readable storage medium storing the program described in claim 10. 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. 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.