JP2017090327A - Wavefront sensor and wavefront processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wavefront sensor with which it is possible to efficiently eliminate the effect of unnecessary light components even when unnecessary light is included in an incident beam.SOLUTION: A wavefront sensor 1 includes a feature value extraction unit for calculating, for a wavefront to be measured, comparison data that indicates the result of comparison of the image component of a first wavefront image outputted from an image-capturing unit 20 when in an aberration-free state with the image component of the output image of the image-capturing unit 20 when in an aberration-free state; correcting the image component of the first wavefront image by a correction amount that corresponds to the result of comparison of the comparison data with reference data; and outputting feature value data that indicates the result of the correction. A measurement error of the wavefront to be measured is calculated using the feature value data.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a technique for measuring the wavefront of a light beam transmitted or reflected by an optical system.

  The wavefront sensor can measure the wavefront shape of a light beam transmitted or reflected by an optical system such as an optical lens, a light reflecting surface, or a living eyeball. As the wavefront sensor, a Shack-Hartmann type wavefront sensor is widely used. For example, Patent Document 1 (Japanese Patent Publication No. 2004-524053) and the following Non-Patent Document 1 are used as the Shack-Hartmann type wavefront sensor. Is disclosed.

  The Shack-Hartmann wavefront sensor disclosed in Patent Document 1 includes a CCD (Charge Coupled Device) array that detects a plurality of light spots formed by a pinhole array or a lenslet array, and a CCD image indicating the detection result. And a processor for calculating a wavefront shape based on a shift amount from the reference point of the barycentric position. This processor can generate a filter image from which non-uniform background noise is removed by filtering the CCD image using a spatial filter having a predetermined profile, and a wavefront shape based on the filter image. Is calculated.

  In Non-Patent Document 1, a correlation Shack-Hartmann wavefront sensor (Correlating Shack-) that calculates a cross-correlation between an image formed by a lenslet array and a reference image and measures a wavefront shape using the calculation result. Hartmann wavefront sensor) is disclosed.

Special table 2004-524053 gazette

Living Reviews in Solar Physics, 8, (2011), 2.

  The emitted light beam of the test optical system to be measured may include stray light such as scattered light or disturbance light as well as light from an ideal light source. In this case, there is a problem that light unnecessary for wavefront measurement (hereinafter referred to as “unnecessary light”) such as stray light or disturbance light reduces the measurement accuracy of the wavefront sensor. As described above, the Shack-Hartmann wavefront sensor of Patent Document 1 can remove non-uniform background noise in a CCD image using a spatial filter. However, if an unexpected unnecessary light component that does not conform to the profile of the spatial filter is included in the CCD image, it is difficult to eliminate the influence of that type of unnecessary light component using the spatial filter.

  Further, in the correlation Shack-Hartmann wavefront sensor of Non-Patent Document 1, when an unnecessary light component is included in the formed image formed by the lenslet array, it is based on the cross-correlation between the formed image and the reference image. Therefore, it is difficult to eliminate the influence of unnecessary light components.

  In view of the above, an object of the present invention is to provide a wavefront sensor and a wavefront processing method capable of efficiently eliminating the influence of unnecessary light components even when unnecessary light such as stray light or disturbance light is included in an incident light beam. It is in.

  A wavefront sensor according to an aspect of the present invention includes a lenslet array that spatially divides a wavefront of incident light to form a plurality of spot optical images, an imaging unit that captures the plurality of spot optical images, A known aberration generating unit that generates a known aberration state in which a known optical aberration amount is imparted to an optical path of incident light to the lenslet array and a non-aberration state in which the known optical aberration amount is not imparted to the optical path; and the lens For the reference wavefront incident on the let array, the image component of the first reference wavefront image output from the imaging unit in the non-aberration state and the second output from the imaging unit in the known aberration state A data storage unit storing reference data indicating a comparison result with an image component of the reference wavefront image of the reference wavefront, and the measured wavefront incident on the lenslet array in the non-aberration state Sometimes, comparison data indicating a comparison result between the image component of the first wavefront image output from the imaging unit and the image component of the second wavefront image output from the imaging unit in the known aberration state is calculated. A feature amount extraction unit that corrects the image component of the first wavefront image with a correction amount according to a comparison result between the comparison data and the reference data, and further outputs feature amount data indicating the correction result; And a wavefront measuring unit that estimates a measurement error of the wavefront to be measured using the feature amount data.

  A wavefront processing method according to another aspect of the present invention includes a lenslet array that spatially divides a wavefront of incident light to form a plurality of spot optical images, and an imaging unit that images the plurality of spot optical images. A known aberration generation unit that generates a known aberration state in which a known optical aberration amount is imparted to the optical path of incident light to the lenslet array and a non-aberration state in which the known optical aberration amount is not imparted to the optical path; The image component of the first reference wavefront image output from the imaging unit when the reference wavefront incident on the lenslet array is in the non-aberration state and the first output from the imaging unit when in the known aberration state. A wavefront processing method executed in a wavefront sensor comprising a data storage unit storing reference data indicating a comparison result with image components of two reference wavefront images, the lens For the wavefront to be measured that is incident on the array, the image component of the first wavefront image output from the imaging unit in the non-aberration state and the second output from the imaging unit in the known aberration state Calculating comparison data indicating a comparison result with the image component of the wavefront image, correcting the image component of the first wavefront image with a correction amount according to the comparison result between the comparison data and the reference data, The method includes a step of outputting feature amount data indicating the correction result, and a step of estimating a measurement error of the wavefront to be measured using the feature amount data.

  According to the present invention, even when unnecessary light such as stray light or disturbance light is included in an incident light beam, the influence of unnecessary light components can be efficiently eliminated. Therefore, a highly reliable measurement error can be calculated.

It is a figure which shows schematic structure of the wavefront sensor of Embodiment 1 which concerns on this invention. It is the schematic of a lenslet array. 3A and 3B are diagrams illustrating examples of reference wavefront images acquired in the reference wavefront measurement mode. It is a figure which shows the synthesized image obtained by superimposing the reference wavefront image shown in FIG. 3A and FIG. 3B, respectively. 6 is a flowchart illustrating an example of a processing procedure of reference wavefront measurement according to the first embodiment. 6A and 6B are diagrams illustrating examples of images acquired in the measured wavefront processing mode. It is a figure which shows the synthesized image obtained by superimposing the captured image respectively shown to FIG. 6A and 6B. It is a flowchart which shows an example of the procedure of a to-be-measured wavefront process. 9A and 9B are diagrams for explaining the method of the feature amount calculation method. 10A to 10C are diagrams for explaining a method of a feature amount calculation method. FIG. 3 is a block diagram illustrating a hardware configuration example of a wavefront processing unit according to the first embodiment. FIG. 6 is a block diagram illustrating another hardware configuration example of the wavefront processing unit according to the first embodiment. It is a figure which shows schematic structure of the wavefront sensor of Embodiment 2 which concerns on this invention. It is a figure which shows schematic structure of the wavefront sensor of Embodiment 3 which concerns on this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the component to which the same code | symbol was attached | subjected in the whole drawing shall have the same structure and the same function.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a schematic configuration of a wavefront sensor 1 according to Embodiment 1 of the present invention. The wavefront sensor 1 is arranged so as to receive a light beam that has propagated from the light source LS via the optical system OJT. The emitted light beam of the light source LS is transmitted or reflected by the optical system OJT, or both transmitted and reflected, and then enters the wavefront sensor 1. As shown in FIG. 1, the wavefront sensor 1 of the present embodiment includes a variable diaphragm mechanism 10, a known aberration generator 11, a collimator lens 12, a lenslet array 13, an imaging unit 20, and a wavefront processor 25.

  The variable aperture mechanism 10 has an opening through which the light beam incident on the wavefront sensor 1 passes. The variable aperture mechanism 10 can change the size of the opening according to the aperture control signal Ca from the wavefront processing unit 25. As will be described later, the variable aperture mechanism 10 is used to form a pinhole portion that outputs a spherical wave having no wavefront aberration. Instead of the variable aperture mechanism 10, a pinhole plate with a slide mechanism may be used.

  The known aberration generating unit 11 responds to the aberration control signal Cn from the wavefront processing unit 25 and has a known optical aberration amount (hereinafter referred to as “known aberration amount”) in the optical path between the variable aperture mechanism 10 and the collimator lens 12. Is a module that selectively generates a known aberration state in which no optical aberration is applied to the optical path. The known aberration generator 11 uses, for example, an optical lens (not shown) that is movable in the optical axis direction or a direction perpendicular thereto, and an electric stage or actuator (not shown) that drives the optical lens. What is necessary is just to be comprised. By displacing this optical lens in a direction perpendicular to the optical axis direction, coma or astigmatism can be generated. It is also possible to generate an optical aberration due to a defocused state by displacing the optical lens along the optical axis direction. With this configuration, it is possible to switch between a known aberration state and a non-aberration state. The configuration of the known aberration generator 11 may be realized using the known aberration generator 50 (FIG. 14) of the third embodiment described later.

The collimator lens 12 converts incident light into parallel light and makes it incident on the lenslet array 13. The lenslet array 13 includes a large number of microlenses (also referred to as lenslets) that are two-dimensionally arranged in a direction perpendicular to the optical axis. FIG. 2 is a diagram illustrating an example of the lenslet array 13 when viewed from the optical axis direction. The lenslet array 13 is composed of an array of a large number of microlenses L ₁ , L ₂ ,..., L _i ,. It has a function of forming an image (hereinafter also referred to as “spot image”).

  The imaging unit 20 performs signal processing on the output signal of the imaging element 21 such as a CCD (Charge-Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor, and a signal that outputs an image signal IS. And a processing unit 22. The imaging unit 20 can capture a plurality of spot optical images formed on the imaging surface of the image sensor 21.

  As shown in FIG. 1, the wavefront processing unit 25 includes a feature amount extraction unit 31, an image comparison unit 32, an image displacement detection unit 33, a wavefront calculation unit 34, an error estimation unit 35, an operation control unit 36, and a data storage unit 37. It is configured with. Of the configuration of the wavefront processing unit 25, the image comparison unit 32, the image displacement detection unit 33, the wavefront calculation unit 34, and the error estimation unit 35 measure the aberration of the measured wavefront and estimate the measurement error of the measured wavefront. A wavefront measuring unit may be configured.

  The operation control unit 36 can supply the aperture control signal Ca to the variable aperture mechanism 10 to control the aperture of the variable aperture mechanism 10, and can supply the aberration control signal Cn to the known aberration generation unit 11 to perform the known aberration described above. A state and an aberration-free state can be selectively generated. Further, the operation control unit 36 supplies the operation mode control signal Sw to the feature amount extraction unit 31, the image comparison unit 32, the image displacement detection unit 33, and the wavefront calculation unit 34, thereby setting the operation mode of the wavefront processing unit 25 as a reference. One of the wavefront processing mode and the measured wavefront processing mode can be switched to the other. In the reference wavefront processing mode, the operation control unit 36 uses the aperture control signal Ca to make the opening of the variable aperture mechanism 10 a pinhole. Thereby, the variable aperture mechanism 10 can emit a spherical wave having a reference wavefront having no wavefront aberration to the known aberration generating unit 11.

In the reference wavefront processing mode, the operation control unit 36 generates a reference wavefront in the variable aperture mechanism 10 by supplying the aperture control signal Ca. Further, the operation control unit 36 causes the known aberration generation unit 11 to sequentially generate a non-aberration state and a known aberration state by supplying the aberration control signal Cn. The image displacement detection unit 33 illustrated in FIG. 1 includes an image displacement detection unit 33R that operates in the reference wavefront processing mode. The reference displacement detection unit 33R is configured to output an image component of the output image (hereinafter referred to as “first reference wavefront image”) IMG1 in the non-aberration state with respect to the reference wavefront and the imaging unit 20 in the known aberration state. Output image (hereinafter, “second reference wavefront image”) IMG2 image components are compared with each other, and reference data indicating the comparison result is calculated. For example, if the local displacement amount Δ _i of the second reference wavefront image IMG2 with respect to the first reference wavefront image IMG1 (i is the number of the local region image corresponding to the microlens L _i ) is calculated as reference data. Good.

3A and 3B are diagrams schematically illustrating examples of the first reference wavefront image IMG1 and the second reference wavefront image IMG2 in the reference wavefront processing mode. In the first reference wavefront image IMG1 shown in FIG. 3A, the center (center of gravity) of the plurality of spot images is indicated by the symbol “+”, and in the second reference wavefront image IMG2 shown in FIG. The center (center of gravity position) of a plurality of spot images displaced locally due to aberration is indicated by the symbol “x”. 4A is a diagram showing a composite image IMG3 obtained by superimposing the first and second reference wavefront images IMG1 and IMG2 shown in FIGS. 3A and 3B, and FIG. 4B shows an i-th microlens L. is a diagram showing a local region image s _i having two spot images formed by _i.

As shown in the example of FIG. 4B, the reference displacement detector 33R is the following equation (1) can be calculated local displacement delta _i is a vector quantity.

Here, Δx _i indicates the amount of displacement in the horizontal pixel direction, and Δy _i indicates the amount of displacement in the vertical pixel direction. The local displacement amount Δ _i is an amount specified by a local coordinate value with the center of each spot image of the first reference wavefront image IMG1 as the origin. Data Td of the local displacement amount Δ _i (hereinafter also referred to as “reference data Td”) is stored in the data storage unit 37.

The wavefront calculation unit 34 shown in FIG. 1 has a known aberration amount calculation unit 34N that operates in the reference wavefront processing mode. The known aberration amount calculating section 34N as equivalent to the local gradient of the reference wavefront local displacement delta _i, can be calculated known aberration ΔW (X, Y). Here, X and Y are values that specify coordinate positions in the entire output image of the imaging unit 20, X is a coordinate value in the horizontal pixel direction, and Y is a coordinate value in the vertical pixel direction. .

Specifically, the local gradient of the reference wavefront can be obtained based on the following equation (2).

Here, f _LA is a focal length of each microlens of the lenslet array 13.

  Then, the known aberration amount calculation unit 34N calculates the known aberration amount ΔW (X, Y) by fitting the local gradient obtained by the equation (2) with a function such as a known Zernike polynomial (Zernike polynomial). can do. This fitting can be performed using, for example, a known least square method. Data Tw of the known aberration amount ΔW (X, Y) is stored in the data storage unit 37.

  FIG. 5 is a diagram schematically showing an example of the procedure of the reference wavefront processing. As shown in FIG. 5, the operation control unit 36 supplies the aperture control signal Ca to the variable aperture mechanism 10 to generate a reference wavefront (step ST1). Next, the operation control unit 36 supplies the aberration control signal Cn to the known aberration generating unit 11 to make the known aberration zero (step ST2). Then, the image displacement detection unit 33 acquires the first reference wavefront image IMG1 by sampling the output image IS of the imaging unit 20 (step ST3). Thereafter, the operation controller 36 supplies the aberration control signal Cn to the known aberration generator 11 to generate a known aberration (step ST4). Then, the image displacement detection unit 33 acquires the second reference wavefront image IMG2 by sampling the output image IS of the imaging unit 20 (step ST5).

Next, as described above, the reference displacement detector 33R calculates the local displacement amount Δ _i between the first and second reference wavefront images IMG1 and IMG2 (step ST6), and indicates these local displacement amounts Δ _i . The reference data Td is recorded in the memory, that is, the data storage unit 37 (step ST7). Thereafter, known aberration amount calculating section 34N, as described above, to calculate a known amount of aberration [Delta] W (X, Y) based on the local displacement delta _i (step ST8), these known aberration [Delta] W (X, Y) Is recorded in the memory, that is, the data storage unit 37 (step ST9).

  Next, the measured wavefront processing mode will be described. At this time, the operation control unit 36 opens the opening of the variable aperture mechanism 10 by the aperture control signal Ca. As a result, the variable aperture mechanism 10 emits a light beam having a wavefront to be measured generated in the optical system OJT to the known aberration generator 11.

  In the measured wavefront processing mode, the operation controller 36 causes the known aberration generator 11 to sequentially generate a non-aberration state and a known aberration state by supplying the aberration control signal Cn. 6A and 6B show an output image of the imaging unit 20 in the non-aberration state (hereinafter, “first wavefront image”) IMG4 and an output image of the imaging unit 20 in the known aberration state (hereinafter, “second wavefront”). FIG. 2 is a diagram illustrating an image “) IMG5. In the first wavefront image IMG4 shown in FIG. 6A, the center (center of gravity position) of the plurality of spot images is indicated by the symbol “◯”, and in the second wavefront image IMG5 shown in FIG. The center (center of gravity position) of a plurality of spot images displaced locally is indicated by the symbol “Δ”. FIG. 7 is a diagram showing a composite image IMG6 obtained by superimposing the first and second wavefront images IMG4 and IMG5 shown in FIGS. 6A and 6B.

  The image comparison unit 32 shown in FIG. 1 has a first image comparison unit 32A and a second image comparison unit 32B that operate in the measured wavefront processing mode, and the image displacement detection unit 33 operates in the measured wavefront processing mode. The first displacement detector 33A and the second displacement detector 33B are provided. The wavefront calculation unit 34 includes a first relative wavefront calculation unit 34A, a second relative wavefront calculation unit 34B, and a measured wavefront calculation unit 34C that operate in the measured wavefront processing mode. The error estimation unit 35 also operates in the measured wavefront processing mode.

  Hereinafter, the measured wavefront process will be described with reference to FIG. FIG. 8 is a diagram illustrating an example of the procedure of the measured wavefront process.

  Referring to FIG. 8, the operation control unit 36 supplies the aberration control signal Cn to the known aberration generation unit 11 to make the known aberration zero (step ST11). Next, the feature quantity extraction unit 31 acquires the first wavefront image IMG4 by sampling the output image IS of the imaging unit 20 (step ST12). Thereafter, the operation controller 36 supplies the aberration control signal Cn to the known aberration generator 11 to generate a known aberration (step ST13). Next, the feature quantity extraction unit 31 acquires the second wavefront image IMG5 by sampling the output image IS of the imaging unit 20 (step ST14). Here, the first wavefront image IMG4 and the second wavefront image IMG5 are stored in an image memory (not shown) because they are also used in the processing of the first image comparison unit 32A and the second image comparison unit 32B. .

  Thereafter, the feature quantity extraction unit 31 detects the feature quantity of the first wavefront image IMG4 (including the feature quantity of the light source LS) based on the first wavefront image IMG4 and the second wavefront image IMG5 (step ST15). ), The feature amount data Tc is recorded in the memory, that is, the data storage unit 37 (step ST16).

  Hereinafter, an example of a feature amount calculation method will be described. In this example, the feature quantity extraction unit 31 first compares the image component of the first wavefront image IMG4 and the image component of the second wavefront image IMG5, and calculates comparison data indicating the comparison result. If attention is paid to a phase component which is a kind of image component, the feature amount extraction unit 31 calculates a difference between the phase component of the first wavefront image IMG4 and the phase component of the second wavefront image IMG5 as comparison data. be able to. Next, the feature amount extraction unit 31 compares such comparison data with the reference data Td, corrects the image component of the first wavefront image IMG4 with a correction amount according to the comparison result, and characterizes the correction result. Can be output as a quantity. This makes it possible to reduce unnecessary light components of the first wavefront image IMG4 as will be described later.

Now, i-th microlens _{L i} corresponding local region image to _{s i} in the first wavefront image IMG4 in aplanatic state, a (x, y) and then, the second wavefront image at a known aberration state IMG5 Let s _{i, b} (x, y) be the local region image corresponding to the i-th microlens L _i at. The feature quantity extraction unit 31 applies the discrete Fourier transform F to the local region image s _{i, a} (x, y), as shown in the following equation (3), so that the spatial frequency component S _{i, a} (k _x , K _y ).

Here, W _N and W _M are defined by the following equation (4).

Further, as shown in the following equation (5), the feature amount extraction unit 31 performs a discrete Fourier transform F on the local region image s _{i, b} (x, y), thereby obtaining a spatial frequency component S _{i, b} ( k _x , k _y ).

The feature quantity extraction unit 31 calculates the difference θ _{i, a} (k _x , k _y ) −θ _{i, b} (k _x , k _y ) between the phase components appearing in the above equations (3) and (5) as comparison data. Then, it can be compared with the reference data Td (local displacement amount Δ _i ). Specifically, the feature quantity extraction unit 31 can perform the comparison based on the phase difference parameter Δθ _i (k _x , k _y ) of the following equation (6).

In an ideal situation where unnecessary light is not generated, the value of the phase difference parameter Δθ _i (k _x , k _y ) is substantially zero. By the way, the comparison between the intensity components appearing in the above equations (3) and (5) is given by the intensity residual parameter ΔA _i (k _x , k _y ) of the following equation (7).

Here, g _{i, a} , g _{i, b} have offset components A _{i, a} (0,0) and A _{i, b} (0,0) set to zero, and intensity components other than the offset components have the same magnitude. It is a uniform gain adjusted to be. In an ideal situation where unnecessary light is not generated, the values of the gains g _{i, a} , g _{i, b} are adjusted so that the value of the intensity residual parameter ΔA _i (k _x , k _y ) becomes substantially zero. ing.

As shown in the following equation (8), the weights D _i (k _x , k _y, ) having the phase difference parameter Δθ _i (k _x , k _y ) and the intensity residual parameter ΔA _i (k _x , k _y ) as independent variables. k _y ) can be defined.

Further, as shown in the following equations (9) and (10), using the weights D _i (k _x , k _y ) and the gains g _{i, a} , the spatial frequency components S _{i, a (k} x, _{k y)} spatial frequency components _P i to _{correct, a (k x, k y} ) can be calculated.

The feature quantity extraction unit 31 can calculate the corrected spatial frequency component P _{i, a} (k _x , k _y ) as a feature quantity. The weight D _i (k _x , k _y ) decreases as the absolute value of the phase difference parameter Δθ _i (k _x , k _y ) increases, and the weight residual parameter ΔA _i (k _x , k _y ) increases. The absolute value is set to be smaller as the absolute value is larger. It is considered that the phase difference parameter Δθ _i (k _x , k _y ) increases as the unnecessary light component increases, or the intensity residual parameter ΔA _i (k _x , k _y ) increases as the unnecessary light component increases. Therefore, the spatial frequency component P _{i, a} (k _x , k _y ) shown in Expression (10) is the spatial frequency of the first wavefront image (hereinafter referred to as “corrected wavefront image”) in which the unnecessary light component is reduced. Can be considered an ingredient.

Next, referring to FIG. 8, after step ST16, the first image comparison unit 32A and the first displacement detection unit 33A in FIG. 1 perform local displacement of the first wavefront image IMG4 based on the feature amount data Tc. The amount Δ _{p, a} (p = 1, 2, 3,...) Is detected (step ST17), and the second image comparison unit 32B and the second displacement detection unit 33B perform the second wavefront based on the feature amount data Tc. A local displacement amount _{Δp, b} (p = 1, 2, 3,...) Of the image IMG5 is detected (step ST18).

Specifically, the first image comparison unit 32A reads the first wavefront image IMG4 from an image memory (not shown), and compares the feature amount data Tc with the image components of the first wavefront image IMG4. . The first displacement detector 33A can calculate the local displacement amount _{Δp, a} of the first wavefront image IMG4 based on the comparison result (step ST17). The second image comparison unit 32B also reads the second wavefront image IMG5 from the image memory (not shown), and compares the feature amount data Tc with the image components of the second wavefront image IMG5. The second displacement detector 33B can calculate the local displacement amount _{Δp, b} of the second wavefront image IMG5 based on the comparison result (step ST18).

More specifically, the first image comparison unit 32A has a feature quantity P _{i, a} (k _x , k _y ) that is a spatial frequency component of the corrected wavefront image and The cross-correlation value with the spatial frequency components K _{i, a} (k _x , k _y ) of the p-th local region image sp _{p, a} of one wavefront image IMG4, that is, the mutual power spectrum R _{p, a} (k _x , k _y ) can be calculated.

Here, i is a specific number, and p can be the number of all local area images (= 1, 2, 3,...). In addition, the first image comparison unit 32A performs an inverse discrete Fourier transform F ⁻¹ on the mutual power spectrum R _{p, a} (k _x , k _y ), as shown in the following equation (12), thereby obtaining a correlation function. r _{p, a} (x, y) can be calculated.

Since the peak position of the correlation function r _{p, a} (x, y) indicates the local displacement amount Δ _{p, a} of the first wavefront image IMG4 with respect to the corrected wavefront image, the first displacement detector 33A uses the correlation function r _{p. , A} (x, y) based on the peak position, the local displacement _{Δp, a} in the following equation (13) can be calculated (step ST17).

Instead of the equation (11), the following equation (14) using only the phase component may be used.

Similarly, the second image comparison unit 32B, as shown in the following equation (15), the feature quantity P _{i, a} (k _x , k _y ), which is the spatial frequency component of the corrected wave front image, and the second wave front image. A cross-correlation value with the spatial frequency components K _{i, b} (k _x , k _y ) of the p-th local region image sp _{p, b} of the IMG 5, that is, a mutual power spectrum R _{p, b} (k _x , k _y ) is calculated. can do.

Here, i is a specific number, and p can be the number of all local area images (= 1, 2, 3,...). In addition, the second image comparison unit 32B performs an inverse discrete Fourier transform F ⁻¹ on the mutual power spectrum R _{p, b} (k _x , k _y ), as shown in the following equation (16), whereby a correlation function is obtained. r _{p, b} (x, y) can be calculated.

The second displacement detector 33B can calculate the local displacement _{Δp, b} of the following equation (17) based on the peak position of the correlation function r _{p, b} (x, y) (step ST18). .

Instead of the equation (15), the following equation (18) using only the phase component may be used.

After step ST18, the measured wavefront calculator 34C calculates the wavefront aberration of the optical system OJT to be measured (step ST19). That is, the measured wavefront calculator 34C measures the aberration amount W (X, Y) of the measured wavefront based on the local displacement amount _{Δp, a} of the first wavefront image, and outputs the measurement data WF. .

Specifically, the measured wavefront calculator 34C calculates the image center of the first wavefront image IMG4 from the local displacement amounts _{Δp, a} (p = 1, 2, 3,...) Of the first wavefront image IMG4. local displacement at position delta _kappa, focused on _{a (p} = kappa), as shown in the following equation (19), in the local displacement delta _{kappa, a,} all the local of the first wavefront image IMG4 By offsetting the displacement amount _{Δp, a} , the local displacement amount _{Δp, c} can be calculated.

Next, the measured wavefront computing unit 34C can obtain the local gradient of the measured wavefront based on the following equation (20).

  Then, the measured wavefront calculator 34C can calculate the wavefront aberration amount W (X, Y) by fitting the local gradient obtained by the equation (20) with a function such as a known Zernike polynomial. (Step ST19).

After step ST19, the first relative wavefront computing unit 34A obtains local gradients of the first wavefront image IMG4 based on the following equation (21), and fits these local gradients with a function such as a known Zernike polynomial. Thus, the relative wavefront distribution W _a (X, Y) is calculated (step ST20).

Further, the second relative wavefront calculation unit 34B obtains local gradients of the second wavefront image IMG5 based on the following equation (22), and fits these local gradients with a function such as a known Zernike polynomial to thereby obtain a relative wavefront. Distribution W _b (X, Y) is calculated (step ST21).

Then, the error estimation unit 35 calculates the measurement error Er (X, Y) of the wavefront to be measured by the following equation (23) and outputs the data Er (step ST22). Thus, the measured wavefront process is completed.

Various information regarding the wavefront accuracy can be obtained from the measurement error Er (X, Y). For example, the RMS (Root Mean Square) error of the wavefront aberration amount W (X, Y) can be estimated by the RMS value of the measurement error Er (X, Y). This RMS value is an average square root of values obtained by squaring the measurement error Er (X, Y). Further, a statistic called an unbiased estimated amount can be obtained by dividing the RMS value of the measurement error Er (X, Y) by ^2½ . Furthermore, as described above, the known aberration amount ΔW (X, Y) and the relative wavefront distributions W _a (X, Y), W _b (X, Y) can be expressed by Zernike polynomial expansion, respectively. Er (X, Y) can also be expressed by Zernike polynomial expansion. For this reason, it is possible to obtain a measurement error of a specific wavefront aberration component (for example, an astigmatism component or a coma aberration component) from each order term of the Zernike polynomial that expresses the measurement error Er (X, Y). .

  The set of steps ST11 and ST12 and the set of steps ST13 and ST14 do not need to be executed in this order, and may be executed in the reverse order or simultaneously. Also, the above steps ST17 and ST18 need not be executed in this order, and may be executed in the reverse order or concurrently. Further, the steps ST20 and ST21 do not need to be executed in this order, and may be executed in the reverse order or concurrently.

By the way, the feature amount calculation process in step ST15 is performed by another method, and the local displacement amount Δ _{p, a} , _{by a} method different from the method in steps ST17 and ST18 using the feature amount obtained by this method. It is also possible to calculate _{Δp, b} . Hereinafter, this method will be described.

The feature quantity extraction unit 31 uses a spot area PA ₁ ,... Having an image component having a brightness (luminance) equal to or higher than a reference value from the local area image s _{i, a of} the first wavefront image IMG4 obtained in an aberration-free state. , _PA K (K is a positive integer) to extract, these spot area _PA 1, ..., put each identification number to PA _K. Next, the feature extraction unit 31, these spot area PA _1, ..., and calculates the respective corresponding barycentric coordinates based on the light amount distribution of PA _K. Similarly, the feature amount extraction unit 31 uses a local region image s _{i, b of} the second wavefront image IMG5 obtained in a known aberration state to have a spot region PB having an image component having brightness (luminance) equal to or higher than a reference value. _1, ..., _PB Q (Q is a positive integer) to extract, these spot area _PB 1, ..., put each identification number PB _Q. Next, the feature amount extraction unit 31 calculates the corresponding barycentric coordinates based on the light amount distribution of the spot regions PB ₁ ,..., PB _Q.
9A and 9B show examples of spot regions PA _{1 to} PA ₄ in the local region image s _{i, a} of the _first wavefront image IMG4 and in the local region image s _{i, b of} the second wavefront image IMG5. of an example of a spot region _PB 1 _{~PB 5} illustrates respectively. Spot areas PA _{1 to} PA ₄ shown in FIG. 9A are a mixture of spot areas representing spot images of a plurality of point light sources forming light source LS in FIG. 1 and false spot areas representing unnecessary light. The same applies to the spot regions PB _{1 to} PB ₅ shown in FIG. 9B.

Next, the feature extraction unit 31, the local region image _{s i,} spot area _PA 1 in _a, ..., PA _K and the local region image _{s i,} spot area _PB 1 in _b, ..., and PB _Q together The comparison is performed, and a difference vector indicating the comparison result is calculated as comparison data. Specifically, the feature amount extraction unit 31 associates the spot areas whose centroid coordinates match or are close to each other between the first wavefront image IMG4 and the second wavefront image IMG5, and centroids of these associated spot areas A difference vector between coordinates is calculated. Now, local region image _{s i,} when expressed in the local region image _{s i} to the spotted area PA _u in _a, the difference vector of the spot region PB _v in _{b δ i (u, v)} , the difference vector [delta] _i ( u, v) is given by:
_{δ i (u, v) =} (x v -x u, y v -y u)

Here, (x _u , y _u ) represents the barycentric coordinates of the u-th spot area PA _u , and (x _v , y _v ) represents the barycentric coordinates of the v-th spot area PB _v .

Next, the feature amount extraction unit 31 compares the difference vector δ _i (u, v) with the reference data Td (local displacement amount Δ _i ), and from the difference vector δ _i (u, v), A difference vector that matches or is close to the local displacement amount Δ _i in the vector space is selected. Specifically, the feature amount extraction unit 31 can select only a difference vector in which the magnitude of the difference between the difference vector δ _i (u, v) and the local displacement amount Δ _i is within a certain range. . Furthermore, the feature extraction unit 31, the local region image s _i, spot area PA 1 in _a, ..., from the PA _K, excluding spot region that does not constitute the selected difference vector.
Figure 10A is a diagram showing an example of a local region image z _{i, a} obtained by excluding a portion the local region image s _i, from _a spot area of Figure 9A. In the local area image z _{i, a} in FIG. 10A, the spot area PA _{4 in} FIG. 9A is excluded as a false spot area representing unnecessary light. Therefore, the local area image z _{i, a} can be regarded as a reduced unnecessary light component in the local area image s _{i, a} in FIG. 9A.

Next, the feature amount extraction unit 31 calculates a relative position vector between spot regions in the local region image zi _{, a} in which unnecessary light components are reduced as _a feature amount. A relative position vector V _{i, a} (t, u) between arbitrary spot areas PA _t , PA _u in the local area image z _{i, a} is given by the following equation.
_{V i, a (t, u} ) = (x u -x t, y u -y t)

Then, the feature quantity extraction unit 31 records the feature quantity data Tc indicating the relative position vector V _{i, a} (t, u) in the data storage unit 37. In the example of FIG. 10A, three relative position vectors V _{i, a} (1,2), V _{i, a} (2,3), V _{i, a} (1,3) are calculated as feature amounts. Such a relative position vector V _i (t, u) represents the characteristics of one or more light sources forming the light source LS, and all the local region images s _{1, a} constituting the first wavefront image IMG4. , S _{2, a} ,... Can be regarded as a common feature amount. Therefore, the relative position vector V _i (t, u) is a specific local region image s _{i, of} the local region images s _{1, a} , s _{2, a} ,... Constituting the first wavefront image IMG4 _{. What} is necessary is just to be calculated about _a .

Thereafter, the first image comparison unit 32A compares the feature amount data Tc with the relative position vectors between the spot regions in the other local region images sp _{, a} (p ≠ i), and the first displacement detection unit 33A detects the local displacement amount Δ _{p, a} (p = 1, 2, 3,...) Of the first wavefront image IMG4 based on the comparison result. Similarly, the second image comparison unit 32B compares the feature amount data Tc with the relative position vectors between the spot regions in the local region image sp _{, b} (p = 1, 2, 3,...), The second displacement detector 33B detects the local displacement amount Δ _{p, b} (p = 1, 2, 3,...) Of the second wavefront image IMG5 based on the comparison result.

Specifically, the first image comparison unit 32A calculates _a relative position vector V _{p, a} (t, u) between the spot areas of the other local area images sp _{, a} (p ≠ i), and calculates the relative Of the position vectors V _{p, a} (t, u), only the relative position vector that matches or is close to the feature data Tc in the vector space is selected, and the selection result is notified to the first displacement detector 33A. The first image comparison unit 32A can select only the relative position vector in which the magnitude of the difference between the relative position vector V _{p, a} (t, u) and the feature amount data Tc is within a certain range. 33 A of 1st displacement detection parts select only the spot area | region which comprises the said selected relative position vector among the spot area | regions in the said other local area | region image sp _{, a} (p ≠ i). Then, the first displacement detection unit 33A selects the selected spot area in the other local area image sp _{, a} (p ≠ i) with respect to the average coordinates of the center of gravity of the spot area in the local area image zi _{, a} . The relative position of the average coordinate of the center of gravity can be calculated as the local displacement amount Δ _{p, a} (p = 1, 2, 3,...).
Figure 10B is a diagram showing an example of the other local region image _{s p,} spot area _PP 1 _{~PP 4} in _a. In this case, the spot area PP ₄ is not selected as representative of unwanted light. Therefore, the first displacement detection unit 33A determines the relative position of the average coordinates of the centroids of the spot areas PP _{1 to} PP _{3 in} FIG. 10B with respect to the average coordinates of the centroids of the spot areas PA _{1 to} PA ₃ in FIG. 10A. Calculate as _{p, a} .

Similarly, the second image comparison unit 32B calculates the relative position vector V _{p, b} (t (t) between the spot areas of the local area image sp _{, b} (p = 1, 2, 3,...) Of the second wavefront image IMG5. , U), and from the relative position vector V _{p, b} (t, u), only the relative position vector that matches or is close to the feature amount data Tc in the vector space is selected, and the selection result is obtained as the second result. Notify the displacement detector 33B. Next, the second displacement detection unit 33B selects only the spot region that constitutes the selected relative position vector from the spot regions in the local region image sp _{, b} . The second displacement detector 33B then compares the average coordinate of the center of gravity of the selected spot area in the local area image sp _{, b with} respect to the average coordinate of the center of gravity of the spot area in the local area image zi _{, a} . The position can be calculated as a local displacement amount Δ _{p, b} (p = 1, 2, 3,...).
FIG. 10C is a diagram illustrating an example of the spot regions PB _{1 to} PB _{5 in} the local region image sp _{, b} . In this case, the spot areas PB ₄ and PB ₅ are not selected as representing unnecessary light. Accordingly, the second displacement detecting unit 33B is to the average coordinates of the center of gravity of the spot area _PA 1 _{~PA 3} in FIG. 10A, the local displacement of the relative position of the average coordinates of the center of gravity of the spot area _PB 1 _{~PB 3} in FIG. 10C delta _It is calculated as _{p and b} .

  The hardware configuration of the wavefront processing unit 25 described above can be realized by a computer with a built-in CPU (Central Processing Unit) such as a workstation or a mainframe. Alternatively, the hardware configuration of the wavefront processor 25 may be an LSI (Large Realized Gate Array) such as DSP (Digital Signal Processor), ASIC (Application Specific Integrated Circuit), or FPGA (Field-Programmable Gate Array). Good.

  FIG. 11 is a block diagram illustrating a hardware configuration example of the wavefront processing unit 25 configured using a signal processing circuit such as an LSI. In the example of FIG. 11, the wavefront processing unit 25 includes a signal processing circuit 70, an input interface unit 71, an output interface unit 72, a recording medium 73, and a signal path 74 such as a bus. The recording medium 73 can be used as a data storage unit 37 and an image memory that temporarily stores the image signal IS. As the recording medium 73, for example, a volatile memory such as SDRAM (Synchronous DRAM), HDD (Hard Disk Drive) or SSD (Solid State Drive) can be used.

  On the other hand, FIG. 12 is a block diagram illustrating a hardware configuration example of the wavefront processing unit 25 configured using a computer. In the example of FIG. 12, the wavefront processing unit 25 includes a processor 80 incorporating a CPU 80c, a RAM (Random Access Memory) 81, a ROM (Read Only Memory) 82, an input interface unit 83, an output interface unit 84, a recording medium 85, and a bus. The signal path 86 is configured as follows. The recording medium 85 can be used as a data storage unit 37 and an image memory that temporarily stores the image signal IS. As the recording medium 85, for example, a volatile memory such as SDRAM, an HDD, or an SSD can be used.

  As described above, the wavefront sensor 1 of the first embodiment measures the wavefront aberration amount W (X, Y) of the optical system OJT using the feature amount data Tc in which the influence of the unnecessary light component is reduced. The measurement error Er (X, Y) of the wavefront to be measured is estimated. Therefore, even when unnecessary light such as stray light or disturbance light is included in the incident light beam, the influence of the unnecessary light component is efficiently removed and the wavefront aberration amount W (X, Y) is measured with high accuracy, and the reliability is high. The measurement error Er (X, Y) can be estimated.

Embodiment 2. FIG.
Next, a second embodiment according to the present invention will be described. FIG. 13 is a diagram showing a schematic configuration of the wavefront sensor 2 according to the second embodiment of the present invention. As shown in FIG. 13, the wavefront sensor 2 is the same as the wavefront sensor 1 of the first embodiment except that the wavefront sensor 2 includes a known aberration generator 40 including a wavelength selection filter 41 and a cemented lens 42 and an imaging unit 20C. It has the same configuration.

  The known aberration generator 40 includes a wavelength selection filter 41 that selectively transmits light in the first wavelength region λ1 and the second wavelength region λ2 of the incident light, and the above-described absence of light for the first wavelength region λ1 of the incident light. A cemented lens 42 that generates the above-mentioned known aberration state for the second wavelength band λ2 of incident light at the same time as generating the aberration state. The cemented lens 42 is a chromatic aberration generating lens configured by bonding a first lens having a positive power and a second lens having a negative power. For example, the cemented lens 42 may be configured by bonding a convex lens made of flint glass and a concave lens made of crown glass. The cemented lens 42 has a configuration optically opposite to a known achromatic lens formed by bonding a convex lens made of crown glass and a concave lens made of flint glass, and therefore generates larger chromatic aberration than a single lens. Can do.

  The imaging unit 20C includes a color imaging element 21C and a signal processing unit 22C that performs signal processing on the output of the color imaging element 21C. The signal processing unit 22C detects the optical image group in the first wavelength region λ1 from the plurality of spot optical images formed by the lenslet array 13 and outputs the first image signal ISa. Among them, it is possible to detect the optical image group in the second wavelength region λ2 and output the second image signal ISb.

  As the color image sensor 21C, for example, a color filter element composed of an array of a filter that transmits light of the first wavelength band λ1 and a filter that transmits light of the second wavelength band λ2, and a single imaging surface Can be used. Alternatively, a multi-plate type imaging device having an imaging surface for detecting light of the color in the first wavelength range λ1 and an imaging surface for detecting light of the color in the second wavelength range λ2 may be used as the imaging device 21C. . A CCD image sensor or a CMOS image sensor can be used for these image sensors.

  Similarly to the wavefront processing unit 25 of the first embodiment, the wavefront processing unit 25C is a feature amount extraction unit 31, an image comparison unit 32, an image displacement detection unit 33, a wavefront calculation unit 34, an error estimation unit 35, and a data storage unit. 37. The wavefront processing unit 25C includes an operation control unit 36C, and the operation control unit 36C supplies the aperture control signal Ca to the variable aperture mechanism 10 in the same manner as the operation control unit 36 of the first embodiment. The function of controlling the diaphragm of the variable diaphragm mechanism 10 and the function of switching the operation mode by supplying the operation mode control signal Sw to the feature amount extraction unit 31, the image comparison unit 32, the image displacement detection unit 33, and the wavefront calculation unit 34 And have.

  With such a configuration, in the reference wavefront processing mode, the wavefront processing unit 25C acquires the above-described first reference wavefront image IMG1 based on the first image signal ISa and the above-described first reference wavefront image IMG1 based on the second image signal ISb. Two reference wavefront images IMG2 can be acquired. In the measured wavefront processing mode, the wavefront processing unit 25C acquires the first wavefront image IMG4 described above based on the first image signal ISa, and the second wavefront image described above based on the second image signal ISb. IMG5 can be acquired. Therefore, the wavefront processing unit 25C according to the present embodiment also measures the wavefront aberration amount W (X, Y) with high accuracy in the same manner as the wavefront processing unit 25 according to the first embodiment, and has a highly reliable measurement error Er. (X, Y) can be estimated. Therefore, the present embodiment can achieve the same effects as those of the first embodiment.

  The configuration of the present embodiment is suitable for a case where the chromatic aberration of the test optical system OJT can be ignored when the test optical system OJT is a reflective optical system or the like. Compared to the case of the first embodiment, the configuration of the present embodiment does not require a movable part for switching between the known aberration state and the no-aberration state. Can be secured.

Embodiment 3 FIG.
Next, a third embodiment according to the present invention will be described. This embodiment is a modification of the first embodiment. That is, as shown in FIG. 14, the configuration of the wavefront sensor 3 of the present embodiment is the same as the configuration of the wavefront sensor 1 of the first embodiment except for the known aberration generator 50.

  The known aberration generator 50 includes a beam splitter 51 that divides incident light from the variable aperture mechanism 10 into a first light beam and a second light beam, a first aberration generating optical system 55, a reflection mirror 56, and a shutter 57. An optical path, a second optical path including a reference optical system 52, a reflection mirror 53, and a shutter 54, and an optical multiplexer 58 disposed at a position where the first optical path and the second optical path merge. Yes. The optical multiplexer 58 combines the light beam propagated through the first optical path and the light beam propagated through the second optical path, and outputs the combined light to the collimator lens 12. As shown in FIG. 14, a non-aberration state occurs in the second optical path including the reference optical system 52, and the known aberration generation optical system 55 generates a known aberration state (for example, chromatic aberration) in the first optical path. Further, either the first optical path or the second optical path can be blocked by the open / close state of the shutters 54 and 57.

  With such a configuration, the imaging unit 20 is in an aberration-free state by closing one shutter 57 to block the first optical path and opening the other shutter 54 to open the second optical path. The time image signal IS can be supplied to the wavefront processing unit 25. Further, the imaging unit 20 is configured to open an image signal in a known aberration state by opening one shutter 57 to open the first optical path and closing the other shutter 54 to block the second optical path. The IS can be supplied to the wavefront processing unit 25. Therefore, similarly to the wavefront processing unit 25 of the first embodiment, the wavefront processing unit 25 of the present embodiment also measures the wavefront aberration amount W (X, Y) with high accuracy, and has a highly reliable measurement error Er. (X, Y) can be estimated.

  The configuration of the present embodiment is suitable for a case where the chromatic aberration of the optical system OJT cannot be ignored when the optical system OJT is a refractive optical system or the like. Further, by simultaneously opening the shutters 54 and 57, there is an advantage that the known aberration amount ΔW (X, Y) can be accurately evaluated and adjusted by the interferometer. Furthermore, since the aberration generation amount does not depend on the motion accuracy of the movable part, the configuration of the present embodiment is also suitable for applications in which the aberration generation amount needs to be maintained for a long time without maintenance.

  As a modification of the third embodiment, a combination of the imaging unit 20C and the wavefront processing unit 25C of the second embodiment may be used instead of the combination of the imaging unit 20 and the wavefront processing unit 25. In this case, it is possible to use a wavelength selective beam splitter instead of the non-wavelength selective beam splitter 51. In this modification, the wavelength selective beam splitter emits light in the first wavelength region λ1 of incident light in the direction of the reference optical system 52, but emits light in other wavelength regions in the direction of the reference optical system 52. do not do. The wavelength selective beam splitter emits light in the second wavelength region λ2 of the incident light in the direction of the known aberration generating optical system 55, but emits light in other wavelength regions in the direction of the known aberration generating optical system 55. Does not emit. With such a configuration, when both the shutters 54 and 57 are in the open state, the imaging unit 20C outputs the first image signal ISa and the second image signal ISb to the wavefront processing unit in the same manner as the imaging unit 20C of the second embodiment. 25C can be output. Therefore, similarly to the wavefront processing unit 25C of the second embodiment, the wavefront processing unit 25C of this modification also measures the wavefront aberration amount W (X, Y) with high accuracy, and has a highly reliable measurement error Er ( X, Y) can be estimated.

  Although various embodiments according to the present invention have been described above with reference to the drawings, these embodiments are examples of the present invention, and various forms other than these embodiments can be adopted.

  In addition, within the scope of the present invention, the above-described first to third embodiments can be freely combined, any constituent element of each embodiment can be modified, or any constituent element of each embodiment can be omitted.

  The present invention is applicable to any device that measures the wavefront shape of light transmitted or reflected by a test optical system. For example, the present invention can be applied to astronomical observation equipment, eyeball wavefront aberration measurement equipment, or equipment for measuring the flatness of a semiconductor wafer.

  OJT optical system to be tested, LS light source, 1 to 3 wavefront sensor, 10 variable aperture mechanism, 11 known aberration generator, 20 imaging unit, 21 imaging element, 22 signal processing unit, 25 wavefront processing unit, 31 feature quantity extraction unit, 32 image comparison unit, 33 image displacement detection unit, 34 wavefront calculation unit, 35 error estimation unit, 36 operation control unit, 37 data storage unit, 40 known aberration generation unit, 41 wavelength selection filter, 42 cemented lens, 50 generation of known aberration Part, 51 beam splitter, 52 contrast optical system, 53 reflecting mirror, 54 shutter, 55 known aberration generating optical system, 56 reflecting mirror, 57 shutter, 58 optical multiplexer.

Claims (17)

A lenslet array that spatially divides the wavefront of the incident light to form a plurality of spot optical images;
An imaging unit for imaging the plurality of spot optical images;
A known aberration generating unit that generates a known aberration state in which a known optical aberration amount is imparted to the optical path of incident light to the lenslet array and a non-aberration state in which the known optical aberration amount is not imparted to the optical path;
The reference wavefront incident on the lenslet array is output from the imaging unit in the known aberration state and the image component of the first reference wavefront image output from the imaging unit in the non-aberration state. A data storage unit storing reference data indicating a comparison result with the image component of the second reference wavefront image;
The measured wavefront incident on the lenslet array was output from the imaging unit in the first wavefront image output from the imaging unit in the non-aberration state and in the known aberration state. Comparing data indicating the comparison result with the image component of the second wavefront image is calculated, and the image component of the first wavefront image is corrected with a correction amount according to the comparison result between the comparison data and the reference data. Further, a feature amount extraction unit that outputs feature amount data indicating the correction result; and
A wavefront sensor comprising: a wavefront measurement unit that estimates a measurement error of the wavefront to be measured using the feature amount data. The wavefront sensor according to claim 1,
The wavefront measuring unit is
An image comparison unit that compares the feature quantity data and the image component of the first wavefront image with each other and compares the feature quantity data with the image component of the second wavefront image; and
An image displacement detection unit that detects a local displacement amount of the first wavefront image and a local displacement amount of the second wavefront image based on a comparison result by the image comparison unit;
A wavefront computing unit that calculates a first relative wavefront distribution based on the local displacement amount of the first wavefront image and calculates a second relative wavefront distribution based on the local displacement amount of the second wavefront image; ,
A wavefront sensor comprising: an error estimation unit that calculates the measurement error based on the first relative wavefront distribution, the second relative wavefront distribution, and the known optical aberration amount.   3. The wavefront sensor according to claim 2, wherein the wavefront calculation unit measures an aberration of the wavefront to be measured based on a local displacement amount of the first wavefront image.   4. The wavefront sensor according to claim 2, wherein the image comparison unit calculates a cross-correlation between the corrected wavefront image and the first wavefront image, thereby calculating the corrected wavefront image and the first wavefront sensor. Comparing the corrected wavefront image with the second wavefront image by comparing the corrected wavefront image with each other and calculating the cross-correlation between the corrected wavefront image and the second wavefront image. Wavefront sensor.   5. The wavefront sensor according to claim 1, wherein the reference data is data indicating a local displacement amount of the second reference wavefront image with respect to the first reference wavefront image. 6. A wavefront sensor characterized by being.   6. The wavefront sensor according to claim 1, wherein the known aberration generation unit selectively generates the known aberration state and the non-aberration state. 7. Wavefront sensor. The wavefront sensor according to any one of claims 1 to 5,
The known aberration generating unit generates the non-aberration state for the first wavelength range of the incident light and simultaneously generates the known aberration state for the second wavelength range of the incident light;
The imaging unit detects an optical image group in the first wavelength region among the plurality of spot optical images and outputs the first wavefront image, and the second wavelength among the plurality of spot optical images. Detecting an optical image group of the region and outputting the second wavefront image;
A wavefront sensor characterized by that.   8. The wavefront sensor according to claim 7, wherein the known aberration generating unit includes an optical element that generates chromatic aberration in the optical path to generate the known aberration state.   9. The wavefront sensor according to claim 8, wherein the optical element is a cemented lens including a first lens having a positive power and a second lens having a negative power. The wavefront sensor according to any one of claims 1 to 5,
The known aberration generator is
A beam splitter that splits the incident light into a first light flux and a second light flux;
A first optical path through which the first light flux propagates;
A second optical path through which the second light flux propagates;
An optical multiplexer disposed at a position where the first optical path and the second optical path merge;
The wavefront sensor wherein the first optical path generates the known aberration state and the second optical path generates the non-aberration state.   11. The wavefront sensor according to claim 10, further comprising a shutter mechanism that blocks one of the first optical path and the second optical path and opens the other optical path. .   12. The wavefront sensor according to claim 1, further comprising a diaphragm mechanism that generates a spherical wave having the reference wavefront.   13. The wavefront sensor according to claim 1, wherein the wavefront measurement unit calculates the reference data and outputs the reference data before the feature amount data is output. A wavefront sensor characterized by memorizing.   14. The wavefront sensor according to claim 1, wherein the wavefront measurement unit includes a known aberration amount calculation unit that calculates the known optical aberration amount based on the reference data. A wavefront sensor characterized by that. A lenslet array that spatially divides a wavefront of incident light to form a plurality of spot optical images, an imaging unit that captures the plurality of spot optical images, and an optical path of incident light to the lenslet array The known aberration generation unit that generates a known aberration state to which a known optical aberration amount is applied and a non-aberration state in which the known optical aberration amount is not applied to the optical path, and the reference wavefront that is incident on the lenslet array Comparison result between the image component of the first reference wavefront image output from the imaging unit in the non-aberration state and the image component of the second reference wavefront image output from the imaging unit in the known aberration state A wavefront processing method executed in a wavefront sensor provided with a data storage unit in which reference data indicating
The measured wavefront incident on the lenslet array was output from the imaging unit in the first wavefront image output from the imaging unit in the non-aberration state and in the known aberration state. Calculating comparison data indicating a comparison result with an image component of the second wavefront image;
Correcting the image component of the first wavefront image with a correction amount according to a comparison result between the comparison data and the reference data, and outputting feature amount data indicating the correction result;
And a step of estimating a measurement error of the wavefront to be measured using the feature amount data. The wavefront processing method according to claim 15,
Comparing the feature quantity data and the image components of the first wavefront image with each other and comparing the feature quantity data with the second wavefront image with each other;
Detecting a local displacement amount of the first wavefront image and a local displacement amount of the second wavefront image based on the comparison result;
Calculating a first relative wavefront distribution based on a local displacement amount of the first wavefront image;
Calculating a second relative wavefront distribution based on a local displacement amount of the second wavefront image,
The wavefront processing method, wherein the measurement error is calculated based on the first relative wavefront distribution, the second relative wavefront distribution, and the known optical aberration amount.   17. The wavefront processing method according to claim 16, further comprising a step of measuring aberration of the measured wavefront based on a local displacement amount of the first wavefront image.

Images