WO2020026432A1 - Optical system evaluation device and optical system evaluation method - Google Patents

Abstract

This optical system evaluation device comprises a spatial light modulation unit (1) for adding wavefront aberration to the light from a plurality of point light sources, a spread function calculation unit (5) for using electrical signals generated by imaging elements (3-1 to 3-J) to calculate point image spread functions indicating the intensity distributions of point images corresponding to the light from the respective light sources, a pixel phase estimation unit (6) for using the electrical signals generated by the imaging elements (3-1 to 3-J) to estimate point image pixel phases for the point images corresponding to the light from the respective light sources, and a spread function generation unit (7) for using the point image pixel phases estimated by the pixel phase estimation unit (6) to generate a high-resolution PSF having a higher resolution than the plurality of PSFs calculated by the spread function calculation unit (5). A wavefront aberration estimation unit 8 estimates the wavefront aberration of an image formation optical system on the basis of the high-resolution PSF generated by the spread function generation unit (7).

Description

Optical system evaluation apparatus and optical system evaluation method

The present invention relates to an optical system evaluation device and an optical system evaluation method for estimating a wavefront aberration of an imaging optical system.

The characteristics of an imaging device used for remote sensing are likely to change due to the influence of vibration or the surrounding environment.
Therefore, conventionally, with respect to an imaging device used for remote sensing, a technology for performing a process of correcting the characteristics of the imaging device at any time so that a high-quality captured image can be continuously obtained during its operation is known. I have. In order to appropriately correct the characteristics of the imaging device, it is necessary to grasp the characteristics of the imaging device when capturing an image. Understanding the characteristics of the imaging device is performed by evaluating an image captured by the operating imaging device.

The wavefront aberration of the imaging optical system may be used as one of the indexes for evaluating the characteristics of the imaging device.
When the wavefront aberration is used as an index for evaluating the characteristics of the imaging device, the wavefront aberration is measured by a device for evaluating an optical system (hereinafter, referred to as an “optical system evaluation device”). Based on the measured wavefront aberration, for example, the imaging optical system is deformed so that the wavefront aberration approaches 0, thereby compensating for the resolution degradation due to the wavefront aberration.

In Non-Patent Document 1 below, a plurality of light sources for evaluation are arranged on the ground so that a plurality of light sources for evaluation are arranged at known intervals, and a plurality of light sources are imaged from the sky. A technique for obtaining a high-resolution point spread function (PSF) from a plurality of included point images is disclosed.
The PSF is a function indicating the intensity distribution of a point image corresponding to each light emitted from a plurality of evaluation light sources.

“In-Flight Performance Assessment of Imaging Systems Using The Specular Array Radiometric Calibration (SPARC) Method,” 11th Annual Joint Joint Agency Commercial Imagery Evaluation (JACIE) Workshop (2012)

The method disclosed in Non-Patent Document 1 assumes that a plurality of light sources for evaluation are arranged on the ground and images of the plurality of light sources are taken from the sky. A plurality of light sources cannot be imaged from above.
Therefore, in the method disclosed in Non-Patent Document 1, there is a problem in that the wavefront aberration cannot be promptly estimated because the execution of the estimation depends on the weather.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an optical system evaluation apparatus and an optical system capable of estimating the wavefront aberration of an imaging optical system without disposing a light source for evaluation on the ground. The purpose is to obtain an evaluation method.

An optical system evaluation apparatus according to the present invention includes: a spatial light modulator that adds a wavefront aberration to each light from a plurality of point light sources; and an imager that forms each light wavefront aberration added by the spatial light modulator. An optical system, a plurality of imaging devices that convert each light imaged by the imaging optical system to generate an electric signal, and a point corresponding to each light from the electric signals generated by the plurality of imaging devices. A distribution function calculation unit that calculates a point spread function indicating an intensity distribution of an image, and a pixel phase estimation unit that estimates a pixel phase of a point image corresponding to each light from an electric signal generated by a plurality of imaging elements. Generating a high-resolution point spread function having a higher resolution than the plurality of point spread functions from the plurality of point spread functions calculated by the distribution function calculator based on the pixel phase estimated by the pixel phase estimator. Distribution A generating unit, is obtained by the high-resolution point spread function generated by the distribution function generating unit, to and a wavefront aberration estimation unit that estimates a wavefront aberration of the imaging optical system.

According to the present invention, the wavefront aberration of the imaging optical system can be estimated without arranging the evaluation light source on the ground.

1 is a configuration diagram illustrating an optical system evaluation device according to a first embodiment. FIG. 2 is a hardware configuration diagram illustrating hardware of an image processing unit 4. FIG. 4 is a hardware configuration diagram of a computer when the image processing unit 4 is realized by software or firmware. 9 is a flowchart illustrating a processing procedure when the image processing unit 4 is realized by software or firmware. It is explanatory drawing which shows the several point image which has the shape which spreads uniformly toward the circumference | surroundings, and the PSF of the shape with high central symmetry. It is explanatory drawing which shows the several point image which has the shape which spreads unequally toward the periphery, and the PSF of the shape with low center symmetry. FIG. 4 is an explanatory diagram showing point images (1) to (3), point image intensity distributions, and pixel values which are electric signals generated by the imaging elements 3-1 to 3-J corresponding to each light. FIG. 3 is an explanatory diagram illustrating a relationship between a point image pixel phase and a pixel value of an image sensor. FIG. 4 is an explanatory diagram illustrating a process of generating a high-resolution PSF by a distribution function generation unit 7; FIG. 9 is a configuration diagram illustrating an optical system evaluation device according to a second embodiment. FIG. 2 is a hardware configuration diagram illustrating hardware of an image processing unit 31. 9 is a flowchart illustrating a processing procedure when the image processing unit 31 is realized by software or firmware.

Hereafter, in order to explain this invention in greater detail, the preferred embodiments of the present invention will be described with reference to the accompanying drawings.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram showing an optical system evaluation device according to the first embodiment.
In FIG. 1, a spatial light modulator 1 adds a wavefront aberration to each light from a plurality of point light sources. Here, the point light source includes an object that emits light itself or an object that reflects incident light.
The spatial light modulator 1 is realized by, for example, a spatial light modulator. The spatial light modulator is a device having an optical element capable of modulating the phase, the polarization direction, the amplitude, the intensity, or the like of the light incident on the spatial modulator.
Further, the spatial light modulator 1 may be realized by a deformable mirror capable of changing the shape of a mirror surface.
Further, the spatial light modulator 1 may be realized by a focus position adjusting mechanism capable of shifting the position of each of the plurality of image sensors. By deviating the position of the image sensor from the focal position, a point image corresponding to each light is defocused, and a point image different from the point image in a focused state is obtained.

The imaging optical system 2 is realized by a lens or a mirror.
The image forming optical system 2 forms each of the lights, to which the wavefront aberration has been added by the spatial light modulator 1, on the image forming surfaces of the plurality of image sensors 3-1 to 3-J. J is an integer of 2 or more.
The imaging unit 3 has a plurality of imaging devices 3-1 to 3-J. The imaging elements 3-1 to 3-J convert the light formed on the imaging planes of the imaging elements 3-1 to 3-J by the imaging optical system 2 to generate electric signals. The imaging elements 3-1 to 3-J output the generated electric signals to a distribution function calculation unit 5 described later and a pixel phase estimation unit 6 described later.

The image processing unit 4 includes a distribution function calculation unit 5, a pixel phase estimation unit 6, a distribution function generation unit 7, a wavefront aberration estimation unit 8, and a wavefront aberration output unit 9.
The image processing unit 4 analyzes the electric signals generated by the imaging elements 3-1 to 3-J of the imaging unit 3 and performs a process of estimating the wavefront aberration of the imaging optical system 2.
FIG. 2 is a hardware configuration diagram illustrating hardware of the image processing unit 4.

The distribution function calculation unit 5 is realized by, for example, a distribution function calculation circuit 11 illustrated in FIG.
The distribution function calculation unit 5 calculates a point spread function (PSF) indicating an intensity distribution of a point image corresponding to each light from the electric signals generated by the imaging elements 3-1 to 3-J. I do. Hereinafter, the plurality of point spread functions calculated for each of the plurality of point images corresponding to each of the plurality of lights are simply referred to as “a plurality of PSFs”.
The distribution function calculation unit 5 outputs the calculated plurality of PSFs to the distribution function generation unit 7.

The pixel phase estimating unit 6 is realized by, for example, the pixel phase estimating circuit 12 shown in FIG.
The pixel phase estimation unit 6 estimates a pixel phase of a point image corresponding to each light (hereinafter, referred to as a “point image pixel phase”) from the electric signals generated by the imaging elements 3-1 to 3-J. Hereinafter, the plurality of point image pixel phases estimated for each of the plurality of point images corresponding to each of the plurality of lights will be simply referred to as “a plurality of point image pixel phases”.
The pixel phase estimating unit 6 outputs the estimated plurality of point image pixel phases to the distribution function generating unit 7.

The distribution function generation unit 7 is realized by, for example, a distribution function generation circuit 13 illustrated in FIG.
The distribution function generation unit 7 has a higher resolution than each of the plurality of PSFs from the plurality of PSFs calculated by the distribution function calculation unit 5 based on the plurality of point image pixel phases estimated by the pixel phase estimation unit 6. A high PSF (hereinafter, referred to as “high resolution PSF”) is generated.
The distribution function generator 7 outputs the generated high-resolution PSF to the wavefront aberration estimator 8.

The wavefront aberration estimating unit 8 is realized by, for example, the wavefront aberration estimating circuit 14 illustrated in FIG.
The wavefront aberration estimator 8 estimates the wavefront aberration of the imaging optical system 2 from the high-resolution PSF generated by the distribution function generator 7.
The wavefront aberration estimating unit 8 outputs the estimated wavefront aberration of the imaging optical system 2 to the wavefront aberration output unit 9.

The wavefront aberration output unit 9 is realized by, for example, the wavefront aberration output circuit 15 illustrated in FIG.
The wavefront aberration output unit 9 stores the wavefront aberration estimated by the wavefront aberration estimation unit 8 in an external storage device or the like.
Further, the wavefront aberration output unit 9 outputs an image indicating the wavefront aberration estimated by the wavefront aberration estimation unit 8 or a coefficient indicating the wavefront aberration to an output device such as a display (not shown).

In FIG. 1, each of the distribution function calculation unit 5, pixel phase estimation unit 6, distribution function generation unit 7, wavefront aberration estimation unit 8, and wavefront aberration output unit 9, which are components of the image processing unit 4, is shown in FIG. It is assumed that it is realized by such dedicated hardware. That is, it is assumed that the image processing unit 4 is realized by the distribution function calculation circuit 11, the pixel phase estimation circuit 12, the distribution function generation circuit 13, the wavefront aberration estimation circuit 14, and the wavefront aberration output circuit 15.
Here, each of the distribution function calculation circuit 11, the pixel phase estimation circuit 12, the distribution function generation circuit 13, the wavefront aberration estimation circuit 14, and the wavefront aberration output circuit 15 is, for example, a single circuit, a composite circuit, a programmed processor, A processor programmed in parallel, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof is applicable.

The components of the image processing unit 4 are not limited to those realized by dedicated hardware, and even if the image processing unit 4 is realized by software, firmware, or a combination of software and firmware. Good.
Software or firmware is stored as a program in the memory of the computer. The computer means hardware for executing a program, for example, a CPU (Central Processing Unit), a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, a processor, or a DSP (Digital Signal Processor). I do.

FIG. 3 is a hardware configuration diagram of a computer when the image processing unit 4 is realized by software or firmware.
When the image processing unit 4 is realized by software or firmware, the processing procedure of the distribution function calculation unit 5, the pixel phase estimation unit 6, the distribution function generation unit 7, the wavefront aberration estimation unit 8, and the wavefront aberration output unit 9 is performed by a computer. A program to be executed is stored in the memory 22. Then, the processor 21 of the computer executes the program stored in the memory 22.
FIG. 4 is a flowchart illustrating a processing procedure when the image processing unit 4 is realized by software or firmware.

FIG. 2 illustrates an example in which each of the components of the image processing unit 4 is realized by dedicated hardware, and FIG. 3 illustrates an example in which the image processing unit 4 is realized by software or firmware. . However, this is only an example, and some components in the image processing unit 4 may be realized by dedicated hardware, and the remaining components may be realized by software or firmware.

Next, the operation of the optical system evaluation apparatus shown in FIG. 1 will be described.
Light incident on the spatial light modulator 1 is light emitted or reflected by each of the plurality of point light sources.
The plurality of point sources may be a number of stars distant from the earth or a number of lights in an urban area at night.
When the optical system evaluation device illustrated in FIG. 1 is mounted on, for example, an artificial satellite, the imaging unit 3 can capture a large number of stars without being affected by the weather.
Since the expected angle of a star distant from the earth is sufficiently smaller than the instantaneous viewing angle of the imaging unit 3, the star distant from the earth can be regarded as a point light source.
When the imaging unit 3 captures images of a large number of lights in an urban area at night, it may not be possible to capture the images of a large number of lights in the urban area due to the presence of clouds above the urban area. However, when the artificial satellite equipped with the optical system evaluation device orbits in orbit, the imaging unit 3 does not have a cloud other than the urban area where the cloud exists in the sky. Since an image of a lamp in an urban area or the like may be captured, the number of image capturing opportunities is increased as compared with a case where a plurality of evaluation light sources arranged on the ground are captured, and the influence of weather is reduced.

When light from a plurality of point light sources enters, the spatial light modulator 1 adds a wavefront aberration to each of the incident lights.
The wavefront aberration added to each light by the spatial light modulator 1 is a wavefront aberration that causes a point image corresponding to each light to have a shape that spreads evenly toward the periphery as shown in FIG.
That is, the spatial light modulating unit 1 controls the point images corresponding to the respective lights so that the change in the point image intensity with respect to the coordinates of the point image intensity distribution on the imaging planes of the imaging elements 3-1 to 3-J becomes gentle. Give defocus to. Alternatively, the spatial light modulator 1 gives a third-order astigmatism having high central symmetry to a point image corresponding to each light.
FIG. 5 is an explanatory diagram showing a plurality of point images each having a shape spreading evenly toward the periphery and a PSF having a shape with high central symmetry.
FIG. 6 is an explanatory diagram showing a plurality of point images each having a shape that spreads unequally toward the periphery, and a PSF having a shape with low central symmetry.
5 and 6 will be described later.

When each light to which the wavefront aberration is added by the spatial light modulator 1 is incident, the imaging optical system 2 forms each light on an imaging plane of the imaging elements 3-1 to 3-J.
The imaging devices 3-1 to 3-J convert each light imaged by the imaging optical system 2 to generate an electric signal.
The imaging unit 3 outputs the electric signals generated by the imaging elements 3-1 to 3-J to each of the distribution function calculation unit 5 and the pixel phase estimation unit 6.
FIG. 7 is an explanatory diagram showing point images (1) to (3), point image intensity distributions, and pixel values, which are electric signals generated by the imaging elements 3-1 to 3-J, corresponding to the respective lights. .
FIG. 7 illustrates a mode in which the imaging elements 3-1 to 3-J are arranged one-dimensionally for simplification of the drawing. However, actually, the imaging elements 3-1 to 3-J are two-dimensionally arranged.
FIG. 7 shows an example in which J = 14, and FIG. 7 shows fourteen image sensors 3-1 to 3-14.
FIG. 7 shows an example in which the number of light is three, and FIG. 7 shows three point images (1) to (3).

The point image (1) is formed on the imaging planes of the imaging devices 3-2 to 3-4. Since the center position of the point image (1) substantially coincides with the center position of the image sensor 3-3, most of the point image (1) is formed on the image plane of the image sensor 3-3. .
Therefore, the pixel value of the imaging element 3-3 is larger than the respective pixel values of the imaging element 3-2 and the imaging element 3-4. The pixel value of the image sensor 3-2 and the pixel value of the image sensor 3-4 are almost the same.
The point image (2) is formed on the image plane of the imaging elements 3-7 to 3-9. The center position of the point image (2) exists in the image plane of the image sensor 3-8, but is slightly shifted to the right side in the figure from the center position of the image sensor 3-8. Most of the point image (2) is also formed on the image plane of the image sensor 3-8. However, since the center position of the point image (2) is slightly shifted to the right from the center position of the image sensor 3-8, the center position of the point image (2) matches the center position of the image sensor 3-8. As compared with the case where a point image is formed, a larger part of the point image (2) is also formed on the image forming surface of the image sensor 3-9.
Therefore, the pixel value of the image sensor 3-8 is larger than each of the pixel values of the image sensor 3-7 and the image sensor 3-9, and the pixel value of the image sensor 3-9 is larger than that of the image sensor 3-9. It is smaller than the pixel value of 3-8, but larger than the pixel value of the image sensor 3-7.

The point image (3) is formed on the image plane of the imaging elements 3-11 to 3-14. Although the center position of the point image (3) exists in the image plane of the image sensor 3-12, it is greatly shifted to the right side in the drawing from the center position of the image sensor 3-12. Since the center position of the point image (3) is greatly shifted to the right side of the center position of the image sensor 3-12, most of the point image (3) is formed in the image sensor 3-12 and the image sensor 3-13, respectively. Are formed on the image forming plane.
Therefore, among the pixel values of the imaging elements 3-11 to 3-14, the pixel value of the imaging element 3-12 is the largest, and then the pixel value of the imaging element 3-13 is the largest. However, the difference between the pixel value of the image sensor 3-12 and the pixel value of the image sensor 3-13 is small.
Each pixel value of the imaging element 3-11 and the imaging element 3-14 is smaller than each pixel value of the imaging element 3-12 and the imaging element 3-13.

When receiving the electric signals from the imaging devices 3-1 to 3-14, the distribution function calculating unit 5 calculates a PSF indicating the intensity distribution of the point image corresponding to each light from the electric signals (step ST1 in FIG. 4). ).
As shown in FIG. 7, when there are three point images (1) to (3), the PSF indicating the intensity distribution of the point image (1) is a series of pixel values of the imaging elements 3-2 to 3-4. Represented by
The PSF indicating the intensity distribution of the point image (2) is represented by a series of pixel values of the image sensors 3-7 to 3-9. The PSF indicating the intensity distribution of the point image (3) is expressed by the image sensors 3-11 to 3-11. It is represented by a series of 3-14 pixel values.
The distribution function calculation unit 5 outputs the PSF corresponding to each light to the distribution function generation unit 7.

Upon receiving the electric signals from the imaging elements 3-1 to 3-14, the pixel phase estimating unit 6 estimates a point image pixel phase for a point image corresponding to each light from the electric signals, and Is output to the distribution function generator 7 (step ST2 in FIG. 4).
The reason why the pixel phase estimating unit 6 estimates the point image pixel phase is that the distribution function generating unit 7 described later can generate a high-resolution PSF even if a plurality of point light sources are not arranged at equal intervals. To do that.
The point image pixel phase corresponds to the center position of the point image as shown in FIG.
FIG. 8 is an explanatory diagram showing the relationship between the point image pixel phase and the pixel value of the image sensor.
R for one point spread (R is an integer of 2 or more) each pixel value in the number of image pickup device, when a G 0 _~ G _R, the center position of a point image corresponding to the point image pixel phase corresponds to the center of gravity of the entire pixel value _G 0 ~ _{G R.}
Therefore, the pixel phase estimating unit 6 can estimate the point image pixel phase by calculating the barycentric position. Since estimating the pixel phase by calculating the position of the center of gravity is a known technique, detailed description thereof will be omitted.
Further, the pixel phase estimating unit 6 can estimate the point image pixel phase with an accuracy of less than one pixel by using a fitting function having the same shape as the point image intensity distribution. Estimating the pixel phase using the fitting function is a well-known technique, and a detailed description thereof will be omitted.

When the pixel phase estimating unit 6 estimates a point image pixel phase using a fitting function, the PSF of the imaging optical system 2 can be used as the fitting function. However, in the optical system evaluation device shown in FIG. 1, the PSF of the imaging optical system 2 is unknown.
When the PSF of the imaging optical system 2 is unknown, the pixel phase estimating unit 6 uses a symmetric function such as a Gaussian function or a sink function as the fitting function.
When the PSF of the imaging optical system 2 is a PSF having a shape with low central symmetry as shown in FIG. 6, even if the pixel phase estimating unit 6 uses a symmetric function as a fitting function, the pixel phase estimating unit 6 calculates the point image pixel phase. It cannot be estimated with high accuracy. In the case of a PSF having a shape with low central symmetry, the pixel phase estimating unit 6 cannot estimate the pixel phase with high accuracy similarly when estimating the point image pixel phase by calculating the position of the center of gravity. .

In the optical system evaluation apparatus shown in FIG. 1, the spatial light modulator 1 applies a wavefront to each of the incident light so that the point image pixel phase can be estimated with high accuracy even if a symmetric function is used as the fitting function. Adds aberration.
That is, the spatial light modulator 1 adds a wavefront aberration to make the point image have a shape that spreads evenly toward the periphery, so that the PSF of the imaging optical system 2 has a central symmetry as shown in FIG. Is a high shape PSF.
When the PSF of the imaging optical system 2 is a PSF having a high central symmetry as shown in FIG. 5, the pixel phase estimating unit 6 uses the symmetric function as the fitting function to change the point image pixel phase. It can be estimated with high accuracy. In the case of a PSF having a shape with high central symmetry, the pixel phase estimating unit 6 estimates the point image pixel phase by calculating the position of the center of gravity to similarly estimate the point image pixel phase with high accuracy. Can be.

The distribution function generator 7 receives the plurality of PSFs calculated from the distribution function calculator 5 and receives the plurality of point image pixel phases estimated from the pixel phase estimator 6.
As illustrated in FIG. 9, the distribution function generation unit 7 calculates a plurality of PSFs calculated by the distribution function calculation unit 5 based on the plurality of point image pixel phases estimated by the pixel phase estimation unit 6, and A high-resolution PSF having a higher resolution than each of the PSFs is generated (step ST3 in FIG. 4).
The distribution function generator 7 outputs the generated high-resolution PSF to the wavefront aberration estimator 8.
FIG. 9 is an explanatory diagram illustrating the generation processing of the high-resolution PSF by the distribution function generation unit 7.
Hereinafter, the generation processing of the high-resolution PSF by the distribution function generation unit 7 will be specifically described with reference to FIG.

In FIG. 9, the distribution function generation unit 7 generates a plurality of PSFs that are PSFs for each of the N point images P _n (n = 0, 1,..., K, k + 1,..., N−1). Thus, an example is shown in which a high-resolution PSF having a resolution N times higher than the plurality of PSFs is generated.
It is assumed that the point images P ₀ to P _N−1 are, for example, a point image group in which the point image pixel phases are shifted from each other by δ = 1 / N [pixel].
For example, the point image pixel phase of the point image P ₀ is 0 [pixel], the point image pixel phase of the point image P ₁ is δ [pixel], and the point image pixel phase of the point image P _k is k × δ [pixel] ], And the point image pixel phase of the point image P _N−1 is (N−1) × δ [pixel].
In FIG. 9, for simplicity of description, the M pixel values of the PSF for each of the point images P ₀ to P _N−1 are shown as being arranged one-dimensionally. Actually, the PSF for each of the point images P ₀ to P _N−1 has M × M pixel values, which are two-dimensionally arranged.
For example, the M pixel values of the PSF for the point image P ₀ are P ₀ (0), P ₀ (1),..., P ₀ (M−1).
For example, the M pixel values of the PSF for the point image P ₁ are P ₁ (0), P ₁ (1),..., P ₁ (M−1).
For example, the M pixel values of the PSF for the point image P _k are P _k (0), P _k (1),..., P _k (M−1).
For example, the M pixel values of the PSF for the point image P _N-1 are P _N-1 (0), P _N-1 (1),..., P _N-1 (M-1). is there.

First, among the M pixel values of the PSF for each of the point images P ₀ to P _N−1 , the distribution function generation unit 7 determines that the first pixel value P ₀ (0), P ₁ from the left in the figure. Focus on (0), ..., P _k (0), ..., P _N-1 (0).
Distribution function generating unit 7, the focused pixel value _{P 0 (0), P 1} (0), ···, P k (0), ···, P N-1 a (0), from the left in the drawing Are arranged in ascending order of the point image pixel phase of the point image having each pixel value.
Next, among the M pixel values of the PSF for each of the point images P ₀ to P _N−1 , the distribution function generation unit 7 calculates the second pixel value P ₀ (1), P 2 _{1 (1), ···, P} k (1), ···, attention is paid to _{P N-1} (1).
Distribution function generating unit 7, the focused pixel value _{P 0 (1), P 1} (1), ···, P k (1), ···, P N-1 (1) was arranged above On the right side of the pixel value P _N-1 (0), the point image pixel phases are arranged in ascending order in the same manner as described above.

The distribution function generator 7 also arranges the third and subsequent M pixel values from the left in the drawing in the same manner as the second M pixel values.
For example, M-1-th pixel value _{P 0 (M-1),} P 1 (M-1), ···, P k (M-1), ···, P N-1 (M-1) Are arranged on the right side of the pixel values P _N-1 (M-2) arranged in ascending order by the point image pixel phase in ascending order.

The distribution function generator 7 arranges the M pixel values of the PSF for each of the point images P ₀ to P _N−1 as described above to obtain a PSF in which the pixel values are arranged as follows.
P ₀ (0), P ₁ (0), ..., P _N-1 (0), P ₀ (1), P ₁ (1), ..., P _N-1 (1), ... ·, P ₀ (M-1), P ₁ (M-1), ..., P _N-1 (M-1)
When obtaining the PSF in which the pixel values are arranged as described above, the distribution function generation unit 7 normalizes the respective pixel values so that the sum of the pixel values is 1, for example, thereby obtaining the point images P ₀ to P ₀ . Generate a high resolution PSF with N times higher resolution than the respective PSF in P _N-1 .

Upon receiving the high-resolution PSF from the distribution function generator 7, the wavefront aberration estimator 8 estimates the wavefront aberration of the imaging optical system 2 from the high-resolution PSF (step ST4 in FIG. 4).
The process itself of estimating the wavefront aberration from the PSF is a known technique, and a detailed description thereof will be omitted.
The wavefront aberration estimating unit 8 outputs the wavefront aberration of the imaging optical system 2 to the wavefront aberration output unit 9.

When receiving the wavefront aberration of the imaging optical system 2 from the wavefront aberration estimating unit 8, the wavefront aberration output unit 9 stores the wavefront aberration in an external storage device or the like.
The wavefront aberration output unit 9 outputs an image indicating the wavefront aberration or a coefficient indicating the wavefront aberration to an output device such as a display (not shown).

In the first embodiment, the spatial light modulator 1 that applies a wavefront aberration to each light from a plurality of point light sources, and the electric signals generated by the imaging devices 3-1 to 3-J are used to convert each light into each light. A distribution function calculating unit 5 for calculating a point spread function indicating an intensity distribution of a corresponding point image, and a point image corresponding to each light from the electric signals generated by the imaging elements 3-1 to 3-J. A pixel phase estimating unit 6 for estimating an image pixel phase, and a plurality of PSFs calculated by the distribution function calculating unit 5 based on the point image pixel phases estimated by the pixel phase estimating unit 6, the resolution of which is higher than the plurality of PSFs. And a distribution function generation unit 7 for generating a high-resolution PSF having a high resolution. Configure optical system evaluation device It was. Therefore, the optical system evaluation device can estimate the wavefront aberration of the imaging optical system without disposing the light source for evaluation on the ground.

Embodiment 2 FIG.
In the second embodiment, a description will be given of an optical system evaluation device in which the wavefront aberration estimation unit 35 estimates the wavefront aberration of the imaging optical system 2 from a plurality of PSFs generated by the distribution function generation unit 34.

FIG. 10 is a configuration diagram showing an optical system evaluation device according to the second embodiment.
10, the same reference numerals as those in FIG. 1 denote the same or corresponding parts, and a description thereof will not be repeated.
Similar to the spatial light modulator 1 shown in FIG. 1, the spatial light modulator 30 is a spatial light modulator that adds wavefront aberration to each light when the light emitted or reflected by each of the plurality of point light sources enters. is there.
The spatial light modulator 30 is different from the spatial light modulator 1 shown in FIG. 1 in that the wavefront aberration is added to each light from a plurality of point light sources while changing the wavefront aberration. 2 is repeatedly output.

The image processing unit 31 includes a distribution function calculation unit 32, a pixel phase estimation unit 33, a distribution function generation unit 34, a wavefront aberration estimation unit 35, and a wavefront aberration output unit 9.
The image processing unit 31 analyzes the electric signals generated by the imaging elements 3-1 to 3-J of the imaging unit 3 and performs a process of estimating the wavefront aberration of the imaging optical system 2.
FIG. 11 is a hardware configuration diagram illustrating hardware of the image processing unit 31.
In FIG. 11, the same reference numerals as those in FIG.

The distribution function calculation unit 32 is realized by, for example, a distribution function calculation circuit 41 illustrated in FIG.
The distribution function calculation unit 32 calculates the PSF corresponding to each light from the electric signals generated by the imaging elements 3-1 to 3-J, similarly to the distribution function calculation unit 5 illustrated in FIG.
The distribution function calculator 32 differs from the distribution function calculator 5 shown in FIG. 1 in that each time the light is converted by the image sensors 3-1 to 3-J to generate an electric signal, the image sensor 3-1 is changed. A PSF corresponding to each light is calculated from the electric signals generated by the steps 3-J.
The distribution function calculation unit 32 outputs the calculated plurality of PSFs to the distribution function generation unit 34.

The pixel phase estimating unit 33 is realized by, for example, a pixel phase estimating circuit 42 illustrated in FIG.
Like the pixel phase estimating unit 6 shown in FIG. 1, the pixel phase estimating unit 33 calculates a point image pixel phase for a point image corresponding to each light from the electric signals generated by the imaging elements 3-1 to 3-J. Is estimated.
The pixel phase estimating unit 33 is different from the pixel phase estimating unit 6 shown in FIG. 1 in that each time each light is converted by the imaging elements 3-1 to 3-J to generate an electric signal, the imaging element 3-1 A point image pixel phase is estimated for a point image corresponding to each light from the electric signals generated by the steps 3-J.
The pixel phase estimating unit 33 outputs the plurality of estimated point image pixel phases to the distribution function generating unit 34.

The distribution function generation unit 34 is realized by, for example, a distribution function generation circuit 43 illustrated in FIG.
Similar to the distribution function generator 7 shown in FIG. 1, the distribution function generator 34 calculates a plurality of point image pixel phases estimated by the pixel phase estimator 33 and calculates a plurality of point image pixel phases calculated by the distribution function calculator 32. From the PSF, a high-resolution PSF having a higher resolution than each of the plurality of PSFs is generated.
Unlike the distribution function generator 7 shown in FIG. 1, the distribution function generator 34 calculates a plurality of PSFs by the distribution function calculator 32 and estimates a plurality of point image pixel phases by the pixel phase estimator 33. Each time, a high-resolution PSF having a higher resolution than each of the plurality of PSFs is generated.
The distribution function generator 34 outputs the generated high-resolution PSF to the wavefront aberration estimator 35.

The wavefront aberration estimating unit 35 is realized by, for example, a wavefront aberration estimating circuit 44 shown in FIG.
The wavefront aberration estimator 35 estimates the wavefront aberration of the imaging optical system 2 from the plurality of high-resolution PSFs generated by the distribution function generator 34.
The wavefront aberration estimating unit 35 outputs the estimated wavefront aberration of the imaging optical system 2 to the wavefront aberration output unit 9.

In FIG. 10, the distribution function calculation unit 32, the pixel phase estimation unit 33, the distribution function generation unit 34, the wavefront aberration estimation unit 35, and the wavefront aberration output unit 9, which are the components of the image processing unit 31, are illustrated in FIG. It is assumed that it is realized by such dedicated hardware. That is, it is assumed that the image processing unit 31 is realized by the distribution function calculation circuit 41, the pixel phase estimation circuit 42, the distribution function generation circuit 43, the wavefront aberration estimation circuit 44, and the wavefront aberration output circuit 15.
Here, each of the distribution function calculation circuit 41, the pixel phase estimation circuit 42, the distribution function generation circuit 43, the wavefront aberration estimation circuit 44, and the wavefront aberration output circuit 15 is, for example, a single circuit, a composite circuit, a programmed processor, A parallel programmed processor, ASIC, FPGA, or a combination thereof is applicable.

The components of the image processing unit 31 are not limited to those realized by dedicated hardware. Even if the image processing unit 31 is realized by software, firmware, or a combination of software and firmware, Good.
When the image processing unit 31 is realized by software or firmware, the processing procedure of the distribution function calculation unit 32, the pixel phase estimation unit 33, the distribution function generation unit 34, the wavefront aberration estimation unit 35, and the wavefront aberration output unit 9 is performed by a computer. The program to be executed is stored in the memory 22 shown in FIG. Then, the processor 21 of the computer executes the program stored in the memory 22.
FIG. 12 is a flowchart illustrating a processing procedure when the image processing unit 31 is realized by software or firmware.

Next, the operation of the optical system evaluation device shown in FIG. 10 will be described.
The spatial light modulating unit 30 repeatedly outputs each of the light to which the wavefront aberration has been added to the imaging optical system 2 while changing the wavefront aberration to be applied to each of the lights from the plurality of point light sources.
In the optical system evaluation device shown in FIG. 10, the spatial light modulator 30 adds different wavefront aberrations to incident light H times. H is an integer of 2 or more.
The wavefront aberration added by the spatial light modulator 30 is a wavefront aberration that causes the point images corresponding to the respective lights to have a shape that spreads evenly toward the periphery, as shown in FIG.
The spatial light modulator 30 outputs each of the lights with the wavefront aberration added to the imaging optical system 2 each time the wavefront aberration is added to each of the lights.

When each light to which the wavefront aberration is added by the spatial light modulator 30 is incident, the imaging optical system 2 forms each light on the imaging surfaces of the imaging elements 3-1 to 3-J.
The imaging devices 3-1 to 3-J convert each light imaged by the imaging optical system 2 to generate an electric signal.
The imaging unit 3 outputs the electric signals generated by the imaging devices 3-1 to 3-J to each of the distribution function calculation unit 32 and the pixel phase estimation unit 33.

Each time the distribution function calculation unit 32 receives an electric signal from the image sensor 3-1 to 3-J, the distribution function calculation unit 32 calculates a point corresponding to each light from the received electric signal, similarly to the distribution function calculation unit 5 illustrated in FIG. The PSF indicating the intensity distribution of the image is calculated (step ST11 in FIG. 12).
The distribution function calculation unit 32 outputs the calculated PSF to the distribution function generation unit 34.

Each time the pixel phase estimating unit 33 receives an electric signal from the imaging elements 3-1 to 3-J, the pixel phase estimating unit 33 calculates a point corresponding to each light from the received electric signal, similarly to the pixel phase estimating unit 6 shown in FIG. The point image pixel phase is estimated for the image (step ST12 in FIG. 12).
The pixel phase estimating unit 33 outputs the estimated point image pixel phase to the distribution function generating unit 34.

The distribution function generator 34 receives the plurality of PSFs calculated from the distribution function calculator 32 and receives the plurality of point image pixel phases estimated from the pixel phase estimator 33.
The distribution function generator 7, like the distribution function generator 7 shown in FIG. 1, calculates a plurality of point image pixel phases estimated by the pixel phase estimator 33 and a plurality of point image pixel phases calculated by the distribution function calculator 32. From the PSF, a high-resolution PSF having a higher resolution than each of the plurality of PSFs is generated (step ST13 in FIG. 12).
The distribution function generator 34 outputs the generated high-resolution PSF to the wavefront aberration estimator 35.

If the number of high-resolution PSFs generated by the distribution function generator 34 is less than H (step ST14: NO), the processing of steps ST11 to ST13 is repeatedly performed.
If the number of high-resolution PSFs generated by the distribution function generator 34 is H (step ST14: YES), the wavefront aberration estimator 35 generates the H high-resolution PSFs generated by the distribution function generator 34. The wavefront aberration of the imaging optical system 2 is estimated from the PSF (step ST15 in FIG. 12).
The wavefront aberration estimating unit 35 can estimate the wavefront aberration from the H high-resolution PSFs, for example, by using a known phase diversity method.
The wavefront aberration estimated from the H high-resolution PSFs has higher accuracy than the wavefront aberration estimated by the wavefront aberration estimating unit 8 shown in FIG.
The following non-patent documents 2 and 3 disclose a phase diversity method.
[Non-Patent Document 2]
J. J. Green, D. C. Redding, S. B. Shaklan, S. A. Basinger, “Extreme wave front sensing accuracy for the Eclipse coronagraphic space telescope,” Proc. SPIE 4860, 266, (2003).
[Non-Patent Document 3]
R. G. Paxman, T. J. Schulz, and J. R. Fienup, “Joint estimation of object and aberrations by using phase diversity,” J. Opt. Soc. Vol. 9, No. 7 (1992).

In the optical system evaluation apparatus according to the second embodiment, the spatial light modulator 30 changes the wavefront aberration applied to each light from the plurality of point light sources while changing the wavefront aberration-added light. Output to the system 2 repeatedly. Each time the light is converted by the imaging elements 3-1 to 3-J to generate an electric signal, the distribution function calculation unit 32 calculates the intensity of the point image corresponding to each light from the generated electric signal. Calculate the PSF indicating the distribution. Each time the light is converted by the imaging elements 3-1 to 3-J to generate an electric signal, the pixel phase estimating unit 33 calculates a point image corresponding to the light from the generated electric signal. Estimate the image pixel phase. The distribution function generation unit 34 calculates a plurality of PSFs by the distribution function calculation unit 32 and every time the pixel phase estimation unit 33 estimates the point image pixel phase, the point image estimated by the pixel phase estimation unit 33 is calculated. Based on the pixel phase, a high-resolution PSF having a higher resolution than each of the plurality of PSFs is generated from the plurality of PSFs calculated by the distribution function calculation unit 32. The wavefront aberration estimator 35 estimates the wavefront aberration of the imaging optical system 2 from the plurality of high-resolution PSFs generated by the distribution function generator 34. Therefore, the optical system evaluation device of the second embodiment can improve the estimation accuracy of the wavefront aberration more than the optical system evaluation device of the first embodiment.

In the present invention, any combination of the embodiments, a modification of an arbitrary component of each embodiment, or an omission of an arbitrary component in each embodiment is possible within the scope of the invention. .

The present invention is suitable for an optical system evaluation device and an optical system evaluation method for estimating the wavefront aberration of an imaging optical system.

1 spatial light modulator, 2 imaging optical system, 3 imaging unit, 3-1 to 3-J imaging device, 4 image processing unit, 5 distribution function calculation unit, 6 pixel phase estimation unit, 7 distribution function generation unit, 8 Wavefront aberration estimating section, 9 ° wavefront aberration output section, 11 ° distribution function calculating circuit, 12 ° pixel phase estimating circuit, 13 ° distribution function generating circuit, 14 ° wavefront aberration estimating circuit, 15 ° wavefront aberration output circuit, 21 ° processor, 22 ° memory, 30 ° spatial light Modulation unit, 31 image processing unit, 32 distribution function calculating unit, 33 pixel phase estimating unit, 34 distribution function generating unit, 35 wavefront aberration estimating unit, 41 distribution function calculating circuit, 42 pixel phase estimating circuit, 43 distribution function generating circuit, 44 ° wavefront aberration estimation circuit.

Claims (4)

A spatial light modulator that adds a wavefront aberration to each light from the plurality of point light sources,
An imaging optical system that forms an image of each light wavefront aberration added by the spatial light modulator,
A plurality of imaging devices that convert each light imaged by the imaging optical system to generate an electric signal,
From the electric signals generated by the plurality of imaging elements, a distribution function calculation unit that calculates a point spread function indicating an intensity distribution of a point image corresponding to each light,
From the electrical signals generated by the plurality of imaging elements, a pixel phase estimating unit that estimates a pixel phase of a point image corresponding to each light,
From the plurality of point spread functions calculated by the distribution function calculation section based on the pixel phase estimated by the pixel phase estimation section, a high resolution point spread function having a higher resolution than the plurality of point spread functions A distribution function generator that generates
A wavefront aberration estimating unit for estimating a wavefront aberration of the imaging optical system from a high-resolution point spread function generated by the distribution function generating unit. The spatial light modulator, while changing the wavefront aberration applied to each light from the plurality of point light sources, repeatedly outputs each light added wavefront aberration to the imaging optical system,
The distribution function calculation unit is configured such that each time each of the light is converted by the plurality of imaging elements to generate an electric signal, a point image corresponding to each light is generated from the electric signal generated by the plurality of imaging elements. Calculate a point spread function indicating the intensity distribution of
The pixel phase estimating unit is configured such that each time each of the light is converted by the plurality of imaging elements to generate an electric signal, a point image corresponding to each light is obtained from the electric signal generated by the plurality of imaging elements. Of the pixel phase of
The distribution function generation unit calculates a plurality of point spread functions by the distribution function calculation unit, and each time the pixel phase is estimated by the pixel phase estimation unit, the pixel estimated by the pixel phase estimation unit Based on the phase, from the plurality of point spread functions calculated by the distribution function calculation unit, to generate the high-resolution point spread function,
The optical system evaluation according to claim 1, wherein the wavefront aberration estimating unit estimates the wavefront aberration of the imaging optical system from a plurality of high-resolution point spread functions generated by the distribution function generating unit. apparatus. 2. The optical system evaluation device according to claim 1, wherein the spatial light modulator applies wavefront aberration to the light in which the point image spreads evenly toward the periphery. A spatial light modulator adds wavefront aberration to each light from the plurality of point light sources,
An imaging optical system forms an image of each light wavefront aberration added by the spatial light modulator,
A plurality of image sensors convert each light imaged by the imaging optical system to generate an electric signal,
A distribution function calculation unit calculates a point spread function indicating an intensity distribution of a point image corresponding to each light from the electric signals generated by the plurality of image sensors,
A pixel phase estimating unit estimates a pixel phase of a point image corresponding to each light from the electric signals generated by the plurality of image sensors,
The distribution function generation unit has a higher resolution than the plurality of point spread functions from the plurality of point spread functions calculated by the distribution function calculation unit based on the pixel phase estimated by the pixel phase estimation unit. Generate a high-resolution point spread function,
An optical system evaluation method, wherein a wavefront aberration estimating unit estimates a wavefront aberration of the imaging optical system from a high-resolution point spread function generated by the distribution function generating unit.

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