A snapshot point-source coded wavefront detection system and method

Abstract

The present application relates to optical detection device and method, specifically to a kind of snapshot point source encoding wave front detection system and method.For solving the deficiency of poor stability, complex system and delay in prior art by using phase recovery method to realize optical system aberration inversion, a kind of snapshot point source encoding wave front detection system of the present application, including first light source module, second light source module, first beam splitter, second beam splitter, microscopic objective, first plane mirror, first imaging lens, polarized camera, first light source module and second light source module are respectively used to provide first linearly polarized light and second linearly polarized light with orthogonal polarization direction, first linearly polarized light is focal plane parallel light, and second linearly polarized light is off-focus parallel light.Based on the above system, a kind of snapshot point source encoding wave front detection method of the present application includes system calibration, system adjustment, image acquisition and pre-processing and wave front inversion etc.

Description

Technical Field

[0001] This invention relates to optical detection devices and methods, specifically to a snapshot-type point source encoded wavefront detection system and method. Background Technology

[0002] Imaging systems in fields such as astronomy and aerospace are gradually developing towards larger apertures and higher resolutions. Since optical systems are extremely sensitive to wavefront errors, even small distortions will lead to a decrease in imaging resolution and contrast. Therefore, it is necessary to perform accurate wavefront detection during the optical system processing and assembly stages, and to guide adjustments based on the wavefront detection results until the detection results meet the design accuracy requirements.

[0003] Currently, commonly used wavefront detection methods in engineering include interferometry, wavefront sensing, and phase retrieval. Interferometry, such as using interferometers, can achieve sub-nanometer measurement accuracy under controlled environments, but the measurement is easily affected by temperature gradients and vibrations in the detection environment, leading to a decrease in measurement stability and accuracy. Wavefront sensing, taking Hartmann-type sensors as an example, has better stability, but the spatial resolution of wavefront measurements is limited by the sampling of the sensor's microlenses, making it difficult to capture high-frequency aberrations. Since the PSF (point spread function) intensity distribution of an optical system is directly affected by its wavefront aberrations, phase retrieval based on point source imaging has also become an important means of wavefront detection in optical systems. This technology has lower requirements for environmental stability and has better spatial resolution.

[0004] There is a many-to-one mapping relationship between wavefront aberrations and PSF intensity distribution, meaning that wavefront aberrations from different systems will result in the same PSF intensity distribution. This makes it difficult to stably and accurately invert system wavefront aberrations from a single frame of PSF intensity image using phase retrieval methods. To address this issue, existing technologies employ modulation and coding at the hardware level, such as motion defocusing, phase plate partitioning coding, or phase mask design. These solutions require multiple acquisitions, the introduction of moving parts or additional components, increasing system complexity and latency, making them unsuitable for dynamic detection scenarios requiring rapid acquisition. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies that use phase retrieval methods to achieve aberration inversion in optical systems, such as poor stability, system complexity, and delay, and to provide a snapshot-type point source encoded wavefront detection system and method.

[0006] The inventive concept of this invention is as follows: First, orthogonal polarization encoding is performed on the focal plane and the defocused point light source, respectively. Then, a polarization camera is used to simultaneously acquire and measure the PSF intensity image of the focal plane and the PSF intensity image of the defocused point light source. By minimizing the consistency between the measured data and the predicted data, the accurate inversion of the wavefront aberration of the optical system under test is achieved.

[0007] To achieve the above objectives, the technical solution provided by this invention is as follows:

[0008] A snapshot-type point source encoded wavefront detection system is disclosed for wavefront detection of an optical system under test, which is a non-polarized optical system. The system is characterized by comprising a first light source module, a second light source module, a first beam splitter, a second beam splitter, a microscope objective, a first plane mirror, a first imaging lens, and a polarization camera. The first and second light source modules provide point light sources for geometric and diffraction imaging, and respectively output first and second linearly polarized light with orthogonal polarization directions, wherein the first and second linearly polarized light are focal plane parallel light and defocused parallel light, respectively. The first beam splitter is configured corresponding to the output ends of the first and second light source modules to refract the first and second linearly polarized light onto the same optical path for output. The light is reflected by the second beam splitter. The microscope objective and the first plane mirror are sequentially arranged in the reflected light path of the second beam splitter. The optical system under test is arranged between the microscope objective and the first plane mirror. The first linearly polarized light and the second linearly polarized light are refracted by the second beam splitter and then sequentially pass through the microscope objective, the optical system under test, and the first plane mirror. After being reflected by the first plane mirror, they return to the second beam splitter and are transmitted. The first imaging lens and the polarization camera are sequentially arranged in the transmitted light path of the second beam splitter. The light transmitted by the second beam splitter passes through the first imaging lens and is received by the polarization camera. The polarization camera is used to perform polarization imaging and obtain the PSF intensity image as the original intensity image. The original intensity image is used to calculate the wavefront aberration of the optical system under test.

[0009] Furthermore, the first light source module includes a first light source and a first pinhole, a second imaging lens, and a first polarizer arranged sequentially along its optical path direction;

[0010] The first pinhole is fixed at the focal plane of the second imaging lens; the first light source is spatially filtered through the first pinhole to form a point light source, and then converted into the first linearly polarized light by the second imaging lens and the first polarizer; the focal point of the microscope objective is conjugate to the first pinhole;

[0011] The second light source module includes a second light source and a second pinhole, a third imaging lens, and a second polarizer arranged sequentially along its optical path. The second light source and the second pinhole are set on a displacement platform for defocus adjustment.

[0012] The second light source is spatially filtered through the second pinhole to form a point light source. The displacement platform is used to control the second pinhole to be positioned at the defocus surface of the third imaging lens. The point light source is converted into the second linearly polarized light by the third imaging lens and the second polarizer.

[0013] The first pinhole and the second pinhole each include multiple small holes of different sizes. The size of the small holes can be adjusted to perform geometric imaging and diffraction imaging of the point light source.

[0014] Furthermore, it also includes a second planar reflector disposed between the first beam splitter and the second beam splitter, the second planar reflector being used to reflect the output light of the first beam splitter to the second beam splitter.

[0015] Furthermore, the first linearly polarized light is horizontally linearly polarized light, and the second linearly polarized light is vertically linearly polarized light;

[0016] It also includes a computing unit electrically connected to the output of the polarization camera. The computing unit decodes the original intensity image to obtain the measured focal plane PSF intensity image and the measured defocus PSF intensity image, and then inverts the wavefront aberration of the optical system under test.

[0017] Meanwhile, the present invention also provides a snapshot-type point source coded wavefront detection method, which, based on the above-mentioned snapshot-type point source coded wavefront detection system, is characterized by including the following steps:

[0018] Step 1, System Calibration: Calibrate the inherent aberrations of the system. ;

[0019] Step 2, System Adjustment: Adjust the defocus amount of the second light source module; Set and adjust the position of the optical system under test so that the object-side focal plane of the microscope objective coincides with the image plane of the optical system under test;

[0020] Step 3, Image Acquisition and Preprocessing: Adjust the first and second light source modules to simultaneously emit first and second linearly polarized light, perform diffraction imaging of the point light source, and acquire the original intensity image I using a polarization camera. raw (x,y), preprocessing yields the measurement image I meas (x,y);

[0021] Step 4, Wavefront Inversion: Decoding Measurement Image I meas (x,y) yields the PSF intensity image at the focal plane. f (x,y) and the image of the defocused PSF intensity I d (x,y), based on the mapping relationship between the theoretical PSF intensity image and the wavefront aberration of the optical system under test, the theoretical PSF intensity image and the measured focal plane PSF intensity image I are minimized. f (x,y) and the image of the defocused PSF intensity I d Wavefront inversion is performed based on the consistency between (x,y) to obtain the wavefront aberration of the optical system under test. .

[0022] Furthermore, step 1 specifically includes:

[0023] A standard reference lens with a known wavefront is placed between the microscope objective and the first plane mirror. The first light source module is controlled to operate. An interferometer is placed corresponding to the focal plane of the polarization camera. Under the same imaging and acquisition conditions as during detection, the observed wavefront of the optical system is measured using the interferometer. The observed wavefront is subtracted from the known wavefront of the standard reference lens to obtain the inherent aberrations of the system. .

[0024] Furthermore, step 2 specifically involves:

[0025] Step 2.1, adjust the defocus amount Δz2 of the second light source module to satisfy the following formula:

[0026]

[0027] in, Let be the focal length of the optical system under test. Where D is the entrance pupil diameter of the optical system under test, corresponding to the wavelength of the light source. and These are the focal lengths of the third imaging lens and the microscope objective, respectively;

[0028] Step 2.2: Adjust the first light source module to perform geometric imaging of the point light source. Adjust the position of the optical system under test along the optical axis so that the point light source is an ideal circle with the smallest size on the image plane of the polarization camera.

[0029] Furthermore, step 1 also includes: acquiring a dark current image D using a polarization camera. T (x,y) and Flat field image norm (x,y);

[0030] In step 3, the preprocessing specifically involves: using the dark current image D T (x,y) represents the original intensity image I raw Dark field subtraction is performed using (x,y), and then a flat field image is used. norm (x,y) is subjected to flat-field correction, then cropped and normalized, and logarithmic transformation is used for intensity stretching to enhance the weak diffraction ring structure distribution of the PSF intensity image, resulting in the measured image I. meas (x,y).

[0031] Furthermore, in step 4, the mapping relationship between the theoretical PSF intensity image and the wavefront aberration of the optical system under test is as follows:

[0032]

[0033] Among them, PSF f (x,y) represents the PSF intensity image of the theoretical focal plane, PSFd (x,y) represents the theoretical defocused PSF intensity image. d (x,y), pupil plane coordinates The pupil amplitude of the optical system under test. pupil plane coordinates Wavefront aberration of the optical system under test at the location pupil plane coordinates The inherent aberrations of the system at that location, This is the Fourier transform, where i is the imaginary unit. pupil plane coordinates Defocus aberration introduced by the second light source module.

[0034] Furthermore, in step 4, the following optimization equation is solved using the phase difference algorithm to achieve wavefront inversion and obtain the wavefront aberration of the optical system under test. ;

[0035] .

[0036] The beneficial effects of this invention are:

[0037] 1. The present invention provides a snapshot-type point source coding wavefront detection system that sets up focal plane and defocus point light sources and performs orthogonal polarization coding on them respectively. By using a polarization camera to acquire the focal plane PSF intensity image and the defocus PSF intensity image in a single exposure, the system can avoid the time delay caused by the moving detector to acquire defocus information. It is suitable for single exposure, detector-free moving parts, and dynamic online testing scenarios.

[0038] 2. The snapshot-type point source encoded wavefront detection system of the present invention has a simple and compact structure, and there are no moving parts during the detection process. It overcomes the influence of environmental vibration and temperature changes on measurement stability and accuracy, has low requirements for environmental stability, low device complexity and measurement cost, and is easy to deploy.

[0039] 3. The original intensity image acquired in the snapshot-type point source coding wavefront detection method of the present invention can be adapted to various phase difference algorithms, which facilitates accurate wavefront estimation and has engineering feasibility. Finally, by minimizing the consistency between the measured data and the predicted data, the accurate inversion of the wavefront aberration of the optical system under test can be achieved. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of an embodiment of the snapshot-type point source encoded wavefront detection system of the present invention;

[0041] Figure 2 This is a flowchart of an embodiment of a snapshot-type point source encoded wavefront detection method according to the present invention;

[0042] Figure 3 This is a schematic diagram of the four-quadrant polarization array of the polarization camera in an embodiment of a snapshot-type point source coded wavefront detection system of the present invention;

[0043] Figure 4 This is a schematic diagram of the decoding process in step 4.2) of an embodiment of the snapshot-type point source coding wavefront detection method of the present invention;

[0044] Figure 5 The known wavefront aberrations in an embodiment of a snapshot-type point source coding wavefront detection method of the present invention;

[0045] Figure 6 The wavefront aberration of the optical system under test is measured in an embodiment of a snapshot-type point source encoded wavefront detection method of the present invention.

[0046] Explanation of reference numerals in the attached figures:

[0047] 1-First light source, 2-First pinhole, 3-Second imaging lens, 4-First polarizer, 5-Second light source, 6-Second pinhole, 7-Displacement platform, 8-Third imaging lens, 9-Second polarizer, 10-First beam splitter, 11-Second plane mirror, 12-Second beam splitter, 13-Microscope objective, 14-Optical system under test, 15-First plane mirror, 16-First imaging lens, 17-Polarization camera, 18-Computing unit. Detailed Implementation

[0048] See Figure 1 The present invention provides a snapshot-type point source encoded wavefront detection system (hereinafter referred to as the system), which includes a first light source module, a second light source module, a first beam splitter 10, a second plane mirror 11, a second beam splitter 12, a microscope objective 13, a first plane mirror 15, a first imaging lens 16, a polarization camera 17, and a computing unit 18.

[0049] The first light source module is used to generate focal plane parallel light, including a first light source 1 and a first pinhole 2, a second imaging lens 3, and a first polarizer 4 arranged sequentially along the optical path direction of the first light source 1. The second light source module is used to generate defocused parallel light, including a second light source 5, a second pinhole 6, a third imaging lens 8, and a second polarizer 9.

[0050] The first light source 1 is spatially filtered through the first pinhole 2 to form a point light source, i.e., a point source. The first pinhole 2 is fixed at the focal plane of the second imaging lens 3. The light source is converted into horizontally linearly polarized light by the second imaging lens 3 and the first polarizer 4 to achieve horizontal linear polarization encoding. The second light source 5 is spatially filtered through the second pinhole 6 to form a point light source. The second pinhole 6 is placed at the defocus plane of the third imaging lens 8. The point light source is converted into vertically linearly polarized light by the third imaging lens 8 and the second polarizer 9 to achieve vertical linear polarization encoding.

[0051] The first beam splitter 10 refracts two orthogonal linearly polarized beams onto the same optical path. After being reflected by the second plane mirror 11, the beam splitter 12 is incident on the second beam splitter 12. The second beam splitter 12 first reflects the light to the microscope objective 13, and then through the optical system under test 14. The outgoing parallel light is reflected by the first plane mirror 15 and returns to the optical system under test 14 and the microscope objective 13. Subsequently, the second beam splitter 12 transmits the light, and the light is focused onto the plane of the polarization camera 17 by the first imaging lens 16. The polarization camera 17 is used to acquire the PSF intensity image as the original intensity image. After preprocessing and decoding, the PSF intensity image yields the horizontally linearly polarized measured focal plane PSF intensity image and the vertically linearly polarized measured defocused PSF intensity image. The calculation unit 18 is electrically connected to the output of the polarization camera 17 and inverts the wavefront distribution of the optical system under test 14 based on the original intensity image.

[0052] The second light source 5 and the second pinhole 6 are mounted on the displacement platform 7 for displacement adjustment, thereby achieving precise adjustment of the defocus amount. The displacement platform 7 is an electrically controlled displacement platform. The displacement platform 7 is only used for displacement adjustment of the second light source 5 and the second pinhole 6 to achieve defocus adjustment. During the detection process, the displacement platform 7 does not need to move at all and remains fixed in its current adjustment position.

[0053] Both the first light source 1 and the second light source 5 use narrow-band LED light sources to reduce the blurring of the PSF intensity image due to color difference, while avoiding interference between the two light sources.

[0054] The positions of the first pinhole 2 and the second pinhole 6 determine the acquisition of the focal plane PSF intensity image and the defocus PSF intensity image. In this embodiment, the first pinhole 2 is fixed in position and placed at the focal plane of the second imaging lens 3 to acquire the focal plane PSF intensity image; the second pinhole 6 is placed at the defocus plane of the third imaging lens 8 to acquire the defocus PSF intensity image. Both the first pinhole 2 and the second pinhole 6 include a series of small holes of different sizes. The different diameters of the small holes determine whether geometric imaging or diffraction imaging is performed on the point light source. When system adjustment is required, i.e., aligning the object-side focal plane of the microscope objective 13 with the image plane of the optical system under test 14, geometric imaging of the point light source is required. When wavefront aberration of the optical system under test needs to be inverted, diffraction imaging of the point light source is required. The first pinhole 2 and the second pinhole 6 are conjugate to the focal plane of the microscope objective 13. The focal lengths of the second imaging lens 3 and the third imaging lens 8 are denoted as _____. and For the first pinhole 2, when the radius of the pinhole is a, its equivalent size on the focal plane of the microscope objective 13 is... As shown below.

[0055]

[0056] Among them, f OLThis is the focal length of microscope objective 13.

[0057] when Smaller than the system Airy disk size When the following formula is satisfied, the diffraction imaging distribution of the point light source can be obtained at polarization camera 17.

[0058]

[0059] Among them, f DUT λ is the focal length of the optical system 14 under test, D is the entrance pupil diameter of the optical system 14 under test, and λ is the wavelength of the corresponding light source.

[0060] The radius 'a' of the first pinhole 2 can be selected according to the following relationship.

[0061]

[0062] The calculation of the second pinhole 6 is similar. In this embodiment, for ease of adjustment, the second imaging lens 3 and the third imaging lens 8 use the same focal length. In other embodiments of the present invention, the second imaging lens 3 and the third imaging lens 8 can also be selected with different focal lengths. The pinhole radii of the first pinhole 2 and the second pinhole 6 are calculated according to the corresponding focal lengths.

[0063] The first polarizer 4 and the second polarizer 9 are conventionally configured to cover the light source spectrum and ensure high transmittance. The polarization directions of the first polarizer 4 and the second polarizer 9 are orthogonal to avoid interference between the two beams. In this embodiment, the first polarizer 4 is set as a horizontal linear polarizer and the second polarizer 9 is set as a vertical linear polarizer.

[0064] Both the first beam splitter 10 and the second beam splitter 12 are 50:50 (R:T) unpolarized beam splitters.

[0065] The microscope objective 13 is a key conjugate and wavefront transmission element in this invention. To match the wavefront detection of different optical systems 14 under test, the microscope objective 13 can achieve a series of different numerical apertures and magnifications. The focal point of the microscope objective 13 is conjugate with the first pinhole 2, which can image the point light source at the focal point and transmit the light carrying the wavefront information of the optical system under test 14 to the image plane through the first imaging lens 16. The following requirements need to be met: the microscope objective 13 is a finite conjugate objective with high manufacturing tolerance to prevent the distortion of the objective itself from masking the wavefront aberration of the optical system under test; the numerical aperture of the microscope objective 13 is larger than the numerical aperture of the optical system under test 14 to ensure that the pupil of the optical system under test 14 is completely filled, avoiding the loss of high-frequency information and vignetting effect. Since the numerical aperture of the microscope objective 13 determines the resolution limit of the snapshot point source encoded wavefront detection system, the numerical aperture of the microscope objective 13 should be high enough to resolve the details of the PSF intensity image caused by small aberrations. The magnification of the microscope objective 13 and the polarization camera 17 together determine the sampling of the PSF intensity image on the image plane, which plays a key role in the inversion accuracy.

[0066] The optical system under test 14 is a non-polarized optical system of any type and entrance pupil diameter. Figure 1 The optical system 14 shown is for illustrative purposes only.

[0067] The size of the first plane mirror 15 is not less than the entrance pupil diameter of the optical system under test 14, so as to ensure that the returned beam is not truncated and to guarantee the integrity of the acquired PSF intensity image and the wavefront inversion accuracy.

[0068] The polarization camera 17 is a high-dynamic sensor with an integrated micro-polarization array, possessing a dynamic range of at least 12 bits, used for polarization imaging, such as... Figure 3 As shown, the sensor integrates a four-quadrant polarization array with linear polarization directions of 0°, 45°, 90°, and 135°, resulting in a spatial undersampling of 2x for a single polarization channel. The polarization camera 17 can simultaneously record information in a specific polarization direction in a single exposure. To improve wavefront inversion accuracy, the diffraction imaging radius of the point source on the image plane must be greater than X effective pixels. Therefore, the detector pixel size of the polarization camera 17... The following conditions must be met:

[0069]

[0070] Among them, NA DUT denoted as the numerical aperture of the optical system 14 under test, and M as the magnification of the microscope objective 13.

[0071]

[0072] in, This is the focal length of the first imaging lens 16.

[0073] This invention provides a snapshot-based point source encoded wavefront detection method. (See also: [link to invention]) Figure 2 Specifically, it includes the following steps:

[0074] 1) System calibration: Calibrate the inherent aberrations of the system. Dark current image D T (x,y) and flat field image Flat norm (x,y).

[0075] Illumination is provided by a first light source 1. A standard reference lens with a known wavefront is placed between the microscope objective 13 and the first plane mirror 15. An interferometer is placed at the corresponding position of the focal plane of the polarization camera 17. Under the same imaging and acquisition conditions as during detection, the observed wavefront of the system is measured using the interferometer. The inherent aberration of the system is obtained by subtracting the observed wavefront from the known wavefront of the standard reference lens. .

[0076] Dark current image D of the acquisition system T (x,y) Flat field image norm (x,y), where x and y are the horizontal and vertical coordinates of the image plane, respectively. The dark current image and the flat field image are used for dark field subtraction and flat field correction, respectively, thereby eliminating the dark noise and image plane light intensity non-uniformity of the polarization camera 17 and improving the stability and accuracy of the inversion.

[0077] When acquiring dark current images, turn off the first light source 1 and the second light source 5, and cover the lens cap of the polarization camera 17 to ensure that no light enters the polarization camera 17. Set the exposure time and gain of the polarization camera 17 to be exactly the same as when measuring the wavefront aberration of the optical system under test. Acquire multiple frames continuously, and obtain the dark current image D by averaging. T (x,y).

[0078] When acquiring the flat-field image, the first light source 1 and the first pinhole 2, as well as the second light source 5 and the second pinhole 6, are removed respectively. The output port of an integrating sphere is placed at the object-side focal plane of the second imaging lens 3 and the third imaging lens 8, respectively. The polarization camera 17 acquires the corresponding horizontal polarization channel flat-field data and vertical polarization channel flat-field data. The two sets of data values ​​are added together and normalized to obtain the flat-field image. norm (x,y).

[0079] The system's inherent aberrations, dark current image, and flat field image are stored as system calibration parameters in the computing unit 18. During the testing of the optical system 14 under test, it is not necessary to repeatedly collect the above-mentioned system calibration parameters.

[0080] 2) System Adjustment: Adjust the axial displacement of the second pinhole 6 via the displacement platform 7 to introduce a suitable defocus amount; adjust the relative position of the microscope objective 13 and the optical system under test 14 so that the object-side focal plane of the microscope objective 13 coincides with the image plane of the optical system under test 14. Specifically, this includes the following steps:

[0081] 2.1) Adjusting the defocus amount: When the defocus aberration PV is approximately equal to 1λ, the highest inversion accuracy is achieved. At this time, the axial displacement of the second pinhole 6 from the focal plane of the third imaging lens 8, i.e., the defocus amount Δz2 of the second light source module, is:

[0082]

[0083] 2.2) Adjusting the image plane coincidence: Replace the first pinhole 2 with a large-sized small hole to perform geometric imaging of the point light source. Adjust the distance between the optical system under test 14 and the microscope objective 13 along the optical axis. When the point light source is in an ideal circle and the size is the smallest on the image plane of the polarization camera 17, it is considered that the object-side focal plane of the microscope objective 13 coincides with the image plane of the optical system under test 14.

[0084] 3) Image acquisition and preprocessing:

[0085] The first pinhole 2 and the second pinhole 6 are adjusted to small-sized holes, and the first light source module and the second light source module are controlled to emit first linearly polarized light and second linearly polarized light to perform diffraction imaging of the point light source. The original intensity image I is then acquired using the polarization camera 17. raw (x,y).

[0086] For the acquired raw intensity image I raw Dark field subtraction, flat field correction, and necessary cropping and normalization are performed on (x,y). Logarithmic transformation is then used for intensity stretching to enhance the weak diffraction ring structure distribution of the PSF intensity image, resulting in the measured image I. meas (x,y), the main processing steps are as follows.

[0087]

[0088] 4) Wavefront Inversion: Derive the mapping relationship between the theoretical PSF intensity image and the wavefront aberration of the optical system under test to obtain theoretical data, i.e., the theoretical focal plane PSF intensity image. f (x,y) and theoretical defocus PSF intensity image PSF d (x,y), decoded measurement image I meas (x,y) yields the measurement data, i.e., the measured focal plane PSF intensity image I. f (x,y) and the image of the defocused PSF intensity I d (x,y), based on the theoretical focal plane PSF intensity image PSF f(x,y) and theoretical defocus PSF intensity image PSF d (x,y), and the measured focal plane PSF intensity image I f (x,y) and the image of the defocused PSF intensity I d (x,y) Calculate the wavefront aberration of the optical system under test. Specifically:

[0089] 4.1) According to the scalar Fraunhofer diffraction law, the complex amplitude at point 17 of the polarization camera... for:

[0090]

[0091] in, This is a Fourier transform, where i is the imaginary unit and k is the wavenumber. For the system's pupil function, These are the horizontal and vertical coordinates of the pupil plane, respectively.

[0092] Theoretically, the PSF intensity image acquired by polarization camera 17 can be represented as:

[0093]

[0094] in, The theoretical PSF intensity image includes the theoretical focal plane PSF intensity image and the theoretical defocus PSF intensity image.

[0095] In the system of this invention, light first passes through the optical system under test 14 once, is reflected by the first planar mirror 15, and returns along the same path to pass through the optical system under test 14 again, for a total of two passes through the optical system under test 14. The pupil plane coordinates are then used to determine the optical system 14. The wavefront aberration of the optical system under test at the location is denoted as Theoretical focal plane PSF intensity image PSF f (x,y) and theoretical defocus PSF intensity image PSF d (x,y) can be expressed as a function of the wavefront aberration of the optical system under test, as shown below:

[0096]

[0097] in, pupil plane coordinates The pupil amplitude of the optical system 14 under test. pupil plane coordinates The inherent aberrations of the system at that location, pupil plane coordinates The defocus aberration introduced by the second light source module, among which, The defocus aberration introduced by the second light source module is calculated using the following formula:

[0098]

[0099] in, This refers to the defocusing amount of the second light source module. Normalized pupil radial coordinates ( ).

[0100] 4.2) As Figure 4 As shown, decoded measurement image I meas (x,y) yields measurement data, including a horizontally linearly polarized encoded measurement focal plane PSF intensity image I. f (x,y), and the measured defocused PSF intensity image I with vertical polarization encoding. d (x,y).

[0101] 4.3) Wavefront inversion is performed by minimizing the consistency between measured and theoretical data, as shown below:

[0102] The wavefront aberration of the optical system under test is obtained by solving the following optimization equation using the phase difference algorithm and performing wavefront inversion. , complete wavefront detection.

[0103]

[0104] like Figure 5 and Figure 6 As shown, this embodiment performs wavefront detection on the optical system under test 14 with known wavefront aberrations, and obtains the wavefront aberrations of the optical system under test (…). Figure 6 ) and its known wavefront aberration ( Figure 5 The results are basically consistent, proving that the results of this invention have high accuracy.

[0105] In summary, the snapshot-type point source encoded wavefront detection system and method proposed in this invention perform orthogonal polarization encoding on the focal plane and defocused point sources, respectively. Utilizing the four-quadrant polarization array characteristics of the polarization camera 17, it simultaneously acquires and measures both the focal plane PSF intensity image and the defocused PSF intensity image. Based on the mapping relationship between the measured focal plane PSF intensity image and the measured defocused PSF intensity image obtained by the system and the wavefront of the optical system under test 14, a phase difference algorithm is used to achieve accurate wavefront inversion of the optical system under test 14. This invention can provide stable and accurate wavefront detection for different types of optical systems in production, assembly, and other scenarios. It eliminates the need for moving parts during measurement, allowing for the acquisition of both the measured focal plane PSF intensity image and the measured defocused PSF intensity image in a single exposure. It overcomes the sensitivity of measurement to environment and vibration, making it suitable for dynamic detection scenarios requiring rapid acquisition. Furthermore, it has low measurement cost and equipment complexity, demonstrating significant engineering application value.

Claims

1. A snapshot-type point source encoded wavefront detection system for wavefront detection of an optical system (14) under test, wherein the optical system (14) under test is a non-polarized optical system, characterized in that: It includes a first light source module, a second light source module, a first beam splitter (10), a second beam splitter (12), a microscope objective (13), a first plane mirror (15), a first imaging lens (16), and a polarization camera (17). The first light source module and the second light source module are used to provide point light sources for geometric imaging and diffraction imaging, and output first linearly polarized light and second linearly polarized light with orthogonal polarization directions, respectively, and the first linearly polarized light and the second linearly polarized light are focal plane parallel light and defocused parallel light, respectively. The first beam splitter (10) is set at the output end of the first light source module and the second light source module, and is used to fold the first linearly polarized light and the second linearly polarized light to the same optical path and output them to the second beam splitter (12) for reflection; The microscope objective (13) and the first plane mirror (15) are sequentially arranged in the reflected light path of the second beam splitter (12). The optical system under test (14) is arranged between the microscope objective (13) and the first plane mirror (15). The first linearly polarized light and the second linearly polarized light are refracted by the second beam splitter (12) and then sequentially pass through the microscope objective (13), the optical system under test (14), and the first plane mirror (15). After being reflected by the first plane mirror (15), they return to the second beam splitter (12) and are transmitted. The first imaging lens (16) and the polarization camera (17) are sequentially arranged in the transmission light path of the second beam splitter (12). The light transmitted by the second beam splitter (12) passes through the first imaging lens (16) and is received by the polarization camera (17). The polarization camera (17) is used to perform polarization imaging and obtain the PSF intensity image as the original intensity image. The original intensity image is used to calculate the wavefront aberration of the optical system under test.

2. The snapshot-type point source encoded wavefront detection system according to claim 1, characterized in that: The first light source module includes a first light source (1) and a first pinhole (2), a second imaging lens (3), and a first polarizer (4) arranged sequentially along its optical path direction; The first pinhole (2) is fixed at the focal plane of the second imaging lens (3); the first light source (1) is spatially filtered through the first pinhole (2) to form a point light source, and then converted into the first linearly polarized light through the second imaging lens (3) and the first polarizer (4); the focal point of the microscope objective (13) is conjugate with the first pinhole (2); The second light source module includes a second light source (5) and a second pinhole (6), a third imaging lens (8), and a second polarizer (9) arranged sequentially along its optical path. The second light source (5) and the second pinhole (6) are arranged on a displacement platform (7) for defocus adjustment. The second light source (5) is spatially filtered through the second pinhole (6) to form a point light source. The displacement platform (7) is used to control the second pinhole (6) to be set at the defocus surface of the third imaging lens (8). The point light source is converted into the second linearly polarized light through the third imaging lens (8) and the second polarizer (9). The first pinhole (2) and the second pinhole (6) each include multiple small holes of different sizes. The size of the small holes is adjusted to perform geometric imaging and diffraction imaging of the point light source.

3. A snapshot-type point source encoded wavefront detection system according to claim 1 or 2, characterized in that: It also includes a second planar reflector (11) disposed between the first beam splitter (10) and the second beam splitter (12), the second planar reflector (11) being used to reflect the output light of the first beam splitter (10) to the second beam splitter (12).

4. The snapshot-type point source encoded wavefront detection system according to claim 3, characterized in that: The first linearly polarized light is horizontally linearly polarized light, and the second linearly polarized light is vertically linearly polarized light; It also includes a computing unit (18) electrically connected to the output of the polarization camera (17). The computing unit (18) decodes the original intensity image to obtain the measured focal plane PSF intensity image and the measured defocus PSF intensity image, and then inverts the wavefront aberration of the optical system under test.

5. A snapshot-type point source coded wavefront detection method, based on the snapshot-type point source coded wavefront detection system of claim 1, characterized in that, Includes the following steps: Step 1, System Calibration: Calibrate the inherent aberrations of the system. ; Step 2, System Adjustment: Adjust the defocus of the second light source module; Set and adjust the position of the optical system under test (14) so ​​that the object-side focal plane of the microscope objective (13) coincides with the image plane of the optical system under test (14); Step 3, Image Acquisition and Preprocessing: Adjust the first light source module and the second light source module to simultaneously emit first linearly polarized light and second linearly polarized light, perform diffraction imaging of the point light source, and acquire the original intensity image I using a polarization camera (17). raw (x,y), preprocessing yields the measurement image I meas (x,y); Step 4, Wavefront Inversion: Decoding Measurement Image I meas (x,y) yields the PSF intensity image at the focal plane. f (x,y) and the measured defocused PSF intensity image I d (x,y), based on the mapping relationship between the theoretical PSF intensity image and the wavefront aberration of the optical system under test, the theoretical PSF intensity image and the measured focal plane PSF intensity image I are minimized. f (x,y) and the measured defocused PSF intensity image I d Wavefront inversion is performed based on the consistency between (x,y) to obtain the wavefront aberration of the optical system under test. .

6. The snapshot-type point source encoded wavefront detection method according to claim 5, characterized in that, Step 1 is as follows: A standard reference lens with a known wavefront is set between the microscope objective (13) and the first plane mirror (15). The first light source module is controlled to work. An interferometer is set corresponding to the focal plane of the polarization camera (17). Under the same imaging and acquisition conditions as during detection, the observed wavefront of the optical system is measured using the interferometer. The observed wavefront is subtracted from the known wavefront of the standard reference lens to obtain the inherent aberration of the system. .

7. The snapshot-type point source encoded wavefront detection method according to claim 6, characterized in that, Step 2 is as follows: Step 2.1, adjust the defocus amount Δz2 of the second light source module to satisfy the following formula: ； in, The focal length of the optical system under test (14) is given by the focal length of the optical system under test. To correspond to the wavelength of the light source, D is the entrance pupil diameter of the optical system under test (14). and The focal lengths of the third imaging lens (8) and the microscope objective (13) are respectively; Step 2.2: Adjust the first light source module to perform geometric imaging of the point light source. Adjust the position of the optical system under test (14) along the optical axis so that the point light source is in an ideal circle and has the smallest size on the image plane of the polarization camera (17).

8. The snapshot-type point source encoded wavefront detection method according to claim 7, characterized in that: Step 1 also includes: acquiring a dark current image D using a polarization camera (17). T (x,y) and Flat field image norm (x,y); In step 3, the preprocessing specifically involves: utilizing the dark current image D T (x,y) represents the original intensity image I raw Dark field subtraction is performed using (x,y), and then a flat field image is used. norm (x,y) is subjected to flat-field correction, then cropped and normalized, and logarithmic transformation is used for intensity stretching to enhance the weak diffraction ring structure distribution of the PSF intensity image, resulting in the measured image I. meas (x,y).

9. A snapshot-type point source encoded wavefront detection method according to any one of claims 5-8, characterized in that: In step 4, the mapping relationship between the theoretical PSF intensity image and the wavefront aberration of the optical system under test is shown below: ； Among them, PSF f (x,y) represents the PSF intensity image of the theoretical focal plane, PSF d (x,y) represents the theoretical defocused PSF intensity image. d (x,y), pupil plane coordinates The pupil amplitude of the optical system under test (14) pupil plane coordinates Wavefront aberration of the optical system under test at the location pupil plane coordinates The inherent aberrations of the system at that location, This is the Fourier transform, where i is the imaginary unit. pupil plane coordinates Defocus aberration introduced by the second light source module.

10. The snapshot-type point source encoded wavefront detection method according to claim 9, characterized in that: In step 4, the following optimization equation is solved using the phase difference algorithm to achieve wavefront inversion and obtain the wavefront aberration of the optical system under test. ; 。

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