Large-aperture optical element surface defect detection device and method

Abstract

The invention relates to a device and a method for detecting surface defects of an optical element, in particular to a device and a method for detecting surface defects of a large-aperture optical element, which are used for solving the problem that quantitative evaluation standards exist or cannot be provided when an existing detection method is used for detecting damage of the large-aperture optical element. Or the efficiency is low, the large-range detection requirement is difficult to effectively meet, or the three-dimensional shape information of the defect cannot be obtained. According to the surface defect detection device for the large-aperture optical element, the diffraction characteristic of the binary deformation diffraction grating is utilized, a plurality of diffraction spots with different diffraction orders are acquired by a camera at a time, and the surface phase of the large-aperture optical element is calculated through a phase recovery algorithm; and the whole surface of the large-aperture optical element is scanned by the laser beam in combination with the two-dimensional translation stage, so that the surface defect detection of the large-aperture optical element is realized.

Description

Technical Field

[0001] The present invention relates to a device and method for detecting surface defects of optical elements, and in particular to a device and method for detecting surface defects of large-aperture optical elements. Background Art

[0002] In ultrashort and ultra-intense laser systems, due to the high intensity and short duration of laser pulses, the interaction between laser and medium usually leads to some complex nonlinear phenomena, among which the self-focusing effect is particularly significant. Self-focusing means that under the action of a strong laser field, the beam itself will be focused to a smaller area due to nonlinear effects, thereby increasing the intensity of the beam, which may cause local damage to optical components.

[0003] For large-aperture optical components, laser damage will occur on the surface and inside under long-term high-intensity laser irradiation. The formation of this damage is closely related to factors such as laser power, focal position, and pulse duration. The damage not only affects the beam quality and causes the focal position to shift, but also may cause thermal effects, which may eventually lead to the rupture of the optical component or local melting of the surface. In addition, the beam diffraction effect at the damage point may also cause additional damage to other optical components, further affecting system performance.

[0004] Existing detection methods can be roughly divided into visual methods and imaging-based detection methods. The visual method relies on the experience of the inspector to conduct damage assessment, but because it relies on manual observation, it cannot provide objective and quantitative detection results. Imaging-based detection methods, such as the area array imaging method, collimate the light source into a large-aperture parallel light to illuminate the surface of the optical component, and then obtain the image through the camera and imaging lens; this method is limited by the resolution and sampling frequency of the area array CCD, and because multiple images need to be stitched together, the overall detection efficiency is low, especially in the detection of large-aperture optical components, it is difficult to effectively respond to a wide range of detection needs; and although dark field imaging and bright field imaging methods can improve imaging resolution, they still face problems such as low detection efficiency and inability to obtain three-dimensional morphological information of defects.

[0005] Therefore, existing detection methods are difficult to provide efficient, accurate and comprehensive solutions when it comes to damage detection of large-aperture optical components. Summary of the invention

[0006] The purpose of the present invention is to provide a device and method for detecting surface defects of large-aperture optical components to solve the shortcomings of existing detection methods, such as being unable to provide quantitative evaluation standards, being inefficient and unable to effectively cope with a wide range of detection needs, or being unable to obtain three-dimensional morphological information of defects when facing damage detection of large-aperture optical components.

[0007] In order to solve the deficiencies of the above-mentioned prior art, the present invention provides the following technical solutions: A large-aperture optical element surface defect detection device, which is special in that it includes a laser, a two-dimensional translation stage, and a collimator, a variable-magnification beam expander, a binary deformable diffraction grating, a focusing lens and a camera arranged in sequence along the optical path; The laser is used to emit a laser beam to a collimator, and the collimator is used to collimate the laser beam; The two-dimensional translation stage is used to place a large-aperture optical element and to change the position where the laser beam irradiates the large-aperture optical element; The variable magnification beam expander is used to expand a laser beam that passes through a large-aperture optical element or a laser beam that is directly input into the variable magnification beam expander through a collimator, and output it to a binary deformable diffraction grating; the binary deformable diffraction grating is used to divide the laser beam into a plurality of diffraction spots of different diffraction orders, and focus them to a detection surface of a camera through the focusing lens. The detection surface of the camera is located on the rear focal plane of the focusing lens. Each diffraction order corresponds to a specific phase shift, which is used to reconstruct the surface phase of the large-aperture optical element, thereby obtaining the surface defect distribution.

[0008] Further, the binary deformed diffraction grating includes two one-dimensional deformed diffraction gratings orthogonal in the X-axis direction and the Y-axis direction; the direction of the laser beam emitted by the laser is the positive direction of the Z-axis, and the positive direction of the X-axis conforms to the left-hand rectangular coordinate system with the positive direction of the Y-axis vertically upward; The grating equation of the one-dimensional deformable diffraction grating in the X-axis direction is as follows: in, , represents the two-dimensional coordinates with the center of the one-dimensional deformed diffraction grating in the X-axis direction as the origin; represents the wavelength of the laser beam, R is the radius of the grating aperture, is the grating period at the pupil center, is an integer, The trajectory of each grating slit of the one-dimensional deformable diffraction grating in the X-axis direction is defined. Corresponding to the grating slit passing through the center of the aperture in the X-axis direction, along the negative direction of the X-axis Decrease one by one, along the positive direction of the X axis Increase one by one; The amount that indicates the defocusing ability of the grating in the X-axis direction; Phase shift in the X-axis direction for: The grating equation of the one-dimensional deformable diffraction grating in the Y-axis direction is as follows: in, represents the amount of defocusing capability of the grating in the Y-axis direction; and ; is an integer, The trajectory of each grating slit of the one-dimensional deformable diffraction grating in the Y-axis direction is defined. Corresponding to the grating slit passing through the center of the aperture in the Y-axis direction, along the negative direction of the Y-axis Decrease one by one, along the positive direction of the Y axis Increase one by one; Phase shift in the Y-axis direction for: Binary Deformed Diffraction Grating Phase Shift The magnitude of the phase shift in the X-axis direction and the phase shift in the Y-axis direction Determination, related to the diffraction order.

[0009] Furthermore, the binary deformable diffraction grating is used to split the laser beam into diffraction spots of nine different diffraction orders; the nine different diffraction orders are respectively (0,0), (-1,0), (+1,0), (0,-1), (0,+1), (-1,+1), (+1,-1), (-1,-1) and (+1,+1); When the laser beam collimated by the collimator is directly input into the variable-magnification beam expander, the detection light intensity received by the camera is , , represents the diffraction order, , , , are all integers, Denotes the diffraction order corresponding to The intensity distribution of the diffraction spot is Represents the coordinates on the detection surface of the camera; When the laser beam collimated by the collimator passes through each scanning position on the large-aperture optical element and then enters the variable-magnification beam expander, the detection light intensity received by the camera is , s, t are the row and column of the current scanning position, s , t , s and t are both positive integers, u and v are the total number of rows and columns of the scan position, respectively. Indicates that the current scanning position corresponds to the diffraction order Intensity distribution of the diffraction spot.

[0010] Furthermore, the intensity distribution of the (0,0)-order diffraction spot is: , the phase shift is , ; in, The coefficient representing the phase change, corresponding to the diffraction order The diffraction spot of The intensity distributions of the (-1,0) and (+1,0) diffraction spots are respectively , , and the corresponding phase shifts are , , , ; The intensity distributions of the (0, -1) and (0, +1) order diffraction spots are respectively , , and the corresponding phase shifts are , , , ; The intensity distributions of the (-1, +1) and (+1, -1) order diffraction spots are respectively , , and the corresponding phase shifts are , , , ; The intensity distributions of the (-1, -1) and (+1, +1) order diffraction spots are respectively , , and the corresponding phase shifts are , , , .

[0011] Furthermore, the variable magnification beam expander includes a beam reducer and a beam expander sequentially arranged along the optical path, and the variable magnification beam expander has a magnification range of 1 to 100.

[0012] A method for detecting surface defects of large-aperture optical components is characterized in that the method adopts the above-mentioned device for detecting surface defects of large-aperture optical components, and comprises the following steps: Step 1: Adjust the magnification of the variable-magnification beam expander to 1, control the two-dimensional translation stage to move the large-aperture optical element out of the light path, and the detection light intensity received by the camera is , , represents the diffraction order, , , , are all integers, Denotes the diffraction order corresponding to The intensity distribution of the diffraction spot is Represents the coordinates on the detection surface of the camera; then the background phase in the optical path is calibrated by the phase recovery algorithm , is the coordinate in front of the binary deformed diffraction grating; Step 2: By controlling the two-dimensional translation stage, the laser beam is scanned on the surface of the large-aperture optical element; at each scanning position, the detection light intensity received by the camera is , s, t are the row and column of the current scanning position, s , t , s and t are both positive integers, u and v are the total number of rows and columns of the scan position, respectively. Indicates that the current scanning position corresponds to the diffraction order The intensity distribution of the diffraction spot; the phase distribution of the scanning position is calculated by the phase recovery algorithm , and then remove the background phase , the surface defect distribution of large-aperture optical components is , s, t are the row and column of the current scanning position; Until the entire scanning process of the surface defects of large-aperture optical components is completed, the surface defect distribution of the splicing is obtained ; Step 3: Move the large-aperture optical element through the two-dimensional translation stage to locate the target defect, adjust the magnification of the variable-magnification beam expander, magnify the target defect, observe the details of the target defect, and use the phase recovery algorithm to obtain the distribution of the target defect after magnification to complete the surface defect detection of the large-aperture optical element.

[0013] Furthermore, in step 1, the process of the phase recovery algorithm is as follows: Step A1: Assume that the light field to be measured in front of the binary deformable diffraction grating is , is the assumed initial phase value, which is a set of constants or a set of random numbers. is a plural unit; , ; Step A2: Using a binary deformed diffraction grating to measure the light field Modulate and calculate the light field after its diffraction is transmitted to the camera , Calculation of Fraunhofer diffraction in the forward direction; Step A3: Maintain the light field The phase part remains unchanged, and the diffraction spot intensity distribution corresponding to the camera is used To update the amplitude part, get the updated light field ; Step A4: Reverse diffraction to update the light field Transmitted to the binary deformable diffraction grating, the phase shift modulation effect is removed to obtain the updated light field ; make , ; judge Is it greater than 1? If so, go to step A5; otherwise, go to step A2; Step A5: Determination Is it less than 1? If so, let , , jump to step A2, otherwise go to step A6; Step A6: Determine the root mean square error Is it less than or equal to If yes, stop the iteration and execute step A7; otherwise, , , jump to step A2; Step A7: Back-diffraction transmission to the preset position of the large-aperture optical element to obtain the background phase , To obtain the angle of the operation, Calculate the inverse angular spectrum.

[0014] Furthermore, in step 2, at each scanning position, the phase distribution of the scanning position is calculated by a phase recovery algorithm. The process is as follows: Step B1, assuming that the current light field to be measured in front of the binary deformable diffraction grating is , is the assumed initial phase value, which is a set of constants or a set of random numbers. is a plural unit; , ; Step B2: Use the binary deformable diffraction grating to measure the current light field Modulate and calculate the diffracted light field transmitted to the camera , Calculation for forward Fraunhofer diffraction; Step B3: Maintain the light field The phase part remains unchanged, and the intensity distribution of the diffraction spot corresponding to the camera is To update the amplitude part, get the updated light field ; Step B4: Reverse diffraction to update the light field Transmitted to the binary deformable diffraction grating, the phase shift modulation effect is removed to obtain the updated light field ; make , ; judge Is it greater than 1? If so, go to step B5; otherwise, go to step B2; Step B5: Determination Is it less than 1? If so, let , , jump to step B2, otherwise go to step B6; Step B6: Determine the root mean square error Is it less than or equal to If yes, stop the iteration and execute step B7; otherwise, , , jump to step B2; Step B7: reverse diffraction transmission to the large-aperture optical element to obtain the current scanning position , To obtain the angle of the operation, Calculate the inverse angular spectrum.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention discloses a device for detecting surface defects of large-aperture optical elements. The device utilizes the diffraction characteristics of a binary deformable diffraction grating to collect multiple diffraction spots of different diffraction orders by a camera at a time, calculates the surface phase of the large-aperture optical element by a phase recovery algorithm, and uses a two-dimensional translation stage to enable a laser beam to scan the entire surface of the large-aperture optical element, thereby realizing the detection of surface defects of the large-aperture optical element. The present invention can realize three-dimensional morphology detection of surface defects by reconstructing the phase information of the surface of the large-aperture optical element, while avoiding damage to the surface of the optical element caused by the self-focusing effect and the interaction between the laser and the medium.

[0016] (2) The variable magnification range of the beam expander in the present invention is 1 to 100, which can achieve a smooth transition from coarse scanning to fine detection, making the detection process not only efficient but also accurate; when scanning over a large range, low magnification can quickly locate potential defect areas, while high magnification can magnify and analyze the target defects in detail to obtain high-resolution three-dimensional defect data.

[0017] (3) The automation and high efficiency of the present invention enable rapid detection during large-scale production, greatly improving the detection efficiency of the production line and meeting the needs of high-throughput detection.

[0018] (4) The present invention provides a method for detecting surface defects of large-aperture optical components. First, a coarse scan is performed using a variable-magnification beam expander and defects are detected using a phase recovery algorithm. The large-aperture optical component is then positioned to the target defect position using a two-dimensional translation stage. The variable-magnification beam expander is then adjusted to magnify the defect, the details of the defect are observed, and the defect distribution after magnification is obtained using a phase recovery algorithm. The present invention enables the surface defects of large-aperture optical components to be quantified with high resolution and precision, thereby ensuring the efficiency and accuracy of defect detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic structural diagram of an embodiment of a large-aperture optical element surface defect detection device of the present invention; The reference numerals are as follows: 01 - large-aperture optical element; 10-laser; 20-collimator; 30-variable magnification beam expander; 31-beam reducer; 32-beam expander; 40-binary deformable diffraction grating; 50-focusing lens; 60-camera; 70-two-dimensional translation stage. DETAILED DESCRIPTION

[0020] The present invention is further described below in conjunction with the accompanying drawings and exemplary embodiments.

[0021] Reference Figure 1 A large-aperture optical element surface defect detection device includes a laser 10, a two-dimensional translation stage 70, and a collimator 20, a variable-magnification beam expander 30, a binary deformable diffraction grating 40, a focusing lens 50 and a camera 60 arranged in sequence along the optical path.

[0022] The laser 10 is used to emit a laser beam to the collimator 20 , and the collimator 20 is used to collimate the laser beam.

[0023] The two-dimensional translation stage 70 is used to place the large-aperture optical element 01 and to change the position of the laser beam irradiating the large-aperture optical element 01, so as to realize the scanning of the large-aperture optical element 01 by the laser beam in the X-axis and Y-axis directions; the positive direction of the Z-axis is the direction of the laser beam emitted by the laser, and the positive direction of the X-axis conforms to the left-hand rectangular coordinate system with the positive direction of the Y-axis vertically upward.

[0024] The variable magnification beam expander 30 is used to expand the laser beam passing through the large-aperture optical element 01 or the laser beam directly input into the variable magnification beam expander 30 by the collimator 20, and output it to the binary deformable diffraction grating 40; the binary deformable diffraction grating 40 is used to divide the laser beam into a plurality of diffraction spots of different diffraction orders, and focus them to the detection surface of the camera 60 through the focusing lens 50, and each diffraction order corresponds to a specific phase shift; the detection surface of the camera 60 is located on the rear focal plane of the focusing lens 50, and is used to reconstruct the surface phase of the large-aperture optical element 01 by analyzing the intensity distribution and phase information of the diffraction spots of a plurality of different diffraction orders, thereby obtaining the surface defect distribution.

[0025] The variable magnification beam expander 30 includes a beam reducer 31 and a beam expander 32 sequentially arranged along the optical path, and the magnification range is 1 to 100, ensuring that the defect information can be clearly imaged on the detection surface of the camera 60.

[0026] The binary deformed diffraction grating 40 has the diffraction characteristics of a grating, and can divide the laser beam into diffraction spots of nine diffraction orders, and the nine diffraction orders are respectively (0,0), (-1,0), (+1,0), (0,-1), (0,+1), (-1,+1), (+1,-1), (-1,-1) and (+1,+1). The binary deformed diffraction grating 40 includes two one-dimensional deformed diffraction gratings that are orthogonal in the X-axis direction and the Y-axis direction.

[0027] The grating equation of the one-dimensional deformable diffraction grating in the X-axis direction is as follows: in, , represents the two-dimensional coordinates with the center of the one-dimensional deformed diffraction grating in the X-axis direction as the origin; represents the wavelength of the laser beam, R is the radius of the grating aperture, is the grating period at the pupil center, is an integer, The trajectory of each grating slit of the one-dimensional deformable diffraction grating in the X-axis direction is defined. Corresponding to the grating slit passing through the center of the aperture in the X-axis direction, along the negative direction of the X-axis Decrease one by one, along the positive direction of the X axis Increase one by one; The amount of defocusing ability of the grating in the X-axis direction is equivalent to the additional optical path of the +1-order diffracted light wavefront at the edge of the pupil, and the phase shift in the X-axis direction introduced thereby for: The grating equation of the one-dimensional deformable diffraction grating in the Y-axis direction is as follows: in, represents the amount of defocusing capability of the grating in the Y-axis direction, and ; is an integer, The trajectory of each grating slit of the one-dimensional deformable diffraction grating in the Y-axis direction is defined. Corresponding to the grating slit passing through the center of the aperture in the Y-axis direction, along the negative direction of the Y-axis Decrease one by one, along the positive direction of the Y axis Increase one by one.

[0028] Phase shift in the Y-axis direction for: Phase shift imposed by binary deformed diffraction grating 40 The magnitude of the phase shift in the X-axis direction and the phase shift in the Y-axis direction Determination, related to the diffraction order.

[0029] The detection surface of the camera 60 receives nine diffraction spots of different diffraction orders, which correspond to different phase shifts. When the laser beam collimated by the collimator 20 is directly input into the variable-magnification beam expander 30, the detection light intensity received by the detection surface of the camera 60 is , , represents the diffraction order, , , , are all integers, Denotes the diffraction order corresponding to The intensity distribution of the diffraction spot is represents the coordinates on the detection surface of the camera 60; when the laser beam collimated by the collimator 20 passes through the scanning position on the large-aperture optical element 01 and enters the variable-magnification beam expander 30, the detection light intensity received by the camera 60 is , s, t are the row and column of the current scanning position, s , t , s and t are both positive integers, u and v are the total number of rows and columns of the scan position, respectively. Indicates that the current scanning position corresponds to the diffraction order Intensity distribution of the diffraction spot.

[0030] The nine different diffraction orders are: (0,0) level: the diffraction spot intensity distribution is , the phase shift is , ; The coefficient representing the phase change, corresponding to the diffraction order The diffraction spot of (-1,0) level and (+1,0) level: the diffraction spot intensity distribution is , , and the corresponding phase shifts are , , , ; (0,-1) level and (0,+1) level: the diffraction spot intensity distribution is , , and the corresponding phase shifts are , , , ; (-1, +1) level and (+1, -1) level: the diffraction spot intensity distribution is respectively , , and the corresponding phase shifts are , , , ; (-1,-1) level and (+1,+1) level: the diffraction spot intensity distribution is , , and the corresponding phase shifts are , , , .

[0031] The specific working process of the present invention is as follows: The laser beam emitted by the laser 10 is collimated by the collimator 20, enters the variable magnification beam expander 30 to expand the beam according to the preset magnification, and then enters the binary deformed diffraction grating 40, which divides the laser beam into nine diffraction spots of different diffraction orders, and focuses the laser beam to the detection surface of the camera 60 through the focusing lens 50; By moving the two-dimensional translation stage 70, the laser beam is scanned on the surface of the large-aperture optical element 01, and finally the surface phase of the large-aperture optical element 01 is obtained using the intensity distribution of the diffraction spots of different diffraction orders and the phase recovery algorithm, thereby realizing the detection of surface defects of the large-aperture optical element 01.

[0032] A method for detecting surface defects of a large-aperture optical component, using the above-mentioned large-aperture optical component surface defect detection device, comprises the following steps: Step 1: Adjust the variable magnification beam expander 30 to 1, control the two-dimensional translation stage 70 to move the large-aperture optical element 01 out of the light path, and the detection light intensity received by the camera 60 is ; Then the background phase in the optical path is calibrated by the phase recovery algorithm , as follows: Step A1: Assume that the light field to be measured in front of the binary deformed diffraction grating 40 is , is the assumed initial phase value, which is a set of constants or a set of random numbers. is a plural unit, is the coordinate in front of the binary deformed diffraction grating 40; make , ; Step A2: using the binary deformable diffraction grating 40 to measure the light field Modulate and calculate the diffracted light field transmitted to the camera 60 , Calculation for forward Fraunhofer diffraction; Step A3: Maintain the light field The phase part remains unchanged, and the diffraction spot intensity distribution corresponding to camera 60 is used Update the amplitude part to get the updated light field ; Step A4: Reverse diffraction to update the light field Transmitted to the binary deformable diffraction grating 40, and the phase shift modulation effect is removed to obtain the updated light field again ; make , ; judge Is it greater than 1? If so, go to step A5; otherwise, go to step A2; Step A5: Determination Is it less than 1? If so, let , , jump to step A2, otherwise go to step A6; Step A6: Determine the root mean square error Is it less than or equal to If yes, stop the iteration and execute step A7; otherwise, , , jump to step A2; Step A7: Back-diffraction transmission to the preset position of the large-aperture optical element 01 to obtain the background phase , To obtain the angle of the operation, It is the inverse angular spectrum calculation; Step 2, scanning and moving the two-dimensional translation stage 70 along the X-axis and Y-axis directions until the laser beam is incident on the upper left corner of the large-aperture optical element 01, which is recorded as the initial position; by controlling the two-dimensional translation stage 70, the laser beam is scanned on the surface of the large-aperture optical element 01 from the initial position; At each scanning position, the detection light intensity received by the camera 60 is , the phase distribution of the scanning position is calculated by the phase recovery algorithm , and then remove the background phase , the surface defect distribution of large-aperture optical element 01 is obtained as , s, t are the row and column of the current scanning position; Until the entire scanning process of the surface defects of the large-aperture optical element 01 is completed, the surface defect distribution of the splicing is obtained , u and v are the total number of rows and columns scanned respectively; The phase distribution of the scanning position The calculation process is as follows: Step B1, assuming that the current light field to be measured in front of the binary deformable diffraction grating 40 is , is the assumed initial phase value, which is a set of constants or a set of random numbers; make , ; Step B2: Using the binary deformable diffraction grating 40 to measure the current light field Modulate and calculate the diffracted light field transmitted to the camera 60 ; Step B3: Maintain the light field The phase part remains unchanged, and the intensity distribution of the diffraction spot corresponding to camera 60 is To update the amplitude part, get the updated light field ; Step B4: Reverse diffraction to update the light field Transmitted to the binary deformable diffraction grating 40, and the phase shift modulation effect is removed to obtain the updated light field again ; make , ; judge Is it greater than 1? If so, go to step B5; otherwise, go to step B2; Step B5: Determination Is it less than 1? If so, let , , jump to step B2, otherwise go to step B6; Step B6: Determine the root mean square error Is it less than or equal to If yes, stop the iteration and execute step B7; otherwise, , , jump to step B2; Step B7: reverse diffraction is transmitted to the large-aperture optical element 01 to obtain the current scanning position. ; Step 3: Move the large-aperture optical element 01 through the two-dimensional translation stage 70 to locate the target defect, adjust the variable-magnification beam expander to 30 times, magnify the target defect, observe the details of the target defect, and use the phase recovery algorithm in step 1 to obtain the distribution of the target defect after magnification.

Claims

1. A large-aperture optical element surface defect detection device, characterized in that: It comprises a laser (10), a two-dimensional translation stage (70), and a collimator (20), a variable-magnification beam expander (30), a binary deformable diffraction grating (40), a focusing lens (50), and a camera (60) which are sequentially arranged along an optical path; The laser (10) is used to emit a laser beam to a collimator (20), and the collimator (20) is used to collimate the laser beam; The two-dimensional translation stage (70) is used to place the large-aperture optical element (01) and to change the position where the laser beam irradiates the large-aperture optical element (01); The variable magnification beam expander (30) is used to expand a laser beam that passes through a large-aperture optical element (01) or a laser beam that is directly input into the variable magnification beam expander (30) by a collimator (20), and output the expanded beam to a binary deformable diffraction grating (40); the binary deformable diffraction grating (40) is used to split the laser beam into a plurality of diffraction spots of different diffraction orders, and focus the spots onto a detection surface of a camera (60) through the focusing lens (50); the detection surface of the camera (60) is located on a rear focal plane of the focusing lens (50); each diffraction order corresponds to a specific phase shift, and is used to reconstruct a surface phase of the large-aperture optical element (01), thereby obtaining a surface defect distribution.

2. The large-aperture optical element surface defect detection device according to claim 1, characterized in that: The binary deformed diffraction grating (40) comprises two one-dimensional deformed diffraction gratings that are orthogonal in the X-axis direction and the Y-axis direction; the direction of the laser beam emitted by the laser (10) is the positive direction of the Z-axis, and the positive direction of the X-axis conforms to a left-hand rectangular coordinate system with the positive direction of the Y-axis vertically upward; The grating equation of the one-dimensional deformable diffraction grating in the X-axis direction is as follows: ； in, , represents the two-dimensional coordinates with the center of the one-dimensional deformed diffraction grating in the X-axis direction as the origin; represents the wavelength of the laser beam, R is the radius of the grating aperture, is the grating period at the pupil center, is an integer, The trajectory of each grating slit of the one-dimensional deformable diffraction grating in the X-axis direction is defined. Corresponding to the grating slit passing through the center of the aperture in the X-axis direction, along the negative direction of the X-axis Decrease one by one, along the positive direction of the X axis Increase one by one; The amount that indicates the defocusing ability of the grating in the X-axis direction; Phase shift in the X-axis direction for: ； The grating equation of the one-dimensional deformable diffraction grating in the Y-axis direction is as follows: ； in, represents the amount of defocusing capability of the grating in the Y-axis direction; and ; is an integer, The trajectory of each grating slit of the one-dimensional deformable diffraction grating in the Y-axis direction is defined. Corresponding to the grating slit passing through the center of the aperture in the Y-axis direction, along the negative direction of the Y-axis Decrease one by one, along the positive direction of the Y axis Increase one by one; Phase shift in the Y-axis direction for: ； Binary deformed diffraction grating (40) phase shift The magnitude of the phase shift in the X-axis direction and the phase shift in the Y-axis direction Determination, related to the diffraction order.

3. The large-aperture optical element surface defect detection device according to claim 2, characterized in that: The binary deformable diffraction grating (40) is used to split the laser beam into diffraction spots of nine different diffraction orders; the nine different diffraction orders are respectively (0,0), (-1,0), (+1,0), (0,-1), (0,+1), (-1,+1), (+1,-1), (-1,-1) and (+1,+1); When the laser beam collimated by the collimator (20) is directly input into the variable-magnification beam expander (30), the detection light intensity received by the camera (60) is , , represents the diffraction order, , , , are all integers, Denotes the diffraction order corresponding to The intensity distribution of the diffraction spot is represents the coordinates on the detection surface of the camera (60); When the laser beam collimated by the collimator (20) passes through each scanning position on the large-aperture optical element (01) and then enters the variable-magnification beam expander (30), the detection light intensity received by the camera (60) is , s, t are the row and column of the current scanning position, s , t , s and t are both positive integers, u and v are the total number of rows and columns of the scan position, respectively. Indicates that the current scanning position corresponds to the diffraction order Intensity distribution of the diffraction spot.

4. The large-aperture optical element surface defect detection device according to claim 3, characterized in that: The intensity distribution of the (0,0) order diffraction spot is: , the phase shift is , ; in, The coefficient representing the phase change, corresponding to the diffraction order The diffraction spot of The intensity distributions of the (-1,0) and (+1,0) diffraction spots are respectively , , and the corresponding phase shifts are , , , ; The intensity distributions of the (0, -1) and (0, +1) order diffraction spots are respectively , , and the corresponding phase shifts are , , , ; The intensity distributions of the (-1, +1) and (+1, -1) order diffraction spots are respectively , , and the corresponding phase shifts are , , , ; The intensity distributions of the (-1, -1) and (+1, +1) order diffraction spots are respectively , , and the corresponding phase shifts are , , , .

5. A large-aperture optical element surface defect detection device according to any one of claims 1 to 4, characterized in that: The variable magnification beam expander (30) comprises a beam reducer (31) and a beam expander (32) which are sequentially arranged along an optical path, and the variable magnification beam expander (30) has a magnification variation range of 1 to 100.

6. A method for detecting surface defects of large-aperture optical components, characterized in that: The large-aperture optical element surface defect detection device according to claim 1 comprises the following steps: Step 1: Adjust the magnification of the variable magnification beam expander (30) to 1, control the two-dimensional translation stage (70) to move the large-aperture optical element (01) out of the light path, and the detection light intensity received by the camera (60) is , , represents the diffraction order, , , , are all integers, Denotes the diffraction order corresponding to The intensity distribution of the diffraction spot is The coordinates on the detection surface of the camera (60) are represented; and then the background phase in the optical path is calibrated by a phase recovery algorithm. , is the coordinate in front of the binary deformed diffraction grating (40); Step 2: By controlling the two-dimensional translation stage (70), the laser beam is scanned on the surface of the large-aperture optical element (01); at each scanning position, the detection light intensity received by the camera (60) is , s, t are the row and column of the current scanning position, s , t , s and t are both positive integers, u and v are the total number of rows and columns of the scan position, respectively. Indicates that the current scanning position corresponds to the diffraction order The intensity distribution of the diffraction spot; the phase distribution of the scanning position is calculated by the phase recovery algorithm , and then remove the background phase , the surface defect distribution of large-aperture optical element (01) is , s, t are the row and column of the current scanning position; Until the entire scanning process of the surface defects of the large-aperture optical element (01) is completed, the surface defect distribution of the splicing is obtained. ; Step 3: Move the large-aperture optical element (01) by a two-dimensional translation stage (70) to locate the target defect, adjust the magnification of the variable-magnification beam expander (30), magnify the target defect, observe the details of the target defect, and use a phase recovery algorithm to obtain the distribution of the magnified target defect, thereby completing the surface defect detection of the large-aperture optical element (01).

7. A method for detecting surface defects of a large-aperture optical element according to claim 6, characterized in that: In step 1, the process of the phase recovery algorithm is as follows: Step A1: Assume that the light field to be measured in front of the binary deformed diffraction grating (40) is , is the assumed initial phase value, which is a set of constants or a set of random numbers. It is a plural unit; make , ; Step A2: using the binary deformed diffraction grating (40) to measure the light field Modulate and calculate the light field after diffraction transmission to the camera (60) , Calculation of Fraunhofer diffraction in the forward direction; Step A3: Maintain the light field The phase part remains unchanged, and the diffraction spot intensity distribution corresponding to the camera (60) is used To update the amplitude part, get the updated light field ; Step A4: Reverse diffraction to update the light field Transmitted to the binary deformed diffraction grating (40), and the phase shift modulation effect is removed to obtain a light field after being updated again ; make , ; judge Is it greater than 1? If so, go to step A5; otherwise, go to step A2; Step A5: Determination Is it less than 1? If so, let , , jump to step A2, otherwise go to step A6; Step A6: Determine the root mean square error Is it less than or equal to If yes, stop the iteration and execute step A7; otherwise, , , jump to step A2; Step A7: Back-diffraction transmission to the preset position of the large-aperture optical element (01) to obtain the background phase , To obtain the angle of the operation, Calculate the inverse angular spectrum.

8. A method for detecting surface defects of a large-aperture optical element according to claim 6 or 7, characterized in that: In step 2, at each scanning position, the phase distribution of the scanning position is calculated by a phase recovery algorithm. The process is as follows: Step B1, assuming that the current light field to be measured in front of the binary deformed diffraction grating (40) is , is the assumed initial phase value, which is a set of constants or a set of random numbers. It is a plural unit; make , ; Step B2: using the binary deformable diffraction grating (40) to measure the current light field Modulate and calculate the light field diffracted and transmitted to the camera (60) , Calculation of Fraunhofer diffraction in the forward direction; Step B3: Maintain the light field The phase part remains unchanged, and the intensity distribution of the diffraction spot corresponding to the camera (60) is To update the amplitude part, get the updated light field ; Step B4: Reverse diffraction to update the light field Transmitted to the binary deformed diffraction grating (40), and the phase shift modulation effect is removed to obtain a light field after being updated again ; make , ; judge Is it greater than 1? If so, go to step B5; otherwise, go to step B2; Step B5: Determination Is it less than 1? If so, let , , jump to step B2, otherwise go to step B6; Step B6: Determine the root mean square error Is it less than or equal to If yes, stop the iteration and execute step B7; otherwise, , , jump to step B2; Step B7: Back-diffracted light is transmitted to the large-aperture optical element (01) to obtain the current scanning position. , To obtain the angle of the operation, Calculate the inverse angular spectrum.

Images