Device and method for measuring surface of optical element

Abstract

The invention discloses an optical element surface measuring device and method. The device comprises a light source module, a motion table, a laser energy monitoring module, a photoelectric detection module, a space triangular focus positioning module, a projection module, a binocular vision module and a processing module. According to the technical scheme, the laser energy monitoring module records laser pulse energy in real time, the photoelectric detection module accurately measures the radius of a focusing light spot, the space triangular focus positioning module accurately positions the focus position, and the projection module projects interference fringes of a periodic structure to the surface of the optical element to be measured. The binocular vision module is used for capturing interference fringe changes, and micro-deformation or damage is judged by combining a phase shift and unwrapping algorithm, so that three-dimensional reconstruction of the micro-deformation and damage morphology of the surface of the optical element is realized. The real-time online measurement of the micro-deformation and the damage threshold of the optical element is realized, and the damage threshold evaluation process is optimized. The method has the advantages of high precision, high real-time performance, high automation degree, wide application range and the like.

Description

Technical Field

[0001] The present invention relates to the field of optical measurement technology, and in particular to an optical element surface measurement device and method. Background Art

[0002] With the widespread application of high-power lasers in scientific research, industrial processing and other fields, the surface quality and damage threshold of optical components have a significant impact on the performance and life of optical systems. Traditional damage threshold measurement methods mainly use offline experiments, static evaluation or optical microscopy to qualitatively analyze surface damage. These methods usually have the following problems:

[0003] 1) Limited measurement accuracy: Traditional methods are not accurate enough to detect small deformations and initial damage on the surface of optical components. They cannot comprehensively evaluate multiple damage mechanisms (such as fatigue, aging, thermal damage, etc.), and it is difficult to detect potential problems in a timely manner. 2) Poor real-time performance: Most methods require the optical components to be removed from the test system for offline measurement, and cannot achieve online, real-time monitoring. 3) Limited scope of application: For optical components with complex shapes or uneven surfaces, traditional methods are difficult to obtain accurate measurement results.

[0004] Therefore, there is an urgent need for a device and method that can measure the micro-deformation and damage threshold of the surface of optical components with high precision, in real time and online. Summary of the invention

[0005] The embodiments of the present invention provide an optical element surface measurement device and method to solve the problems of low measurement accuracy, poor real-time performance and limited application scope in the prior art.

[0006] According to one aspect of the present invention, there is provided an optical element surface measuring device, comprising:

[0007] A light source module, the light source module is used to output a laser beam with adjustable intensity to the optical element to be measured;

[0008] A motion stage, the motion stage is used to carry the optical element to be tested, the slit element or the resolution test board, and is also used to drive the optical element to be tested, the slit element or the resolution test board to move in multiple directions;

[0009] A laser energy monitoring module, the laser energy monitoring module is used to record the energy of each laser pulse emitted by the light source module when the optical element to be tested is tested;

[0010] A photoelectric detection module, wherein the photoelectric detection module is used to measure the radius of the laser focus spot by using a slit method when the slit element is arranged on the moving stage;

[0011] A spatial triangulation focus positioning module, wherein the spatial triangulation focus positioning module is used to locate the spatial coordinates of the optical element to be measured when the motion stage adjusts the spatial position of the optical element to be measured to the focus;

[0012] A projection module, the projection module is used to generate periodic interference fringes and project them onto the surface of the optical element to be measured;

[0013] A binocular vision module, the binocular vision module comprising a first camera and a second camera, the first camera and the second camera are both used to obtain interference fringe images on the surface of the optical element to be measured, wherein the first camera obtains a coaxial light beam and the second camera obtains an off-axis light beam;

[0014] A processing module, wherein the light source module, the motion stage, the laser energy monitoring module, the photoelectric detection module, the spatial triangulation focus positioning module, the projection module and the binocular vision module are all connected to the processing module, and the processing module is used to detect the micro-deformation or damage threshold of the surface of the optical element to be measured according to the interference fringe image;

[0015] The motion stage comprises a self-centering bracket, a rotational angular displacement stage, a Z-axis lifting displacement stage, a first X-axis linear displacement stage and a Y-axis linear displacement stage, wherein the self-centering bracket is used to fix the optical element to be measured, the slit element or the resolution test board, and the rotational angular displacement stage, the Z-axis lifting displacement stage, the first X-axis linear displacement stage and the Y-axis linear displacement stage are used to adjust the rotation angle, Z-direction position, X-direction position and Y-direction position of the optical element to be measured, the slit element or the resolution test board, respectively, wherein the X-axis, the Y-axis and the Z-axis are perpendicular to each other;

[0016] The photoelectric detection module includes a bandpass filter and a photodetector. When the slit element is fixed on the self-centering bracket, the focused light spot is received by the photodetector after passing through the slit of the slit element and the bandpass filter. The first X-axis linear translation stage is used to drive the slit element to move. The processing module is also used to measure the radius of the focused light spot according to the signal of the photodetector.

[0017] Optionally, the light source module includes a first laser, a half-wave plate, a polarization beam splitter, a dichroic mirror and a first focusing lens group, and the first focusing lens group includes at least one focusing lens;

[0018] The output beam of the first laser is incident on the polarization beam splitter after being transmitted through the half-wave plate and split into a first beam and a second beam, the first beam is incident on the laser energy monitoring module, and the second beam is converged to the optical element to be measured after passing through the dichroic mirror and the first focusing lens group;

[0019] Wherein, when the half-wave plate is rotated along the optical axis of the half-wave plate, the intensities of the first light beam and the second light beam are adjusted.

[0020] Optionally, the laser energy monitoring module includes a first energy meter, a second energy meter and a second X-axis linear displacement stage, and the second energy meter is fixed on the second X-axis linear displacement stage;

[0021] The first energy meter is used to receive the first light beam. When calibrating the spectroscopic curve of the output light beam of the first laser, the second X-axis linear translation stage drives the second energy meter to be located in the light path of the second light beam. When measuring the optical element to be measured, the second X-axis linear translation stage drives the second energy meter to be located outside the light path of the second light beam.

[0022] Optionally, the spatial triangulation focus positioning module includes a second laser and a third laser, the outgoing light beams of the second laser and the third laser are obliquely incident on the optical element to be measured, the Z-axis lifting and translation stage, the first X-axis linear translation stage and the Y-axis linear translation stage adjust the spatial position of the optical element to be measured, and the spatial triangulation focus positioning module locates the spatial coordinates of the optical element to be measured according to the triangulation positioning method.

[0023] Optionally, the projection module includes a fourth laser, a linear polarizer, a polarization grating and a second focusing lens group, the second focusing lens group includes at least one focusing lens, the output light beam of the fourth laser generates periodic interference fringes after passing through the linear polarizer and the polarization grating, and the periodic interference fringes converge to the surface of the optical element to be measured through the second focusing lens group.

[0024] Optionally, the processing module includes a motion stage controller, a data synchronization collector and a computer, the motion stage is connected to the motion stage controller, the laser energy monitoring module, the photoelectric detection module and the binocular vision module are all connected to the data synchronization collector, and the motion stage controller and the data synchronization collector are both connected to the computer.

[0025] According to another aspect of the present invention, there is provided a method for measuring the surface of an optical element, which is performed using the above-mentioned optical element surface measuring device, and the optical element measuring method comprises:

[0026] S1. Using a laser energy monitoring module to measure the spectral curve of a light source module;

[0027] S2, placing the slit element on the workbench, and measuring the radius of the laser focus spot by using the slit method through the photoelectric detection module;

[0028] S3, marking the focal position measured by the spatial triangulation focal positioning module, replacing the slit element with a resolution test plate, and performing system parameter calibration and pixel density calibration on the binocular vision module;

[0029] S4, fixing the optical element to be measured on the workbench, adjusting the workbench to position the optical element to be measured to the measured focal position, projecting periodic interference fringes to the optical element to be measured by a projection module, and obtaining the corresponding position and pixel intensity information of the interference fringes reflected from the surface of the optical element to be measured in the world coordinate system by the binocular vision module;

[0030] S5, continuously adjusting the light source module, gradually increasing the laser energy acting on the optical element to be measured, using the laser energy monitoring module to obtain the laser energy acting on the optical element to be measured, obtaining the change of the interference fringes on the surface of the optical element to be measured after the corresponding pulse laser is acted on by the binocular vision module, combining the phase shift algorithm and the unwrapping algorithm to restore the true phase of the interference fringes, and judging whether the optical element to be measured has micro-deformation and damage. If the optical element to be measured has micro-deformation or damage, the output of the light source module is stopped and the deformation morphology or damage morphology and the corresponding threshold value are given;

[0031] S6: Repeat S1 to S5 to implement 1-to-1 and S-to-1 online tests of the damage threshold of the optical element to be tested;

[0032] Wherein, S is an integer greater than 1, and the fringe function after being reflected by the optical element to be measured is expressed as:

[0033] ;

[0034] ;

[0035] in, is the coordinate point on the image plane, is the light intensity of the projection module, b is the fringe amplitude, is the additional phase modulation, and is the phase modulation introduced into the optical element to be measured.

[0036] Optionally, whether the optical element to be tested has micro-deformation and damage is determined according to the following conditions:

[0037] According to the measured phase change and system noise and deformation threshold By comparison, the states of the optical element to be tested are divided into three categories:

[0038] when When , it is determined that the optical element to be measured has not been deformed;

[0039] when When the optical element to be measured is determined to have a slight deformation;

[0040] when When , it is determined that the optical element to be tested exceeds a deformation threshold;

[0041] Before the damage threshold test is performed, multiple interference fringe images of the optical element are collected under the same conditions, and the first image is used as the baseline initial reference state. , calculate the standard deviation of the phase difference at each image point :

[0042] ;

[0043] The system noise is defined as ;

[0044] According to the interference fringe image, as an auxiliary judgment basis, when the interference fringe is distorted but still continuous, it is judged that the optical element to be measured is deformed, and when the interference fringe is broken and discontinuous, it is judged that the optical element to be measured is damaged; the deformation threshold is defined according to the material parameters of the optical element to be measured , the phase change corresponding to the deformation threshold is:

[0045] .

[0046] The optical element surface measuring device provided by an embodiment of the present invention includes: a light source module, a motion platform, a laser energy monitoring module, a photoelectric detection module, a space triangulation focus positioning module, a projection module, a binocular vision module and a processing module, the binocular vision module includes a first camera and a second camera, and the light source module, the motion platform, the laser energy monitoring module, the photoelectric detection module, the space triangulation focus positioning module, the projection module and the binocular vision module are all connected to the processing module. The light source module outputs a laser beam with adjustable intensity to the optical element to be tested; the moving platform carries the optical element to be tested, the slit element or the resolution test board, and drives the optical element to be tested, the slit element or the resolution test board to move in multiple directions; the laser energy monitoring module records the energy of each laser pulse emitted by the light source module during the test of the optical element to be tested; the photoelectric detection module uses the slit method to measure the radius of the laser focus spot when the slit element is set on the moving platform; the spatial coordinates of the optical element to be tested are located when the spatial position of the optical element to be tested is adjusted to the focus on the moving platform by the spatial triangulation focus positioning module; the projection module generates periodic interference fringes and projects them onto the surface of the optical element to be tested; the first camera of the binocular vision module obtains the interference fringes image corresponding to the coaxial light beam, and the second camera obtains the interference fringes image corresponding to the off-axis light beam; the processing module detects the micro-deformation or damage threshold of the surface of the optical element to be tested according to the interference fringes image, so as to solve the problems of low measurement accuracy, poor real-time performance and limited scope of application existing in the prior art.

[0047] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0049] Figure 1 A structural block diagram of an optical element surface measuring device provided by an embodiment of the present invention;

[0050] Figure 2 A schematic structural diagram of an optical element surface measuring device provided by an embodiment of the present invention;

[0051] Figure 3 A schematic diagram of a process for measuring the surface of an optical element provided by an embodiment of the present invention;

[0052] Figure 4A schematic diagram of a slit element provided in an embodiment of the present invention;

[0053] Figure 5 A schematic diagram of a resolution test board provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0054] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0055] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0056] Figure 1 A structural block diagram of an optical element surface measuring device provided by an embodiment of the present invention, Figure 2 A schematic diagram of the structure of an optical element surface measuring device provided by an embodiment of the present invention, referring to Figure 1 and Figure 2 The optical element measuring device comprises: a light source module 100, the light source module 100 is used to output a laser beam with adjustable intensity to the optical element to be measured 6. Optionally, the light source module 100 comprises a first laser 1, a half-wave plate 2, a polarization beam splitter 3, a dichroic mirror 4 and a first focusing lens group 5, the first focusing lens group 5 comprises at least one focusing lens ( Figure 2 A focusing lens is schematically shown in the figure, which is not a limitation of the embodiments of the present invention); the output light beam of the first laser 1 is incident on the polarization beam splitter 3 after being transmitted through the half-wave plate 2 and split into a first light beam a1 and a second light beam b1, the first light beam a1 is incident on the laser energy monitoring module 300, and the second light beam b1 is converged to the optical element to be measured 6 after passing through the dichroic mirror 4 and the first focusing lens group 5; wherein, when the half-wave plate 2 is rotated along the optical axis of the half-wave plate 2, the intensities of the first light beam a1 and the second light beam b1 are adjusted.

[0057] Among them, the first laser 1 can output a laser beam of constant intensity, and the polarization state of the laser beam is changed when the half-wave plate 2 rotates along the optical axis. The polarization beam splitter 3 can be a polarization beam splitter prism PBS, for example, it can transmit horizontal polarized light p and reflect vertical polarized light s, or reflect horizontal polarized light p and transmit vertical polarized light s. When the half-wave plate 2 rotates, the proportions of p light and s light are different, so the intensity of the first light beam a1 and the second light beam b1 can be adjusted.

[0058] The moving platform 200 is used to carry the optical element 6 to be measured, the slit element ( Figure 2 not shown) or resolution test board ( Figure 2 (not shown), and is also used to drive the optical element 6 to be tested, the slit element or the resolution test board to move in multiple directions. Optionally, the motion stage 200 includes a self-centering bracket 7, a rotating angular displacement stage 8, a Z-axis lifting displacement stage 9, a first X-axis linear displacement stage 10 and a Y-axis linear displacement stage 11, the self-centering bracket 7 is used to fix the optical element 6 to be tested, the slit element or the resolution test board, the rotating angular displacement stage 8, the Z-axis lifting displacement stage 9, the first X-axis linear displacement stage 10 and the Y-axis linear displacement stage 11 are respectively used to adjust the rotation angle, Z-direction position, X-direction position and Y-direction position of the optical element 6 to be tested, the slit element or the resolution test board, wherein the X-axis, the Y-axis and the Z-axis are perpendicular to each other.

[0059] Among them, the self-centering bracket 7 is mainly used for centering the optical element. Any optical element can reach the maximum internal diameter of the bracket itself, and can be placed and fixed conveniently, accurately, quickly and repeatedly. The center position is independent of the diameter of the optical element. The rotating angular displacement stage 8 is used to rotate the angle of the optical element 6 to be tested to achieve damage threshold measurement under different incident angles. The Z-axis lifting displacement stage 9, the first X-axis linear displacement stage 10 and the Y-axis linear displacement stage 11 can drive the optical element 6 to be tested, the slit element or the resolution test board to achieve three-dimensional movement, so that the optical element 6 to be tested, the slit element or the resolution test board can reach the preset position.

[0060] The laser energy monitoring module 300 is used to record the energy of each laser pulse emitted by the light source module 100 when the optical element 6 to be tested is tested. Optionally, the laser energy monitoring module 300 includes a first energy meter 12, a second energy meter 13 and a second X-axis linear displacement stage 14, and the second energy meter is fixed on the second X-axis linear displacement stage 14; the first energy meter 12 is used to receive the first light beam a1, when calibrating the spectroscopic curve of the output light beam of the first laser 1, the second X-axis linear displacement stage 14 drives the second energy meter 13 to be located in the optical path of the second light beam b1, and when measuring the optical element 6 to be tested, the second X-axis linear displacement stage 14 drives the second energy meter 13 to be located outside the optical path of the second light beam b1.

[0061] It is understandable that to measure the damage threshold of the optical element 6 to be measured, it is necessary to know the light energy incident on the optical element 6 to be measured, so it is necessary to calibrate the spectroscopic curve of the output light beam of the first laser 1. In specific implementation, the first energy meter 12 always receives the first light beam a1. Before measuring the element 6 to be measured, the second X-axis linear translation stage 14 drives the second energy meter 13 to be located in the optical path of the second light beam b1 ( Figure 2 Indicated by the dotted line in the middle), by rotating the half-wave plate 2, a spectral curve can be obtained according to the measurement values ​​of the first energy meter 12 and the second energy meter 13, and a corresponding relationship between the two can be established. In subsequent measurements, the second X-axis linear translation stage 14 drives the second energy meter 13 to be located outside the optical path of the second light beam b1. It is only necessary to monitor the reading of the first energy meter 12 to accurately calculate the laser energy acting on the optical element 6 to be measured.

[0062] Photoelectric detection module 400, the photoelectric detection module 400 is used to measure the radius of the laser focus spot by using the slit method when the slit element is set on the moving stage 200. Optionally, the photoelectric detection module 400 includes a bandpass filter 15 and a photodetector 16. When the slit element is fixed on the self-centering bracket 7, the focus spot passes through the slit of the slit element and the bandpass filter 15 and is received by the photodetector 16. The first X-axis linear translation stage 10 is used to drive the slit element to move. The processing module 800 is also used to measure the radius of the focus spot according to the signal of the photodetector 16.

[0063] The bandpass filter 15 is used to filter out light of non-working wavelengths to ensure that the photodetector 16 receives only the target laser signal. The slit method is used to move the position of the slit element using the first X-axis linear translation stage 10. Each time a part of the light beam of the focused light spot passes through the slit, the light intensity signal of the photodetector 16 is recorded to obtain a light spot intensity distribution curve. The radius of the focused light spot is calculated using curve fitting.

[0064] The spatial triangulation focus positioning module 500 is used to locate the spatial coordinates of the optical element 6 to be measured when the motion stage 200 adjusts the spatial position of the optical element 6 to be measured to the focus. Optionally, the spatial triangulation focus positioning module 500 includes a second laser 17 and a third laser 18, the outgoing light beams of the second laser 17 and the third laser 18 are obliquely incident on the optical element 6 to be measured, the Z-axis lifting and displacement stage 9, the first X-axis linear displacement stage 10 and the Y-axis linear displacement stage 11 adjust the spatial position of the optical element 6 to be measured, and the spatial triangulation focus positioning module 500 locates the spatial coordinates of the optical element 6 to be measured according to the triangulation positioning method.

[0065] The second laser 17 and the third laser 18 can both be semiconductor lasers, and their inclination angles can be designed according to actual conditions, which are not limited in the embodiment of the present invention. By adjusting the Z-axis lifting and displacement stage 9, the first X-axis linear displacement stage 10 and the Y-axis linear displacement stage 11, the two laser beams are made to overlap on the surface of the optical element 6 to be measured, thereby achieving accurate positioning of the focal position.

[0066] The projection module 600 is used to generate periodic interference fringes and project them onto the surface of the optical element 6 to be measured. Optionally, the projection module 600 includes a fourth laser 21, a linear polarizer 22, a polarization grating 23, and a second focusing lens group 24, wherein the second focusing lens group 24 includes at least one focusing lens ( Figure 2 A focusing lens is schematically shown in the figure, which is not a limitation of the embodiments of the present invention). The output light beam of the fourth laser 21 generates periodic interference fringes after passing through the linear polarizer 22 and the polarization grating 23. The periodic interference fringes are converged to the surface of the optical element 6 to be measured through the second focusing lens group 24.

[0067] Among them, the wavelengths of the output light beam of the first laser 1 and the output light beam of the fourth laser 21 can be set to be different. The output light beam of the first laser 1 is transmitted when passing through the dichroic mirror 4, thereby being incident on the optical element to be measured 6, and the output light beam of the fourth laser 21 is reflected when passing through the dichroic mirror 4, thereby making the interference fringe light beam reflected by the optical element to be measured 6 be incident on the first camera 19.

[0068] Binocular vision module 700, the binocular vision module 700 includes a first camera 19 and a second camera 20, both of which are used to obtain interference fringe images on the surface of the optical element 6 to be measured, wherein the first camera 19 obtains a coaxial light beam, and the second camera 20 obtains an off-axis light beam. In specific implementation, the second camera 20 can be set at 45°, that is, the angle between the optical axis of the second camera 20 and the optical axis of the second light beam b1 is 45°. The first camera 19 and the second camera 20 can both be CMOS cameras. The binocular vision module 700 collects the interference fringe image on the surface of the optical element 6 to be measured by the first camera 19 at a coaxial angle with the incident laser, and collects the interference fringe image on the surface of the optical element 6 to be measured by the second camera 20 at an angle of 45°, and combines the phase deflection algorithm to achieve three-dimensional reconstruction of small deformations or damages on the surface of the optical element.

[0069] The processing module 800, the light source module 100, the motion stage 200, the laser energy monitoring module 300, the photoelectric detection module 400, the spatial triangulation focus positioning module 500, the projection module 600 and the binocular vision module 700 are all connected to the processing module 800 ( Figure 2The processing module 800 is used to detect the micro deformation or damage threshold of the surface of the optical element 6 to be tested according to the interference fringe image. Optionally, the processing module 800 includes a motion stage controller 25, a data synchronization collector 26 and a computer 27, the motion stage 200 is connected to the motion stage controller 25, the laser energy monitoring module 300, the photoelectric detection module 400 and the binocular vision module 700 are all connected to the data synchronization collector 26, and the motion stage controller 25 and the data synchronization collector 26 are all connected to the computer 27.

[0070] Specifically, the rotating angular displacement stage 8, the Z-axis lifting displacement stage 9, the first X-axis linear displacement stage 10, the Y-axis linear displacement stage 11, and the second X-axis linear displacement stage 14 are all connected to the motion stage controller 25, which is used to accurately control the rotating angular displacement stage 8, the Z-axis lifting displacement stage 9, the first X-axis linear displacement stage 10, the Y-axis linear displacement stage 11, and the second X-axis linear displacement stage 14, so as to achieve accurate positioning of the optical element 6 to be measured in three-dimensional space. The first energy meter 12, the second energy meter 13, the photoelectric detector 16, the first camera 19, and the second camera 20 are all connected to the data synchronization collector 26, which is used to synchronously collect data from the energy meter, the photoelectric detector, and the CMOS camera to ensure the consistency of the data of each module in time. The motion stage controller 25 and the data synchronization collector 26 are both connected to the computer 27, which are used to control the entire measurement process, process and analyze the collected data in real time, and generate a three-dimensional morphology and damage report of the optical element.

[0071] The technical solution of the embodiment of the present invention records the laser pulse energy in real time through the laser energy monitoring module, accurately measures the radius of the focusing spot through the photoelectric detection module, accurately locates the focus position through the spatial triangulation focus positioning module, projects the periodic structure interference fringes onto the surface of the optical element to be measured through the projection module, captures the changes in the interference fringes using the binocular vision module, combines the phase shift and unwrapping algorithm to judge micro-deformation or damage, and realizes three-dimensional reconstruction of the micro-deformation and damage morphology of the optical element surface. Real-time online measurement of micro-deformation and damage threshold of optical elements is realized, and the damage threshold evaluation process is optimized. The present invention has the advantages of high precision, strong real-time performance, high degree of automation and wide range of application.

[0072] Figure 3 A schematic flow chart of a method for measuring the surface of an optical element provided in an embodiment of the present invention. The method for measuring the surface of an optical element is performed using the optical element surface measuring device provided in the above embodiment. Figure 2 and Figure 3 , the optical element measurement method comprises:

[0073] S1. Use the laser energy monitoring module to measure the spectral curve of the light source module.

[0074] The process of the spectral curve measurement step includes: starting the first laser 1, changing the polarization state of the laser by adjusting the rotation angle of the half-wave plate 2, and then controlling the spectral ratio after passing through the polarization beam splitter 3. Recording the readings of the first energy meter 12 and the second energy meter 13 at different angles of the half-wave plate 2. Plotting the spectral curve between the first energy meter 12 and the second energy meter 13, and establishing the corresponding relationship between the two. In subsequent measurements, it is only necessary to monitor the reading of the first energy meter 12 to accurately calculate the laser energy acting on the optical element 6 to be measured.

[0075] S2. Place the slit element on a workbench and measure the radius of the laser focus spot using the slit method through a photoelectric detection module.

[0076] The process of the focus spot radius measurement step includes: removing the optical element 6 to be measured from the self-centering bracket 7 and replacing it with a slit element. Starting the photoelectric detection module 400, the bandpass filter 15 filters out the light of non-working wavelengths to ensure that the photoelectric detector 16 only receives the target laser signal. Using the slit method, the position of the slit is moved, and the light intensity signal of the photoelectric detector 16 is recorded to obtain the spot intensity distribution curve. Using curve fitting, the radius of the focus spot is calculated.

[0077] S3. Mark the focal position measured by the spatial triangulation focus positioning module, replace the slit element with a resolution test board, and perform system parameter calibration and pixel density calibration on the binocular vision module.

[0078] The process of the system parameter calibration and pixel density calibration step includes: using the spatial triangulation focus positioning module 500, adjusting the Z-axis lifting and displacement stage 9, the first X-axis linear displacement stage 10 and the Y-axis linear displacement stage 11, so that the laser beams emitted by the second laser 17 and the third laser 18 overlap at the slit position of the slit element, and accurately positioning the focus position. The slit element is replaced with a standard resolution test plate with a pattern of known size and shape. Exemplarily, Figure 4 A schematic diagram of a slit element provided in an embodiment of the present invention, Figure 5 Schematic diagram of a resolution test board provided in an embodiment of the present invention. The binocular vision module 700 is started, and the image of the resolution test board is collected by the first camera 19 and the second camera 20 respectively. The image is processed by the computer 27, the internal and external parameters of the camera are calculated, and the relationship between the pixel density and the spatial coordinates is calibrated.

[0079] S4. Fix the optical element to be measured on a workbench, adjust the workbench to position the optical element to be measured to the measured focal position, use the projection module to project periodic interference fringes to the optical element to be measured, and obtain the corresponding position and pixel intensity information of the interference fringes reflected from the surface of the optical element to be measured in the world coordinate system through the binocular vision module.

[0080] The specific process of this step includes: mounting the optical element 6 to be measured on the self-centering bracket 7 and placing it on the rotating angular displacement stage 8. Adjusting the rotating angular displacement stage 8 to set the required incident angle to meet different experimental conditions. Using the motion stage controller 25 to accurately control the Z-axis lifting displacement stage 9, the first X-axis linear displacement stage 10 and the Y-axis linear displacement stage 11, the optical element 6 to be measured is positioned at the focal position determined by the spatial triangulation focus positioning module 500. Start the projection module 600, and the laser emitted by the fourth laser 21 is processed by the linear polarizer 22 and the polarization grating 23 to form a structured light with sinusoidal periodicity, which is projected onto the surface of the optical element 6 to be measured through the second focusing lens group 24 to generate interference fringes. The first camera 19 and the second camera 20 of the binocular vision module 700 simultaneously capture interference fringe images on the surface of the optical element 6 to be measured from different angles.

[0081] S5. Continuously adjust the light source module to gradually increase the laser energy applied to the optical element to be tested. Use the laser energy monitoring module to obtain the laser energy applied to the optical element to be tested. Use the binocular vision module to obtain the change of the interference fringes on the surface of the optical element to be tested after the corresponding pulse laser is applied. Combine the phase shift algorithm and the unwrapping algorithm to restore the true phase of the interference fringes and determine whether the optical element to be tested is slightly deformed or damaged. If the optical element to be tested is slightly deformed or damaged, stop the output of the light source module and give the deformation morphology or damage morphology and the corresponding threshold.

[0082] Among them, the fringe function after reflection from the optical element to be measured is expressed as:

[0083] ;

[0084] ;

[0085] in, is the coordinate point on the image plane, is the light intensity of the projection module, b is the fringe amplitude, is the additional phase modulation, which is the phase modulation introduced by the optical element to be measured.

[0086] The specific process of this step includes: by gradually increasing the laser energy, monitoring the micro-deformation and damage of the optical element 6 to be tested in real time, and determining its damage threshold. Continuously adjust the angle of the half-wave plate 2 to gradually increase the laser energy acting on the optical element 6 to be tested. After each adjustment, wait for the system to stabilize. Use the first energy meter 12 to record the transmitted energy in real time, and calculate the laser energy actually acting on the optical element 6 to be tested based on the spectral curve of S1. After each laser pulse, the binocular vision module 700 synchronously collects the interference fringe image on the surface of the optical element 6 to be tested. The data synchronization collector 26 ensures the temporal consistency of the data of the energy meter and the camera. Use the phase shift algorithm and the unwrapping algorithm to process the collected interference fringe image to restore the true phase distribution. Phase change It reflects the slight deformation of the surface of the optical element to be measured. The phase difference is calculated to generate a three-dimensional morphology map of the optical element to be measured 6. By comparing the morphology changes under different energies, it is determined whether micro-deformation or damage occurs. If the phase change is within the system noise range, it is determined that the optical element to be measured has not been deformed, and the laser energy continues to be increased; if a slight phase change is detected, but there is no obvious damage on the surface, the corresponding laser energy is recorded as the deformation threshold; if the phase change is significant, and an abnormality appears in the interference fringe image, such as fringe breakage, distortion, etc., it is determined that the optical element to be measured is damaged. The system automatically stops the output of the first laser 1 to avoid further damage. The computer 27 records the deformation or damage morphology, as well as the corresponding laser energy and position information, and generates a detailed damage report.

[0087] S6: Repeat S1 to S5 to implement 1-to-1 and S-to-1 online tests of the damage threshold of the optical element to be tested.

[0088] Wherein, S is an integer greater than 1. This step includes: repeating the test, replacing the optical element 6 to be tested, repeating S1 to S5, and measuring the damage thresholds of different optical elements. Summarizing all test results, analyzing the overall performance and quality of the optical element to be tested.

[0089] Optionally, whether the optical element to be tested has micro deformation and damage is determined according to the following conditions:

[0090] According to the measured phase change and system noise and deformation threshold By comparing the status of the optical components to be tested, the status of the optical components to be tested can be divided into three categories:

[0091] when When , it is determined that the optical element to be tested has not been deformed;

[0092] when When , it is determined that a slight deformation has occurred in the optical element to be tested;

[0093] when When , it is determined that the optical element to be tested exceeds the deformation threshold;

[0094] Before the damage threshold test, multiple interference fringe images of the optical element are collected under the same conditions, and the first image is used as the baseline initial reference state. , calculate the standard deviation of the phase difference at each image point :

[0095] ;

[0096] The system noise is defined as ;

[0097] According to the interference fringe image, as an auxiliary judgment basis, when the interference fringe is distorted but still continuous, it is judged that the optical element to be tested is deformed; when the interference fringe is broken and discontinuous, it is judged that the optical element to be tested is damaged; different coating materials and substrate materials have different sensitivity and tolerance to deformation, and the deformation threshold is defined according to the material parameters of the optical element to be tested. , the phase change corresponding to the deformation threshold is:

[0098] .

[0099] The technical solution of the embodiment of the present invention has the following effects:

[0100] 1) Real-time online measurement to improve detection efficiency:

[0101] The embodiment of the present invention can monitor the surface damage process of optical components under high-energy laser irradiation in real time, avoiding the hysteresis of traditional offline measurement methods. Real-time online measurement enables users to obtain damage information of optical components in a timely manner and respond quickly, thereby improving detection efficiency and productivity.

[0102] 2) Real-time monitoring and verification of laser energy to ensure energy stability:

[0103] The laser energy detection module monitors the energy of each laser pulse in real time and verifies the spectroscopic curve. Real-time monitoring and verification of energy ensures the stability of laser output, reduces measurement errors caused by energy fluctuations, and improves the accuracy of damage threshold measurement.

[0104] 3) Accurately measure the spot radius and accurately evaluate the damage threshold:

[0105] Through the slit method and photoelectric detection module, bandpass filters and photoelectric detectors are used to accurately measure the radius of the laser focus spot. Accurate measurement of the spot radius is crucial for calculating the light intensity distribution and evaluating the damage threshold of optical components, which improves the accuracy and reliability of the measurement results.

[0106] 4) Precise focus positioning to adapt to uneven samples:

[0107] By introducing the spatial triangulation focus positioning module, the laser focus position can be accurately positioned. Even for special-shaped optical components with uneven surfaces, precise focus positioning and measurement can be achieved, expanding the scope of application of the device.

[0108] 5) Automatic protection mechanism to prevent excessive damage to samples:

[0109] When the photoelectric detection module detects a significant step in the laser signal (damage to the surface of the optical element), the system can automatically stop the laser output to prevent excessive damage to the sample.

[0110] 6) Highly sensitive micro-damage detection and three-dimensional reconstruction:

[0111] The projection module and binocular vision module can detect tiny deformations and damages on the surface of optical components with high sensitivity, and realize three-dimensional reconstruction of the damaged area, providing data support for in-depth analysis of damage mechanisms and optimization of optical component design.

[0112] 7) Multi-angle incident measurement to meet diverse testing needs:

[0113] By adjusting the rotation angle stage, the damage threshold measurement under different incident angles can be achieved. The damage characteristics of optical components under different incident angles may be different. The embodiments of the present invention can meet the needs of users for a variety of test conditions and provide the possibility for comprehensive evaluation of the performance of optical components.

[0114] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An optical element surface measuring device, characterized in that: include: A light source module, the light source module is used to output a laser beam with adjustable intensity to the optical element to be measured; A motion stage, the motion stage is used to carry the optical element to be tested, the slit element or the resolution test board, and is also used to drive the optical element to be tested, the slit element or the resolution test board to move in multiple directions; A laser energy monitoring module, the laser energy monitoring module is used to record the energy of each laser pulse emitted by the light source module when the optical element to be tested is tested; A photoelectric detection module, wherein the photoelectric detection module is used to measure the radius of the laser focus spot by using a slit method when the slit element is arranged on the moving stage; A spatial triangulation focus positioning module, wherein the spatial triangulation focus positioning module is used to locate the spatial coordinates of the optical element to be measured when the motion stage adjusts the spatial position of the optical element to be measured to the focus; A projection module, the projection module is used to generate periodic interference fringes and project them onto the surface of the optical element to be measured; A binocular vision module, the binocular vision module comprising a first camera and a second camera, the first camera and the second camera are both used to obtain interference fringe images on the surface of the optical element to be measured, wherein the first camera obtains a coaxial light beam and the second camera obtains an off-axis light beam; A processing module, wherein the light source module, the motion stage, the laser energy monitoring module, the photoelectric detection module, the spatial triangulation focus positioning module, the projection module and the binocular vision module are all connected to the processing module, and the processing module is used to detect the micro-deformation or damage threshold of the surface of the optical element to be measured according to the interference fringe image; The motion stage comprises a self-centering bracket, a rotational angular displacement stage, a Z-axis lifting displacement stage, a first X-axis linear displacement stage and a Y-axis linear displacement stage, wherein the self-centering bracket is used to fix the optical element to be measured, the slit element or the resolution test board, and the rotational angular displacement stage, the Z-axis lifting displacement stage, the first X-axis linear displacement stage and the Y-axis linear displacement stage are used to adjust the rotation angle, Z-direction position, X-direction position and Y-direction position of the optical element to be measured, the slit element or the resolution test board, respectively, wherein the X-axis, the Y-axis and the Z-axis are perpendicular to each other; The photoelectric detection module includes a bandpass filter and a photodetector. When the slit element is fixed on the self-centering bracket, the focused light spot is received by the photodetector after passing through the slit of the slit element and the bandpass filter. The first X-axis linear translation stage is used to drive the slit element to move. The processing module is also used to measure the radius of the focused light spot according to the signal of the photodetector.

2. The optical element surface measuring device according to claim 1, characterized in that: The light source module comprises a first laser, a half-wave plate, a polarization beam splitter, a dichroic mirror and a first focusing lens group, wherein the first focusing lens group comprises at least one focusing lens; The output beam of the first laser is incident on the polarization beam splitter after being transmitted through the half-wave plate and split into a first beam and a second beam, the first beam is incident on the laser energy monitoring module, and the second beam is converged to the optical element to be measured after passing through the dichroic mirror and the first focusing lens group; Wherein, when the half-wave plate is rotated along the optical axis of the half-wave plate, the intensities of the first light beam and the second light beam are adjusted.

3. The optical element surface measuring device according to claim 2, characterized in that: The laser energy monitoring module comprises a first energy meter, a second energy meter and a second X-axis linear translation stage, wherein the second energy meter is fixed on the second X-axis linear translation stage; The first energy meter is used to receive the first light beam. When calibrating the spectroscopic curve of the output light beam of the first laser, the second X-axis linear translation stage drives the second energy meter to be located in the light path of the second light beam. When measuring the optical element to be measured, the second X-axis linear translation stage drives the second energy meter to be located outside the light path of the second light beam.

4. The optical element surface measuring device according to claim 1, characterized in that: The spatial triangulation focus positioning module comprises a second laser and a third laser, the outgoing light beams of the second laser and the third laser are incident on the optical element to be measured at an angle, the Z-axis lifting and translation stage, the first X-axis linear translation stage and the Y-axis linear translation stage adjust the spatial position of the optical element to be measured, and the spatial triangulation focus positioning module locates the spatial coordinates of the optical element to be measured according to the triangulation positioning method.

5. The optical element surface measuring device according to claim 1, characterized in that: The projection module includes a fourth laser, a linear polarizer, a polarization grating and a second focusing lens group, the second focusing lens group includes at least one focusing lens, the output light beam of the fourth laser generates periodic interference fringes after passing through the linear polarizer and the polarization grating, and the periodic interference fringes converge to the surface of the optical element to be measured through the second focusing lens group.

6. The optical element surface measuring device according to claim 1, characterized in that: The processing module includes a motion stage controller, a data synchronization collector and a computer. The motion stage is connected to the motion stage controller. The laser energy monitoring module, the photoelectric detection module and the binocular vision module are all connected to the data synchronization collector. The motion stage controller and the data synchronization collector are both connected to the computer.

7. A method for measuring the surface of an optical element, characterized in that: The optical element surface measuring method is performed using the optical element surface measuring device according to any one of claims 1 to 6, and the optical element measuring method comprises: S1. Using a laser energy monitoring module to measure the spectral curve of a light source module; S2, placing the slit element on the workbench, and measuring the radius of the laser focus spot by using the slit method through the photoelectric detection module; S3, marking the focal position measured by the spatial triangulation focal positioning module, replacing the slit element with a resolution test plate, and performing system parameter calibration and pixel density calibration on the binocular vision module; S4, fixing the optical element to be measured on the workbench, adjusting the workbench to position the optical element to be measured to the measured focal position, projecting periodic interference fringes to the optical element to be measured by a projection module, and obtaining the corresponding position and pixel intensity information of the interference fringes reflected from the surface of the optical element to be measured in the world coordinate system by the binocular vision module; S5, continuously adjusting the light source module, gradually increasing the laser energy acting on the optical element to be measured, using the laser energy monitoring module to obtain the laser energy acting on the optical element to be measured, obtaining the change of the interference fringes on the surface of the optical element to be measured after the corresponding pulse laser is acted on by the binocular vision module, combining the phase shift algorithm and the unwrapping algorithm to restore the true phase of the interference fringes, and judging whether the optical element to be measured has micro-deformation and damage. If the optical element to be measured has micro-deformation or damage, the output of the light source module is stopped and the deformation morphology or damage morphology and the corresponding threshold value are given; S6: Repeat S1 to S5 to implement 1-to-1 and S-to-1 online tests of the damage threshold of the optical element to be tested; Wherein, S is an integer greater than 1, and the fringe function after being reflected by the optical element to be measured is expressed as: ； ； in, is the coordinate point on the image plane, is the light intensity of the projection module, b is the fringe amplitude, is the additional phase modulation, is the phase modulation introduced into the optical element to be measured.

8. The optical element surface measurement method according to claim 7, characterized in that: Whether the optical element to be tested has micro deformation and damage is determined according to the following conditions: According to the measured phase change and system noise and deformation threshold By comparison, the states of the optical element to be tested are divided into three categories: when When , it is determined that the optical element to be measured has not been deformed; when When the optical element to be measured is determined to have undergone a slight deformation; when When , it is determined that the optical element to be tested exceeds a deformation threshold; Before the damage threshold test is performed, multiple interference fringe images of the optical element are collected under the same conditions, and the first image is used as the baseline initial reference state. , calculate the standard deviation of the phase difference at each image point : ； The system noise is defined as ; According to the interference fringe image, as an auxiliary judgment basis, when the interference fringe is distorted but still continuous, it is judged that the optical element to be measured is deformed, and when the interference fringe is broken and discontinuous, it is judged that the optical element to be measured is damaged; the deformation threshold is defined according to the material parameters of the optical element to be measured , the phase change corresponding to the deformation threshold is: 。

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