System and method for comprehensively detecting convex aspheric surface through CGH and reflector

Abstract

The invention discloses a system and a method for comprehensively detecting a convex aspheric surface through a CGH and a reflector. According to the high-precision detection device and method for the large-aperture convex aspheric surface, the CGH and the auxiliary reflector are combined with the sub-aperture splicing technology, only one-time reflection of the auxiliary reflector is needed, the requirement for the surface shape precision of the auxiliary reflector is lowered, and the reflector manufacturing possibility is improved. The auxiliary reflecting mirror is obliquely arranged, so that the problem that the central area of a full-aperture optical element cannot be measured and the problem that a hole needs to be formed in the center when a traditional Hindle ball is used for auxiliary detection are solved. And the auxiliary reflecting mirror can be a plane reflecting mirror, so that the problem that an auxiliary hindle ball is difficult to manufacture can be avoided. In addition, by adopting the sub-aperture splicing technology, the manufacturing difficulty of the CGH and the auxiliary reflecting mirror is reduced. The invention provides a detection device easy to operate and a data processing method for high-precision detection of the large-aperture convex aspheric surface.

Description

Technical Field

[0001] The invention belongs to the technical field of advanced optical manufacturing and detection, and in particular relates to a system and method for comprehensive detection of convex aspheric surfaces using CGH and a reflector. Background Art

[0002] With the development of science and technology, large-aperture rotationally symmetric convex aspheric components have become an indispensable and important part of high-performance optical systems due to their unique imaging characteristics and wide application requirements. Such components are widely used in semiconductors, aerospace, national defense, astronomical observation, precision measurement and other fields, and have a vital impact on the performance of optical systems. However, with the increasing precision requirements for aspheric components, their processing and detection technologies are also facing huge challenges.

[0003] Traditional large-aperture aspheric surface detection technologies, such as interferometer direct measurement, are limited by the interferometer's lens field of view and measurement accuracy, making it difficult to directly perform high-precision measurements on large-aperture aspheric surfaces as a whole. In addition, due to the complex surface profile of aspheric components, direct measurement often results in large measurement errors, affecting the iteration of the optical manufacturing process and the final optical system performance. Therefore, how to achieve high-precision and high-efficiency detection of large-aperture rotationally symmetric convex aspheric surfaces has become an urgent problem to be solved.

[0004] Computer generated hologram (CGH) can compensate the aberration of the aspheric element to be measured, thereby achieving high-precision measurement of the aspheric surface.

[0005] For example, the invention application with publication number CN114252023A discloses a computer-aided adjustment device and method for aspheric computer holographic detection, in which a phase-shifting interferometer is installed on a marble beam; the computer hologram is fixed to the phase-shifting interferometer through a holographic adjustment frame, and the computer hologram is adjusted through the holographic adjustment frame; the measuring platform composed of a detection tooling, an axial displacement table and a tilt adjustment table is installed on a lifting device connected to a marble base, and the spatial posture of the aspheric component to be measured during the measurement process is monitored in real time through two vertically installed autocollimator angle measurement systems; the computer system is connected to the phase-shifting interferometer to collect the surface shape information of the aspheric surface to be measured; the required adjustment amount of the aspheric surface to be measured is obtained by analyzing the collected surface shape information, and the position adjustment table is controlled to quantitatively adjust the aspheric surface according to the autocollimator detection data to achieve accurate adjustment of the detection optical path.

[0006] However, for large-aperture aspheric elements, the field of view of a single CGH is still limited and cannot cover the entire element surface.

[0007] The invention application with the publication number CN118224996A discloses a detection method for a spliced ​​CGH semi-compensated detection of a large-aperture non-continuous aspheric surface. A detection method for a spliced ​​CGH semi-compensated detection of a large-aperture non-continuous aspheric surface is proposed for a large-aperture non-continuous aspheric reflector. The detection device composed of a laser interferometer, a mirror to be inspected and a CGH is used to realize the conversion from a spherical wave to an aspheric wave and the acquisition of the full-aperture surface shape information of the mirror to be inspected. The non-continuous aspheric surface is fitted according to two non-continuous aspheric surface equations, and a fitting aspheric surface is designed. The CGH is designed according to the fitting aspheric surface. If the line density of the CGH is too high, the coefficient of the fitting aspheric surface is changed until the CGH fringe density meets the requirement, and the best fitting aspheric surface is obtained. The prior art can only detect concave surfaces, but not convex surfaces. Moreover, the prior art detects non-continuous aspheric surfaces, and the actual problem solved is that a relatively obvious step will appear at the junction of two non-spherical surfaces for the non-continuous aspheric surface, and is not suitable for continuous convex aspheric surface detection. Summary of the invention

[0008] In view of the above-mentioned deficiencies in the prior art, the present invention provides a system and method for comprehensive detection of convex aspheric surfaces by using CGH and reflectors. The sub-aperture areas are reasonably divided by a computer control system, the aberration of the aspheric surface to be measured is compensated by using CGH, and the light is reflected by an auxiliary reflector to achieve high-precision measurement of each sub-aperture area. The rotation function of the translation stage can conveniently achieve the measurement of each sub-aperture, and the full-aperture surface information can be obtained by data splicing processing. This method not only improves the measurement accuracy and efficiency, but also simplifies the data processing process, providing a new solution for high-precision detection of large-aperture convex aspheric surfaces.

[0009] The present invention first provides a method for comprehensively detecting a convex aspheric surface using a CGH and a reflector, comprising the following steps:

[0010] (1) dividing the convex aspheric surface to be measured into a plurality of sub-aperture regions, each sub-aperture region having an overlapping region with at least one of the other sub-aperture regions;

[0011] (2) Detection is performed using an interferometer, a computer-generated hologram, and an auxiliary reflector, wherein the interferometer includes a lens,

[0012] First, the first sub-aperture area is tested, and the interference pattern of the first sub-aperture area is made to present a zero-fringe state by adjusting the positions of the convex aspheric surface to be tested, the computational hologram, and the auxiliary reflector, and the surface shape data of the first sub-aperture area is collected;

[0013] (3) Repeat step (2) to detect the remaining sub-aperture areas in turn and collect surface shape data of the remaining sub-aperture areas;

[0014] (4) Using a stitching algorithm, the surface shape data of each sub-aperture area is stitched together to obtain the complete surface shape data of the convex aspheric surface to be measured.

[0015] Preferably, in step (1), the area of ​​the overlapping region in each sub-aperture region is 20% to 30% of the total area of ​​the sub-aperture region.

[0016] Preferably, in step (2), the convex aspheric surface to be measured is rotationally symmetric or non-rotationally symmetric. If it is rotationally symmetric, each sub-aperture area on the circumference has the same surface shape, and the same computational hologram can be used. If it is non-rotationally symmetric, it is necessary to design a corresponding computational hologram for each sub-aperture area. Of course, if the surface shapes of two sub-aperture areas are the same, the same computational hologram can be used for these two sub-aperture areas with the same surface shape.

[0017] Preferably, in step (2), the computer-generated hologram uses Bianry2 surface type, binary phase hologram, diffraction -1 order, and the computer-generated hologram is designed based on ray tracing optimization. The design results are as follows: the phase etching depth is 2μm, the duty cycle is 0.5, the minimum fringe period is 20μm, the substrate material is fused quartz, and the computer-generated hologram is produced using laser direct writing technology.

[0018] Preferably, in step (4), during the splicing, a discrete phase-based splicing algorithm is used, with the principle of minimizing the error in the overlapping area.

[0019] The present invention further provides a system for comprehensively detecting convex aspheric surfaces using a CGH and a reflector, comprising:

[0020] Mounting frame;

[0021] An interferometer, disposed on the mounting frame, comprising a lens;

[0022] Computational holography;

[0023] A computer-generated hologram adjustment frame, used for placing the computer-generated hologram and adjusting the position and angle of the computer-generated hologram;

[0024] An auxiliary reflector, used for reflecting light, and reflecting the light to between the convex aspheric surface to be measured and the interferometer, so as to assist in realizing interference detection;

[0025] An auxiliary reflector adjustment frame, used for placing the auxiliary reflector and adjusting the position and angle of the auxiliary reflector;

[0026] The translation stage is used to place the convex aspheric surface to be measured, and the translation stage can move in the three directions of X, Y, and Z in the global coordinate system and rotate around the X, Y, and Z axes.

[0027] Preferably, the shape parameters of the convex aspheric surface to be measured are arbitrary curvature and aperture; the convex aspheric surface to be measured is a transmissive optical element or a reflective optical element.

[0028] The interferometer has selection criteria for the lens and component curvature, and the interferometer and the corresponding lens that can be used for detection are selected according to the component curvature range that the lens can match.

[0029] Preferably, the CGH adjustment frame can adjust the CGH to move in the Z direction in the global coordinate system;

[0030] The auxiliary reflector adjustment frame can adjust the auxiliary reflector to move in the Z direction in the global coordinate system.

[0031] Preferably, the translation platform is mounted on a vibration isolation base.

[0032] Preferably, the translation platform comprises a six-degree-of-freedom guide rail or a six-degree-of-freedom robot.

[0033] Beneficial effects of the present invention:

[0034] The present invention proposes a high-precision detection device and method for large-aperture convex aspheric surfaces based on CGH and auxiliary reflectors combined with sub-aperture stitching technology. In the present invention, only one reflection of the auxiliary reflector is required, which reduces the requirements for the surface accuracy of the auxiliary reflector and improves the possibility of reflector manufacturing. The tilted placement of the auxiliary reflector avoids the problem that the central area of ​​the full-aperture optical element cannot be measured, and the problem that the traditional Hindle ball needs a central opening for auxiliary detection. And the auxiliary reflector can be a plane reflector to avoid the problem that the auxiliary Hindle ball is difficult to manufacture. In addition, the use of sub-aperture stitching technology reduces the difficulty of manufacturing CGH and auxiliary reflectors. The present invention provides an easy-to-operate detection device and data processing method for high-precision detection of large-aperture convex aspheric surfaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the system structure of the CGH and reflector for comprehensive detection of convex aspheric surfaces of the present invention.

[0036] Figure 2 Schematic diagram of the structure of the translation stage.

[0037] Figure 3 It is a schematic diagram of the method for comprehensively detecting convex aspheric surfaces using CGH and a reflector according to the present invention.

[0038] Figure 4 Schematic diagram of convex aspheric sub-aperture division, data collection and stitching.

[0039] Figure 5 A flow chart of the system and method for comprehensively detecting convex aspheric surfaces using CGH and reflectors of the present invention.

[0040] Figure numerals: mounting frame 1, interferometer 2, interferometer power supply 3, interferometer controller 4, computer-generated hologram 5, computer-generated hologram adjustment frame 6, computer-generated hologram adjustment frame power supply 7, computer-generated hologram adjustment frame controller 8, auxiliary reflector 9, auxiliary reflector adjustment frame 10, auxiliary reflector adjustment frame power supply 11, auxiliary reflector adjustment frame controller 12, convex aspheric surface to be measured 13, displacement stage 14, displacement stage power supply 15, displacement stage controller 16, vibration isolation base 17, computer control system 18. DETAILED DESCRIPTION

[0041] like Figures 1 to 4 As shown, a system for comprehensively detecting convex aspheric surfaces using CGH and reflectors includes a mounting frame 1, an interferometer 2, an interferometer power supply 3, an interferometer controller 4, a computer-generated hologram 5, a computer-generated hologram adjustment frame 6, a computer-generated hologram adjustment frame power supply 7, a computer-generated hologram adjustment frame controller 8, an auxiliary reflector 9, an auxiliary reflector adjustment frame 10, an auxiliary reflector adjustment frame power supply 11, an auxiliary reflector adjustment frame controller 12, a convex aspheric surface to be measured 13, a displacement stage 14, a displacement stage power supply 15, a displacement stage controller 16, a vibration isolation base 17, and a computer control system 18.

[0042] Interferometer 2 is arranged on mounting frame 1, and interferometer 2 includes a lens. The lens used in interferometer 2 has a certain applicable range for the curvature range of the element to be detected, so a suitable lens can be selected according to the approximate situation of the curvature range of the element to be detected. At the same time, the lens will also affect the size of the sub-aperture that can be measured. CGI adjustment frame 6 is arranged on mounting frame 1, and CGI adjustment frame 6 is used to place CGI 5 and adjust the position and angle of CGI 5. CGI adjustment frame 6 can adjust the movement of CGI 5 in the Z direction in the global coordinate system.

[0043] The auxiliary reflector 9 is used to reflect the light, and reflects the light to between the convex aspheric surface 13 to be measured and the interferometer 2, so as to assist in the interference detection. Figure 3 A schematic diagram of detecting light is given in the figure. The light is emitted from the laser of the interferometer 2, and is computed holographically generated to the convex aspheric surface 13 to be measured. Since the convex aspheric surface 13 to be measured is a convex surface, the light beam will diverge after reaching the convex aspheric surface. An auxiliary reflector 9 is added to reflect the light so that the light re-enters the interferometer 2 to realize interference detection. The auxiliary reflector adjustment frame 10 is used to place the auxiliary reflector 9 and adjust the position and angle of the auxiliary reflector 9. The auxiliary reflector adjustment frame 10 can adjust the movement of the auxiliary reflector 9 in the Z direction in the global coordinate system. Due to the reflective divergence characteristics of the convex aspheric surface on the light, the auxiliary reflector 9 is used to reflect and focus the light. By adjusting the position and angle of the auxiliary reflector 9, the reflected light can cover the entire sub-aperture area to be measured.

[0044] The translation stage 14 is used to place the convex aspheric surface 13 to be measured, and the translation stage 13 can move in the three directions of X, Y, and Z in the global coordinate system and rotate around the axes of X, Y, and Z. The translation stage 14 includes a six-degree-of-freedom guide rail or a six-degree-of-freedom robot.

[0045] The translation stage 14 is mounted on a vibration isolation base 17 to avoid vibration errors caused by the optical elements and the lens of the interferometer 2 during movement or rotation.

[0046] In the present application, the shape parameters of the convex aspheric surface 13 to be measured are arbitrary curvature and aperture; the convex aspheric surface 13 to be measured is a transmissive optical element or a reflective optical element.

[0047] A method for comprehensively detecting a convex aspheric surface using a CGH and a reflector, comprising the following steps:

[0048] (1) dividing the convex aspheric surface to be measured into a plurality of sub-aperture regions, each sub-aperture region having an overlapping region with at least one of the other sub-aperture regions;

[0049] In step (1), the shape of each sub-aperture region is

[0050] In step (1), the area of ​​the overlapping region in each sub-aperture region is greater than 20% of the total area of ​​the sub-aperture region.

[0051] (2) Detection using interferometer, computer generated hologram and auxiliary mirror,

[0052] First, the first sub-aperture area is tested, and the interference pattern of the first sub-aperture area is made to present a zero-fringe state by adjusting the positions of the convex aspheric surface to be tested, the computational hologram, and the auxiliary reflector, and the surface shape data of the first sub-aperture area is collected;

[0053] In step (2), the computer-generated hologram uses Bianry2 surface type, binary phase hologram, diffraction -1 order, and the computer-generated hologram is designed based on ray tracing optimization. The design results are as follows: the phase etching depth is 2μm, the duty cycle is 0.5, the minimum fringe period is 20μm, the substrate material is fused quartz, and the computer-generated hologram is produced using laser direct writing technology.

[0054] (3) Repeat step (2) to detect the remaining sub-aperture areas in turn and collect surface shape data of the remaining sub-aperture areas;

[0055] (4) Using a stitching algorithm, the surface shape data of each sub-aperture area is stitched together to obtain the complete surface shape data of the convex aspheric surface to be measured.

[0056] In step (4), during the splicing, a discrete phase-based splicing algorithm is used, with the principle of minimizing the error in the overlapping area.

[0057] Example 1

[0058] A method for comprehensively detecting convex aspheric surfaces using CGH and a reflector, the method of using is as follows: Figure 5 As shown, the steps are as follows:

[0059] Step a: The convex aspheric surface to be measured is a rotationally symmetrical structure with an aperture of 200 mm. The aspheric surface equation is as follows:

[0060]

[0061] Wherein, z represents the vertical distance from the reference plane to the surface point, and x represents the coordinate of the horizontal distance to the optical axis. A laser interferometer with an aperture of 150 mm and a laser wavelength of 632.8 nm is selected, and a lens with an F number of 3.3 is matched. The surface profile equation, shape and size, and lens F number of the rotationally symmetric convex aspheric surface to be measured are input into the computer control system, and the overlapping area size is set to be greater than 20%. According to the software calculation: the sub-aperture area is divided into 6, and the diameter of the circular domain where each sub-aperture area is located is 140 mm. The angle formed by the center of the adjacent sub-aperture circle and the center of the aspheric aperture is 60°.

[0062] According to the aspheric parameters to be measured and the laser parameters, the Bianry2 surface type, binary phase hologram, diffraction -1 order are selected, and the CGH is optimized based on ray tracing optimization. The design results are as follows: the phase etching depth is 2μm, the duty cycle is 0.5, the minimum fringe period is 20μm, the substrate material is fused quartz, and the corresponding CGH is made by laser direct writing technology.

[0063] Step b: Place the convex aspheric surface to be measured, CGH and auxiliary reflector adjustment frame on the optical element translation stage, CGH adjustment frame and auxiliary reflector adjustment frame respectively. First, calibrate the position of CGH and auxiliary reflector, and then adjust CGH to align it with the interferometer, the optical element to be measured and the auxiliary reflector.

[0064] Step c: The convex aspheric surface to be tested is adjusted by the computer control system to be initially positioned to the first sub-aperture detection position, and the convex aspheric surface to be tested is adjusted based on the displacement platform until clear, non-distorted interference fringes are displayed on the interference pattern, and then the convex aspheric surface to be tested is fine-tuned until the interference pattern of the sub-aperture area to be tested presents a zero-fringe state. The computer control system records the position of the sub-aperture center at this time as (x1, y1), and collects the surface data F1(x1, y1) of the sub-aperture through the interferometer.

[0065] Step d: Set the rotation angle of the translation stage where the optical element is located to 60°, adjust the subaperture to be measured to the second subaperture area to be measured, repeat step c, fine-tune the convex aspheric surface to be measured so that the interference pattern of the second subaperture area to be measured presents a zero-fringe state, and the computer control system records the position of the subaperture center at this time as (x2, y2), and collects the surface data F2 (x2, y2) of the subaperture through the interferometer; collect the surface data of the remaining subapertures one by one, and fine-tune the optical element appropriately to obtain the subaperture zero-fringe state. The computer control system records and stores the position and interference pattern of each subaperture, namely F1 (x1, y1), F2 (x2, y2), F3 (x3, y3), F4 (x4, y4) F5 (x5, y5), F6 (x6, y6).

[0066] Step f: stitch the sub-apertures using a discrete phase-based stitching algorithm with the principle of minimizing the error in the overlapping area. The calculation process is as follows:

[0067] The overlapping area between the first subaperture and the second subaperture is:

[0068] D 1-2 (x 1-2 ,y 1-2 )=F1(x1,y1)-F2(x2,y2),

[0069] The error model including tilt, translation and rotation is constructed to describe the overlapping area as follows:

[0070] D 1-2 (x 1-2 ,y 1-2 )=a 1-2 +b 1-2 x 1-2 +c 1-2 y 1-2 ,

[0071] Based on the principle of least squares method, the independent variable coefficients for solving the overlap area with the minimum error are as follows:

[0072] [a 1-2 ,b 1-2 ,c 1-2 ] = argmin(a 1-2 +b 1-2 x 1-2 +c 1-2 y 1-2 );

[0073] Taking the position of the first subaperture as the reference, based on the a obtained by solving 1-2 ,b 1-2 ,c 1-2The coefficient is adjusted to correct the second sub-aperture area, and the first sub-aperture area and the second sub-aperture area are spliced.

[0074] Step g: Taking the second sub-aperture area as a reference, perform the calculation process of step f on the data of the third sub-aperture, and use the obtained a 2-3 ,b 2-3 ,c 2-3 The adjustment coefficient is used to correct the third sub-aperture area, and the second sub-aperture area and the third sub-aperture area are spliced; the calculation process of step f is performed once for the fourth sub-aperture area, the fifth sub-aperture area, and the sixth sub-aperture area to realize the splicing calculation of the full-aperture information of the convex aspheric surface to be measured.

Claims

1. A method for comprehensive detection of convex aspheric surfaces using CGH and reflectors, characterized in that: The following steps are involved: (1) dividing the convex aspheric surface to be measured into a plurality of sub-aperture regions, each sub-aperture region having an overlapping region with at least one of the other sub-aperture regions; (2) Detection is performed using an interferometer, a computer-generated hologram, and an auxiliary reflector, wherein the interferometer includes a lens, First, the first sub-aperture area is tested, and the interference pattern of the first sub-aperture area is made to present a zero-fringe state by adjusting the positions of the convex aspheric surface to be tested, the computational hologram, and the auxiliary reflector, and the surface shape data of the first sub-aperture area is collected; (3) Repeat step (2) to detect the remaining sub-aperture areas in turn and collect surface shape data of the remaining sub-aperture areas; (4) Using a stitching algorithm, the surface shape data of each sub-aperture area is stitched together to obtain the complete surface shape data of the convex aspheric surface to be measured.

2. The method for comprehensive detection of convex aspheric surfaces by using CGH and a reflector according to claim 1, characterized in that: In step (1), the area of ​​the overlapping region in each sub-aperture region is 20% to 30% of the total area of ​​the sub-aperture region.

3. The method for comprehensive detection of convex aspheric surfaces by using CGH and reflector according to claim 1, characterized in that: In step (2), the convex aspheric surface to be measured is rotationally symmetric or non-rotationally symmetric.

4. The method for comprehensive detection of convex aspheric surfaces by using CGH and a reflector according to claim 1, characterized in that: In step (2), the computer-generated hologram uses Bianry2 surface type, binary phase hologram, diffraction -1 order, and the computer-generated hologram is designed based on ray tracing optimization. The design results are as follows: the phase etching depth is 2μm, the duty cycle is 0.5, the minimum fringe period is 20μm, the substrate material is fused quartz, and the computer-generated hologram is produced using laser direct writing technology.

5. The method for comprehensive detection of convex aspheric surfaces by using CGH and reflector according to claim 1, characterized in that: In step (4), during the splicing, a discrete phase-based splicing algorithm is used, with the principle of minimizing the error in the overlapping area.

6. A system for comprehensive detection of convex aspheric surfaces by CGH and reflector, characterized in that: include: Mounting frame; An interferometer, disposed on the mounting frame, comprising a lens; Computational holography; A computer-generated hologram adjustment frame, used for placing the computer-generated hologram and adjusting the position and angle of the computer-generated hologram; An auxiliary reflector, used for reflecting light, and reflecting the light to between the convex aspheric surface to be measured and the interferometer, so as to assist in realizing interference detection; An auxiliary reflector adjustment frame, used for placing the auxiliary reflector and adjusting the position and angle of the auxiliary reflector; The translation stage is used to place the convex aspheric surface to be measured, and the translation stage can move in the three directions of X, Y, and Z in the global coordinate system and rotate around the X, Y, and Z axes.

7. The system for comprehensive detection of convex aspheric surfaces by CGH and reflector according to claim 6, characterized in that: The shape parameters of the convex aspheric surface to be measured are arbitrary curvature and aperture; The convex aspheric surface to be measured is a transmission optical element or a reflection optical element.

8. The system for comprehensive detection of convex aspheric surfaces by CGH and reflector according to claim 6, characterized in that: The CGH adjustment frame can adjust the CGH to move in the Z direction in the global coordinate system; The auxiliary reflector adjustment frame can adjust the auxiliary reflector to move in the Z direction in the global coordinate system.

9. The system for comprehensive detection of convex aspheric surfaces by CGH and reflector according to claim 6, characterized in that: The translation platform is installed on a vibration isolation base.

10. The system for comprehensive detection of convex aspheric surfaces by CGH and reflector according to claim 6, characterized in that: The translation platform includes a six-degree-of-freedom guide rail or a six-degree-of-freedom robot.

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