Spherical mirror surface shape and parameter synchronous detection method and device

Abstract

According to the spherical mirror surface shape and parameter synchronous detection method and device, high-precision measurement of the surface shape and the vertex curvature radius can be completed at the same time in the same light path, the defects of multiple optical elements, step-by-step measurement and complex installation and adjustment in a traditional method are overcome, and integrated, lightweight and high-precision synchronous detection of the surface shape and parameters is achieved. The method comprises the following steps: (1) designing a spatial multiplexing computer generated hologram (CGH), carrying out measurement light path modeling in Zemax according to a nominal value of a spherical mirror to be measured, and optimizing to obtain additional phase values of different regions of the CGH; (2) modeling a virtual formal parameter synchronous measurement system; (3) building an actual form parameter synchronous measurement system; (4) carrying out residual wavefront extraction and Zernike fitting; (5) optimizing to obtain a compensation distance; and (6) the curvature radius is obtained through inversion.

Description

Technical Field

[0001] This invention relates to the field of photoelectric detection technology, and more particularly to a method for synchronously detecting the shape and parameters of a spherical mirror, and also to a device for synchronously detecting the shape and parameters of a spherical mirror. Background Technology

[0002] As modern optical systems continue to advance towards higher resolution, larger apertures, and higher stability, their performance increasingly depends on improvements in the precision of optical component fabrication and testing. Spherical mirrors, as one of the most common optical components, directly determine the imaging performance and stability of the system through their surface accuracy and geometric parameters, particularly the vertex radius of curvature R. Therefore, developing an efficient, integrated, and high-precision measurement technology is of great significance for modern optical manufacturing and applications.

[0003] Traditional computational hologram (CGH) techniques are primarily used to generate compensated wavefronts that match the optical element under test, enabling surface shape error detection under zero-compensation conditions in an interferometer. However, this method typically assumes that the geometric parameters of the element under test are known, thus limiting its application to surface shape measurements and significantly restricting the acquisition of geometric parameters such as vertex radius of curvature. Existing methods for measuring vertex radius of curvature are mainly divided into contact and non-contact types.

[0004] Contact methods, such as profilometers and coordinate measuring machines, fit the vertex radius of curvature by scanning point by point. These methods rely on high-precision displacement stages or probe sensors, but are susceptible to repeatability errors, systematic errors, and environmental disturbances. Furthermore, contact between the probe and the measured surface can cause surface damage or micro-deformation, making them unsuitable for the non-destructive testing requirements of high-end optical components. Non-contact methods avoid physical contact and are mainly divided into non-interferometric methods and interferometric methods. Non-interferometric methods are simple in principle but limited by equipment, resulting in limited measurement accuracy and range. Interferometric methods, due to their high sensitivity and accuracy, are widely used for vertex radius of curvature measurement; typical zero-compensation interferometric systems can achieve an accuracy better than 0.1%. In recent years, domestic scholars have proposed various measurement methods based on compensation position and compensation distance, such as the partial zero-compensation method and the optimal compensation position aberration analysis method, improving the accuracy of vertex radius of curvature measurement to 0.025% or even 0.1591‰.

[0005] Although these methods have demonstrated the feasibility of high-precision vertex curvature radius measurement, they generally rely on external high-precision displacement measurement equipment or optical systems to establish spatial references. This means that the surface shape and vertex curvature radius must be measured step by step, which increases system complexity and reduces assembly stability. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the technical problem to be solved by the present invention is to provide a method for synchronous detection of surface shape and parameters of a spherical mirror, which can simultaneously complete high-precision measurement of surface shape and vertex curvature radius in the same optical path, avoiding the drawbacks of multiple optical elements, step-by-step measurement and complex assembly in traditional methods, and realizing integrated, lightweight and high-precision synchronous detection of surface shape and parameters.

[0007] The technical solution of this invention is: a method for synchronously detecting the shape and parameters of a spherical mirror, comprising the following steps:

[0008] (1) Design a spatial multiplexing computational hologram (CGH). Based on the nominal value of the spherical mirror to be measured, perform measurement optical path modeling in Zemax and optimize to obtain additional phase values ​​in different regions of the CGH, including: additional phase of the main holographic region and additional phase of the reference holographic region.

[0009] (2) Virtual parameter synchronous measurement system modeling. The virtual parameter synchronous measurement system simulates the real interferometric measurement device. The parameters, orientation and relative position of each optical element are initialized according to the ideal values ​​of the actual system. The ideal compensation distance d0 is recorded. The compensation distance is the distance from CGH to the spherical mirror under test. This system is used for subsequent inverse optimization to solve the true vertex curvature radius R of the spherical mirror under test.

[0010] (3) Build an actual form parameter synchronous measurement system. Based on the relative positions between the optical elements of the measurement optical path obtained by modeling the virtual form parameter synchronous measurement system, perform optical path adjustment between CGH and the spherical mirror under test. Utilize the CGH's main holographic surface shape compensation function to measure the surface shape error of the spherical mirror.

[0011] (4) Residual wavefront extraction and Zernike fitting: Based on the surface shape measurement, while keeping the optical path adjustment unchanged, the residual wavefront corresponding to the current reference hologram is measured and obtained. The defocus term of the reference hologram is extracted through Zernike fitting.

[0012] (5) Optimize the acquisition compensation distance, take the defocus term of the reference holography as the optimization target and bring it into the virtual reference holography measurement system, and perform reverse iterative optimization to obtain the optimal compensation distance d. Then, bring d into the virtual master holography measurement system to obtain the defocus term of the virtual master holography.

[0013] (6) Obtain the curvature radius by inversion. In the virtual master holographic measurement system, the compensation distance is set to the ideal value d0. The virtual master holographic defocus term is used as the optimization target. The curvature radius R of the spherical mirror vertex is obtained by inverse iterative optimization.

[0014] This invention introduces a spatial multiplexing design on a single CGH, enabling the main hologram to perform surface shape compensation and the reference hologram to perform vertex curvature radius parameter measurement, thereby achieving synchronous detection of surface shape and parameters within the same optical path. This method relies on only a single interferometric measurement to complete the calculation of surface shape and parameters, supporting dynamic measurement requirements. The spatial multiplexing design not only enables high-precision surface shape compensation in the central region but also vertex curvature radius calculation in the outer ring region, balancing high-precision surface shape measurement with overall parameter acquisition. It possesses multi-target measurement capabilities, thus enabling high-precision synchronous detection of the surface shape and vertex curvature radius of a spherical mirror. Furthermore, the measurement system structure is significantly simplified, greatly improving detection efficiency and allowing the method to operate efficiently on portable devices.

[0015] A device for synchronously detecting the shape and parameters of a spherical mirror is also provided, comprising:

[0016] The spatial reuse CGH design module is configured to perform measurement optical path modeling in Zemax based on the nominal value of the spherical mirror under test, and optimize the additional phase distribution of different regions of the main hologram and the reference hologram.

[0017] The virtual synchronous measurement system modeling module is configured to construct a virtual parametric synchronous measurement system to simulate a real interferometric measurement device. The parameters, orientation, and relative position of each optical element are initialized according to the ideal values ​​of the actual system. The ideal compensation distance d0 is recorded. The compensation distance is the distance from CGH to the spherical mirror under test. This system is used for subsequent inverse optimization to solve the true vertex curvature radius R of the spherical mirror under test.

[0018] The actual synchronous measurement system construction module is configured to build an actual form parameter synchronous measurement system. Based on the relative positions between the optical elements of the measurement optical path obtained by modeling the virtual form parameter synchronous measurement system, the optical path of the CGH and the spherical mirror under test is adjusted. The surface shape error of the spherical mirror is measured by using the CGH's master holographic surface shape compensation function.

[0019] The residual wavefront extraction and Zernike fitting module is configured for residual wavefront extraction and Zernike fitting. Based on the surface shape measurement, while keeping the optical path adjustment unchanged, the residual wavefront corresponding to the current reference hologram is measured and obtained. Through Zernike fitting, the defocus term of the reference hologram is extracted.

[0020] The compensation distance optimization module is configured to optimize the acquisition of compensation distance. It takes the defocus term of the reference hologram as the optimization target and inputs it into the virtual reference hologram measurement system. It then performs reverse iterative optimization to obtain the optimal compensation distance d. Finally, it inputs d into the virtual master hologram measurement system to obtain the defocus term of the virtual master hologram.

[0021] The curvature radius inversion module is configured to invert and obtain the curvature radius. In the virtual master holographic measurement system, the compensation distance is set to the ideal value d0. With the virtual master holographic defocus term as the optimization target, the curvature radius R of the spherical mirror vertex is obtained through inverse iterative optimization. Attached Figure Description

[0022] Figure 1 This is a flowchart of the method for synchronous detection of spherical mirror shape and parameters according to the present invention.

[0023] Figure 2 This refers to the distribution of CGH functional areas.

[0024] Figure 3 It is a virtual master holographic surface shape measurement optical path.

[0025] Figure 4 It is a virtual reference holographic parameter measurement optical path.

[0026] Figure 5 It is the optical path for synchronous measurement of actual parameters.

[0027] Figure 6 It represents the change in the wavefront diagram during the reverse iterative optimization process. Detailed Implementation

[0028] like Figure 1 As shown, this method for synchronously detecting the shape and parameters of a spherical mirror includes the following steps:

[0029] (1) Design a spatial multiplexing computational hologram (CGH). Based on the nominal value of the spherical mirror to be measured, perform measurement optical path modeling in Zemax and optimize to obtain additional phase values ​​in different regions of the CGH, including: additional phase of the main holographic region and additional phase of the reference holographic region.

[0030] (2) Virtual parameter synchronous measurement system modeling. The virtual parameter synchronous measurement system simulates the real interferometric measurement device. The parameters, orientation and relative position of each optical element are initialized according to the ideal values ​​of the actual system. The ideal compensation distance d0 is recorded. The compensation distance is the distance from CGH to the spherical mirror under test. This system is used for subsequent inverse optimization to solve the true vertex curvature radius R of the spherical mirror under test.

[0031] (3) Build an actual form parameter synchronous measurement system. Based on the relative positions between the optical elements of the measurement optical path obtained by modeling the virtual form parameter synchronous measurement system, perform optical path adjustment between CGH and the spherical mirror under test. Utilize the CGH's main holographic surface shape compensation function to measure the surface shape error of the spherical mirror.

[0032] (4) Residual wavefront extraction and Zernike fitting: Based on the surface shape measurement, while keeping the optical path adjustment unchanged, the residual wavefront corresponding to the current reference hologram is measured and obtained. The defocus term of the reference hologram is extracted through Zernike fitting.

[0033] (5) Optimize the acquisition compensation distance, take the defocus term of the reference holography as the optimization target and bring it into the virtual reference holography measurement system, and perform reverse iterative optimization to obtain the optimal compensation distance d. Then, bring d into the virtual master holography measurement system to obtain the defocus term of the virtual master holography.

[0034] (6) Obtain the curvature radius by inversion. In the virtual master holographic measurement system, the compensation distance is set to the ideal value d0. The virtual master holographic defocus term is used as the optimization target. The curvature radius R of the spherical mirror vertex is obtained by inverse iterative optimization.

[0035] This invention introduces a spatial multiplexing design on a single CGH, enabling the main hologram to perform surface shape compensation and the reference hologram to perform vertex curvature radius parameter measurement, thereby achieving synchronous detection of surface shape and parameters within the same optical path. This method relies on only a single interferometric measurement to complete the calculation of surface shape and parameters, supporting dynamic measurement requirements. The spatial multiplexing design not only enables high-precision surface shape compensation in the central region but also vertex curvature radius calculation in the outer ring region, balancing high-precision surface shape measurement with overall parameter acquisition. It possesses multi-target measurement capabilities, thus enabling high-precision synchronous detection of the surface shape and vertex curvature radius of a spherical mirror. Furthermore, the measurement system structure is significantly simplified, greatly improving detection efficiency and allowing the method to operate efficiently on portable devices.

[0036] Preferably, in step (1), the proportion of the space reuse area is reasonably divided according to the area of ​​the selected CGH etching substrate. At the same time, the system modeling is completed in Zemax, the additional phase values ​​of different areas are obtained and the phase encoding is completed to ensure that the scribing density is greater than 4μm, so as to meet the requirements of subsequent CGH physical processing.

[0037] Preferably, in step (2), a virtual morphological synchronous measurement system is modeled based on the nominal value of the spherical mirror to be measured. This includes two Zemax systems: a virtual master holographic measurement system and a virtual reference holographic measurement system. The two Zemax systems differ in that they use different regions of the substrate and additional phase on the surface. The parameters and relative positions of the optical elements in the optical path are completely identical. The nominal value of the spherical mirror to be measured includes: the aperture of the spherical mirror, the vertex curvature radius R, and the aperture, thickness, and spatial reuse area division of the etched substrate. d0 is recorded at this time.

[0038] Preferably, in step (3), based on the relative positions of each optical element in the virtual measurement optical path modeling, the initial construction of the actual form parameter synchronous measurement system is carried out, and the optical path assembly and adjustment of the CGH and the spherical mirror under test are completed in sequence. Specifically, the CGH completes the optical path assembly and adjustment by using the light reflected from the etched substrate itself, and the spherical mirror under test is adjusted by tilting until the main holographic region is completely zero-fringe. At this time, the optical path assembly and adjustment is completed. The surface shape measurement of the spherical mirror is completed by using the main holographic surface shape compensation function.

[0039] Preferably, in step (4), based on completing step (3), without changing the position of any component in the optical path, keeping the optical path assembly unchanged, the measurement of the corresponding region of the reference hologram is completed synchronously to obtain the residual wavefront corresponding to the current reference hologram, and the reference hologram defocus term is extracted by using Zernike Fringe fitting.

[0040] Preferably, in step (5), the defocus term of the reference hologram is taken as the optimization target and substituted into the virtual reference holographic measurement system constructed in step (2). The compensation distance is set as the optimization variable, and the optimal compensation distance d is obtained by reverse optimization and recorded. The optimal compensation distance d is substituted into the virtual master holographic measurement system to obtain the defocus term of the virtual master holographic measurement system at this time.

[0041] Preferably, in step (6), in the virtual master holographic measurement system, the compensation distance is set to the ideal value d0, the defocus term of the virtual master holographic measurement system obtained in step (5) is used as the optimization target, and the vertex curvature radius R of the spherical mirror to be measured is used as the optimization variable for optimization. The true vertex curvature radius R of the spherical mirror to be measured is obtained through reverse iterative optimization.

[0042] Those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium. When executed, the program includes the steps of the methods of the above embodiments. The storage medium can be ROM / RAM, magnetic disk, optical disk, memory card, etc. Therefore, corresponding to the method of the present invention, the present invention also includes a spherical mirror shape and parameter synchronization detection device, which is typically represented in the form of functional modules corresponding to the steps of the method. The device includes:

[0043] The spatial reuse CGH design module is configured to perform measurement optical path modeling in Zemax based on the nominal value of the spherical mirror under test, and optimize the additional phase distribution of different regions of the main hologram and the reference hologram.

[0044] The virtual synchronous measurement system modeling module is configured to construct a virtual parametric synchronous measurement system to simulate a real interferometric measurement device. The parameters, orientation, and relative position of each optical element are initialized according to the ideal values ​​of the actual system. The ideal compensation distance d0 is recorded. The compensation distance is the distance from CGH to the spherical mirror under test. This system is used for subsequent inverse optimization to solve the true vertex curvature radius R of the spherical mirror under test.

[0045] The actual synchronous measurement system construction module is configured to build an actual form parameter synchronous measurement system. Based on the relative positions between the optical elements of the measurement optical path obtained by modeling the virtual form parameter synchronous measurement system, the optical path of the CGH and the spherical mirror under test is adjusted. The surface shape error of the spherical mirror is measured by using the CGH's master holographic surface shape compensation function.

[0046] The residual wavefront extraction and Zernike fitting module is configured for residual wavefront extraction and Zernike fitting. Based on the surface shape measurement, while keeping the optical path adjustment unchanged, the residual wavefront corresponding to the current reference hologram is measured and obtained. Through Zernike fitting, the defocus term of the reference hologram is extracted.

[0047] The compensation distance optimization module is configured to optimize the acquisition of compensation distance. It takes the defocus term of the reference hologram as the optimization target and inputs it into the virtual reference hologram measurement system. It then performs reverse iterative optimization to obtain the optimal compensation distance d. Finally, it inputs d into the virtual master hologram measurement system to obtain the defocus term of the virtual master hologram.

[0048] The curvature radius inversion module is configured to invert and obtain the curvature radius. In the virtual master holographic measurement system, the compensation distance is set to the ideal value d0. With the virtual master holographic defocus term as the optimization target, the curvature radius R of the spherical mirror vertex is obtained through inverse iterative optimization.

[0049] Preferably, in the space reuse CGH design module, the proportion of the space reuse area is reasonably divided according to the area of ​​the selected CGH etching substrate. At the same time, the system modeling is completed in Zemax, the additional phase values ​​of different areas are obtained and the phase encoding is completed to ensure that the scribing density is greater than 4μm, so as to meet the requirements of subsequent CGH physical processing.

[0050] In the virtual synchronous measurement system modeling module, a virtual form parameter synchronous measurement system model is completed based on the nominal value of the spherical mirror under test. This includes two Zemax systems: a virtual master holographic measurement system and a virtual reference holographic measurement system. The two Zemax systems differ in that they use different regions of the substrate and surface-added phases. The parameters and relative positions of the optical elements in the optical path are completely identical. The nominal value of the spherical mirror under test includes: the aperture of the spherical mirror, the vertex radius of curvature R, and the aperture, thickness, and spatial multiplexing area division of the etched substrate; record d0 at this time.

[0051] In the actual synchronous measurement system construction module, based on the relative positions of each optical element in the virtual measurement optical path modeling, the initial construction of the actual form parameter synchronous measurement system is performed. Simultaneously, the optical path assembly and adjustment of the CGH and the spherical mirror under test are completed sequentially.

[0052] CGH utilizes the reflected light from the etched substrate to complete the optical path assembly. The spherical mirror under test is tilted and adjusted until the main holographic region has zero fringes, at which point the optical path assembly is complete. The surface shape of the spherical mirror is measured using the main holographic surface shape compensation function.

[0053] Preferably, in the residual wavefront extraction and Zernike fitting module, the position of any component in the optical path is not changed, the optical path is kept unchanged, the measurement of the corresponding region of the reference hologram is completed synchronously, the residual wavefront corresponding to the current reference hologram is obtained, and the Zernike Fringe fitting is used to extract the defocus term of the reference hologram.

[0054] In the compensation distance optimization module, the defocus term of the reference holography is taken as the optimization target and substituted into the virtual reference holographic measurement system constructed in the virtual synchronous measurement system modeling module. The compensation distance is set as the optimization variable, and the optimal compensation distance d is obtained by reverse optimization and recorded. The optimal compensation distance d is substituted into the virtual master holographic measurement system to obtain the defocus term of the virtual master holographic measurement system at this time.

[0055] In the curvature radius inversion module, the compensation distance is set to the ideal value d0 in the virtual master holographic measurement system. The defocus term of the virtual master holographic measurement system obtained in the compensation distance optimization module is used as the optimization target, and the vertex curvature radius R of the spherical mirror under test is used as the optimization variable for optimization. The true vertex curvature radius R of the spherical mirror under test is obtained through inverse iterative optimization.

[0056] The following details specific embodiments of the present invention.

[0057] A method for synchronous detection of the shape and parameters of a spherical mirror based on spatially reused CGH is implemented as follows:

[0058] The process for synchronous detection of spherical mirror shape and parameters based on spatially reused CGH is as follows: Figure 1 As shown, the specific implementation steps are as follows:

[0059] Step 1: Design Space Reuse CGH

[0060] In this example, the nominal values ​​of the spherical mirror under test are: aperture 25.4 mm, radius of curvature -101.6 mm; the etching substrate is Corning 7980: used for etching a 20 mm aperture and a 3 mm thickness, with functional area distribution as follows. Figure 2As shown, the measurement optical path was modeled in Zemax, and the additional phases on the main hologram and reference hologram surfaces were obtained and encoded. The scribing density was verified to be greater than 4μm, which meets the requirements for subsequent processing.

[0061] Step 2: Modeling the Virtual Parameter Synchronous Measurement System

[0062] In the example, Zemax software is used to build such a... Figure 3 , 4 The optical path for synchronous measurement of the form parameters shown includes a virtual master holographic measurement system and a virtual reference holographic measurement system. It is initialized according to the ideal value of the actual system to obtain the relative position of each optical element and record the ideal compensation distance d0 = 135.26723986 mm. This system is used for subsequent reverse optimization to calculate the true vertex curvature radius R.

[0063] Step 3: Establish a real-world parameter synchronous measurement system

[0064] In the example, based on the relative positions of each optical element in the virtual system, an actual parameter synchronous measurement system is built, such as... Figure 5 As shown, the optical path of the CGH and the spherical mirror under test is adjusted. The spherical mirror under test is tilted and tilted until the main holographic region is completely zero-fringe, thus completing the surface shape measurement function.

[0065] Step 4: Residual Wavefront Extraction and Zernike Fitting

[0066] In the example, keeping the optical path unchanged, the corresponding region of the reference hologram is measured synchronously to obtain the residual wavefront of the current reference hologram region. Zernike fitting is then performed to extract the defocus term Z4 = -0.08346767.

[0067] Step 5: Optimize the acquisition of compensation distance

[0068] In this example, the term Z4 = -0.08346767 obtained in step four is substituted into the virtual reference holographic measurement system. Through reverse iterative optimization, the optimal compensation distance d = 135.24723986 mm is obtained. Substituting d into the virtual master holographic measurement system, the virtual master holographic defocus term Z4 = -0.24781654 is obtained. The wavefront diagram change process during the reverse iterative optimization is as follows: Figure 6 As shown.

[0069] Step Six: Inversion to Obtain the Radius of Curvature

[0070] In this example, in the virtual master holographic measurement system, the compensation distance is set to the ideal value d0 = 135.26723986 mm. The virtual master holographic defocus term Z4 = -0.24781654 obtained in step five is used as the optimization objective, and the vertex curvature radius R of the spherical mirror under test is used as the optimization variable. Through inverse iterative optimization, the true vertex curvature radius R of the spherical mirror under test is obtained as -101.57999659 mm. Compared with the vertex curvature radius measurement results obtained using a profilometer, the relative measurement error is 6.487 × 10⁻⁶ mm. -5 %.

[0071] The beneficial effects of this invention are as follows:

[0072] 1. The present invention discloses a method for synchronous detection of spherical mirror shape and parameters based on spatially reused CGH. By introducing spatial reuse design on a single CGH, the master hologram realizes the surface shape compensation function, and the reference hologram realizes the parameter measurement function of vertex curvature radius. This method can achieve high-precision synchronous measurement of spherical mirror shape and vertex curvature radius R.

[0073] 2. The method for synchronous detection of spherical mirror surface shape and parameters based on spatial multiplexing CGH disclosed in this invention can complete the calculation of surface shape and parameters by relying on only a single interferometric measurement, which has strong anti-interference ability and can realize dynamic measurement.

[0074] 3. The spherical mirror shape and parameter synchronous detection method based on spatial reuse CGH disclosed in this invention has the ability to measure multiple targets, realize two functions in the same system, greatly simplify the measurement system structure, and significantly improve detection efficiency and detection accuracy.

[0075] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for synchronously detecting the shape and parameters of a spherical mirror, characterized in that: It comprises the following steps: (1) Designing a spatial multiplexing computer generated hologram (CGH), modeling a measurement optical path in Zemax according to a nominal value of a to-be-measured spherical mirror, and obtaining additional phase values of different regions of the CGH through optimization, including: main holographic region additional phase, reference holographic region additional phase; (2) Modeling a virtual parameter synchronous measurement system, which simulates a real interferometric measurement device, wherein parameters, directions and relative positions of each optical element are initialized according to ideal values of an actual system, and an ideal compensation distance d0 is recorded, the compensation distance being a distance from the CGH to the to-be-measured spherical mirror, the system being used for subsequent reverse optimization to inversely solve a real vertex curvature radius R of the to-be-measured spherical mirror; (3) Building an actual parameter synchronous measurement system, according to the relative positions between the optical elements in the virtual parameter synchronous measurement system modeling, performing optical path assembly and adjustment of the CGH and the to-be-measured spherical mirror, and measuring a surface shape error of the spherical mirror by using a main holographic surface shape compensation function of the CGH; (4) Residual wavefront extraction and Zernike fitting, on the basis of the surface shape measurement, keeping the optical path assembly and adjustment unchanged, measuring and obtaining a residual wavefront corresponding to the current reference hologram, and extracting a reference holographic defocus term through Zernike fitting; (5) Optimizing to obtain a compensation distance, taking the reference holographic defocus term as an optimization target and bringing it into a virtual reference holographic measurement system, and inversely and iteratively optimizing to obtain an optimal compensation distance d, and bringing d into a virtual main holographic measurement system to obtain a virtual main holographic defocus term; (6) Inversion to obtain a curvature radius, in the virtual main holographic measurement system, setting the compensation distance as the ideal value d0, taking the virtual main holographic defocus term as an optimization target, and inversely and iteratively optimizing to obtain a vertex curvature radius R of the spherical mirror.

2. The method according to claim 1, wherein: In the step (1), according to a selected CGH etching substrate area, the spatial multiplexing region proportion is reasonably divided, and system modeling is completed in Zemax to obtain additional phase values of different regions and complete phase encoding, so as to ensure that the ruling density is greater than 4 μm, thereby meeting the subsequent CGH physical processing requirements.

3. The method of claim 2, wherein: In the step (2), according to a nominal value of a to-be-measured spherical mirror, a virtual parameter synchronous measurement system modeling is completed, which contains two Zemax systems, one being a virtual main holographic measurement system and the other being a virtual reference holographic measurement system, the two Zemax systems differing in using different regions and surface additional phases of a substrate and the relative relationship between parameters and positions of optical elements in the optical path being completely the same, the nominal value of the to-be-measured spherical mirror including: an aperture of the spherical mirror, a vertex curvature radius R, and an aperture, a thickness and a spatial multiplexing region division of the etching substrate; and recording d0 at this time.

4. The method of claim 3, wherein: In the step (3), according to the relative positions between the optical elements in the virtual measurement optical path modeling, a preliminary building of an actual parameter synchronous measurement system is performed, and optical path assembly and adjustment of the CGH and the to-be-measured spherical mirror are sequentially completed, wherein: the CGH completes optical path assembly and adjustment by using reflected light of the etching substrate itself, the to-be-measured spherical mirror is adjusted by adjusting pitch and tilt until the main holographic region is completely zero fringe, at which time the optical path assembly and adjustment are completed; and the surface shape measurement of the spherical mirror is completed by using the main holographic surface shape compensation function.

5. The method of claim 4, wherein: In the step (4), on the basis of completing the step (3), without changing the positions of any elements in the optical path, the optical path alignment is kept unchanged, the corresponding reference holographic measurement is synchronously completed, the current reference holographic corresponding residual wavefront is obtained, the Zernike Fringe fitting is used, and the reference holographic defocus term is extracted.

6. The method of claim 5, wherein: In the step (5), the reference holographic defocus term is taken as an optimization target, is brought into the virtual reference holographic measurement system constructed in the step (2), the compensation distance is set as an optimization variable, the optimal compensation distance d is obtained through reverse optimization and is recorded; the optimal compensation distance d is brought into the virtual main holographic measurement system, and the defocus term of the virtual main holographic measurement system at this time is obtained.

7. The method of claim 6, wherein: In the step (6), in the virtual main holographic measurement system, the compensation distance is set as the ideal value d0, the defocus term of the virtual main holographic measurement system obtained in the step (5) is taken as an optimization target, and the vertex curvature radius R of the to-be-measured spherical mirror is taken as an optimization variable to perform optimization, so that the real vertex curvature radius R of the to-be-measured spherical mirror is obtained through reverse iterative optimization.

8. A device for simultaneous measurement of the surface shape and parameters of a spherical mirror, characterized in that: It comprises: a spatial multiplexing CGH design module configured to perform measurement optical path modeling in Zemax according to a nominal value of a to-be-measured spherical mirror, and to optimize additional phase distribution of different regions of a main hologram and a reference hologram; a virtual synchronous measurement system modeling module configured to construct a virtual parameter synchronous measurement system to simulate a real interference measurement device, wherein parameters, directions and relative positions of each optical element are initialized according to ideal values of an actual system, an ideal compensation distance d0 is recorded, the compensation distance is a distance from a CGH to a to-be-measured spherical mirror, and the system is used for subsequent reverse optimization and inverse solution of a real vertex curvature radius R of the to-be-measured spherical mirror; an actual synchronous measurement system building module configured to build an actual parameter synchronous measurement system, to perform optical path alignment of a CGH and a to-be-measured spherical mirror according to relative positions among measurement optical elements obtained by virtual parameter synchronous measurement system modeling, and to measure surface shape error of the spherical mirror by using a surface shape compensation function of the CGH main hologram; a residual wavefront extraction and Zernike fitting module configured for residual wavefront extraction and Zernike fitting, to keep the optical path alignment unchanged on the basis of surface shape measurement, to measure and obtain a residual wavefront corresponding to a current reference hologram, and to extract a reference holographic defocus term through Zernike fitting; a compensation distance optimization module configured to optimize and obtain a compensation distance, to take the reference holographic defocus term as an optimization target and bring it into a virtual reference holographic measurement system, to obtain an optimal compensation distance d through reverse iterative optimization, to bring d into a virtual main holographic measurement system, and to obtain a defocus term of the virtual main hologram; a curvature radius inversion module configured to inversely obtain a curvature radius, to set the compensation distance as an ideal value d0 in the virtual main holographic measurement system, to take the defocus term of the virtual main hologram as an optimization target, and to obtain the vertex curvature radius R of the spherical mirror through reverse iterative optimization.

9. The apparatus for sphero-surface figure and parameter synchronous detection according to claim 8, characterized in that: In the spatial multiplexing CGH design module, the spatial multiplexing area proportion is reasonably divided according to the selected CGH etching substrate area, and system modeling is completed in Zemax to obtain different area additional phase values and complete phase encoding, so that the ruling density is greater than 4 μm, to meet the subsequent CGH physical processing requirements. In the virtual synchronous measurement system modeling module, the virtual parameter synchronous measurement system modeling is completed according to the nominal value of the to-be-measured spherical mirror, which includes two Zemax systems, one is a virtual main holographic measurement system, and the other is a virtual reference holographic measurement system. The two Zemax systems differ in the use of different areas of the substrate and surface additional phase, and the relative relationship of the parameters and positions of the optical elements in the optical path is completely the same. The nominal value of the to-be-measured spherical mirror includes the aperture of the spherical mirror, the vertex curvature radius R, and the aperture, thickness and spatial multiplexing area division of the etching substrate; d0 is recorded at this time. In the actual synchronous measurement system building module, the relative positions between the optical elements in the virtual measurement optical path modeling are obtained, and the preliminary building of the actual parameter synchronous measurement system is performed, and the optical path adjustment of the CGH and the to-be-measured spherical mirror is completed in turn, wherein: The CGH uses the reflected light of the etching substrate itself to complete the optical path adjustment, and the to-be-measured spherical mirror is adjusted by adjusting the pitch and tilt until the main holographic area is completely zero fringe, at which time the optical path adjustment is completed; the surface shape of the spherical mirror is measured by using the main holographic surface shape compensation function. In the remaining wavefront extraction and Zernike fitting module, without changing the positions of any elements in the optical path, the optical path adjustment is kept unchanged, the reference holographic corresponding area measurement is completed synchronously, the current reference holographic corresponding residual wavefront is obtained, and the reference holographic defocus term is extracted by using Zernike Fringe fitting; 10. The apparatus for sphero-surface figure and parameter synchronous detection according to claim 9, characterized in that: In the compensation distance optimization module, the reference holographic defocus term is taken as an optimization target and is brought into the virtual reference holographic measurement system built in the virtual synchronous measurement system modeling module, the compensation distance is set as an optimization variable, the best compensation distance d is obtained by reverse optimization and is recorded; the best compensation distance d is brought into the virtual main holographic measurement system, and the defocus term of the virtual main holographic measurement system at this time is obtained; In the curvature radius inversion module, in the virtual main holographic measurement system, the compensation distance is set as the ideal value d0, the defocus term of the virtual main holographic measurement system obtained in the compensation distance optimization module is taken as an optimization target, and the vertex curvature radius R of the to-be-measured spherical mirror is taken as an optimization variable for optimization, and the real vertex curvature radius R of the to-be-measured spherical mirror is obtained by reverse iterative optimization. ​

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