Method and device for measuring double-surface profile of transparent optical element

Abstract

The invention relates to a double-surface profile measurement method and device for a transparent optical element. The method comprises the following steps: acquiring a first diffraction pattern of a to-be-measured element; the to-be-measured element is a transparent optical element with a to-be-measured double-surface profile; performing phase recovery on the first diffraction pattern based on coherent modulation imaging to obtain a reconstruction result of the reflected wavefront of the to-be-measured element; based on the reconstruction result of the reflected wavefront of the to-be-measured element, establishing a dual-surface profile coupling model of the reflected wavefront of the to-be-measured element; the double-surface profile coupling model only contains double-surface synthesis information of the to-be-tested element; and reversely decoupling the double-surface profile coupling model so as to separate the front surface profile information and the rear surface profile information of the to-be-tested element from the double-surface synthesis information. According to the scheme provided by the invention, the problems of unsuitability for dynamic measurement, sensitivity to noise, unsuitability for large-aperture device measurement, high implementation cost and the like in the related technology can be solved.

Description

Technical Field

[0001] The present application relates to the field of optical processing technology, and in particular to a method and device for measuring the double-surface profile of a transparent optical element. Background Art

[0002] Transparent optical components are currently undergoing a comprehensive revolution, from materials to applications. Through the integration of multiple disciplines, transparent optical components are playing an increasingly important role in intelligent sensing, quantum computing, biomedicine, and other fields. In the precision manufacturing of transparent optical components, the geometric profile of the optical surface provides great flexibility in controlling light propagation. Therefore, high-precision optical surface profile measurement of transparent optical components is of great significance.

[0003] The measurement technologies in the related art include three-dimensional profilometers, three-coordinate measuring machines, fringe reflection phase deflectometers and various interferometers. Among them, interferometers are currently the main equipment for measuring the surface profile of transparent optical components. However, interferometers are extremely sensitive to noise during the measurement process, so they have strict requirements on the measurement environment. For example, interferometers require that there must be no vibration in the measurement environment. In addition, for large-aperture devices, the ultra-long optical path will limit the effectiveness of physical vibration isolation, so interferometers are not suitable for measuring large-aperture devices. In addition, the above-mentioned measurement technologies all suppress one surface while measuring another surface, so they all have a common limitation: they cannot be applied to dual-surface profile measurements under single exposure conditions in dynamic scenes and are expensive. Summary of the Invention

[0004] In order to solve or partially solve the problems existing in the related art, the present application provides a dual-surface profile measurement method and device for transparent optical elements, which can solve the problems in the related art such as being unsuitable for dynamic measurement, sensitive to noise, unsuitable for large-aperture device measurement, and high implementation cost.

[0005] A first aspect of the present application provides a method for measuring the dual-surface profile of a transparent optical element, comprising: Acquiring a first diffraction pattern of a component to be measured, wherein the component to be measured is a transparent optical component whose double-surface profile is to be measured; Performing phase recovery on the first diffraction pattern based on coherent modulation imaging to obtain a reconstruction result of the reflected wavefront of the element under test; Based on the reconstruction result of the reflected wavefront of the element under test, a dual-surface profile coupling model of the reflected wavefront of the element under test is established; the dual-surface profile coupling model only includes the dual-surface synthesis information of the element under test; The dual-surface profile coupling model is reversely decoupled to separate the front surface profile information and the back surface profile information of the device under test from the dual-surface composite information.

[0006] In one embodiment, the reconstruction result is an initial coupling model; and performing phase recovery on the first diffraction pattern based on coherent modulation imaging to obtain a reconstruction result of a reflected wavefront of the device under test includes: Phase recovery is performed on the first diffraction pattern based on coherent modulation imaging to reconstruct an initial coupling model of the reflected wavefront of the element under test; the initial coupling model includes dual-surface synthesis information of the element under test and illumination light information of a measurement system used to measure the element under test.

[0007] In one embodiment, the step of establishing a dual-surface profile coupling model of the reflected wavefront of the device under test based on the reconstruction result of the reflected wavefront of the device under test includes: The illumination light information is removed from the initial coupling model to establish a dual-surface profile coupling model for obtaining the reflected wavefront of the device under test.

[0008] In one embodiment, removing the illumination light information from the initial coupling model to establish a dual-surface profile coupling model for obtaining the reflected wavefront of the device under test includes: Obtaining a second diffraction pattern of a standard element; the standard element is a transparent optical element with known single surface profile information and high flatness; performing phase recovery on the second diffraction pattern based on the coherent modulation imaging to obtain a reconstruction result of the reflected wavefront of the standard element; the reconstruction result of the reflected wavefront of the standard element includes the known single surface profile information and the illumination light information; using the reconstructed result of the reflected wavefront of the standard element as pre-calibration information of the measurement system; The pre-calibration information is removed from the initial coupling model to establish a dual-surface profile coupling model for obtaining the reflected wavefront of the component under test.

[0009] In one embodiment, the reverse decoupling of the dual-surface profile coupling model to separate the front surface profile information and the back surface profile information of the device under test from the dual-surface composite information includes: determining a first transfer function of the front surface of the device under test, and determining a second transfer function of the rear surface of the device under test; determining target decoupling parameters of the dual-surface profile coupling model based on the first transfer function and the second transfer function; the target decoupling parameters include a first decoupling parameter and a second decoupling parameter, the first decoupling parameter being used to separate the front surface profile information of the device under test, and the second decoupling parameter being used to separate the back surface profile information of the device under test; The front surface profile information is reversely solved from the dual-surface profile coupling model using the phase information of the first decoupling parameter, and the rear surface profile information is reversely solved from the dual-surface profile coupling model using the phase information of the second decoupling parameter.

[0010] In one embodiment, the reflected wavefront of the DUT is generated based on coherent light sources of different wavelengths; and determining the target decoupling parameters of the dual-surface profile coupling model based on the first transfer function and the second transfer function includes: Using a quasi-Newton iteration method, two sets of solutions of the second transfer function at each wavelength are calculated respectively; the two sets of solutions include a true solution and a twin solution; screening out a true solution of the second transfer function at each wavelength from the two groups of solutions of the second transfer function at each wavelength; Calculating the true solution of the first transfer function at each wavelength respectively by using the dual-surface profile coupling model and the true solution of the second transfer function at each wavelength; A true solution of the first transfer function at a target wavelength is used as a first decoupling parameter, and a true solution of the second transfer function at the target wavelength is used as a second decoupling parameter; wherein the target wavelength is any one of the wavelengths.

[0011] In one embodiment, filtering out a true solution of the second transfer function at each wavelength from the two sets of solutions of the second transfer function at each wavelength includes: respectively calculating the standard deviation between each group of solutions of the second transfer function at different wavelengths to obtain a plurality of standard deviation values; determining a minimum standard deviation value from the plurality of standard deviation values; Each group of solutions corresponding to the minimum standard deviation value is selected as a true solution of the second transfer function at each wavelength.

[0012] A second aspect of the present application provides a dual-surface profile measuring device for a transparent optical element, comprising: A first acquisition module is configured to acquire a first diffraction pattern of a component to be measured, wherein the component to be measured is a transparent optical component whose double-surface profile is to be measured; a first reconstruction module, configured to perform phase recovery on the first diffraction pattern based on coherent modulation imaging to obtain a reconstruction result of the reflected wavefront of the element under test; A modeling module, configured to establish a dual-surface profile coupling model of the reflected wavefront of the element under test based on a reconstruction result of the reflected wavefront of the element under test; the dual-surface profile coupling model only includes dual-surface synthesis information of the element under test; The decoupling module is used to reversely decouple the dual-surface profile coupling model so as to separate the front surface profile information and the back surface profile information of the device under test from the dual-surface composite information.

[0013] A third aspect of the present application provides an electronic device, including: processor; and The memory stores executable codes thereon, and when the executable codes are executed by the processor, the processor is caused to execute the method described above.

[0014] A fourth aspect of the present application provides a computer-readable storage medium having executable code stored thereon. When the executable code is executed by a processor of an electronic device, the processor is caused to execute the method described above.

[0015] A fifth aspect of the present application provides a computer program product, which includes computer instructions, and when the computer instructions are executed by a processor, implements the method described above.

[0016] The technical solution provided by this application may include the following beneficial results: The technical solution of the present application is to obtain a first diffraction pattern of a DUT; the DUT is a transparent optical element whose dual-surface profile is to be measured; phase recovery is performed on the first diffraction pattern based on coherent modulation imaging to obtain a reconstruction result of the reflected wavefront of the DUT; a dual-surface profile coupling model of the reflected wavefront of the DUT is established based on the reconstruction result of the reflected wavefront of the DUT; the dual-surface profile coupling model only contains the dual-surface composite information of the DUT; and the dual-surface profile coupling model is reversely decoupled to separate the front surface profile information and the back surface profile information of the DUT from the dual-surface composite information. The present application can realize rapid reconstruction of the reflected wavefront of the DUT under single-exposure conditions based on coherent modulation imaging, and then establish a dual-surface profile coupling model of the reflected wavefront of the DUT based on the reconstruction result, so that the dual-surface profile information of the DUT can be obtained by decoupling the dual-surface profile coupling model. Therefore, the present application can be applied to dual-surface profile measurement under single-exposure conditions in dynamic scenes, reducing implementation costs. In addition, since coherent modulation imaging has high robustness, it can reduce the requirements for the measurement environment and is suitable for cross-scale measurement.

[0017] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other objects, features and advantages of the present application will become more apparent by describing in more detail exemplary embodiments of the present application in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the present application.

[0019] Figure 1 1 is a flow chart of a method for measuring the double-surface profile of a transparent optical element according to an embodiment of the present application; Figure 2 is a structural schematic diagram of a single-shot dual-surface profile measurement system based on coherent modulation imaging shown in an embodiment of the present application; Figure 3 1 is another flow chart of a method for measuring the dual-surface profile of a transparent optical element according to an embodiment of the present application; Figure 4 is the double-surface reconstruction result of the spherical lens in the simulation shown in the embodiment of the present application; Figure 5 is the double-surface reconstruction result of the free-form surface lens in the simulation shown in the embodiment of the present application; Figure 6 Schematic diagram of the amplitude and phase of a modulator calibrated on an optical experimental platform according to an embodiment of the present application; Figure 7 1 is a schematic diagram comparing the measurement results obtained in the embodiment of the present application in the simulation shown in the embodiment of the present application with the measurement results obtained using an interferometer in the related art; Figure 8 1 is a schematic structural diagram of a dual-surface profile measuring device for a transparent optical element according to an embodiment of the present application; Figure 9 It is a structural diagram of an electronic device shown in an embodiment of the present application. DETAILED DESCRIPTION

[0020] The following describes embodiments of the present application in more detail with reference to the accompanying drawings. Although the accompanying drawings illustrate embodiments of the present application, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. Rather, these embodiments are provided to make the present application more thorough and complete, and to fully convey the scope of the present application to those skilled in the art.

[0021] The terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application. As used in this application and the appended claims, the singular forms "a," "an," "the," and "the" are intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0022] It should be understood that although the terms "first", "second", "third", etc. may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of this application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0023] Measurement technologies in the related art include three-dimensional profilometers, three-dimensional coordinate measuring machines, fringe reflection phase deflectometers, and various interferometers. Among them, interferometers are currently the main equipment for measuring the surface profile of transparent optical components. However, interferometers are extremely sensitive to noise during the measurement process, so they have strict requirements for the measurement environment. For example, interferometers require that there must be no vibration in the measurement environment. In addition, for large-aperture devices, the ultra-long optical path limits the effectiveness of physical vibration isolation, so interferometers are not suitable for measuring large-aperture devices. In addition, the above measurement technologies all measure each surface separately. Taking interferometers as an example, when measuring the surface profile of a transparent optical component, parasitic fringes will be generated due to the interference between the two surfaces of the transparent optical component. Parasitic fringes will cause phase calculation errors and detector image blur. Therefore, when measuring one surface, the interferometer will suppress the other surface. For example, when the interferometer uses the reflected light of the front surface to measure the front surface profile, it will suppress the reflected light of the back surface. Therefore, interferometers cannot be used for dual-surface profile measurement under single exposure conditions in dynamic scenes and are expensive (the same is true for other measurement technologies in the related art).

[0024] In response to the above problems, an embodiment of the present application provides a dual-surface profile measurement method for a transparent optical element. Based on coherent modulation imaging, rapid reconstruction of the reflected wavefront of the element to be measured under single exposure conditions can be achieved, and then a dual-surface profile coupling model of the reflected wavefront of the element to be measured is established based on the reconstruction result, so that the dual-surface profile information of the element to be measured can be obtained by decoupling the dual-surface profile coupling model. Therefore, it can be suitable for dual-surface profile measurement under single exposure conditions in dynamic scenes, reducing implementation costs. In addition, since coherent modulation imaging has high robustness, it can reduce the requirements for the measurement environment and is suitable for cross-scale measurement.

[0025] The technical solutions of the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0026] Figure 1 It is a flow chart of a dual-surface profile measurement method of a transparent optical element shown in an embodiment of the present application.

[0027] See also Figure 1 The dual-surface profile measurement method of a transparent optical element of the present application may include: S110 , obtaining a first diffraction pattern of a component to be measured; the component to be measured is a transparent optical component whose double-surface profile is to be measured.

[0028] In an embodiment of the present application, it can be applied to a computing device, which is communicatively connected to a single-shot dual-surface profile measurement system based on coherent modulation imaging (hereinafter referred to as the "measurement system"). The computing device can obtain a first diffraction pattern of the element to be measured from the measurement system, and the element to be measured refers to a transparent optical element whose dual-surface profile is to be measured.

[0029] like Figure 2 As shown, the measurement system includes a wavefront sensor, an illumination device, a beam splitter, and a collimating lens. The wavefront sensor can be used to measure the reflected wavefront distribution of the measured component (such as the component to be measured / standard component) at two wavelengths. The dotted box in the upper right corner is a schematic diagram of the formation of the reflected wavefront of the measured component. The wavefront sensor includes a CMOS (Complementary Metal-Oxide-Semiconductor) image detector, a modulator, and a virtual aperture.

[0030] In a specific implementation, the DUT is placed on the DUT (i.e. Figure 2 The position of the sample to be tested in the virtual aperture) indicates that the current element under test is the element to be tested. The computing device can send a first control instruction to the measurement system. In response to the first control instruction, the measurement system controls the illumination device to output a dual-wavelength light source. The dual-wavelength light source passes through a beam splitter and a collimating lens in sequence and is vertically incident on the element to be tested, so that the element to be tested generates a reflected wavefront. Since the beam splitter is positioned at an angle, the beam splitter can propagate the reflected wavefront of the element to be tested to the support domain plane of the virtual aperture. The virtual aperture can converge the reflected wavefront at the support domain plane. The converged reflected wavefront is propagated to the modulator plane. The modulator can modulate the converged reflected wavefront at the modulator plane. When the modulated reflected wavefront is propagated to the detector plane, a diffraction pattern is generated. For ease of distinction, the diffraction pattern of the element to be tested is defined as a first diffraction pattern. At this time, the measurement system can control the CMOS image detector to collect the first diffraction pattern at the detector plane. The computing device obtains the first diffraction pattern from the measurement system.

[0031] It should be noted that the reflected wavefront refers to the phase plane of the light wave that leaves after being reflected by the surface of the transparent optical element. Since the element under test has two surfaces (i.e., front surface + back surface), the element under test has a phase plane of the light wave that leaves after being reflected by the surface of the transparent optical element. i The reflected wavefronts under the test are formed by the front and back surfaces of the component under test based on the corresponding wavelength λ i Coherent light source P iThe two sub-wavefronts generated are respectively composed of Figure 2 As shown in the dotted box in the upper right corner, the component under test is at wavelength λ1 (i.e. Figure 2 The reflected wavefront at wavelength 1) is composed of the sub-wavefront generated by the coherent light source P1 with wavelength λ1 on the front surface of the element under test and the sub-wavefront generated by the coherent light source P1 with wavelength λ1 on the back surface of the element under test. The reflected wavefront at wavelength λ2 (i.e. Figure 2 The reflected wavefront at wavelength 2) shown is composed of a sub-wavefront generated by the coherent light source P2 with wavelength λ2 on the front surface of the element under test and a sub-wavefront generated by the coherent light source P2 with wavelength λ2 on the back surface of the element under test.

[0032] S120 , performing phase recovery on the first diffraction pattern based on coherent modulation imaging to obtain a reconstruction result of a reflected wavefront of the component under test.

[0033] Since the response of the surface profile of the component under test (such as the DUT / standard component) to the incident light is mainly concentrated in the phase information, the complex amplitude distribution of the reflected wavefront of the component under test can be completely reconstructed through phase recovery, so as to subsequently invert the surface profile of the component under test.

[0034] In practical applications, after obtaining the first diffraction pattern of the DUT, the computing device can perform phase recovery on the first diffraction pattern based on coherent modulation imaging (CMI) to obtain the reconstructed result of the reflected wavefront of the DUT. , reconstruction results Characterize the reflected wavefront distribution of the DUT at the reconstructed support plane.

[0035] Wherein, i represents the i-th wavelength (i is a positive integer). The embodiment of the present application can use two wavelengths (i.e., i=2) or more than two wavelengths (i.e., i≥2). Since the twin terms existing in the decoupling process can be filtered out by using two wavelengths in the subsequent process to obtain the true solution, more than two wavelengths do not increase the effective information. Therefore, the embodiment of the present application can use two wavelengths (i.e., i=2).

[0036] The key step in the modulator plane is to apply and remove the modulator transfer function T(r m ) as a priori condition: Formula 1 Formula 2 Where i represents the i-th wavelength, k represents the k-th iteration, represents the raw wavefront estimate, represents the updated wavefront estimate, represents the front plane of the modulator plane, represents the back plane of the modulator plane, is a constant that determines the gradient update rate, It is a transfer function based on the following equation 4 Normalize to get .

[0037] It should be noted that as long as the experimental parameter settings remain unchanged, the transfer function of the modulator at each wavelength only needs to be calibrated once.

[0038] In particular, when the ray converges, a strong 0-1 constraint is imposed on the reflected wavefront distribution by using a virtual aperture of variable radius at the support plane, rather than a true circular hole. When the norm constraint is imposed at the detector plane, the estimate for each wavelength is updated as follows: Formula 3 Where I represents the intensity of the diffraction pattern (such as the first diffraction pattern of the element to be tested / the second diffraction pattern of the standard element) collected by the CMOS image detector, represents the detector plane.

[0039] exist Figure 2 In the measurement system shown, the embodiment of the present application uses the Fresnel propagation algorithm to propagate the reflected wavefront between three planes (i.e., the support domain plane, the modulator plane, and the detector plane). The reflected wavefront is continuously propagated and constrained between these three planes for several iterations. When the convergence judgment condition is met, the reflected wavefront estimate at the support domain plane is the reflected wavefront distribution obtained by phase recovery.

[0040] It can be seen that coherent modulation imaging achieves rapid reconstruction of the wavefront distribution under a single exposure by introducing a modulator with a known wavefront distribution. Therefore, the embodiment of the present application uses coherent modulation imaging to achieve rapid reconstruction of the reflected wavefront of the component to be measured under single exposure conditions. In addition, coherent modulation imaging has a simple lens-free system structure and is not affected by quality problems such as lens aberrations. The theoretical spatial resolution reaches the diffraction limit, and the measurement accuracy can reach one hundredth of the wavelength. Therefore, the embodiment of the present application uses coherent modulation imaging to provide high spatial resolution and high precision for the dual-surface profile measurement of transparent optical elements. In addition, the introduction of the modulator helps to eliminate the twin images and spatial offset ambiguity solutions in the iterative process, achieve robust convergence of a single exposure, and make coherent modulation imaging highly robust. Therefore, the embodiment of the present application uses coherent modulation imaging to reduce the requirements of the measurement environment and is suitable for cross-scale measurement, such as the measurement of large-aperture transparent optical elements.

[0041] S130 , establishing a dual-surface profile coupling model of the reflected wavefront of the component under test based on the reconstruction result of the reflected wavefront of the component under test; the dual-surface profile coupling model only includes dual-surface synthesis information of the component under test.

[0042] Due to the reconstruction of the reflected wavefront of the device under test In addition to the dual-surface composite information of the device under test, it also contains the illumination light information P of the measurement system. i , in order to avoid the illumination light information P i In order to affect the subsequent decoupling results, the embodiment of the present application can pre-calibrate the measurement system to obtain pre-calibration information of the measurement system, which includes the illumination light information P i In the embodiment of the present application, the reconstructed result of the reflected wavefront from the device under test is obtained. Remove the pre-calibration information and you can remove the illumination light information P i At the same time, the inevitable optical path coupling errors introduced by the optical components such as collimating lenses, beam splitters and the geometric structure of the measurement system can also be removed.

[0043] Reconstruction results of the reflected wavefront from the DUT After removing the pre-calibration information, a double-surface profile coupling model of the reflected wavefront of the component under test can be established. , dual surface profile coupling model It only contains the double-surface composite information of the component to be measured, and does not contain the illumination light information P of the measurement system. i .

[0044] S140 , reversely decoupling the dual-surface profile coupling model to separate the front surface profile information and the back surface profile information of the device under test from the dual-surface composite information.

[0045] The dual-surface composite information refers to the information synthesized by the front surface profile information of the device under test and the back surface profile information of the device under test. Therefore, the embodiment of the present application can reversely analyze the dual-surface profile coupling model. Decoupling is performed to separate the front surface profile information and the back surface profile information of the component under test from the dual-surface composite information.

[0046] Since the embodiment of the present application can realize the double-surface shape reconstruction of the device under test under single exposure (i.e. ), so a single exposure also means that continuous exposure can be used to observe the continuous changes in the dual-surface topography over a certain period of time. Compared with interferometry in related technologies, the embodiments of the present application have broad application prospects in dynamic measurement. For example, the effectiveness of the embodiments of the present application in the field of dual-surface profilometry has been verified using continuous phase plates (CPP) and quartz window plates.

[0047] As can be seen from this example, the solution provided by the present application obtains a first diffraction pattern of the element under test; the element under test is a transparent optical element whose dual-surface profile is to be measured; based on coherent modulation imaging, phase recovery is performed on the first diffraction pattern to obtain a reconstruction result of the reflected wavefront of the element under test; based on the reconstruction result of the reflected wavefront of the element under test, a dual-surface profile coupling model of the reflected wavefront of the element under test is established; the dual-surface profile coupling model only contains the dual-surface composite information of the element under test; and the dual-surface profile coupling model is reversely decoupled to separate the front surface profile information and the back surface profile information of the element under test from the dual-surface composite information. The present application can realize rapid reconstruction of the reflected wavefront of the element under test under single exposure conditions based on coherent modulation imaging, and then establish a dual-surface profile coupling model of the reflected wavefront of the element under test based on the reconstruction result, so that the dual-surface profile information of the element under test can be obtained by decoupling the dual-surface profile coupling model. Therefore, it can be applied to dual-surface profile measurement under single exposure conditions in dynamic scenes, reducing implementation costs. In addition, since coherent modulation imaging has high robustness, it can reduce the requirements for the measurement environment and is suitable for cross-scale measurement.

[0048] Figure 3 1 is another flow chart of the dual-surface profile measurement method of a transparent optical element shown in the present application.

[0049] See also Figure 3 The dual-surface profile measurement method of a transparent optical element of the present application may include: S310, obtaining a first diffraction pattern of a component to be measured; the component to be measured is a transparent optical component whose double-surface profile is to be measured.

[0050] This step can refer to the description of step S110 above, which will not be repeated here.

[0051] S320, performing phase recovery on the first diffraction pattern based on coherent modulation imaging to reconstruct an initial coupling model of the reflected wavefront of the element under test; the initial coupling model includes dual-surface synthesis information of the element under test and illumination light information of a measurement system used to measure the element under test.

[0052] This step can be referred to the description of step S120 above, which will not be repeated here.

[0053] It should be noted that the initial coupling model of this step is the reconstruction result of step S120 , so the initial coupled model Contains the dual-surface composite information of the component under test and the illumination light information P of the measurement system i .

[0054] It should be noted that in the actual light propagation process, the incident light will be reflected multiple times between the two surfaces of the transparent optical element. Taking quartz glass with a refractive index n≈1.5 as an example, the energy of the second-order reflected light is 1.6% of the energy of the first-order reflected light. In order to estimate the maximum impact of the second-order reflected light on the complete reflected wave field, it is assumed that its phase difference relative to other reflected components is , the error corresponding to the measurement result is less than , the error magnitude can be ignored within the required range. Therefore, in order to facilitate the initial coupling model Reconstruction and dual surface profile coupling model For decoupling, the embodiment of the present application approximately assumes that the reflected wavefront of the element under test consists only of the first-order reflected wavefronts generated by its front and rear surfaces respectively.

[0055] When representing the profile of a single surface, the embodiment of the present application takes the lowest point of the surface as the zero point of the surface height, and the relative height of the surface profile relative to the zero point can be expressed as h. When the irradiation light P is vertically incident on a certain surface, the relationship between the transfer function of the surface and the profile h of the surface can be expressed as follows: Formula 4 in, , which represents the wave number, j represents the imaginary number .

[0056] Based on the above formula 4, the profile of the front surface of the DUT can be expressed as h f Indicates that the profile of the rear surface of the component under test can be expressed as h r express.

[0057] When the illumination light P (such as Figure 2 When the dual-wavelength light source shown in the figure is incident vertically on the DUT, the front surface of the DUT generates reflected light and transmitted light respectively. The transmitted light on the front surface will continue to propagate through the medium (the medium distribution is uniform by default) to the rear surface of the DUT, and the reflected light generated on the rear surface will again transmit through the front surface of the DUT. Therefore, the reflected light on the front surface of the DUT is and the reflected light from the back surface of the DUT They can be expressed as follows: Formula 5 Formula 6 in, represents the refractive index of the medium of the component under test at the i-th wavelength, It represents the reflectivity of the medium of the component to be measured at the i-th wavelength, It represents the transmittance of the medium of the component under test at the i-th wavelength, represents a coherent light source of wavelength i.

[0058] The complete reflected wavefront of the component under test (i.e., the initial coupling model of step S320) can be expressed as the reflected light from the front surface of the DUT and the reflected light from the back surface of the DUT Based on the above equations 5 and 6, the following equation 7 can be obtained: Formula 7 S330 , removing the illumination light information from the initial coupling model to establish a dual-surface profile coupling model for obtaining the reflected wavefront of the component under test; the dual-surface profile coupling model only includes dual-surface composite information of the component under test.

[0059] Due to the initial coupling model of the reflected wavefront of the device under test In addition to the dual-surface composite information of the device under test, it also contains the illumination light information P of the measurement system. i , in order to avoid the illumination light information P i In order to affect the subsequent decoupling results, the embodiment of the present application can pre-calibrate the measurement system to obtain pre-calibration information of the measurement system, which includes the illumination light information P i In the embodiment of the present application, the reconstructed result of the reflected wavefront from the device under test is obtained. Remove the pre-calibration information and you can remove the illumination light information P i At the same time, the inevitable optical path coupling errors introduced by the optical components such as collimating lenses, beam splitters and the geometric structure of the measurement system can also be removed.

[0060] Initial coupling model of the reflected wavefront from the DUT After removing the pre-calibration information, a double-surface profile coupling model of the reflected wavefront of the component under test can be established. , dual surface profile coupling model It only contains the double-surface composite information of the component to be measured, and does not contain the illumination light information P of the measurement system. i .

[0061] In one embodiment, removing illumination light information from the initial coupling model to establish a dual-surface profile coupling model for obtaining the reflected wavefront of the device under test may include: A second diffraction pattern of a standard element is obtained; the standard element is a transparent optical element with known single-surface profile information and high flatness; phase recovery is performed on the second diffraction pattern based on coherent modulation imaging to obtain a reconstruction result of the reflected wavefront of the standard element; the reconstruction result of the reflected wavefront of the standard element includes the known single-surface profile information and illumination light information; the reconstruction result of the reflected wavefront of the standard element is used as pre-calibration information of the measurement system; and the pre-calibration information is removed from the initial coupling model to establish a dual-surface profile coupling model for obtaining the reflected wavefront of the element to be measured.

[0062] In the process of pre-calibrating the measurement system, the embodiment of the present application can first select a transparent optical element whose single surface has been measured and has high flatness as a standard element, that is, the standard element refers to a transparent optical element with known single surface profile information, and the known single surface profile information characterizes that the flatness of the single surface of the standard element is high and the surface fluctuation is small enough to be regarded as a pure plane, for example, the known surface fluctuation of the standard element is close to zero.

[0063] Then, the embodiment of the present application can place the standard element on the element to be tested (ie Figure 2 The position of the sample to be tested in the virtual aperture) indicates that the current measured element is a standard element. The computing device can send a second control instruction to the measurement system. In response to the second control instruction, the measurement system controls the illumination device to output a dual-wavelength light source. The dual-wavelength light source passes through the beam splitter and the collimating lens in sequence and is vertically incident on the standard element, so that the standard element generates a reflected wavefront. Since the beam splitter is positioned at an angle, the beam splitter can propagate the reflected wavefront of the standard element to the support domain plane of the virtual aperture. The virtual aperture can converge the reflected wavefront at the support domain plane. The converged reflected wavefront is propagated to the modulator plane. The modulator can modulate the converged reflected wavefront at the modulator plane. When the modulated reflected wavefront is propagated to the detector plane, a diffraction pattern is generated. For ease of distinction, the diffraction pattern of the standard element is defined as a second diffraction pattern. At this time, the measurement system can control the CMOS image detector to collect the second diffraction pattern at the detector plane, and the computing device obtains the second diffraction pattern from the measurement system.

[0064] After obtaining the second diffraction pattern of the standard element, the computing device can perform phase recovery on the second diffraction pattern based on coherent modulation imaging to obtain a reconstruction result of the reflected wavefront of the standard element. , reconstruction results Characterize the reflected wavefront distribution of the standard element at the reconstructed support domain plane, and the reconstruction result of the reflected wavefront of the standard element It can be expressed as follows: Style 8 in, It represents the reflectivity of the standard component medium at the i-th wavelength. Since the reflected light propagates from the optically sparse medium (air) to the optically dense medium (the component is usually made of quartz), it is introduced , which represents the half-wave loss.

[0065] Similarly, the reconstruction result of the reflected wavefront of the standard element is In addition to the known single surface profile information of the standard component, it also contains the illumination light information P of the measurement system i Since the standard element and the element to be measured are both in the same measurement environment, the reconstruction result of the reflected wavefront of the standard element is Contains lighting information P i Initial coupling model with the reflected wavefront of the DUT Contains lighting information P i Similarly, since the single surface of the standard element is a plane, that is, the known surface shape of the standard element is close to zero, the embodiment of the present application can reconstruct the reflection wavefront of the standard element. As pre-calibration information of the measurement system, the initial coupling model of the reflected wavefront from the device under test is obtained. Remove the pre-calibration information, that is, the initial coupling model of the reflected wavefront from the device under test Reconstruction result of the reflected wavefront after removing the standard element , which can be equivalent to the initial coupling model of the reflected wavefront from the DUT Remove the illumination light information P of the measurement system i , so that the double surface profile coupling model of the reflected wavefront of the device under test It only contains the double-surface composite information of the component to be measured, and does not contain the illumination light information P of the measurement system. i .

[0066] If the illumination light is measured directly, the energy of the illumination light is two orders of magnitude higher than the energy of the reflected wavefront, and the illumination light cannot be measured using the same measurement system. Therefore, the embodiment of the present application uses the initial coupling model of the reflected wavefront of the device under test to obtain the initial coupling model of the reflected wavefront of the device under test. Reconstruction result of the reflected wavefront after removing the standard element , the initial coupling model of the reflected wavefront from the DUT can be realized Remove the illumination light information P of the measurement system i .

[0067] Furthermore, the accuracy of interferometric measurements in related art techniques relies heavily on high-quality reference planes, which are typically limited to planar or spherical shapes, making it difficult to measure zero values ​​on aspheric surfaces. Compared to the high-quality reference planes required in related art techniques, the plane of the standard element in the embodiments of the present application can have some undulations, thus eliminating the need for a high-quality reference plane. Furthermore, the embodiments of the present application impose no shape restrictions on the surface profile of the component under test, so the embodiments of the present application are applicable regardless of whether the surface profile of the component under test is planar, spherical, or aspheric (such as a hyperboloid, freeform surface, etc.).

[0068] In addition, the interferometer in the related art obtains an interference pattern by interfering the reflected light of the reference plane with the reflected light of the plane to be measured. Therefore, the reference plane needs to be used in each measurement in the related art. Compared with the multiple use of the reference plane in the related art, the reconstruction result of the reflected wavefront of the standard element in the embodiment of the present application is It is not affected by the component under test, so the embodiment of the present application only needs to perform pre-calibration once, thereby greatly reducing the number of pre-calibration times.

[0069] S340 , reversely decoupling the dual-surface profile coupling model to separate the front surface profile information and the back surface profile information of the component under test from the dual-surface composite information.

[0070] This step can be referred to the description of step S140 above, which will not be repeated here.

[0071] In one embodiment, reversely decoupling the dual-surface profile coupling model to separate the front surface profile information and the back surface profile information of the device under test from the dual-surface composite information may include: A first transfer function of the front surface of the element under test is determined, and a second transfer function of the rear surface of the element under test is determined; target decoupling parameters of a dual-surface profile coupling model are determined based on the first transfer function and the second transfer function; the target decoupling parameters include a first decoupling parameter and a second decoupling parameter, the first decoupling parameter being used to separate the front surface profile information of the element under test, and the second decoupling parameter being used to separate the rear surface profile information of the element under test; the front surface profile information is reversely solved from the dual-surface profile coupling model using phase information of the first decoupling parameter, and the rear surface profile information is reversely solved from the dual-surface profile coupling model using phase information of the second decoupling parameter.

[0072] According to the above formula (4) and the characteristics of the front surface of the DUT, the first transfer function of the front surface of the DUT can be determined as , and according to the above formula 4 and the characteristics of the rear surface of the device under test, the second transfer function of the rear surface of the device under test can be determined , the first transfer function and the second transfer function They can be expressed as follows: Formula 9 Style 10 According to the first transfer function and the second transfer function , determine the dual surface profile coupling model The target decoupling parameter may include a first decoupling parameter and a second decoupling parameter, the first decoupling parameter may be used to separate the front surface profile information of the device under test, the second decoupling parameter may be used to separate the back surface profile information of the device under test, and then extract its phase information from the first decoupling parameter , and extract its phase information from the second decoupling parameter ,in, and The physical meaning of is the optical path difference introduced by the front and back surfaces of the element to be measured. In this embodiment of the application, the phase information of the first decoupling parameter can be used. , from the dual-surface profile coupling model Reverse solve the front surface contour information , and the phase information using the second decoupling parameter , from the dual-surface profile coupling model Reverse solve the surface profile information .

[0073] In one embodiment, the reflected wavefront of the DUT is generated based on coherent light sources of different wavelengths; and determining the target decoupling parameters of the dual-surface profile coupling model based on the first transfer function and the second transfer function may include: A quasi-Newton iteration method is used to calculate two sets of solutions of the second transfer function at each wavelength; the two sets of solutions include true solutions and twin solutions; the true solution of the second transfer function at each wavelength is screened out from the two sets of solutions of the second transfer function at each wavelength; a dual-surface profile coupling model and the true solution of the second transfer function at each wavelength are used to calculate the true solution of the first transfer function at each wavelength; the true solution of the first transfer function at the target wavelength is used as the first decoupling parameter, and the true solution of the second transfer function at the target wavelength is used as the second decoupling parameter; wherein the target wavelength is any wavelength.

[0074] The reflected wavefront of the component under test is generated based on coherent light sources of different wavelengths, such as Figure 2As shown, the reflected wavefront of the element under test is generated based on a coherent light source (P1 and P2) of dual wavelengths (λ1 and λ2). In the embodiment of the present application, a dual-wavelength light source is used to illuminate the element under test so that the twin solutions (also called twin terms) existing in the decoupling process are filtered out based on the different optical path lengths introduced by the same surface profile of the element under test at different wavelengths to obtain the true solution, and the dual surface profiles of the element under test are inversely calculated.

[0075] In a specific implementation, the following formula 11 can be obtained according to the above formulas 7, 8, 9, and 10: Formula 11 Ideally, since the surface of the DUT is transparent, the first transfer function of the front surface of the DUT is and the second transfer function of the rear surface can be approximately regarded as pure phase modulation, that is, .

[0076] Based on the above constraints, the embodiment of the present application can derive the decoupling process as a nonlinear problem, which can be expressed as follows: Formula 12 The embodiment of the present application uses the quasi-Newton iteration method to calculate the second transfer function The solution at each wavelength , where j = [1, 2], which represents two sets of solutions at a certain wavelength. The two sets of solutions can include real solutions and twin solutions. Specifically, the initial coupling model of the reflected wavefront of the DUT is obtained by the above phase recovery. and the reconstruction results of the reflected wavefront of the standard element ,Will and Substituting into the above formula 11, the dual surface profile coupling model can be obtained , at each wavelength λ i (i=[1,2]), and Substituting into the above formula 12, the second transfer function can be obtained At the corresponding wavelength λ i The true solution and its twin solution (also called the twin term) under , that is, each wavelength corresponds to two sets of solutions: the true solution and the twin solution.

[0077] In order to eliminate the influence of the twin solution, the embodiment of the present application respectively calculates the second transfer function At each wavelength λ i Two sets of solutions under (i=[1,2]) ), filter out the second transfer function At each wavelength λ iThe true solution under (i=[1,2]): and ,in, is the second transfer function The true solution at wavelength λ1 is, is the second transfer function The true solution at wavelength λ2.

[0078] After filtering out the second transfer function At each wavelength λ i The true solution under (i=[1,2]) and ), the embodiment of the present application can couple the dual surface profile model , the transmittance of the medium of the component under test at the i-th wavelength , the second transfer function At each wavelength λ i The true solution under and ) is substituted into the above formula 11, and the first transfer function is obtained respectively. At each wavelength λ i The true solution is: and ,in, is the first transfer function The true solution at wavelength λ1 is, is the first transfer function The real solution at wavelength λ2. Specifically, at wavelength λ1 (i.e., i=1), the embodiment of the present application can 、 and Substituting into the above formula 11, the first transfer function can be obtained The real solution Similarly, at wavelength λ2 (i.e., i=2), the embodiment of the present application can 、 and Substituting into the above formula 11, the first transfer function can be obtained The real solution .

[0079] In summary, ( , )and( , ) is the real solution obtained at different wavelengths. In the embodiment of the present application, any set of real solutions can be selected as the target decoupling parameters. Specifically, in the embodiment of the present application, the first transfer function can be The true solution at the target wavelength is used as the first decoupling parameter, and the second transfer function The true solution at the target wavelength is used as the second decoupling parameter, where the target wavelength can be any wavelength. For example, if the target wavelength is wavelength λ1, then the first decoupling parameter is the first transfer function The real solution , the second decoupling parameter is the second transfer function The real solution , so the target decoupling parameter is ( , ); If the target wavelength is wavelength λ2, the first decoupling parameter is the first transfer function The real solution , the second decoupling parameter is the second transfer function The real solution , so the target decoupling parameter is ( , ).

[0080] In one example, the target decoupling parameter is ( , ) as an example, the embodiment of the present application can adopt the target decoupling parameter as ( , ) for front surface profile information and rear surface profile information Specifically, from the first decoupling parameter Extract its phase information , and from the second decoupling parameter Extract its phase information According to the above formulas 4, 5, 6, 7 and 11, the first decoupling parameter Phase information and the second decoupling parameter Phase information Inversion to obtain front surface contour information and rear surface profile information , which can be expressed as follows: Style Thirteen Formula 14 In one embodiment, filtering out the true solution of the second transfer function at each wavelength from the two sets of solutions of the second transfer function at each wavelength may include: The standard deviations between each set of solutions of the second transfer function at different wavelengths are calculated respectively to obtain a plurality of standard deviation values; the minimum standard deviation value is determined from the plurality of standard deviation values; and each set of solutions corresponding to the minimum standard deviation value is selected as the true solution of the second transfer function at each wavelength.

[0081] Since the second transfer function The twin solutions at different wavelengths are different, so the embodiment of the present application can calculate the second transfer function separately The standard deviation between each set of solutions at different wavelengths, resulting in multiple standard deviation values , and then from these standard deviation values Determine the minimum standard deviation in , the minimum standard deviation Each corresponding set of solutions is the second transfer function The true solution at each wavelength.

[0082] Specifically, the specific process of screening out the true solution by calculating the standard deviation can be expressed as follows: Formula 15 Formula 16 Formula 17 Where N represents The sampling number of a single side in the λ is the number of pixels on a single side used to collect the first diffraction pattern. m represents the mth group of solutions in the wavelength λ1, and n represents the nth group of solutions in the wavelength λ2. express The pixel value at the coordinate (p,q) is the size of the pixel value at the coordinate (p,q). Indicates the difference between the measurement results of different wavelengths, Represents the mean.

[0083] At multiple standard deviations , select one to use The set with the smallest value ( , ), then the corresponding set and The second transfer function is The true solution at each wavelength.

[0084] In order to verify the effectiveness and accuracy of the method proposed in the embodiment of the present application, the embodiment of the present application is verified by the following three simulation experiments: Simulation experiment 1: Figure 4 This is the double-surface reconstruction result of the standard spherical lens in the simulation.

[0085] In simulation experiment 1, two refractive lenses were generated to verify the proposed method. One was a standard spherical lens, and the other was a free-form lens composed of two randomly generated continuous optical surfaces. In this embodiment, the uniformity of the element medium was used as the default condition.

[0086] exist Figure 4In the figure, (a) is the front surface of the measured spherical lens, (b) is the back surface of the measured spherical lens, (c)~(f) are two sets of reconstructed surfaces (using illumination light with a wavelength of 1053nm), and (g)~(j) are the residuals between (c)~(f) in (a)~(b) and their corresponding nominal profiles, where (i)~(j) profiles correspond to the dotted lines in (a)~(b) and (e)~(f).

[0087] The front and back surface profiles of the standard spherical lens simulated in the embodiment of the present application are as follows Figure 4 As shown in (a) and (b), the peak-to-valley values ​​are 372.71nm and 283.28nm respectively. In the simulation, the wavelengths of the illumination light sources selected in the embodiment of the present application are 633nm and 1053nm respectively, and the reconstructed RMSE (Root Mean Square Error) is less than For ease of presentation, Figure 4 Only two sets of decoupling results with a wavelength of 633 nm are shown. Figure 4 (c)~(f). Among them, Figure 4 (g)~(j) show Figure 4 The residual between the results of (c) to (f) and their corresponding nominal surface profiles. After the screening of σ in the above formulas 15 to 17, Figure 4 The two dotted boxes in the figure represent the true solution and its corresponding residual, and the PV (Peak to Valley) values ​​are 0.687nm and 0.455nm respectively. This means that the method proposed in the embodiment of the present application can well achieve the matching between the generated surface and the reconstructed surface, achieving nanometer-level detection accuracy. Figure 4 (k)~(l) show the dotted contour of the nominal surface and Figure 4 For a direct comparison of the measured surface profiles, see the enlarged images of (k) to (l). Figure 4 The lower half of the graph shows that the horizontal axis is the peak-to-valley value, the vertical axis is the surface undulation size (i.e., surface contour), the dark curve is the reconstruction result obtained by coherent modulation imaging in the embodiment of the present application, and the light curve is the actual result of the simulation, such as Figure 4 As shown in (k) to (l), the dark curve completely coincides with the light curve, thus verifying that the reconstruction result obtained by the coherent modulation imaging in the embodiment of the present application is completely consistent with the actual result of the simulation.

[0088] The method proposed in the embodiment of the present application only requires a single exposure and acquisition, which meets the application scenario that requires dynamic measurement of certain components. When performing coherent modulation imaging (CMI) to reconstruct the complex amplitude distribution, the number of samples per side is set to 512, and a real binary phase plate is used as the modulator in the wavefront sensor, so that the number of reconstruction iterations is less than 350. Therefore, on a computing device equipped with an Intel Core i7-12700F 2.10 GHz CPU, 32 GB RAM, an x64 processor, and an NVIDIA GeForce RTX4060 GPU, the total time, including the full phase recovery and dual surface profile decoupling process, is approximately 44.79 seconds, which can simultaneously achieve fast and stable front and back surface profile measurement.

[0089] In order to further verify the universality of the method proposed in the embodiment of the present application for the surface profile of a transparent optical element, the embodiment of the present application provides a second simulation experiment: Figure 5 This is the double-surface reconstruction result of the free-form lens in the simulation.

[0090] exist Figure 5 In the figure, (a) is the front surface of the free-form surface lens under test, (b) is the back surface of the free-form surface lens under test, (c)~(f) are two sets of reconstructed surfaces (using illumination light with a wavelength of 1053nm), and (g)~(j) are the residuals between (c)~(f) in (a)~(b) and their corresponding nominal profiles, where the profiles (i)~(j) correspond to the dotted lines in (a)~(b) and (c)~(d).

[0091] The embodiment of the present application simulates a free-form surface refractive index lens for testing. Figure 5 (a) and (b) are random generalized front and back surfaces, with PV values ​​of 73.20 nm and 90.97 nm, respectively. The other experimental parameters are the same as those for the standard spherical lens mentioned in Simulation Experiment 1. Similarly, the dashed boxes represent the true solution and its corresponding residual, with PV values ​​of 1.64 nm and 1.66 nm, respectively.

[0092] The present embodiment also provides a simulation experiment 3 to demonstrate the effectiveness and accuracy of the method proposed in the present embodiment. According to the proposed method, the present embodiment built a measurement system on an optical experimental platform and calibrated the amplitude and phase of the modulator, such as Figure 6 As shown, A is the amplitude of the binary random amplitude modulation board, B is the phase of the binary random amplitude modulation board, and the binary random amplitude modulation board is the modulator.

[0093] The modulator in the wavefront sensor is a key component of the measurement system. Before performing dual-surface profile measurement, it is necessary to accurately understand the transfer function of the modulator relative to the image detector ( The experiment used a binary random amplitude modulation plate with a line width of 15 μm. Its distribution is similar to the grid division of a checkerboard. The transmittance of each grid unit to the light beam is approximately 0 or 1. In this embodiment of the application, the modulator is preloaded on a bidirectional translation stage and the transfer function of the modulator is calculated using the ePIE algorithm ( ) for reconstruction.

[0094] Figure 7 : is a schematic diagram comparing the measurement results obtained in the embodiment of the present application in simulation with the measurement results obtained using an interferometer in the related art. Figure 7 , (a) is the front surface profile measured in the embodiment of the present application, (b) is the front surface profile measured by an interferometer in the related art, (c) and (d) correspond to the profile values ​​at the dotted lines in (a) and (b), respectively, wherein (c) and (d) respectively show the amplitude and phase distribution of the calibrated modulator, (e) is the rear surface profile measured in the embodiment of the present application, (f) is the rear surface profile measured by an interferometer in the related art, and (g) and (h) correspond to the profile values ​​at the dotted lines in (e) and (f), respectively.

[0095] It should be noted that the light sources used in the experiment have wavelengths of 632.8nm and 405nm. After passing through a 2-inch achromatic doublet collimating lens with a focal length of 300mm, the resulting collimated beam is perpendicularly incident on the DUT. The reflected wavefront from the DUT is then converged by the collimating lens again. The converged beam is deflected by a beam splitter, modulated by a modulator, and ultimately propagated to the detector plane. The image detector used in the experiment has a maximum resolution of 4104×3006, a pixel size of 3.45 microns, and a 12-bit analog-to-digital converter (ADC).

[0096] The element to be measured is a 2-inch transparent optical window. The measurement results obtained in the embodiment of the present application are compared with the measurement results obtained by using an interferometer in the related art to verify the effectiveness and accuracy of the method proposed in the embodiment of the present application. Specifically, the embodiment of the present application selects a wedge-shaped optical window with a wedge angle of 30' and a center thickness of 10 mm as a standard element to pre-calibrate the measurement system. Since there is a fixed wedge angle between the front and rear surfaces of the standard element, the reflected light from the rear surface will be deflected away from the detector plane during pre-calibration. Therefore, the image detector only receives the reflected wavefront information from the front surface of the standard element. The refractive index of the medium of the element to be measured at wavelengths of 632.8 nm and 405 nm are 1.457 and 1.470, respectively, and the medium is assumed to be uniform by default. The diameter and average thickness of the element to be measured are 50.8 mm and 4 mm, respectively.

[0097] exist Figure 7 In the embodiment of the present application, the decoupled double-surface profile result at a wavelength of 405 nm is used as an example for verification experiment demonstration and compared with the measurement results obtained by using an interferometer in the related art. Among them, (c), (d), (g), and (h) correspond to the profile lines at the dotted lines in (a), (b), (e), and (f), respectively. In terms of actual measurement values, the peak-to-valley values ​​(PV) of the front and rear surfaces measured by the embodiment of the present application are 227.5 nm and 240.5 nm, respectively, and the corresponding measurement results of the interferometer are 230.3 nm and 234.8 nm, respectively. The peak-to-valley value error is less than It can be seen that the measurement results obtained in the embodiment of the present application are consistent with the measurement results obtained using the interferometer in the related art, thereby verifying the effectiveness and accuracy of the method proposed in the embodiment of the present application.

[0098] from Figure 4 、 Figure 5 and Figure 7 It can be seen that the method proposed in the embodiment of the present application can simultaneously achieve effective and accurate measurement of the double-surface profiles of the transparent optical element.

[0099] Through the above-mentioned simulation experiments 1, 2, and 3, it can be verified that the method proposed in the embodiment of the present application can measure the dual-surface profile of transparent optical components with a measurement accuracy of nanometers. In addition, it can also be applied to the detection of non-continuous or non-optical components to a certain extent. The embodiment of the present application provides a new method for in-situ and dynamic measurement of transparent optical components.

[0100] It can be seen that the measurement results obtained by using coherent modulation imaging in the embodiment of the present application are compared with the measurement results obtained by using an interferometer in the related art, which confirms that the embodiment of the present application has high accuracy and stability in simultaneously measuring the dual-surface profiles of transparent optical elements.

[0101] As can be seen from this example, the solution provided in the present application can realize the rapid reconstruction of the reflected wavefront of the element to be measured under single exposure conditions based on coherent modulation imaging, and then establish a dual-surface profile coupling model of the reflected wavefront of the element to be measured based on the reconstruction result, so that the dual-surface profile information of the element to be measured can be obtained by decoupling the dual-surface profile coupling model. Therefore, it can be suitable for dual-surface profile measurement under single exposure conditions in dynamic scenes, reducing implementation costs. In addition, since coherent modulation imaging has high robustness, it can reduce the requirements for the measurement environment and is suitable for cross-scale measurement.

[0102] Furthermore, the solution provided in the present application can get rid of the high-quality reference plane and has no shape restrictions on the surface profile of the component to be measured. Therefore, the solution provided in the present application is applicable regardless of whether the surface profile of the component to be measured is a plane, a spherical surface or an aspherical surface (such as a hyperbolic surface, a free-form surface, etc.).

[0103] Furthermore, the solution provided by this application is to reconstruct the reflected wavefront of the standard element. It is not affected by the component under test, so the solution provided by this application only needs to be pre-calibrated once, thereby greatly reducing the number of pre-calibrations.

[0104] Corresponding to the aforementioned embodiment of the method for realizing the application function, the present application also provides a dual-surface profile measuring device for a transparent optical element, an electronic device, and corresponding embodiments.

[0105] Figure 8 Schematic diagram of the structure of a dual-surface profile measuring device for a transparent optical element shown in an embodiment of the present application.

[0106] See also Figure 8 The present application provides a dual-surface profile measuring device for a transparent optical element, which may include: A first acquisition module 810 is configured to acquire a first diffraction pattern of a component to be measured; the component to be measured is a transparent optical component whose double-surface profile is to be measured; A first reconstruction module 820 is configured to perform phase recovery on the first diffraction pattern based on coherent modulation imaging to obtain a reconstruction result of a reflected wavefront of the device under test; A modeling module 830 is configured to establish a dual-surface profile coupling model of the reflected wavefront of the element under test based on the reconstruction result of the reflected wavefront of the element under test; the dual-surface profile coupling model only includes dual-surface synthesis information of the element under test; The decoupling module 840 is used to reversely decouple the dual-surface profile coupling model so as to separate the front surface profile information and the back surface profile information of the device under test from the dual-surface composite information.

[0107] In one embodiment, the reconstruction result is an initial coupling model; the first reconstruction module 820 may include: The first reconstruction submodule is used to perform phase recovery on the first diffraction pattern based on coherent modulation imaging to reconstruct an initial coupling model of the reflected wavefront of the element under test; the initial coupling model includes dual-surface synthesis information of the element under test and illumination light information of a measurement system used to measure the element under test.

[0108] In one embodiment, the modeling module 830 may include: The modeling submodule is used to remove the illumination light information from the initial coupling model so as to establish a double-surface profile coupling model for obtaining the reflected wavefront of the component to be measured.

[0109] In one embodiment, the modeling submodule may include: a second acquisition unit, configured to acquire a second diffraction pattern of a standard element; the standard element being a transparent optical element with known single surface profile information and high flatness; a second reconstruction unit, configured to perform phase recovery on the second diffraction pattern based on coherent modulation imaging to obtain a reconstruction result of a reflection wavefront of the standard element; the reconstruction result of the reflection wavefront of the standard element includes known single surface profile information and illumination light information; A first definition unit is configured to use the reconstruction result of the reflected wavefront of the standard element as pre-calibration information of the measurement system; The modeling unit is used to remove the pre-calibration information from the initial coupling model so as to establish a dual-surface profile coupling model for obtaining the reflected wavefront of the component to be measured.

[0110] In one embodiment, the decoupling module 840 may include: a transfer function determination submodule, configured to determine a first transfer function of the front surface of the device under test, and a second transfer function of the rear surface of the device under test; a target decoupling parameter determination submodule, configured to determine target decoupling parameters of the dual-surface profile coupling model based on the first transfer function and the second transfer function; the target decoupling parameters comprising a first decoupling parameter and a second decoupling parameter, the first decoupling parameter being used to separate the front surface profile information of the DUT, and the second decoupling parameter being used to separate the back surface profile information of the DUT; The inversion submodule is used to use the phase information of the first decoupling parameter to reversely solve the front surface profile information from the dual-surface profile coupling model, and to use the phase information of the second decoupling parameter to reversely solve the rear surface profile information from the dual-surface profile coupling model.

[0111] In one embodiment, the reflected wavefront of the DUT is generated based on coherent light sources of different wavelengths; the target decoupling parameter determination submodule may include: The first calculation unit is used to calculate two sets of solutions of the second transfer function at each wavelength using a quasi-Newton iteration method; the two sets of solutions include a true solution and a twin solution; a screening unit, configured to screen out a true solution of the second transfer function at each wavelength from the two groups of solutions of the second transfer function at each wavelength; a second calculation unit, configured to calculate the true solution of the first transfer function at each wavelength by using the dual-surface profile coupling model and the true solution of the second transfer function at each wavelength; The second definition unit is configured to use the true solution of the first transfer function at the target wavelength as the first decoupling parameter, and use the true solution of the second transfer function at the target wavelength as the second decoupling parameter; wherein the target wavelength is any wavelength.

[0112] In one embodiment, the screening unit may include: a third calculation subunit, configured to respectively calculate the standard deviation between each set of solutions of the second transfer function at different wavelengths to obtain a plurality of standard deviation values; a minimum value determining subunit, configured to determine a minimum standard deviation value from a plurality of standard deviation values; The screening subunit is used to screen each group of solutions corresponding to the smallest standard deviation value as the true solution of the second transfer function at each wavelength.

[0113] As can be seen from this example, the solution provided by the present application obtains a first diffraction pattern of the element under test; the element under test is a transparent optical element whose dual-surface profile is to be measured; based on coherent modulation imaging, phase recovery is performed on the first diffraction pattern to obtain a reconstruction result of the reflected wavefront of the element under test; based on the reconstruction result of the reflected wavefront of the element under test, a dual-surface profile coupling model of the reflected wavefront of the element under test is established; the dual-surface profile coupling model only contains the dual-surface composite information of the element under test; and the dual-surface profile coupling model is reversely decoupled to separate the front surface profile information and the back surface profile information of the element under test from the dual-surface composite information. The present application can realize rapid reconstruction of the reflected wavefront of the element under test under single exposure conditions based on coherent modulation imaging, and then establish a dual-surface profile coupling model of the reflected wavefront of the element under test based on the reconstruction result, so that the dual-surface profile information of the element under test can be obtained by decoupling the dual-surface profile coupling model. Therefore, it can be applied to dual-surface profile measurement under single exposure conditions in dynamic scenes, reducing implementation costs. In addition, since coherent modulation imaging has high robustness, it can reduce the requirements for the measurement environment and is suitable for cross-scale measurement.

[0114] Regarding the apparatus in the above embodiment, the specific manner in which each module performs operations has been described in detail in the embodiment of the method, and will not be elaborated again here.

[0115] Figure 9 It is a structural diagram of an electronic device shown in an embodiment of the present application.

[0116] See also Figure 9 , the electronic device 900 includes a memory 910 and a processor 920 .

[0117] The processor 920 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor. Memory 910 may include various types of storage units, such as system memory, read-only memory (ROM), and permanent storage. ROM may store static data or instructions required by processor 920 or other computer modules. Permanent storage may be a readable and writable storage device. Permanent storage may be a non-volatile storage device that retains stored instructions and data even when the computer is powered off. In some embodiments, the permanent storage device utilizes a mass storage device (e.g., a magnetic or optical disk, flash memory). In other embodiments, the permanent storage device may be a removable storage device (e.g., a floppy disk, optical drive). System memory may be a readable and writable storage device or a volatile readable and writable storage device, such as dynamic random access memory (DRAM). System memory may store some or all instructions and data required by the processor during operation. Furthermore, memory 910 may include any combination of computer-readable storage media, including various types of semiconductor memory chips (e.g., DRAM, SRAM, SDRAM, flash memory, programmable read-only memory), as well as magnetic disks and / or optical disks. In some embodiments, the memory 910 may include a readable and / or writable removable storage device, such as a compact disc (CD), a read-only digital versatile disc (e.g., DVD-ROM, dual-layer DVD-ROM), a read-only Blu-ray disc, an ultra-density optical disc, a flash memory card (e.g., SD card, mini SD card, Micro-SD card, etc.), a magnetic floppy disk, etc. Computer-readable storage media do not include carrier waves and transient electronic signals transmitted wirelessly or wired.

[0118] The memory 910 stores executable codes. When the executable codes are processed by the processor 920 , the processor 920 may execute part or all of the above-mentioned methods.

[0119] In addition, the method according to the present application may also be implemented as a computer program or a computer program product, which includes computer program code instructions for executing some or all of the steps in the above method of the present application.

[0120] Alternatively, the present application can also be implemented as a computer-readable storage medium (or non-transitory machine-readable storage medium or machine-readable storage medium), which stores executable code (or computer program or computer instruction code) and, when executed by a processor of an electronic device (or server, etc.), enables the processor to perform part or all of the steps of the above-mentioned method according to the present application.

[0121] The present application also provides a computer program product, which includes computer instructions, and when the computer instructions are executed by a processor, the method described above is implemented.

[0122] The embodiments of the present application have been described above. The above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is selected to best explain the principles of the embodiments, their practical applications, or improvements to the technology in the market, or to enable other persons skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for measuring the double-surface profile of a transparent optical element, characterized in that: include: Acquiring a first diffraction pattern of the component to be tested; The component to be measured is a transparent optical component whose double-surface profile is to be measured; Performing phase recovery on the first diffraction pattern based on coherent modulation imaging to obtain a reconstruction result of the reflected wavefront of the element under test; Based on the reconstruction result of the reflected wavefront of the element under test, a dual-surface profile coupling model of the reflected wavefront of the element under test is established; the dual-surface profile coupling model only includes the dual-surface synthesis information of the element under test; The dual-surface profile coupling model is reversely decoupled to separate the front surface profile information and the back surface profile information of the device under test from the dual-surface composite information.

2. The method according to claim 1, characterized in that The reconstruction result is an initial coupling model; and the phase recovery of the first diffraction pattern based on coherent modulation imaging to obtain a reconstruction result of the reflected wavefront of the element under test includes: Phase recovery is performed on the first diffraction pattern based on coherent modulation imaging to reconstruct an initial coupling model of the reflected wavefront of the element under test; the initial coupling model includes dual-surface synthesis information of the element under test and illumination light information of a measurement system used to measure the element under test.

3. The method according to claim 2, characterized in that The step of establishing a dual-surface profile coupling model of the reflected wavefront of the element under test based on the reconstruction result of the reflected wavefront of the element under test comprises: The illumination light information is removed from the initial coupling model to establish a dual-surface profile coupling model for obtaining the reflected wavefront of the device under test.

4. The method according to claim 3, characterized in that The step of removing the illumination light information from the initial coupling model to establish a dual-surface profile coupling model for obtaining the reflected wavefront of the device under test comprises: Obtaining a second diffraction pattern of a standard element; the standard element is a transparent optical element with known single surface profile information and high flatness; performing phase recovery on the second diffraction pattern based on the coherent modulation imaging to obtain a reconstruction result of the reflected wavefront of the standard element; the reconstruction result of the reflected wavefront of the standard element includes the known single surface profile information and the illumination light information; using the reconstructed result of the reflected wavefront of the standard element as pre-calibration information of the measurement system; The pre-calibration information is removed from the initial coupling model to establish a dual-surface profile coupling model for obtaining the reflected wavefront of the component under test.

5. The method according to claim 1, wherein The reverse decoupling of the dual-surface profile coupling model to separate the front surface profile information and the back surface profile information of the device under test from the dual-surface composite information includes: determining a first transfer function of the front surface of the device under test, and determining a second transfer function of the rear surface of the device under test; determining target decoupling parameters of the dual-surface profile coupling model based on the first transfer function and the second transfer function; the target decoupling parameters include a first decoupling parameter and a second decoupling parameter, the first decoupling parameter being used to separate the front surface profile information of the device under test, and the second decoupling parameter being used to separate the back surface profile information of the device under test; The front surface profile information is reversely solved from the dual-surface profile coupling model using the phase information of the first decoupling parameter, and the rear surface profile information is reversely solved from the dual-surface profile coupling model using the phase information of the second decoupling parameter.

6. The method according to claim 5, characterized in that The reflected wavefront of the element under test is generated based on coherent light sources of different wavelengths; and determining the target decoupling parameters of the dual-surface profile coupling model according to the first transfer function and the second transfer function includes: Using a quasi-Newton iteration method, two sets of solutions of the second transfer function at each wavelength are calculated respectively; the two sets of solutions include a true solution and a twin solution; screening out a true solution of the second transfer function at each wavelength from the two groups of solutions of the second transfer function at each wavelength; Calculating the true solution of the first transfer function at each wavelength respectively by using the dual-surface profile coupling model and the true solution of the second transfer function at each wavelength; A true solution of the first transfer function at a target wavelength is used as a first decoupling parameter, and a true solution of the second transfer function at the target wavelength is used as a second decoupling parameter; wherein the target wavelength is any one of the wavelengths.

7. The method according to claim 6, characterized in that The step of filtering out a true solution of the second transfer function at each wavelength from the two groups of solutions of the second transfer function at each wavelength comprises: respectively calculating the standard deviation between each group of solutions of the second transfer function at different wavelengths to obtain a plurality of standard deviation values; determining a minimum standard deviation value from the plurality of standard deviation values; Each group of solutions corresponding to the minimum standard deviation value is selected as a true solution of the second transfer function at each wavelength.

8. A dual-surface profile measuring device for a transparent optical element, characterized in that: include: A first acquisition module, configured to acquire a first diffraction pattern of the component to be tested; The component to be measured is a transparent optical component whose double-surface profile is to be measured; a first reconstruction module, configured to perform phase recovery on the first diffraction pattern based on coherent modulation imaging to obtain a reconstruction result of the reflected wavefront of the element under test; A modeling module, configured to establish a dual-surface profile coupling model of the reflected wavefront of the element under test based on a reconstruction result of the reflected wavefront of the element under test; the dual-surface profile coupling model only includes dual-surface synthesis information of the element under test; The decoupling module is used to reversely decouple the dual-surface profile coupling model so as to separate the front surface profile information and the back surface profile information of the device under test from the dual-surface composite information.

9. An electronic device, characterized in that: include: processor; as well as A memory having executable codes stored thereon, which, when executed by the processor, causes the processor to execute the method according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that An executable code is stored thereon, and when the executable code is executed by a processor of an electronic device, the processor is caused to execute the method according to any one of claims 1 to 7.

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