Micro-nano structure reflector machining method and system and micro-nano structure reflector

Abstract

The invention provides a micro-nano structure reflecting mirror processing method and system and a micro-nano structure reflecting mirror, and the method can comprise the steps: processing a mirror surface of an initial mirror structure, and obtaining an initial lens; wherein the surface shape of the mirror surface of the initial lens reaches a first set threshold value; plating a reflecting film on the first surface of the initial lens to obtain an initial reflector; performing surface shape correction on the second surface of the initial reflector; processing a micro-nano structure on the second surface after surface shape correction to obtain a micro-nano structure reflector; wherein the second surface and the first surface are different surfaces. Through the processing method, the precision of the micro-nano structure reflector can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of lens processing, and more specifically, to a method and system for manufacturing a micro-nano structure mirror and a micro-nano structure mirror. Background Art

[0002] As an important optical element, mirrors are widely used in laser systems, astronomical telescopes, and solar energy devices.

[0003] Traditional mirrors rely on curved reflecting surfaces to deflect and converge the propagation direction of light beams. In addition, mirrors also need to deposit a reflective film layer to achieve the reflection function. After the preparation of the reflective film layer, there are inevitably residual stresses such as thermal stress and intrinsic stress. Under the action of the stress, there may be trends such as shrinkage and expansion, which may all cause the bending deformation of the mirror blank, thus affecting the surface shape accuracy of the mirror. Summary of the Invention

[0004] The purpose of the present application is to provide a method and system for manufacturing a micro-nano structure mirror and a micro-nano structure mirror, which can improve the surface shape accuracy of the mirror.

[0005] In a first aspect, the present invention provides a method for manufacturing a micro-nano structure mirror, including: processing the mirror surface of an initial mirror structure to obtain an initial lens; wherein, the surface shape of the mirror surface of the initial lens reaches a first set threshold; depositing a reflective film on the first surface of the initial lens to obtain an initial mirror; performing surface shape correction on the second surface of the initial mirror; processing a micro-nano structure on the second surface after surface shape correction to obtain a micro-nano structure mirror; wherein, the second surface and the first surface are different surfaces.

[0006] In the above implementation, surface shape correction can also be performed after depositing the reflective film, which can reduce the influence of the stress generated by depositing the reflective film on the surface shape of the mirror, thereby improving the surface shape accuracy.

[0007] In an alternative embodiment, the performing surface shape correction on the second surface of the initial mirror includes: obtaining the surface shape correction parameters of the second surface of the initial mirror based on the internal reflection surface shape of the initial mirror; using the surface shape correction parameters to perform surface shape correction on the second surface of the initial mirror to reduce the surface shape undulation of the internal reflection surface of the initial mirror; wherein, the surface shape of the internal reflection surface of the initial mirror after surface shape correction reaches a second set threshold, the surface shape characterized by the second set threshold has less undulation than the surface shape characterized by the first set threshold, and the internal reflection wavefront of the internal reflection surface shape of the initial mirror after surface shape correction reaches the set accuracy.

[0008] In the above implementation manner, the parameters for correcting the surface shape can be determined based on the inner reflection surface shape of the initial mirror, so that the surface shape correction parameters can be determined to more accurately match the correction requirements of the mirror. Further, the surface shape obtained after surface shape correction can reach the second set threshold, better meeting the requirements for deflection and convergence of the light beam propagation direction of the mirror.

[0009] In an alternative implementation manner, obtaining the surface shape correction parameters of the second surface of the initial mirror based on the inner reflection surface shape of the initial mirror includes: detecting the inner reflection surface shape of the initial mirror to obtain the surface shape parameters of the inner reflection surface of the initial mirror; and obtaining the surface shape correction parameters of the second surface of the initial mirror based on the surface shape parameters and the size of the initial mirror.

[0010] In the above implementation manner, the surface shape can be detected, and the surface shape correction parameters of the second surface can be determined based on the surface shape detection, so that the determined surface shape correction parameters can better meet the processing requirements of the second surface of the initial mirror.

[0011] In an alternative implementation manner, correcting the surface shape of the second surface of the initial mirror includes: a. detecting the inner reflection surface shape of the initial mirror; b. determining the surface shape correction parameters of the second surface of the initial mirror based on the detection result of the inner reflection surface shape of the initial mirror; c. using the surface shape correction parameters to correct the surface shape of the second surface of the initial mirror; if the inner reflection surface shape of the initial mirror after surface shape correction does not reach the second set threshold, then execute the above steps a to c; until the inner reflection surface shape of the initial mirror after surface shape correction reaches the second set threshold.

[0012] In the above implementation manner, multiple surface shape corrections can be implemented in a loop manner, and the surface shape correction parameters can be re-determined for each correction. After each surface shape correction, the surface shape can be detected to determine whether the requirements are met. The corrections completed through such a loop multiple times can make the correction result better meet the requirements and make the accuracy of the corrected surface shape higher.

[0013] In an alternative implementation manner, detecting the surface shape of the inner reflection surface of the initial mirror includes: using a test light beam to irradiate from the second surface of the initial mirror into its interior, then propagating to the inner reflection surface, and then reflecting the test light beam out, and obtaining the detection result of the inner reflection surface shape of the initial mirror based on the reflected test light beam.

[0014] In an alternative embodiment, processing the second surface of the mirror after surface shape correction to obtain a micro-nano structure mirror includes: using an etching technique to process the second surface of the initial mirror to form a micro-nano structure, thereby obtaining a micro-nano structure mirror; or, using a turning technique to process the second surface of the initial mirror to form a micro-nano structure, thereby obtaining a micro-nano structure mirror; or, using a nanoimprinting technique to process the second surface of the initial mirror to form a micro-nano structure, thereby obtaining a micro-nano structure mirror.

[0015] In an alternative embodiment, processing the mirror surface of the initial mirror structure to obtain an initial lens includes: performing rough polishing on the mirror surface of the initial mirror structure so that the surface shape of the mirror surface reaches a first set threshold, thereby obtaining an initial lens; wherein, the rough polishing includes one or more of ring polishing, small grinding head polishing, ion beam polishing, and magnetorheological polishing.

[0016] In the above implementation, the surface shape of the mirror surface can be processed through various alternative polishing methods, which can make the processing means of the surface shape more flexible.

[0017] In an alternative embodiment, depositing a reflective film on the first surface of the initial lens to obtain an initial mirror includes: using an evaporation coating technique to deposit a reflective film on the first surface of the initial lens, thereby obtaining an initial mirror; or, using a magnetron sputtering coating technique to deposit a reflective film on the first surface of the initial lens, thereby obtaining an initial mirror.

[0018] In a second aspect, the present invention provides a micro-nano structure mirror processing system, including: a processing tool for performing the steps of the method according to any one of the foregoing embodiments.

[0019] In a third aspect, the present invention provides a micro-nano structure mirror, which is a micro-nano structure mirror processed by using the method according to any one of the foregoing embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0021] Figure 1 It is a flowchart of the micro-nano structure mirror processing method provided by the embodiments of the present application;

[0022] Figures 2a to 2e It is a schematic diagram of a semi-finished lens during the micro-nano structure mirror processing method provided by the embodiments of the present application;

[0023] Figure 3 This is a partial flowchart of the method for manufacturing a micro-nano structure mirror provided by an embodiment of the present application;

[0024] Figure 4 This is another partial flowchart of the method for manufacturing a micro-nano structure mirror provided by an embodiment of the present application. Detailed implementation manners

[0025] Next, the technical solutions in the embodiments of the present application will be described with reference to the accompanying drawings in the embodiments of the present application.

[0026] It should be noted that similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. At the same time, in the description of the present application, terms such as "first" and "second" are only used for distinguishing descriptions and cannot be construed as indicating or implying relative importance.

[0027] The inventors have studied and learned that traditional mirrors with curved configurations usually deflect and converge the light beam propagation direction by bending the reflecting surface. The mirrors formed in this way have problems such as low design freedom, heavy structure, and complex system, and it is difficult to meet the requirements of the lightweight, integration, and large-aperture development of mirrors. Due to the above problems of traditional mirrors, micro-nano structure mirrors have received extensive attention from researchers. Compared with traditional mirrors, micro-nano structure mirrors modulate light waves through the micro-nano structures on their surfaces. The mirrors realized in this way can be planarized and lightweight, providing a new research direction for the development of large-aperture optical systems.

[0028] During the manufacturing process of the mirror, the reflection function is realized by coating a reflective film layer. Residual stresses such as thermal stress and intrinsic stress inevitably exist during and after the preparation of the reflective film layer. From the different effects on the mirror blank, the residual stress can be divided into two types: tensile stress and compressive stress. Under the action of tensile stress and compressive stress, the reflective film has a tendency to expand and contract respectively. Whichever tendency it is, it will cause the bending deformation of the mirror blank of the lens, thereby affecting the surface shape accuracy of the mirror. The surface shape accuracy of the mirror is an important index of the mirror. Especially in imaging applications, in order to obtain good imaging effects, high requirements are imposed on the surface shape accuracy of the mirror.

[0029] The inventor has conducted research on improving the surface shape accuracy and learned that in order to reduce the influence of film residual stress on the surface shape accuracy of the lens, on the one hand, the process of depositing the reflective film can be optimized to reduce the film stress and thus reduce the deformation amount of the lens after depositing the reflective film, thereby reducing the influence of depositing the reflective film on the surface shape accuracy of the reflective mirror. However, the research results show that the film stress can be reduced but not eliminated. Especially when the strength of the mirror blank is insufficient and the requirements for surface shape accuracy are relatively high, the reduced film residual stress will still have a non-negligible impact on the surface shape accuracy of the reflective mirror. Another way to reduce the influence of film residual stress on the surface shape accuracy of the lens is to improve the mechanical strength of the reflective mirror. Reducing the diameter-to-thickness ratio of the reflective mirror is an effective means to improve its mechanical strength. The diameter-to-thickness ratio refers to the ratio of the lens diameter to the thickness. When the lens diameter is determined, increasing the thickness of the mirror blank can reduce the diameter-to-thickness ratio. However, as the thickness of the mirror blank increases, the weight of the mirror blank will increase accordingly, and the lens will become bulky. Therefore, the thickness of the mirror blank cannot be increased arbitrarily. Especially for application scenarios with lightweight requirements for the lens, such as space telescopes, there are strict restrictions on the weight of the lens. Therefore, there are also some obstacles to reducing the diameter-to-thickness ratio of the reflective mirror, and it is impossible to effectively solve the influence of depositing the reflective film on the surface shape accuracy of the reflective mirror.

[0030] Further research has learned that the change trend and change amount of the surface shape before and after depositing the reflective film can be tested in advance, and then compensation can be carried out in advance during the process of processing the surface shape of the mirror blank, and the surface shape of the mirror blank can be processed into a surface shape result opposite to the change amount of the surface shape after depositing the reflective film. However, inevitably, the influence brought by coating may be uncertain, and the deformations caused by depositing the reflective film in different times may not be unique, which makes it difficult to carry out compensation in advance during the process of processing the surface shape of the mirror blank.

[0031] Since the surface shape accuracy of the mirror blank is the basis for the surface shape accuracy of the micro-nano structure reflective mirror, when the surface shape accuracy of the mirror blank cannot be guaranteed, the surface shape of the reflective mirror after completing the micro-nano structure processing naturally cannot be guaranteed either.

[0032] Based on the above research, the embodiments of the present application provide a method and system for processing a micro-nano structure reflective mirror and a micro-nano structure reflective mirror, which can improve the surface shape accuracy of the reflective mirror.

[0033] Please refer to Figure 1 , which is a flowchart of the method for processing a micro-nano structure reflective mirror provided by the embodiments of the present application. The method for processing a micro-nano structure reflective mirror provided by the embodiments of the present application can be applied to a micro-nano structure reflective mirror processing system, and the steps in the method for processing a micro-nano structure reflective mirror are executed through the micro-nano structure reflective mirror processing system. The following will elaborate on the Figure 1 specific process shown in detail.

[0034] Step 110, process the mirror surface of the initial mirror structure to obtain an initial lens.

[0035] Among them, the surface shape of the mirror surface of the initial lens reaches the first set threshold.

[0036] Before processing into the initial lens, the outer shape of the original lens blank can also be processed first, so that the outer shape of the lens can generally meet the shape requirements of the mirror. Exemplarily, if a circular mirror is required, the lens blank can be processed into a circular shape first. Exemplarily, if there are requirements for the diameter of the lens, the outer shape of the original lens blank can also be processed according to the required diameter to obtain an initial lens structure with the required size.

[0037] Optionally, the milling and grinding forming method can be used to process the outer shape of the original lens blank. For example, the processing drawing of the shape of the lens can be designed in advance, and the outer shape of the original lens blank can be processed based on this processing drawing to obtain an initial lens structure that can meet the requirements.

[0038] Optionally, the processing of the initial lens structure in step 110 can also be to process its surface shape to obtain a lens with a surface shape that meets the requirements.

[0039] In this embodiment, the first set threshold can be used to limit the threshold of the surface shape, and this threshold can be used to represent the undulation degree of the surface shape. This threshold can also be used to represent the error between the processed surface shape and the surface shape in the target state. The surface shape in the target state can be the surface shape set according to the actual requirements of the mirror, and the parameters of the surface shape in the target state can be set in advance according to the requirements of the mirror. For example, flatness, surface shape amplitude, surface shape roughness, etc. In one example, the first set threshold can be expressed as the root mean square error (RMS) of the surface shape, and the optical surface shape quality of the initial lens can be described by this first set threshold.

[0040] Exemplarily, the surface shape of the mirror surface of the initial lens reaching the first set threshold can mean that the RMS of the surface shape of the mirror surface of the initial lens is equal to or smaller than the first set threshold.

[0041] Since surface shape correction will be performed after step 110, based on this, in order to improve the processing efficiency of the lens, the first set threshold of step 110 can be set to a relatively large value, and on the premise of meeting the optical imaging requirements, the processing difficulty can also be reduced. In one example, the first set threshold can be a value between 0.05λ and 0.12λ. For example, taking the wavelength of 632.8nm as an example, the first set threshold can be values such as 0.1λ@632.8nm, 0.068λ@632.8nm, 0.12λ@632.8nm, 0.05λ@632.8nm, etc.

[0042] Optionally, step 110 may adopt a rough polishing process to make the surface shape of the obtained initial lens mirror reach the first set threshold.

[0043] Optionally, the above-mentioned rough polishing process may include one or more of ring polishing, small grinding head polishing, ion beam polishing, and magnetorheological polishing. Exemplarily, only one of the processing methods can be selected to achieve rough polishing, or two or more rough polishing methods can be combined to achieve the rough polishing process. Exemplarily, since the accuracy requirement of the surface shape of step 110 is relatively low, this step can adopt the ring polishing method to process the initial mirror structure.

[0044] Step 120, deposit a reflective film on the first surface of the initial lens to obtain an initial mirror.

[0045] Optionally, deposit a reflective film on the first surface of the initial lens based on requirements such as the working wavelength band and reflectivity. Among them, the working wavelength band and reflectivity are input parameters determined before designing the mirror. It can be understood that the determination of the working wavelength band and reflectivity is a pre-work and has been determined before the processing flow.

[0046] Optionally, the reflective film can be a metal reflective film or a dielectric reflective film layer.

[0047] Exemplarily, the material of the metal reflective film can be a film such as a gold film, a silver film, or an aluminum film.

[0048] In order to improve the safety of the reflective film, a protective film and an auxiliary film can also be deposited during the deposition of the reflective film. The protective film can be used to prevent damage and oxidation of the reflective film. The auxiliary film can be used to improve the adhesion of the reflective film.

[0049] Exemplarily, the material of the dielectric reflective film layer can be SiO2, HfO2, TiO2, Ta2O5, ZrO2, etc. By using the matching of film layer materials with high and low refractive indices, the reflection can be enhanced. In this embodiment, the specific material of the film can be selected based on the requirements of the working wavelength band and reflectivity of the reflection. In one example, the reflective film can be a reflective film system formed by Cr, Cu, Ag, Al2O3, Ta2O5, and SiO2 film layers based on an Ag film layer, and this example reflective film has a high reflectivity in the visible light wavelength band.

[0050] Optionally, an evaporation coating technology can be used to deposit a reflective film on the first surface of the initial lens to obtain an initial mirror.

[0051] Optionally, a magnetron sputtering coating technology can be used to deposit a reflective film on the first surface of the initial lens to obtain an initial mirror.

[0052] Exemplarily, the reflection film can be deposited using an electron beam evaporation coating technique. After the reflection film is deposited, an interferometer is used to detect the surface shape of the internal reflection surface.

[0053] Step 130: Correct the surface shape of the second surface of the initial mirror.

[0054] In the above step 110, processing the surface shape of the lens can make the RMS of the surface shape reach the first set threshold. However, in step 120, depositing the reflection film will cause the surface shape of the lens to change. Further, through step 130, the surface shape of the second surface of the mirror can be corrected, thereby eliminating the influence of depositing the reflection film in step 120 on the surface shape of the lens, improving the surface shape accuracy of the internal reflection surface, and making the internal reflection wavefront of the mirror reach the set accuracy.

[0055] Among them, the second surface is different from the first surface. Taking the initial mirror as a circular lens as an example, the first surface can be one of the circular surfaces, and the second surface can be the other circular surface.

[0056] Optionally, the surface shape of the second surface of the initial mirror can be corrected based on the gap between the internal reflection surface shape of the initial mirror obtained in step 120 and the internal reflection surface shape in the target state.

[0057] Exemplarily, the amount of mirror blank removal can be determined based on the gap between the internal reflection surface shape of the initial mirror and the internal reflection surface shape in the target state, and the surface shape of the second surface of the initial mirror can be corrected based on the amount of mirror blank removal.

[0058] Step 140: Process a micro-nano structure on the second surface after surface shape correction to obtain a micro-nano structure mirror.

[0059] Based on different actual requirements, the required processed micro-nano structures may also be different. Exemplarily, the micro-nano structure can be determined based on requirements such as the focal length, F-number, and working wavelength of the mirror. In some instances, the micro-nano structure can be a multi-layer stepped structure, a continuous surface shape structure, a single-layer stepped structure, etc.

[0060] As Figures 2a to 2e shown, Figures 2a to 2e respectively show the processing process of the lens. Under the action of step 110, the lens can change from the Figure 2a structure to the Figure 2b shown structure. The upper surface is exaggerated to show a larger processing amplitude, and the lower surface is also processed. Since the processing amplitude is small, it is only distinguished by the thickness of the lines in the figure; under the action of step 120, the lens can change from the Figure 2b structure to the Figure 2cIn the structure shown, due to the stress generated during the deposition of the reflective film, there are some changes in the inner reflective surface and the outer reflective surface of the initial mirror; under the action of step 130, the surface shape of the inner reflective surface of the initial mirror can be corrected, and the lens can be changed from Figure 2c the structure of Figure 2d to the structure shown; under the action of step 140, a micro-nano structure can be formed on the side of the lens away from the reflective surface, that is, the second surface, and the lens can be changed from Figure 2d the structure of Figure 2e to the structure shown. To clearly show the micro-nano structure on the mirror, the size of the micro-nano structure in Figure 2e is enlarged for drawing. Actually, Figure 2d the thickness of the substrate S1 of the mirror blank in the white part is in the millimeter range, and Figure 2e the thickness of the micro-nano structure in Figure 2d is in the micron range. From the examples shown in Figure 2e , it can be seen that the thickness of the substrate S1 of the mirror blank is greater than the thickness of the micro-nano structure Ms. It can be understood that Figure 2d and Figure 2e are only examples. In actual situations, the thickness difference between the thickness of the substrate S1 of the mirror blank and the thickness of the micro-nano structure Ms may vary due to different mirror blanks actually processed, or may also vary due to different requirements for the micro-nano structure mirror to be processed.

[0061] Conventional micro-nano structure mirrors process the micro-nano structure on the reflective film. Since the physical morphology of the reflective film changes, its optical parameters also change, affecting the optical performance of the mirror. Moreover, the thickness of the reflective film layer is usually in the micron range, and the depth of the micro-nano structure is also in the micron range. Processing the micro-nano structure will break the stress balance state of the reflective film layer, thereby causing uncontrollability of the mirror surface shape. In contrast, the micro-nano structure mirror of the present invention deposits the reflective film on the first surface of the lens; the surface shape is corrected through the second surface to eliminate the influence of depositing the reflective film on the surface shape of the inner reflective surface of the first surface, providing a basis for processing the micro-nano structure on the second surface. In addition, since the micro-nano structure is processed on the second surface rather than the reflective film on the first surface, the thickness of the substrate of the mirror blank is much greater than the thickness of the micro-nano structure. Therefore, processing the micro-nano structure will not affect the surface shape of the mirror blank. The micro-nano structure mirror processed by the present application can exert the function of the micro-nano structure while avoiding the influence of micro-nano structure processing on the optical performance of the mirror.

[0062] Through the above method process, the surface shape of the lens can be preliminarily corrected before depositing the reflective film. After depositing the reflective film, the surface shape can be further corrected based on the deviation, which can improve the accuracy of the surface shape of the obtained mirror.

[0063] In different scenarios, different surface shape correction parameters may be obtained due to different target surface shapes. With different surface shape correction parameters, the logic of surface shape correction can also be different. The above step 130 will be described below through different implementation manners.

[0064] In one implementation manner, through the detection of the surface shape, the surface shape correction parameters for correcting the surface shape can be determined, and the surface shape correction can be completed at one time based on the surface shape correction parameters, so as to implement the second surface shape correction of the initial mirror. As Figure 3 shown, the above step 130 may include step 131 and step 132.

[0065] Step 131, based on the inner reflection surface shape of the initial mirror, obtain the surface shape correction parameters of the second surface of the initial mirror.

[0066] Among them, the inner reflection surface of the initial mirror may represent the interface between the reflective film and the mirror body.

[0067] The surface shape correction parameters may include parameters such as the surface shape removal amount of the second surface of the initial mirror and the curvature of the surface shape.

[0068] In some scenarios, when there are also requirements for the surface of the mirror, in this case, the surface shape correction parameters may also include parameters such as the smoothness of the second surface of the initial mirror.

[0069] Optionally, based on the different tools used for surface shape correction, the representation forms of the surface shape correction parameters may also be different. The surface shape correction parameters may also be the working parameters of the surface shape correction tool determined based on the surface shape removal amount of the second surface of the initial mirror. Exemplarily, when using the ion beam polishing technology to perform surface shape correction on the second surface of the initial mirror, the surface shape correction parameters may be manifested as the working parameters of the tool used in the ion beam polishing technology, for example, parameters such as the polishing working duration, the rotation speed of the sample stage, and the swing angle. Of course, based on the different tools actually used for surface shape correction, there may be more presentation forms of the representation forms of the surface shape correction parameters.

[0070] Optionally, the inner reflection surface shape of the initial mirror can be detected to obtain the surface shape parameters of the inner reflection surface of the initial mirror; then, based on the surface shape parameters and the size of the initial mirror, the surface shape correction parameters of the second surface of the initial mirror can be obtained.

[0071] Exemplarily, use a test beam to irradiate from the second surface of the initial mirror into its interior, then propagate to the inner reflection surface, and then reflect the test beam out, and obtain the detection result of the inner reflection surface shape of the initial mirror based on the reflected test beam.

[0072] Exemplarily, the surface shape parameter may include the surface shape RMS of the inner reflecting surface of the initial mirror. The surface shape parameter may also include parameters such as surface shape accuracy parameter, surface roughness parameter, surface profile parameter, surface waviness, surface integrity, etc.

[0073] The surface shape accuracy parameter may be the surface shape error. For example, the maximum height difference, i.e., the peak-to-valley value, between the inner reflecting surface of the initial mirror and the surface shape in the target state. It can reflect the degree of deviation of the entire surface from the ideal shape. The surface shape accuracy parameter may be the root mean square error. For example, it is obtained by taking the root mean square of the deviations of each point on the inner reflecting surface of the initial mirror from the surface shape in the target state. It can more comprehensively reflect the roughness and irregularity of the surface.

[0074] The surface roughness parameter may include parameters such as arithmetic mean roughness and maximum roughness. The arithmetic mean roughness can represent the arithmetic mean of the absolute values of the profile offsets within a sampling length. It intuitively reflects the average height of the microscopic undulations of the inner reflecting surface of the initial mirror and can be used to represent the smoothness of the inner reflecting surface of the initial mirror. The maximum roughness can represent the maximum peak-to-valley height difference of the profile within the sampling length. It can reflect the largest height change on the surface of the inner reflecting surface of the initial mirror and can be used to indicate whether there are large protrusions or depressions on the inner reflecting surface of the initial mirror.

[0075] The surface profile parameter may include parameters such as slope error and radius of curvature. The slope error can represent the difference between the inclination degree of the inner reflecting surface of the initial mirror in a certain direction and the surface shape in the target state, usually in units of degrees or radians. This slope error will affect the refraction and reflection characteristics of the mirror for light. The radius of curvature determines the refraction and focusing characteristics of light on the inner reflecting surface of the initial mirror. Different optical applications have different precision requirements for the radius of curvature. For example, in the reflector of an astronomical telescope, the precision of the radius of curvature may be required to reach the millimeter or even sub-millimeter level.

[0076] The surface waviness can represent the periodic or non-periodic surface undulations between the macroscopic surface shape error and the microscopic roughness. The surface waviness can be represented by the amplitude and wavelength of the waviness. The surface waviness will affect the scattering characteristics and imaging quality of the initial mirror.

[0077] The surface integrity is used to indicate whether there are defects such as scratches, cracks, and pitting on the surface of the initial mirror.

[0078] Optionally, the surface shape correction parameter of the second surface of the initial mirror can be determined by combining the surface shape of the initial mirror and the deviation between the surface shape of the initial mirror and the surface shape in the target state.

[0079] Step 132: Use the surface shape correction parameters to correct the second surface of the initial mirror to reduce the surface shape undulation of the internal reflection surface of the initial mirror.

[0080] Among them, the surface shape of the internal reflection surface of the initial mirror after surface shape correction reaches the second set threshold.

[0081] In this embodiment, the surface shape characterized by the second set threshold has less undulation than the surface shape characterized by the first set threshold, and the internal reflection wavefront of the surface shape of the internal reflection surface of the initial mirror after surface shape correction reaches the set accuracy.

[0082] In this embodiment, based on the different representations of the surface shape in the target state, the representation of the second set threshold can also be different. Among them, the second set threshold can be expressed as surface shape accuracy, surface roughness, surface profile parameters, surface waviness, surface integrity, etc.

[0083] It can be understood that when the surface shape of the internal reflection surface of the initial mirror after surface shape correction reaches the second set threshold, the deviation between the surface shape of the internal reflection surface of the initial mirror after surface shape correction and the surface shape in the target state can be relatively small.

[0084] In the above implementation manner, the surface shape parameters and surface shape correction parameters can be determined in combination with the detection of the surface shape, so that the obtained surface shape correction parameters can better meet the correction requirements of the initial mirror in the current real-time state, and the accuracy of the corrected initial mirror can also better meet the accuracy requirements. Further, under this logic, even in the case of high wavefront accuracy requirements, after one processing, the expected accuracy can be achieved, so there is no need for repeated detection and processing, and the surface shape correction can be realized more efficiently.

[0085] In one implementation manner, the surface shape of the initial mirror can be corrected by multiple rounds of surface shape correction. Each round of surface shape correction can include detecting the surface shape of the mirror in the current state to determine the surface shape correction parameters currently used to correct the surface shape, and using the real-time determined surface shape correction parameters to implement the current surface shape correction. As Figure 4 shown, the above step 130 may include steps 133 to 135.

[0086] Step 133: Detect the surface shape of the internal reflection surface of the initial mirror.

[0087] Step 134: Based on the detection result of the surface shape of the internal reflection surface, determine whether the surface shape of the internal reflection surface of the initial mirror reaches the second set threshold.

[0088] If it reaches the second set threshold, end the current process; if it does not reach the second set threshold, continue to execute step 135.

[0089] Step 135: Determine the surface shape correction parameters of the second surface of the initial mirror based on the detection result of the inner reflecting surface shape of the initial mirror.

[0090] Optionally, use a test beam to irradiate into the initial mirror from its second surface, then propagate to the inner reflecting surface, and then reflect the test beam out, and obtain the detection result of the inner reflecting surface shape of the initial mirror based on the reflected test beam.

[0091] In this embodiment, the surface shape correction parameters of the second surface of the initial mirror can be determined based on the detection result of the inner reflecting surface shape of the initial mirror and the setting accuracy of the inner reflection wavefront.

[0092] Optionally, the method for determining the surface shape correction parameters of the second surface of the initial mirror in step 135 can be the same as the method for determining the surface shape correction parameters of the second surface of the initial mirror in the foregoing step 131. For details, refer to the description in the foregoing step 131 and will not be elaborated here.

[0093] In this embodiment, when this step 133 is executed for the first time, the initial mirror can represent the mirror obtained in step 120; when this step 133 is executed for the nth time, the initial mirror can represent the mirror obtained after the surface shape correction in the (n - 1)th execution of step 136. Here, n is a positive integer greater than 2.

[0094] Step 136: Perform surface shape correction on the second surface of the initial mirror using the surface shape correction parameters.

[0095] Optionally, the method for performing surface shape correction on the second surface of the initial mirror in step 136 can be the same as the method for performing surface shape correction on the second surface of the initial mirror in the foregoing step 132. For details, refer to the description in the foregoing step 132 and will not be elaborated here.

[0096] In this embodiment, the surface shape parameters of the inner reflecting surface of the initial mirror in the current state can be obtained based on the surface shape detection implemented in this step 133. Based on the surface shape parameters, it can be determined whether the inner reflecting surface shape of the initial mirror in the current state reaches the second set threshold.

[0097] In step 133, based on the detection result, it can be determined whether the inner reflecting surface shape of the initial mirror in the real-time state reaches the second set threshold.

[0098] If the inner reflecting surface shape of the initial mirror after surface shape correction does not reach the second set threshold, then execute the above steps 133 to 136.

[0099] If the surface shape of the inner reflecting surface of the initial mirror after surface shape correction has reached the second set threshold, it indicates that the surface shape of the inner reflecting surface of the current corrected initial mirror meets the requirements, and the surface shape correction of the second surface is ended.

[0100] In the above embodiment, step 130 can adopt a multi-round surface shape correction method to correct the surface shape of the initial mirror, which can improve the accuracy of surface shape correction and make the obtained result after correction better meet the accuracy requirements.

[0101] There can also be various choices for the formation means of micro-nano structures. Based on different actual usage environments, engraving tools used, etc., different micro-nano structure formation means can be selected.

[0102] In one embodiment, the above step 140 may include: using an etching technique to process the second surface of the initial mirror to form a micro-nano structure, obtaining a micro-nano structure mirror.

[0103] In one embodiment, the above step 140 may include: using a turning technique to process the second surface of the initial mirror to form a micro-nano structure, obtaining a micro-nano structure mirror.

[0104] In one embodiment, the above step 140 may include: using a nanoimprint technique to process the second surface of the initial mirror to form a micro-nano structure, obtaining a micro-nano structure mirror.

[0105] Based on actual needs and the differences in equipment at the actual processing site, any one or more micro-nano structure formation means can be selected to form micro-nano structures. By providing multiple micro-nano structure formation means, the formation of micro-nano structures can be made more flexible.

[0106] The following describes the full process of the micro-nano structure mirror processing method provided based on the embodiments of the present application in combination with an example:

[0107] Exemplarily, the original mirror blank is a quartz mirror body, and the target micro-nano structure mirror can be an annular quartz micro-nano structure mirror. The surface shape of the target micro-nano structure mirror can be the surface shape in the aforementioned target state. The outer diameter of the lens of the target micro-nano structure mirror is Ф330mm, the effective light passing aperture is Ф300mm, the inner diameter of the lens is 120mm, the lens thickness is 8.8mm, and the diameter-thickness ratio is 37.5. First, using a milling and forming method, the outer shape of the original mirror blank is processed to obtain an annular initial mirror structure.

[0108] Then, based on the target micro-nano structure mirror, a processing threshold is set, and this processing threshold can be the aforementioned first set threshold. The first set threshold can be set to RMS of 0.1λ@632.8nm. Based on this first set threshold, the initial mirror structure is processed. For example, conventional polishing techniques such as ring polishing can be used to quickly achieve it. In the case of achieving rapid processing, it can also establish a good base surface shape for the subsequent correction of the second surface of the initial mirror by ion beam polishing, reduce the correction amount of ion beam polishing, and improve the processing efficiency. The initial mirror structure is polished to an initial lens with a surface shape value reaching RMS of 0.068λ@632.8nm by using the ring polishing method.

[0109] A reflective film is deposited on the initial lens. This reflective film can be based on an Ag film layer and consists of a reflective film system composed of Cr, Cu, Ag, Al2O3, Ta2O5, and SiO2 film layers, which has a high reflectivity in the visible light band. Electron beam evaporation coating can be used to complete the deposition of the reflective film. After the reflective film is deposited, the initial mirror is obtained. The internal reflection surface shape of the initial mirror can be tested using an interferometer. The RMS of the reflection surface shape of the initial mirror drops from 0.068λ before the reflective film is deposited to 0.089λ after the reflective film is deposited, with a decrease amplitude of 0.021λ. When the requirement for the mirror surface shape is relatively high, this change amount cannot be ignored, which may cause the reflection surface shape index of the mirror not to meet the requirements. Therefore, in this application,

[0110] After the reflective film is deposited, the internal reflection surface shape of the initial mirror is corrected by correcting the second surface of the initial mirror.

[0111] Then, the internal reflection surface shape of the initial mirror can be corrected. Ion beam polishing can be used to correct the internal reflection surface shape of the initial mirror. An optional method is to determine the ion beam polishing parameters from the internal reflection surface shape of the initial mirror to the surface shape of the target micro-nano structure mirror based on the detection result of the internal reflection surface shape of the initial mirror, and perform ion beam polishing processing based on these ion beam polishing parameters. After the surface shape is corrected by ion beam polishing, the internal reflection surface shape of the mirror is detected again using an interferometer. The detection result shows that the RMS of the internal reflection surface shape is 0.036λ. The RMS of the internal reflection surface shape increases from 0.089λ after the reflective film is deposited to 0.036λ, with an increase amplitude of 0.053λ. In this embodiment, if the single surface shape correction does not reach 1 / 30λ of the imaging requirement, the internal reflection surface shape can be corrected again.

[0112] After the opposite surface is corrected, micro-nano structure processing can be performed on the side without the deposited reflective film. Optionally, laser direct writing technology can be used to process micro-nano functional structures on the uncoated surface. After the processing is completed, the surface shape of the micro-nano structure reflecting mirror is detected, and the RMS of the reflected wavefront is 0.045λ, which already meets the requirements for high-quality imaging. Then, the processing process of the mirror can be ended.

[0113] An embodiment of the present application can also provide a micro-nano structure mirror processing system, including: a processing tool, which is used to execute the steps in the micro-nano structure mirror processing method provided in the foregoing embodiment.

[0114] Exemplarily, the processing tool may involve tools used for the outer shape processing of the mirror blank, tools used for the surface shape processing or correction of the mirror body, tools used for depositing the reflective film, tools used for micro-nano structure processing, etc. Based on the differences in the technologies actually used in the processing, the tools involved are also different.

[0115] An embodiment of the present application can also provide a micro-nano structure mirror, which is a micro-nano structure mirror processed by using the micro-nano structure mirror processing method provided in the foregoing embodiment.

[0116] In this embodiment, a micro-nano structure may be formed on the side without the deposited reflective film of the micro-nano structure mirror processed based on the above micro-nano structure mirror processing method. This micro-nano structure may vary in different usage environments. It can be understood that based on the differences in the parameters involved in the foregoing micro-nano structure mirror processing method, the micro-nano structure formed by this micro-nano structure mirror is also different.

[0117] The foregoing is only the preferred embodiment of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application. It should be noted that similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0118] The foregoing is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, and all should be covered by the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A method for fabricating a micro-nano structure mirror, characterized in that, Including: Processing the mirror surface of the initial mirror structure to obtain an initial lens; wherein, the surface shape of the mirror surface of the initial lens reaches a first set threshold; Coating a reflective film on the first surface of the initial lens to obtain an initial mirror; Performing surface shape correction on the second surface of the initial mirror; Processing a micro-nano structure on the second surface after surface shape correction to obtain a micro-nano structure mirror; wherein, the second surface is a different surface from the first surface.

2. The method according to claim 1, characterized in that, The performing surface shape correction on the second surface of the initial mirror includes: Obtaining the surface shape correction parameters of the second surface of the initial mirror based on the surface shape of the internal reflection surface of the initial mirror; Using the surface shape correction parameters to perform surface shape correction on the second surface of the initial mirror to reduce the surface shape fluctuation of the internal reflection surface of the initial mirror; Wherein, the surface shape of the internal reflection surface of the initial mirror after surface shape correction reaches a second set threshold, the surface shape characterized by the second set threshold has a smaller fluctuation than the surface shape characterized by the first set threshold, and the internal reflection wavefront of the surface shape of the internal reflection surface of the initial mirror after surface shape correction reaches the set accuracy.

3. The method according to claim 2, wherein The obtaining the surface shape correction parameters of the second surface of the initial mirror based on the surface shape of the internal reflection surface of the initial mirror includes: Detecting the surface shape of the internal reflection surface of the initial mirror to obtain the surface shape parameters of the internal reflection surface of the initial mirror; Obtaining the surface shape correction parameters of the second surface of the initial mirror based on the surface shape parameters and the size of the initial mirror.

4. The method according to claim 1, wherein The performing surface shape correction on the second surface of the initial mirror includes: a. Detecting the surface shape of the internal reflection surface of the initial mirror; b. Determining the surface shape correction parameters of the second surface of the initial mirror based on the detection result of the surface shape of the internal reflection surface of the initial mirror; c. Using the surface shape correction parameters to perform surface shape correction on the second surface of the initial mirror; If the surface shape of the internal reflection surface of the initial mirror after surface shape correction does not reach the second set threshold, then execute the above steps a to c; until the surface shape of the internal reflection surface of the initial mirror after surface shape correction reaches the second set threshold.

5. The method according to claim 3 or 4, characterized in that The detecting the surface shape of the internal reflection surface of the initial mirror includes: Using a test beam to irradiate from the second surface of the initial mirror into its interior, then propagating to the internal reflection surface, and then reflecting the test beam out, and obtaining the detection result of the surface shape of the internal reflection surface of the initial mirror based on the reflected test beam.

6. The method according to claim 1, wherein The processing a micro-nano structure on the second surface after surface shape correction to obtain a micro-nano structure mirror includes: Using an etching technique to process the second surface of the initial mirror to form a micro-nano structure to obtain a micro-nano structure mirror; or, Using a turning technique to process the second surface of the initial mirror to form a micro-nano structure to obtain a micro-nano structure mirror; or, Using a nanoimprinting technique to process the second surface of the initial mirror to form a micro-nano structure to obtain a micro-nano structure mirror.

7. The method according to claim 1, wherein The processing the mirror surface of the initial mirror structure to obtain an initial lens includes: Roughly polish the mirror surface of the initial mirror structure so that the surface shape of the mirror surface reaches the first set threshold to obtain an initial lens; wherein, the rough polishing treatment includes one or more of ring polishing treatment, small grinding head polishing treatment, ion beam polishing treatment, and magnetorheological polishing treatment.

8. The method according to claim 1, wherein Depositing a reflective film on the first surface of the initial lens to obtain an initial mirror, including: Using an evaporation coating technology to deposit a reflective film on the first surface of the initial lens to obtain an initial mirror; or, Using a magnetron sputtering coating technology to deposit a reflective film on the first surface of the initial lens to obtain an initial mirror.

9. A micro-nano structure mirror processing system, characterized in that, Including: A processing tool for performing the steps of the method according to any one of claims 1 to 8.

10. A micro-nano structure mirror, characterized in that, A micro-nano structure mirror processed by using the method according to any one of claims 1 to 8.

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