WO2024017275A1 - Element tolerance analysis method and device for optical system, and element quality evaluation method and device for optical system - Google Patents

Abstract

An element tolerance analysis method for an optical system, comprising: determining a wave aberration tolerance corresponding to an optical curved surface of an optical element to be analyzed (S11); and according to the wave aberration tolerance corresponding to the optical curved surface of the optical element to be analyzed, determining surface profile tolerances of different points on the optical curved surface of the optical element to be analyzed so as to obtain the local area surface profile tolerance distribution of the curved surface (S12). Also provided are an element quality evaluation method and device for an optical system. The method comprises: determining a quality evaluation function of an optical curved surface of an optical element to be evaluated (S71); and according to the quality evaluation function, determining a quality evaluation function value corresponding to quality evaluation of the optical element to be evaluated (S72). Further provided are an element tolerance analysis device for an optical system and an element quality evaluation device for an optical system. The surface profile accuracy of an optical element to be analyzed having local area distribution characteristics on an optical curved surface can be effectively analyzed, and the quality of the optical element to be analyzed in an optical system can be effectively evaluated on the basis of imaging quality.

Description

A method and device for component tolerance analysis and quality evaluation of optical systems

This application claims the priority of the Chinese patent application submitted on July 22, 2022, with the application number 202210873378.7, and the invention title is "Optical System Component Analysis and Evaluation Method", and also claims the priority of the Chinese patent application submitted on June 27, 2023, with the application number 202310768431.1 , the priority of the Chinese patent application titled "A method and device for component tolerance analysis and quality evaluation of optical systems", the entire content of which is incorporated into this application by reference.

Technical field

The present disclosure relates to the field of optics, and in particular, to a method and device for component tolerance analysis and quality evaluation of an optical system.

Background technique

High-performance optical imaging systems are an important part of human scientific exploration and engineering application instruments, and the manufacturing of high-precision optical surfaces is one of the long-term research topics. For more than half a century, the tolerance analysis method has been considered the most effective component analysis method in optical systems. Among them, the tolerance given by the tolerance analysis method is the maximum wave aberration root mean square RMS of the entire curved surface geometry of the optical component. Or wave aberration peak-trough PV value. At the same time, during the manufacturing process of optical components, the RMS or PV value accuracy of the entire curved surface geometry is also used to evaluate component quality. However, components with higher geometric surface precision may not necessarily have better image quality. Therefore, in order to improve the imaging performance of the optical system, an effective component tolerance analysis and quality evaluation method of the optical system is urgently needed.

Contents of the invention

In view of this, the present disclosure proposes a method and device for component tolerance analysis and quality evaluation of an optical system.

According to one aspect of the present disclosure, a method for component tolerance analysis of an optical system is provided, including: for the optical component to be analyzed in the optical system, determining the wave aberration tolerance corresponding to the optical curved surface of the optical component to be analyzed; according to The wave aberration tolerance corresponding to the optical surface of the optical element to be analyzed determines the local surface shape tolerance distribution of the optical element to be analyzed, wherein the local surface shape tolerance distribution of the optical element to be analyzed includes all Describe the surface tolerances at different points on the optical surface of the optical element to be analyzed.

In a possible implementation, determining the wave aberration tolerance corresponding to the optical curved surface of the optical element to be analyzed for the optical element to be analyzed in the optical system includes: determining at least one corresponding to the optical system Sampling field of view; for any of the sampling field of view, determine the optical curved surface of the optical element to be analyzed in the sampling field of view according to the wave aberration design peak value and the wave aberration design valley value corresponding to the sampling field of view. The corresponding wave aberration tolerance is below.

In a possible implementation, determining the local surface shape tolerance distribution of the optical element to be analyzed based on the wave aberration tolerance corresponding to the optical curved surface of the optical element to be analyzed includes: for any one of the Determine the local surface shape tolerance of the optical element to be analyzed under the sampling field of view based on the wave aberration tolerance corresponding to the optical curved surface of the optical element to be analyzed under the sampling field of view. Distribution; find the intersection of the local surface shape tolerance distribution of the optical element to be analyzed under the at least one sampling field of view to obtain the local surface shape tolerance distribution of the optical element to be analyzed.

In a possible implementation, the wave aberration tolerance of the optical curved surface of the optical element to be analyzed under the sampling field of view is determined to determine whether the optical element to be analyzed is under the sampling field of view. The local surface shape tolerance distribution includes: according to the wave aberration tolerance corresponding to the optical curved surface of the optical element to be analyzed under the sampling field of view, determining the optical curved surface of the optical element to be analyzed under the sampling field of view. The upper limit and the lower limit of wave aberration under the field; determine multiple sampling points on the optical surface of the optical element to be analyzed; and according to the wave image of the optical surface of the optical element to be analyzed under the sampling field of view The upper limit of the difference and the lower limit of the wave aberration determine the surface shape tolerance at each sampling point on the optical curved surface of the optical element to be analyzed under the sampling field of view; according to the optical element to be analyzed under the sampling field of view The surface shape tolerance at the plurality of sampling points on the optical curved surface is determined to determine the local surface shape tolerance distribution of the optical element to be analyzed under the sampling field of view.

In a possible implementation, the wave aberration upper limit and the wave aberration lower limit of the optical element to be analyzed in the sampling field of view are determined according to the wave aberration limit of the optical surface to be analyzed in the sampling field of view. The surface shape tolerance at each sampling point on the optical curved surface of the optical element includes: for any one of the plurality of sampling points, according to the optical curved surface of the optical element to be analyzed, in the sampling field of view The upper limit of wave aberration under the sampling field of view is determined to determine the surface deviation at the sampling point on the optical curved surface of the optical element to be analyzed; according to the optical curved surface of the optical element to be analyzed in the sampling field of view The lower limit of wave aberration under the field is determined to determine the surface deviation at the sampling point on the optical surface of the optical element to be analyzed under the sampling field of view; The difference between the upper surface deviation and the lower surface deviation at the sampling point on the optical curved surface is determined as the surface shape tolerance at the sampling point on the optical curved surface of the optical element to be analyzed under the sampling field of view.

In a possible implementation, the optical system includes a plurality of optical elements to be analyzed; for any one of the sampling fields of view, the peak value and wave aberration are designed according to the wave aberration corresponding to the sampling field of view. Design the valley value to determine the wave aberration tolerance corresponding to the optical surface of the optical element to be analyzed under the sampling field of view, including: designing the wave aberration peak value and the wave aberration design valley corresponding to the sampling field of view. value, as well as the first allocation condition and the second allocation condition, assign the corresponding wave aberration tolerance under the sampling field of view to each optical surface of the optical element to be analyzed, wherein the first allocation condition is the The variation in wave aberration caused by the surface shape error of the optical surfaces of the plurality of optical elements to be analyzed satisfies a linear superposition relationship, and the second distribution condition is the sum of the wave aberrations corresponding to the optical curved surfaces of the plurality of optical elements to be analyzed. and is greater than or equal to the wave aberration tolerance valley value corresponding to the sampling field of view and less than or equal to the wave aberration tolerance peak value corresponding to the sampling field of view.

In a possible implementation, the method further includes: manufacturing the optical element to be analyzed according to the local surface shape tolerance distribution of the optical element to be analyzed, wherein the manufacturing error of the optical element to be analyzed satisfies The local surface shape tolerance distribution of the optical element to be analyzed.

In a possible implementation, the method further includes: when the manufacturing error of the optical element to be analyzed causes a radius deviation in the radius of the optical curved surface, the method further includes: according to the radius deviation of the radius of the optical curved surface of the optical element to be analyzed. , compensation is performed by moving the position of the optical element to be analyzed; for the compensated optical element to be analyzed, the optical element to be analyzed is re-determined according to the wave aberration tolerance corresponding to the optical surface of the optical element to be analyzed. Local surface tolerance distribution of components.

According to one aspect of the present disclosure, a method for evaluating component quality of an optical system is provided, including: for an optical component to be evaluated in an optical system, determining a quality evaluation function of an optical surface of the optical component to be evaluated; according to the quality An evaluation function determines the quality evaluation function value corresponding to the optical element to be evaluated, wherein the quality evaluation function value is used to evaluate the quality of the optical element to be evaluated.

In a possible implementation, determining the quality evaluation function value corresponding to the optical element to be evaluated according to the quality evaluation function includes: determining at least one sampling field of view corresponding to the optical system; Manufacturing errors at different points on the optical surface of the optical element to be evaluated, initial wave aberrations at different points on the optical surface of the optical element to be evaluated in each of the sampling fields, optical curved surfaces of the optical element to be evaluated Based on the irradiance of different points in each of the sampling fields of view, determine the root mean square of the wave aberration corresponding to the optical element to be evaluated in each of the sampling fields of view; use the quality evaluation function, according to The root mean square of wave aberration corresponding to the optical element to be evaluated in the at least one sampling field of view determines the quality evaluation function value corresponding to the optical element to be evaluated.

In a possible implementation, the quality evaluation function is used to determine the optical element to be evaluated based on the root mean square of wave aberration corresponding to the optical element to be evaluated in the at least one sampling field of view. The corresponding quality evaluation function value includes: using the quality evaluation function, the root mean square of wave aberration corresponding to the optical element to be evaluated in the at least one sampling field of view, and the corresponding value of each sampling field of view. The weight is determined to determine the quality evaluation function value corresponding to the optical element to be evaluated.

According to one aspect of the present disclosure, an element tolerance analysis device for an optical system is provided, including: a wave aberration tolerance allocation module, configured to determine the optical tolerance of the optical element to be analyzed for the optical element to be analyzed in the optical system. The wave aberration tolerance corresponding to the curved surface; the local surface shape tolerance determination module determines the local surface shape tolerance distribution of the optical element to be analyzed according to the wave aberration tolerance corresponding to the optical curved surface of the optical element to be analyzed, Wherein, the local surface shape tolerance distribution of the optical element to be analyzed includes surface shape tolerances at different points on the optical curved surface of the optical element to be analyzed.

According to one aspect of the present disclosure, an element quality evaluation device for an optical system is provided, including: a function determination module for determining the quality evaluation of the optical curved surface of the optical element to be evaluated in the optical system. Function; a quality evaluation module, configured to determine the quality evaluation function value corresponding to the optical element to be evaluated according to the quality evaluation function, wherein the quality evaluation function value is used to perform quality evaluation of the optical element to be evaluated.

In the embodiment of the present disclosure, for the optical element to be analyzed in the optical system, the wave aberration tolerance corresponding to the optical curved surface of the optical element to be analyzed is determined, and then based on the wave aberration tolerance corresponding to the optical curved surface of the optical element to be analyzed, Determine the local surface tolerance distribution including surface tolerances at different points on the optical surface of the optical element to be analyzed, thereby achieving effective analysis of the surface precision of the optical element to be analyzed whose optical surface has local distribution characteristics.

In the embodiment of the present disclosure, for the optical element to be evaluated in the optical system, the quality evaluation function of the optical surface of the optical element to be evaluated is determined, and then based on the quality evaluation function, the quality evaluation function value corresponding to the optical element to be evaluated is determined, so that Realize effective evaluation of the quality of the optical elements to be analyzed in the optical system based on imaging quality.

Other features and aspects of the present disclosure will become apparent from the following detailed description of exemplary embodiments with reference to the accompanying drawings.

Description of drawings

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments, features, and aspects of the disclosure and together with the description serve to explain the principles of the disclosure.

Figure 1 shows a flow chart of a component tolerance analysis method of an optical system according to an embodiment of the present disclosure;

Figure 2 shows a schematic diagram of a single point jump model and a perturbation light according to an embodiment of the present disclosure;

FIG. 3 shows a schematic diagram of a wave aberration model of the perturbed light ray shown in FIG. 2 according to an embodiment of the present disclosure;

Figure 4 shows a schematic diagram of the local surface shape tolerance distribution of the optical element to be analyzed under two sampling fields of view according to an embodiment of the present disclosure;

Figure 5 shows a schematic diagram of the local surface shape tolerance distribution of the optical element to be analyzed according to an embodiment of the present disclosure;

Figure 6 shows a flow chart for determining the local surface tolerance distribution of multiple optical elements to be analyzed in an optical system according to an embodiment of the present disclosure;

Figure 7 shows a flow chart of a component quality evaluation method of an optical system according to an embodiment of the present disclosure;

Figure 8 shows a schematic diagram of a two-dimensional structural diagram, a field of view diagram, and three-mirror sampling data points of a free-form off-axis three-mirror system according to an embodiment of the present disclosure;

Figure 9 shows a schematic diagram of the optimized tolerance distribution of the three mirrors in the free-form off-axis three-mirror system shown in Figure 8 according to an embodiment of the present disclosure;

Figure 10 shows a two-dimensional structural diagram, a field of view diagram, a schematic diagram of the primary mirror aperture, and a schematic diagram of the secondary mirror aperture of a coaxial two-reverse Cassegrain system according to an embodiment of the present disclosure;

Figure 11 shows a schematic diagram of the local surface tolerance distribution of the primary mirror and the secondary mirror in the coaxial two-reverse Cassegrain system shown in Figure 10 according to an embodiment of the present disclosure;

Figure 12 shows the primary mirror and the secondary mirror in the coaxial two-reverse Cassegrain system shown in Figure 10 according to an embodiment of the present disclosure. The primary mirror and the secondary mirror are simultaneously superimposed to meet the local tolerance requirements shown in Figure 11 after the surface error. Statistical diagram of the wave aberration PV value of the secondary mirror;

Figure 13 shows a schematic diagram of the local surface tolerance distribution of the primary mirror after position compensation is performed on the coaxial two-reverse Cassegrain system shown in Figure 10 according to an embodiment of the present disclosure;

Figure 14 shows the optical path diagram of a high-precision laser collimation system according to an embodiment of the present disclosure and the wave aberration pupil diagram of the system in the central field of view;

Figure 15 shows a schematic diagram of the local tolerance distribution of the first surface in the high-precision laser collimation optical system shown in Figure 14 according to an embodiment of the present disclosure;

Figure 16 shows a schematic diagram of RWE statistics of a primary mirror with surface shape error according to an embodiment of the present disclosure;

Figure 17 shows a schematic diagram of the surface shape error distribution of the primary mirror according to an embodiment of the present disclosure;

Figure 18 shows a block diagram of a component tolerance analysis device of an optical system according to an embodiment of the present disclosure;

FIG. 19 shows a block diagram of an element quality evaluation device of an optical system according to an embodiment of the present disclosure.

Detailed ways

Various exemplary embodiments, features, and aspects of the present disclosure will be described in detail below with reference to the accompanying drawings. The same reference numbers in the drawings identify functionally identical or similar elements. Although various aspects of the embodiments are illustrated in the drawings, the drawings are not necessarily drawn to scale unless otherwise indicated.

The word "exemplary" as used herein means "serving as an example, example, or illustrative." Any embodiment described herein as "exemplary" is not necessarily to be construed as superior or superior to other embodiments.

In addition, in order to better explain the present disclosure, numerous specific details are given in the following detailed description. It will be understood by those skilled in the art that the present disclosure may be practiced without certain specific details. In some instances, methods, means, components and circuits that are well known to those skilled in the art are not described in detail in order to emphasize the subject matter of the disclosure.

Optical imaging systems are widely used in biomedicine, material detection, astronomical observation, chip manufacturing and other fields. They are an important part of human scientific exploration and engineering application instruments. Based on the demand for scientific exploration and major projects, a series of high-performance optical systems have been gradually proposed, such as laser nuclear fusion devices (NIF), lithography machine lenses, James Webb Space Telescope (JWST), and new generation of very large ground-based telescopes. -Thirty Meter Telescope (TMT), Giant Magellan Telescope (GMT), etc. The optical elements in these optical systems may be optical surfaces in the form of spherical or aspherical surfaces. Due to the large diameter of the optical surfaces of the optical elements and the high requirements for processing precision, they are extremely difficult to manufacture. In addition, in recent years, optical elements with free-form surfaces are gradually being used in high-precision optical imaging systems due to their higher degree of design freedom, better correction of aberrations, and compact structure. However, the non-rotational symmetry of free-form surfaces additionally increases the difficulty of manufacturing optical components. The manufacturing of these high-precision, large-aperture, and complex-surface optical elements is often the bottleneck of optical imaging systems. Their manufacturing accuracy directly determines the pace of human scientific exploration and engineering applications. Therefore, the manufacturing of high-precision optical components is an eternal research topic for mankind.

In the related art, the RMS or PV value of the surface shape of the entire optical surface of the optical element is generally used to evaluate the manufacturing accuracy of the optical element. The tolerance given by the tolerance analysis method in the related art is also a unified description of the entire optical surface shape of the optical element, which stipulates the maximum value of the optical surface shape error RMS value or PV value. This tolerance analysis method is an analysis method based on Monte Carlo probability statistics, which is suitable for analyzing the tolerance of optical components manufactured in large quantities. This method has been considered the most effective for more than half a century. method.

However, the actual situation of the optical system is relatively complex and localized in many aspects. Different areas of the curved surface contribute differently to the imaging quality of the system. In order to ensure certain imaging quality requirements, the amount of change in imaging quality allowed by different light rays caused by surface shape errors in different areas of the optical element is different. At the same time, since the surface shape sensitivity of different areas of the optical surface of the optical element is different, it is not difficult to know that the tolerance requirements of different areas of the optical surface are also different, that is, the tolerance of the optical surface is localized. However, the tolerance given by the Monte-Carlo tolerance analysis method in the related art is a unified description of the entire optical surface shape, and cannot give different tolerance requirements for different areas of the optical surface. Therefore, it cannot indicate which areas of the optical surface. Tolerances are loose and which areas have tight tolerances. This tolerance analysis method, which gives uniform tolerance requirements for the entire optical surface, has been this way since its inception, without taking into account the locality of the tolerance of the optical surface.

In addition, in the related art, the RMS value or PV value of the surface shape error of optical elements has been used to evaluate the quality of optical elements. It reflects the geometric deviation of the manufacturing curved surface of the optical element from the ideal surface shape. . However, even if different manufactured optical elements have the same PV value or RMS value of surface shape error, their imaging performance in the optical system is likely to be different. The evaluation based on the manufacturing accuracy of optical elements in related technologies cannot reflect the differences in the initial wave aberrations of different light rays in the design system and the locality of the surface shape sensitivity of the optical elements. Therefore, it is impossible to judge the imaging quality of the optical elements in the optical system. good or bad. In related technologies, the imaging quality of the final optical system is generally ensured by improving the geometric surface accuracy of optical elements during the manufacturing process. However, optical surfaces with high geometric surface precision may not necessarily guarantee higher imaging quality of the final system. In fact, what the optical system really cares about is the imaging performance of the final system. If the quality of optical components can be evaluated from the perspective of imaging quality, it can avoid blindly improving the manufacturing accuracy of optical components to ensure the imaging quality of the system. Therefore, an optical evaluation function based on imaging quality needs to be proposed urgently.

The embodiment of the present disclosure discloses an element tolerance analysis method and a quality evaluation method for an optical system aimed at designing a system, which can accurately obtain different tolerance requirements for different areas on the optical curved surface of the optical element, thereby enabling different areas of the curved surface to be processed according to different requirements. Precision is required for manufacturing, and the quality of optical components can be evaluated based on their imaging quality. The component tolerance analysis method and quality evaluation method of an optical system according to the embodiment of the present disclosure are described in detail below.

FIG. 1 shows a flow chart of a component tolerance analysis method of an optical system according to an embodiment of the present disclosure. As shown in Figure 1, the method includes:

In step S11, for the optical element to be analyzed in the optical system, the wave aberration tolerance corresponding to the optical curved surface of the optical element to be analyzed is determined.

In step S12, the local surface shape tolerance distribution of the optical element to be analyzed is determined according to the wave aberration tolerance corresponding to the optical surface of the optical element to be analyzed, wherein the local surface shape tolerance distribution of the optical element to be analyzed includes the Analyze the surface tolerances at different points on the optical surface of optical components.

In the embodiment of the present disclosure, for the optical element to be analyzed in the optical system, the wave aberration tolerance corresponding to the optical curved surface of the optical element to be analyzed is determined, and then based on the wave aberration tolerance corresponding to the optical curved surface of the optical element to be analyzed, Determine the local surface tolerance distribution including surface tolerances at different points on the optical surface of the optical element to be analyzed, thereby achieving effective analysis of the surface precision of the optical element to be analyzed whose optical surface has local distribution characteristics.

In one example, an embodiment of the present disclosure proposes an isolated point jump model to simulate the surface shape error of the optical surface of the optical element, and uses a local tolerance model to solve the tolerance of each point on the optical surface of the optical element point by point, and then , obtain the local surface shape tolerance of the optical element.

The surface shape error generated during the manufacturing process of the optical surface of optical components will cause the points on the optical surface to deviate from the designed surface. The solitary point jump model can be used to simulate the surface shape error of the optical surface. This model is suitable for any optical surface, such as , reflective surfaces, refractive surfaces, diffraction surfaces, optical surfaces of phase elements, metasurfaces, etc. The following uses a reflective surface as an example to describe the solitary point jump model in detail.

FIG. 2 shows a schematic diagram of a single point jump model and a perturbation ray according to an embodiment of the present disclosure. As shown in Figure 2, in the solitary point jump model, the manufacturing error at a certain point P on the curved surface (the mirror shown in Figure 2) causes point P to jump to point P'. Use the jump amount d ₀ of point P along the normal line of the surface at this point to simulate the manufacturing error at this point. When enough points are sampled on the surface, the jump amount d(x,y,z) of all sampling points on the surface along their respective normal directions can be used to simulate the surface shape error of the surface. The positive and negative manufacturing errors at a certain point on the surface can be simulated by the positive and negative jumps at that point respectively. Points all jump away along their normals. For reflective surfaces, when a point jumps to the side with incident light, it is a positive jump amount, and vice versa, it is a negative jump amount. As shown in Figure 2, d ₀ is the positive jump amount. The surface shape error changes the propagation path of light passing through each point on the curved surface. Taking the field of view F as an example, the light ray passing through the point P' after the error disturbance (the red dotted line shown in Figure 2) is called a perturbation ray of the field of view F.

The surface shape error causes the wave aberration of the perturbed light rays to change at each point on the surface after the perturbation. Therefore, by establishing the relationship between the manufacturing error at each point on the optical surface of the optical element and the corresponding wave aberration of the disturbing light, the tolerance of each point on the optical surface of the optical element can be analyzed point by point.

The same manufacturing error changes the optical path of light at different incident angles differently. For an optical system, the incident angles of light in different areas on the optical surface of the optical element are different. Therefore, the surface shape error sensitivity of the optical surface of the optical element has local characteristics. Before performing local tolerance analysis on the optical surface of optical components, the surface shape sensitivity analysis of the optical surface is first introduced. The surface shape sensitivity of the optical surface is analyzed by calculating the changes in the wave aberration of the optical system caused by manufacturing errors at each point on the optical surface.

Taking the above-mentioned Figure 2 as an example, under the field of view F shown in Figure 2, analyze the wave aberration changes of the disturbing light caused by the manufacturing error of point P on the reflective surface. FIG. 3 shows a schematic diagram of a wave aberration model of the perturbed light ray shown in FIG. 2 according to an embodiment of the present disclosure. As shown in Figure 3, the manufacturing error causes point P to jump to point P', the wave aberration of the disturbance light passing through point P' changes, and point A' on the reference wave surface also deviates from point A on the nominal wave surface. The chief ray, reference wavefront and nominal wavefront of the field of view F all pass through the exit pupil center O' of the field of view. The wave aberration of the light passing through point P is W ₀ , and the wave aberration of the disturbed light passing through point P' is W _E . The difference between them, ΔW= _WE - W ₀ , is the change in the wave aberration of the disturbed light. quantity.

The size of ΔW reflects the sensitivity of the imaging quality of the optical system to manufacturing errors at a certain point on the optical surface. When the manufacturing errors at all points on the optical surface are the same, the greater the wave aberration change ΔW of the perturbed light at a certain point, the more sensitive the imaging quality will be to the manufacturing errors at that point. Obviously, the same manufacturing error has different effects on the wave aberration of the disturbed light at different points on the optical surface, that is, the surface shape sensitivity of the optical surface of the optical element is localized.

If it is expected that the imaging quality of the optical system will not be lower than the design value after the optical surface of the optical element has manufacturing errors. For example, after the optical system has manufacturing errors, the system's wave aberration PV value W _EXP will not exceed the initial designed PV value. , then the imaging quality of the manufacturing system can be better than that of the design system. The local surface shape tolerance of the optical surface at this time can be called optimization tolerance. Manufacturing errors have always been considered harmful to the imaging quality of optical systems. The existence of optimized tolerances can change the perception that manufacturing errors must be harmful. In the manufacturing process of optical elements, allowing the manufacturing errors of optical elements to meet the requirements of optimized tolerances can ensure that the imaging quality of the final optical system is not lower than that of the designed system, or even exceeds the design value. The following is a detailed description of the local surface shape tolerance analysis of the optical surface of a single optical element to be analyzed in the optical system.

In a possible implementation, for the optical element to be analyzed in the optical system, determining the wave aberration tolerance corresponding to the optical curved surface of the optical element to be analyzed includes: determining at least one sampling field of view corresponding to the optical system; for any A sampling field of view, based on the design peak value of wave aberration and the design valley value of wave aberration corresponding to the sampling field of view, determine the corresponding wave aberration tolerance of the optical surface of the optical element to be analyzed under the sampling field of view.

First, sample the entire field of view of the optical system, select enough sampling fields for optimization tolerance analysis, and set wave aberration tolerances for all sampling fields.

If it is expected that the imaging quality of the optical system will not be lower than the design value despite manufacturing errors, the wave aberration PV value of each sampling field of view of the optical system should not exceed its initial design value. For any sampling field of view F, design the peak value according to the wave aberration corresponding to the sampling field of view F. Sum wave aberration design valley value Determine the wave aberration tolerance corresponding to the optical surface of the optical element to be analyzed under the sampling field of view F.

In one possible implementation, the local surface shape tolerance distribution of the optical element to be analyzed is determined based on the wave aberration tolerance corresponding to the optical surface of the optical element to be analyzed, including: for any sampling field of view, according to the to-be-analyzed The corresponding wave aberration tolerance of the optical surface of the optical element under the sampling field of view determines the local surface shape tolerance distribution of the optical element to be analyzed under the sampling field of view; the local surface tolerance distribution of the optical element to be analyzed under at least one sampling field of view The intersection of the surface tolerance distribution is obtained to obtain the local surface tolerance distribution of the optical element to be analyzed.

After setting the wave aberration tolerance for all sampling fields of view, for any sampling field of view of the optical system, find the surface tolerance (optimization tolerance) of each point on the optical surface of the optical element to be analyzed point by point, and obtain the The local surface shape tolerance distribution of the optical surface of the optical element within the working area of the sampling field of view (local optimized tolerance distribution). Furthermore, the above operation is repeated for all sampling fields of view to obtain the local surface shape tolerance distribution (local optimized tolerance distribution) of the optical curved surface of the optical element to be analyzed in the working area of each sampling field of view. Finally, the local surface shape tolerance distribution (local optimized tolerance distribution) of the optical element to be analyzed under all sampling fields of view is intersected, and finally the local surface shape tolerance distribution (optimized tolerance distribution) of the optical surface of the optical element to be analyzed is obtained. . Since the optimized tolerance requirements at different points on the optical surface of the optical element to be analyzed are different, what is finally obtained is a localized optimized tolerance distribution.

Next, for any sampling field of view of the optical system, the local surface tolerance distribution (local optimized tolerance distribution) of the optical surface of the optical element to be analyzed in the working area of the sampling field will be analyzed in detail.

In one possible implementation, the local surface shape tolerance distribution of the optical element to be analyzed under the sampling field of view is determined based on the wave aberration tolerance corresponding to the optical surface of the optical element to be analyzed under the sampling field of view, including: According to the corresponding wave aberration tolerance of the optical surface of the optical element to be analyzed under the sampling field of view, determine the upper limit and lower limit of wave aberration of the optical surface of the optical element to be analyzed under the sampling field of view; in the optical element to be analyzed Determine multiple sampling points on the optical surface; according to the upper limit and lower limit of wave aberration of the optical surface of the optical element to be analyzed under the sampling field of view, determine each sample on the optical surface of the optical element to be analyzed under the sampling field of view. The surface shape tolerance at points; based on the surface shape tolerance at multiple sampling points on the optical surface of the optical element to be analyzed under the sampling field of view, the local surface shape tolerance distribution of the optical element to be analyzed under the sampling field of view is determined.

For any sampling field of view F, the peak value of the wave aberration corresponding to the sampling field of view F is designed. Sum wave aberration design valley value After determining the corresponding wave aberration tolerance of the optical surface of the optical element to be analyzed under the sampling field of view F, further determine the wave aberration of the optical surface of the optical element to be analyzed under the sampling field of view F according to the following formula (1) upper limit Lower limit of sum wave aberration

According to the imaging requirements of the above formula (1), it can be ensured that after manufacturing errors occur in the optical surface of the optical element to be analyzed, the imaging quality of the optical system will not be lower than the imaging quality of the designed system.

Under the sampling field of view F, select multiple sampling points on the optical surface of the optical element to be analyzed, and then according to the wave aberration requirements of the above formula (1), solve point by point the optical surface of the optical element to be analyzed in the sampling field of view F The surface tolerance (optimized tolerance) of each sampling point in the working area is used to obtain the local surface tolerance distribution (local optimized tolerance distribution) of the optical surface of the optical element to be analyzed in the working area of the sampling field of view F.

In one possible implementation, each sampling point on the optical surface of the optical element to be analyzed under the sampling field of view is determined based on the upper limit and lower limit of wave aberration of the optical surface of the optical element to be analyzed under the sampling field of view. The surface tolerance at the point includes: for any one of the multiple sampling points, determine the optical quality of the optical element to be analyzed under the sampling field of view based on the upper limit of the wave aberration of the optical surface of the optical element to be analyzed under the sampling field of view. The deviation of the surface shape at the sampling point on the surface; according to the lower limit of the wave aberration of the optical surface of the optical element to be analyzed under the sampling field of view, determine the lower limit of the surface shape at the sampling point on the optical surface of the optical element to be analyzed under the sampling field of view. Deviation; determine the difference between the upper surface deviation and the lower surface deviation at the sampling point on the optical surface of the optical element to be analyzed under the sampling field of view as the deviation at the sampling point on the optical surface of the optical element to be analyzed under the sampling field of view. Surface tolerance.

Assume that a certain sampling point P on the optical surface of the optical element to be analyzed is within the working area of the sampling field of view F. The sampling point P (x, y, z) can have a positive or negative jump amount, so that the wave aberration of the perturbed light at the sampling point P' after the error perturbation changes occur. The wave aberration of the disturbed light that finally passes through the sampling point P' should not exceed the upper limit of the wave aberration. Lower limit of sum wave aberration The following formula (2) can be obtained:

in, It is the wave aberration of any disturbance light in the sampling field F after the optical surface of the optical element to be analyzed has manufacturing errors. According to the imaging requirements of the above formula (2), the surface shape tolerance of each point on the optical surface of the optical element to be analyzed can be called the optimization tolerance. The positive jump amount of the sampling point P makes the wave aberration of the disturbance light at the sampling point P' increases when wave aberration When reaching its maximum value, the positive jump amount of sampling point P reaches the extreme value. The negative jump amount of point sampling P makes the wave aberration of the perturbed light at sampling point P' decreases when the wave aberration When reaching its minimum value, the negative jump amount of the sampling point P reaches the extreme value. Since the wave aberration of the disturbed light passing through the sampling point P does not exceed the upper limit of the wave aberration Lower limit of sum wave aberration Therefore, when the wave aberration of the perturbed light at the sampling point P' are the upper limit of wave aberration respectively. Lower limit of sum wave aberration When , the extreme value of the positive jump amount and the extreme value of the negative jump amount of the sampling point P can be solved. They respectively determine the upper and lower limits of the manufacturing error at the sampling point P, which can be called the upper deviation and lower deviation of the sampling point P. The difference between the upper deviation and the lower deviation at the sampling point P is the optimization tolerance of the sampling point P.

For all other sampling points on the optical surface of the optical element to be analyzed, repeat the above steps, analyze the optimization tolerances at each sampling point of the optical surface in turn, and obtain the local surface tolerance distribution of the optical surface within the working area of the sampling field of view F ( Locally optimized tolerance distribution).

Change the sampling field of view, repeat the above steps, and solve in turn to obtain the local surface shape tolerance distribution (local optimized tolerance distribution) of the optical surface of the optical element to be analyzed in the working area of each sampling field of view. FIG. 4 shows a schematic diagram of the local surface shape tolerance distribution of the optical element to be analyzed under two sampling fields of view according to an embodiment of the present disclosure. As shown in Figure 4, the local surface tolerance distribution of the optical element (reflector) to be analyzed under the two sampling fields of view includes: the upper deviation distribution of the optical surface of the optical element to be analyzed in the working area of the sampling field of view A (red solid line shown in Figure 4), lower deviation distribution (blue solid line shown in Figure 4); upper deviation distribution of the optical surface of the optical element to be analyzed within the working area of the sampling field of view B (Figure 4 (red dashed line shown in Figure 4), lower deviation distribution (blue dashed line shown in Figure 4). As shown in Figure 4, it can be seen that the upper deviation, lower deviation of the sampling points (P ₁ and P ₂ ) on the optical surface of the optical element (reflector) to be analyzed in the working area of sampling field A and sampling field B deviation.

The intersection of the local surface shape tolerance distribution of the optical element (reflector) to be analyzed under the sampling field of view A and the sampling field of view B shown in Figure 4 can be obtained. The local surface shape tolerance distribution of the optical element to be analyzed can be obtained ( Optimized tolerance distribution). FIG. 5 shows a schematic diagram of a local surface shape tolerance distribution of an optical element to be analyzed according to an embodiment of the present disclosure. As shown in Figure 5, the upper deviation distribution of all sampling fields of view is intersected to obtain the upper deviation distribution of the optical surface. The lower deviation distribution of all sampling fields of view is intersected to obtain the lower deviation distribution of the optical surface. Finally, the local surface shape is obtained. Tolerance distribution.

When the optical system includes multiple optical elements to be analyzed, the surface tolerances between the multiple optical surfaces corresponding to the multiple optical elements to be analyzed affect each other. If the surface of the optical surface of an optical element to be analyzed is The shape tolerance requirements are relaxed, and the surface shape tolerance requirements of the optical surfaces of the remaining optical components to be analyzed may be stricter. The following is a detailed description of the local surface shape tolerance analysis of multiple optical elements to be analyzed in the optical system.

In one possible implementation, the optical system includes multiple optical elements to be analyzed; for any sampling field of view, the optical system to be analyzed is determined based on the wave aberration design peak and wave aberration design valley corresponding to the sampling field of view. The corresponding wave aberration tolerance of the optical surface of the component under the sampling field of view includes: the wave aberration design peak value and the wave aberration design valley value corresponding to the sampling field of view, as well as the first distribution condition and the second distribution condition, as Each optical surface of the optical element to be analyzed is assigned a corresponding wave aberration tolerance under the sampling field of view, where the first allocation condition is that the change in wave aberration caused by the surface shape error of the optical surfaces of multiple optical elements to be analyzed satisfies Linear superposition relationship. The second distribution condition is that the sum of wave aberrations corresponding to the optical surfaces of multiple optical elements to be analyzed is greater than or equal to the wave aberration tolerance valley corresponding to the sampling field of view and is less than or equal to the wave aberration corresponding to the sampling field of view. Tolerance peak.

First, establish the relationship between the impact of surface shape errors of multiple optical surfaces corresponding to multiple optical elements to be analyzed in the optical system on imaging quality at the same time and the impact of individual surface shape errors of each optical surface on imaging quality. Taking the sampling field of view F as an example, the light ray R in the sampling field of view F sequentially intersects the optical curved surface S of each optical element of the optical system at the point P _S (x, y, z) on each optical surface. The initial value of the ray R is Wave aberration is expressed as When an optical surface has a surface tolerance, the intersection coordinates of light R and other optical surfaces can be considered to be approximately unchanged. In the embodiment of the present disclosure, the total change in the wave aberration of the disturbance light R' caused by the manufacturing errors of all optical curved surfaces is approximately equal to the linear superposition of the changes in the wave aberration of the disturbance light R' caused by the individual manufacturing errors of each optical curved surface. , as shown in the following formula (3):

Among them, n is the total number of optical surfaces in the optical system, is the wave aberration change of light R' after surface shape errors exist on all optical surfaces at the same time. ΔW ^{(S, F)} (x, y, z) is the wave aberration of light R' caused by the single surface shape error of optical surface S. Aberration variation. The above formula (3) describes that the wave aberration changes of the disturbed light caused by the surface shape errors of the optical surfaces of multiple optical elements to be analyzed satisfy a linear superposition relationship, and the above formula (3) can be determined as the first distribution condition.

The manufacturing errors at each point on the optical surface are positive or negative, which will cause the wave aberration of the disturbing light to become larger or smaller. The manufacturing errors of all optical surfaces in the optical system will cause changes in the wave aberration of the disturbance light R', so that the final wave aberration of the disturbance light R' is at the upper limit of the wave aberration of the sampling field of view F Between the sum wave aberration lower limit W _- ^(F) , as shown in the following formula (4):

The above formula (4) describes that the sum of the wave aberrations corresponding to the optical surfaces of multiple optical elements to be analyzed is greater than or equal to the lower limit of wave aberration corresponding to the sampling field of view and less than or equal to the upper limit of wave aberration corresponding to the sampling field of view. The above can be Formula (4) is determined as the second distribution condition.

According to the first distribution condition and the second distribution condition shown in the above formula (3) and formula (4), the wave aberration tolerance can be assigned to multiple optical elements to be analyzed in the optical system, and then the parameters of each optical element to be analyzed can be solved. Local surface shape tolerance of optical surfaces. The following takes an optical system with two optical surfaces of optical elements to be analyzed as an example to introduce the local surface tolerance analysis of multiple optical surfaces in detail.

The first step is to determine the upper limit and lower limit of the wave aberration of each sampling field F of the optical system based on the expected wave aberration W _EXP of the optical system. Different imaging expectations can be given for different sampling fields of view according to actual needs, that is, the imaging expectations of each sampling field of view can be obtained. The imaging expectations of different sampling fields of view may be the same or different, and this disclosure does not specifically limit this. The following is an example where the wave aberration expectations of each sampling field are the same.

Let the average wave aberration of the sampling field of view F be expressed as In one example, one can As the wave aberration reference for each sampling field of view. In addition, the wave aberration standard can also be changed according to actual needs, for example, the wave aberration RMS value of each sampling field of view can be used as the standard, etc. This disclosure does not specifically limit this. Without loss of generality, in an example, the wave aberration can be averaged Subtract and add W _EXP /2 respectively as the upper limit of wave aberration W ₊ ^(F) and the lower limit of wave aberration W _- ^(F) of the optical system in the sampling field of view F. The upper limit and lower limit of wave aberration obtained in this way contribute to the symmetry of the final surface tolerance, that is, the values of the upper deviation and the lower deviation are approximately symmetrical. In addition, the upper limit of wave aberration W ₊ ^(F) and the lower limit of wave aberration W _- ^(F) of each field of view can also be determined according to actual needs, as long as the difference between the upper limit of wave aberration and the lower limit of wave aberration is ensured. That is, this disclosure does not specifically limit this.

In the second step, tolerance analysis is performed on any selected optical surface S in the optical system. According to actual needs, assign the wave aberration tolerance W _EXP ^(S) to the optical surface S. For the sampling field of view F, the wave aberration tolerance W _EXP ^(S) assigned to the optical surface S is used to determine the upper limit of the wave aberration W ₊ for all disturbance rays in the sampling field of view F when only the optical surface S has surface shape errors. ^(S,F) and the lower limit of wave aberration W _- ^(S,F) , as shown in the following formula (5):

According to the requirements of the above formula (5) and the above solitary point jump model, the local surface shape tolerance distribution of the optical surface S in the working area of each sampling field of view is solved in turn. The local surface shape tolerance distribution of all sampling fields of view is intersected to obtain the local surface shape tolerance distribution of the optical surface S.

In the third step, based on the local surface shape tolerance distribution of the optical surface S in each sampling field of view, the relationship between the linear superposition of the wave aberration changes according to the above formula (3) and the final optical system shown in the above formula (4) Imaging requires these two distribution conditions, and the fields of view are sampled one by one to solve the local surface shape tolerance distribution of another optical surface in each sampling field of view.

Finally, the local surface shape tolerance distribution of another optical surface in all sampling fields of view is intersected to obtain the local surface shape tolerance distribution of another optical surface.

FIG. 6 shows a flowchart for determining the local surface tolerance distribution of multiple optical elements to be analyzed in an optical system according to an embodiment of the present disclosure. As shown in Figure 6,

In step S601, the optical curved surface of a certain optical element to be analyzed in the optical system is selected.

In step S602, a wave aberration tolerance is assigned to the optical curved surface of the optical element to be analyzed.

In step S603, a certain sampling field of view to be solved in the optical system is selected for analysis.

In step S604, the upper limit and lower limit of wave aberration of the sampling field of view are set.

In step S605, a certain sampling point to be solved on the optical curved surface of the optical element to be analyzed is selected.

In step S606, the surface shape tolerance of the optical curved surface of the optical element to be analyzed at the sampling point is solved.

In step S607, it is determined whether all sampling points on the optical curved surface of the optical element to be analyzed have been solved. If not, jump to step S608; if yes, jump to step S609.

In step S608, another sampling point to be solved on the optical curved surface of the optical element to be analyzed is selected, and then step S606 is executed.

In step S609, the local surface shape tolerance distribution of the optical curved surface of the optical element to be analyzed under the sampling field of view is determined.

In step S610, it is determined whether all sampling fields of view in the optical system have been solved. If not, jump to step S611; if yes, jump to step S612.

In step S611, another sampling field of view to be solved in the optical system is selected, and then jumps to step S604.

In step S612, the local surface shape tolerance distribution of the optical curved surface of the optical element to be analyzed in all sampling fields of view is determined.

In step S613, the intersection of the local surface shape tolerance distributions of the optical curved surface of the optical element to be analyzed under all sampling fields of view is obtained to obtain the local surface shape tolerance of the optical curved surface of the optical element to be analyzed.

In step S614, it is determined whether the optical surfaces of all optical elements to be analyzed in the optical system have been solved. If not, jump to step S615; if yes, jump to step S616.

In step S615, the optical curved surface of another optical element to be analyzed in the optical system is selected, and then jumps to step S602.

In step S616, the local surface shape tolerance distribution of the optical curved surfaces of all optical elements to be analyzed in the optical system is obtained.

In the embodiment of the present disclosure, in addition to performing analysis on an optical surface-by-sampling field-by-sampling point-by-sampling point basis as shown in FIG. 6 above, parallel analysis can also be performed. For example, after allocating wave aberration tolerances to multiple optical elements to be analyzed, multiple optical surfaces and multiple sampling fields of view can be analyzed in parallel, and even multiple sampling points can be analyzed in parallel on each optical surface. This disclosure does not elaborate on this. limited.

On the optical surface of any optical element to be analyzed in any optical system, the selection of sampling points on the optical surface can be uniform or uneven, and there is no specific limit on this. In one example, the analysis is performed with uniform sampling based on a rectangular grid. In another example, sampling points are selected based on polar coordinates or other methods. In one example, the sampling points on the optical surface are flexibly selected according to actual needs.

In one example, the local surface tolerance distribution of the optical surface can be obtained by calculating the surface tolerance at all sampling points; it is also possible to calculate the surface tolerance at some sampling points, and then calculate the surface tolerance at these sampling points. The tolerance is interpolated or fitted to obtain the surface tolerance of more sampling points, thereby finally obtaining the local surface tolerance distribution of the optical surface, which is not specifically limited in this disclosure.

The field of view of an optical system can be uniformly sampled or non-uniformly sampled. In the embodiments of the disclosure, uniform sampling of the field of view is used as an example for analysis, but this does not constitute a limitation on the disclosure. In addition, according to design needs, the field of view corresponding to a specific area of the optical curved surface can also be encrypted and sampled, and this disclosure does not specifically limit this.

In addition, embodiments of the present disclosure can simultaneously analyze the surface shape tolerance and positional tolerance of the optical curved surface of the optical element. First, the imaging performance is assigned to the surface shape tolerance and position tolerance of the optical surface according to actual needs. Then based on the assigned imaging performance requirements, the local surface shape tolerance distribution of the optical surface is calculated according to the method described above. And, based on the assigned imaging performance requirements, follow traditional methods, such as optical design software CODEV, to analyze the position tolerance of the optical surface. The process shown in Figure 6 is only a special example of actual analysis and does not impose any restrictions on this disclosure.

The disclosed local surface shape tolerance analysis method solves the surface shape tolerance of each point on the optical surface of the optical element in the optical system by ensuring the final wave aberration of each light ray. This tolerance analysis method is different from the traditional tolerance analysis method which provides a single surface shape error PV value or RMS value requirement for the entire optical surface. It is a local surface shape tolerance analysis.

In the above-mentioned local surface tolerance analysis of multiple optical surfaces, if it is hoped that the imaging quality of the optical system will not be lower than the design value after manufacturing errors occur in the optical system, then the imaging quality of the manufacturing system can be achieved better than the designed system. At this time, the PV value of the wave aberration in each field of view of the optical system should not exceed its initial design value. At this time, the above formula (4) can be converted into the following formula (6). Such imaging requirements can ensure the reliability of the manufacturing system. Image quality does not decrease.

in, is the design peak value of wave aberration in the field of view F in the design system, is the design valley value of the wave aberration of the field of view F in the design system. It is the wave aberration of any disturbing light ray in the field of view F after manufacturing error. According to the imaging requirements of the above formula (6), the above-mentioned local tolerance model can be used to solve the optimal tolerance of each point on the optical surface of each optical element to be analyzed in the optical system, that is, the optimal tolerance analysis of multiple optical surfaces can be realized. The specific process can be referred to the above-mentioned optimization tolerance analysis process of each point on the optical surface of a single optical element, which will not be described in detail here.

In a possible implementation, the method further includes: manufacturing the optical element to be analyzed according to the local surface shape tolerance distribution of the optical element to be analyzed, wherein the manufacturing error of the optical element to be analyzed satisfies the local tolerance distribution of the optical element to be analyzed. Surface tolerance distribution.

In the manufacturing process of the optical element to be analyzed, as long as the manufacturing error is ensured to meet the optimized tolerance distribution, the imaging performance of the optical element will not be lower than its design value, or even exceed its design value.

In a possible implementation, the method further includes: when the manufacturing error of the optical element to be analyzed causes a radius deviation in the radius of the optical curved surface, according to the radius deviation of the radius of the optical curved surface of the optical element to be analyzed, by moving the optical element to be analyzed The position of the optical element is compensated; for the compensated optical element to be analyzed, the local surface shape tolerance distribution of the optical element to be analyzed is re-determined according to the wave aberration tolerance corresponding to the optical surface of the optical element to be analyzed.

The radius R of an optical surface is a parameter that reflects the power of the surface. In the case where the manufacturing error of the optical element to be analyzed causes the radius R of the optical curved surface to deviate, position compensation can be performed by adjusting the position of the optical curved surface. Then, for the position-compensated optical element to be analyzed, the local surface shape tolerance distribution of the optical element to be analyzed is re-determined according to the wave aberration tolerance corresponding to the optical curved surface of the optical element to be analyzed. The position compensation process will be described in detail later using a specific optical system as an example, and will not be described in detail here. In addition to position compensation by moving the position of the optical element to be analyzed, other compensation methods in related technologies can also be used, such as rotating optical elements, etc., which is not specifically limited in this disclosure.

Based on the local surface shape tolerance analysis model described in the above embodiments, embodiments of the present disclosure disclose a method for quality evaluation of optical elements in an optical system based on imaging quality.

FIG. 7 shows a flow chart of a component quality evaluation method of an optical system according to an embodiment of the present disclosure. As shown in Figure 7, the method includes:

In step S71, for the optical element to be evaluated in the optical system, the quality evaluation function of the optical curved surface of the optical element to be evaluated is determined.

In step S72, a quality evaluation function value corresponding to the optical element to be evaluated is determined based on the quality evaluation function, where the quality evaluation function value is used to evaluate the quality of the optical element to be evaluated.

In the embodiment of the present disclosure, for the optical element to be evaluated in the optical system, the quality evaluation function of the optical surface of the optical element to be evaluated is determined, and then based on the quality evaluation function, the quality evaluation function value corresponding to the optical element to be evaluated is determined, so that Realize effective evaluation of the quality of the optical elements to be analyzed in the optical system based on imaging quality.

In a possible implementation, determining the quality evaluation function value corresponding to the optical element to be evaluated based on the quality evaluation function includes: determining at least one sampling field of view corresponding to the optical system; The manufacturing error of the point, the initial wave aberration of different points on the optical surface of the optical element to be evaluated in each sampling field of view, the irradiance of different points on the optical surface of the optical element to be evaluated in each sampling field of view, Determine the root mean square of the wave aberration corresponding to the optical element to be evaluated in each sampling field of view; determine the corresponding quality of the optical element to be evaluated based on the root mean square of the wave aberration corresponding to the optical element to be evaluated in at least one sampling field of view Evaluation function value.

The embodiment of the present disclosure discloses a quality evaluation function for evaluating the quality of optical elements based on imaging quality. This quality evaluation function comprehensively considers the initial wave aberration of all fields of view, all light rays, and the change in imaging performance caused by component manufacturing errors. Among them, the imaging performance is not limited to wave aberration, but can also be modulation transfer function (MTF), point spread function (PSF), distortion, or specific aberration, etc., which is not specifically limited in this disclosure. This quality evaluation function is not limited to a single optical element to be evaluated in the optical system, it can also be evaluated together with multiple optical elements to be evaluated or the entire optical system. The following describes in detail how the change in wave aberration caused by manufacturing errors is used to evaluate the quality of a single optical element to be evaluated.

If the surface shape error of the optical surface of a single optical element to be evaluated in the optical system is d(x, y, z), then the change in the perturbation light wave aberration of a certain sampling field F in the optical system ΔW ^(F) (x ,y,z) can be the following formula (7):

Among them, θ ^(F) (x, y, z) and θ′ ^(F) (x, y, z) are the incident angle and refraction angle of the light incident on the point (x, y, z) in the sampling field of view F , n and n′ are the refractive index of the incident side and the refracted side respectively. The above formula (7) respectively corresponds to the change in wave aberration after the reflective surface and refractive surface of the optical element to be evaluated are disturbed by the surface shape error.

The average value of the wave aberration after the perturbation of the sampling field of view F is As shown in the following formula (8):

Among them, A is the working area of the light ray from the sampling field of view F on the curved surface, W ₀ ^(F) (x, y, z) is the initial wave aberration corresponding to the light ray, ρ ^(F) (x, y, z) ) is the ratio of the irradiance of the light ray in the sampling field F at point (x, y, z) on the optical surface to the peak irradiance on the optical surface, ρ ^(F) is the normalized irradiation of the sampling field F Spend. The normalized irradiance can be calculated assuming that the irradiance at the entrance pupil is uniform, and can also take into account the spectral information of the object, the radiance distribution of the object, the spectral responsivity of the detector, and the spectral transmission of the optical system. pass rate, etc., this disclosure does not specifically limit this. At this time, the corresponding root mean square wave aberration RWE ^(F) value (quality evaluation function value) under the sampling field of view F can be expressed as the following formula (9), where, (RMS of the Wavefront error of the system with the surface with figure Errors) is RWE ^(F) .

The quality of the optical element to be evaluated can be evaluated by the average RWE of RWE ^(F) under all sampling fields of view, as shown in the following formula (10). Among them, FOV is the field of view of the optical system.

It can be seen from the above formulas (7)-(10) that the RWE of the optical element to be evaluated reflects the average wave aberration RWE of all fields of view of the optical system after using the optical element to be evaluated, which is the initial wave aberration W ₀ ^(F) , the incident angle θ ^(F) and the normalized irradiance distribution ρ ^(F) . The above formulas (7)-(10) give the evaluation function based on the imaging quality of the reflective or refractive optical element to be evaluated. However, the evaluation function is not limited to the above situation. It can also evaluate the performance of diffraction elements, phase devices, and metasurface devices. Quality, this disclosure does not specifically limit this.

The larger the RWE of the optical element to be evaluated, the worse the imaging quality of the final optical system using the element to be evaluated. The correctness of the quality evaluation function is verified later and will not be described in detail here. The initial wave aberration W ₀ ^(F) , incident angle θ ^(F) and normalized irradiance distribution ρ ^(F) are independent data separated from the design system. They have partial information of the system and can reflect the initial system characteristics. In other words, only partial information of the optical system is needed to evaluate the quality of optical components without the need for complete optical system lens files. After the optical element is manufactured, the manufacturing error d at any position of the optical element can be obtained through curved surface inspection. Therefore, after a single optical element is manufactured and tested, the impact of the optical element on the imaging quality can be evaluated, thereby achieving quality evaluation of the optical element.

In a possible implementation, the quality evaluation function is used to determine the quality evaluation function value corresponding to the optical element to be evaluated based on the root mean square of wave aberration corresponding to the optical element to be evaluated in at least one sampling field of view, including: using The quality evaluation function determines the quality evaluation function value corresponding to the optical element to be evaluated based on the root mean square of wave aberration corresponding to the optical element to be evaluated in at least one sampling field of view and the weight corresponding to each sampling field of view.

In addition, the above quality evaluation function can be improved according to needs. For example, when calculating the quality evaluation function value RWE, the weight μ ^(F) corresponding to each sampling field of view can be introduced according to the difference in importance of the field of view of the optical system. The quality evaluation function shown in the above formula (10) can be improved to The following formula (11):

In one example, when evaluating a refractive element, the evaluation functions at different operating wavelengths can be calculated separately, and then they can be averaged or weighted, or integrated in other ways to obtain the final element quality evaluation function value. , this disclosure does not specifically limit this

Taking three optical systems as examples, we first use the local surface tolerance model proposed above to analyze the local surface tolerance of the optical surfaces of the optical elements in these three optical systems, and then analyze the local surface tolerance results. have a discussion. Then, the component quality evaluation function proposed above is used to evaluate the primary mirror in the optical system example 2, and distinguish the quality differences of the primary mirrors with different manufacturing surface error distributions.

Local surface tolerance analysis of free-form off-axis three-reflection system.

The first optical system is a free-form off-axis three-mirror system operating in the long-wave infrared band (8-12μm). Its relevant parameters are: F number 1.5, focal length 100mm, and field of view 3°×4°. The system field of view deviates in the vertical direction, and the central field of view is (0, -33.2°). The system is symmetrical about the YOZ plane. The three mirrors are all free-form surfaces described by 6th-order XY polynomials, and the secondary mirror is the aperture stop of the system. Figure 8 shows a schematic diagram of a two-dimensional structural diagram, a field of view diagram, and three-mirror sampling data points of a free-form off-axis three-mirror system according to an embodiment of the present disclosure. The two-dimensional structure diagram of the system is shown in Figure 8 (a). The average value of the wave aberration RMS value of the system AVG RMS WFE is 0.01λ (λ = 10 μm), as shown in (b) in Figure 8. Among them, the maximum value of the RMS WFE of all fields of view is 0.014λ, and the minimum value is 0.007λ.

Taking three mirrors as an example to conduct optimization tolerance analysis. The third mirror is a free-form surface with a circular aperture and a diameter of 130mm. The data points of the three mirrors are sampled according to the rectangular grid method. The sampling intervals of the data points in the X direction and Y direction are both 0.5mm, as shown in (c) in Figure 8. The field of view of the system is also sampled, and the sampling intervals of the field of view in the horizontal and vertical directions are 0.3° and 0.4° respectively. The optimization tolerance of the three mirrors was analyzed based on the optimization tolerance analysis method proposed above. FIG. 9 shows a schematic diagram of the optimized tolerance distribution of the three mirrors in the free-form off-axis three-mirror system shown in FIG. 8 according to an embodiment of the present disclosure. As can be seen from Figure 9, the optimization tolerances in different areas of the three mirrors are also different. The optimization tolerances in most areas of the curved surface are tight, a few nanometers, indicating that higher manufacturing accuracy requirements are needed in these areas. There are only a few areas where the optimization tolerance is looser, reaching 76nm. Figure 9(d) is a detailed view of the optimized tolerance distribution of the area outlined by the dotted circle in Figure 9(c). Although the optimization tolerance changes in some areas of the surface appear to be drastic, they are all continuous changes.

Similar to the above verification of the shape tolerance distribution, we also verify the optimized tolerance distribution of the three mirrors shown in Figure 9. 3000 groups of random surface errors that meet the optimization tolerance requirements were constructed and sequentially superimposed on the three mirrors to examine the changes in the imaging quality of the system. The system uniformly sampled 3 fields of view in the X direction and Y direction, and a total of 9 fields of view were sampled. Calculate the PV values of wave aberration in these fields of view for the designed system and the system with three-mirror disturbances. It has been verified that after the three-mirror superposition error, the imaging quality of each field of view of all systems is slightly improved. The PV values of each field of view wave aberration of one of the systems are listed here, as shown in Table 1. Table 1 shows the wave aberration PV value of each field of view after the random surface error of the three mirrors in the off-axis three-mirror system is superimposed to meet the optimization tolerance requirements, unit: λ (λ = 10 μm). This result demonstrates the effectiveness of the optimized tolerance proposed by embodiments of the present disclosure.

Table 1

Local surface tolerance analysis of coaxial two-reverse Cassegrain system.

The second system is a rotationally symmetrical coaxial two-reverse Cassegrain system operating in the mid-wave infrared band (3-5μm), with an F number of 5, a focal length of 1.5m, and a field of view of 0.3°×0.3 °. The aperture diaphragm of the system is the primary mirror, its surface shape is a quadratic surface, and the secondary mirror is an 8th-order aspheric surface. Figure 10 shows a two-dimensional structural diagram, a field of view diagram, a schematic diagram of the primary mirror aperture, and a schematic diagram of the secondary mirror aperture of a coaxial two-reverse Cassegrain system according to an embodiment of the present disclosure. The two-dimensional structure diagram of the system is shown in Figure 10 (a). The average AVG RMS WFE of the wave aberration RMS value of each field of view of the system is 0.0171λ (λ = 3μm), as shown in Figure 10 (b). The RMS WFE of the center field of view is 0.0001λ. As the field of view increases, the RMS WFE of the field of view increases, and the RMS WFE of the edge field of view is 0.042λ.

The system uniformly sampled 81 fields of view for tolerance analysis, in which the sampling field intervals along the horizontal and vertical directions were 0.0375°. The apertures of the primary mirror and the secondary mirror are shown in Figure 10 (c) and Figure 10 (d). The sampling intervals of the data points in the X and Y directions of the primary mirror are both 1 mm. The sampling intervals of the data points in the X and Y directions of the secondary mirror are The sampling intervals of data points in the Y direction are all 0.5mm. The expected wave aberration PV value of the system is λ4. The multi-surface tolerance analysis method proposed in the embodiment of the present disclosure is used to simultaneously solve the surface tolerance of the primary mirror and the secondary mirror. Considering that the primary mirror has a larger diameter and is more difficult to process, the expected wave aberration PV assigned to the primary mirror in this analysis is 3λ16. After manufacturing errors exist in both the primary mirror and the secondary mirror, the expected wave aberration PV value of the system still does not exceed λ4. The final obtained local surface tolerance distribution of the primary mirror and secondary mirror. FIG. 11 shows a schematic diagram of the local surface tolerance distribution of the primary mirror and the secondary mirror in the coaxial two-reverse Cassegrain system shown in FIG. 10 according to an embodiment of the present disclosure. As shown in Figure 11, it includes the upper surface deviation distribution, lower surface deviation distribution, and local surface tolerance distribution of the primary mirror, as well as the upper surface deviation distribution, lower surface deviation distribution, and local surface tolerance distribution of the secondary mirror. distributed.

It can be seen from Figure 11 that the surface tolerances of the primary mirror and the secondary mirror are symmetrical about the XOZ and YOZ planes respectively, and show obvious local characteristics. Among them, the tolerance requirement in the area with the strictest tolerance of the primary mirror is 0.16 μm, while the tolerance in the area with loose tolerance is 0.26 μm. For the secondary mirror, the tightest tolerance requirement is 0.08μm, while tolerances in the loose tolerance area can reach 0.22μm. Second, whether it is the primary mirror or the secondary mirror, the surface tolerance is not rotationally symmetrical, which is caused by the non-rotationally symmetrical field of view. The shape of the designed field of view in the optical system will affect the local tolerance distribution of the optical surface. If the rotationally symmetric system has a circular field of view, the final local surface tolerance distribution of the optical surface should also be rotationally symmetrical. The tolerances of multiple surfaces in the system affect each other. If one surface in the system has a looser tolerance, the remaining surfaces will have a tighter tolerance. In addition to the conclusions known from this traditional method, from the perspective of the local tolerance distribution shape of the surface, if the local tolerance of a certain surface changes, it will also change the local tolerance distribution of other surfaces.

Next, the local surface shape tolerance of the multi-curved surface shown in Figure 11 is verified. Within the local tolerance range of the primary mirror and secondary mirror shown in Figure 11, 3000 random surface errors are randomly constructed, and they are combined to obtain 3000 perturbation optical systems. Figure 12 shows the primary mirror and the secondary mirror in the coaxial two-reverse Cassegrain system shown in Figure 10 according to an embodiment of the present disclosure. The primary mirror and the secondary mirror are simultaneously superimposed to meet the local tolerance requirements shown in Figure 11 after the surface error. Statistical diagram of the PV value of the wave aberration of the secondary mirror. Figure 12 (a) shows the wave aberration PV values of 25 fields of view of one of the perturbation optical systems, in which the maximum wave aberration PV value MAX PV WFE is 0.224λ. The statistical results of MAX PV WFE for all perturbation optical systems are shown in Figure 12(b). The MAX PV WFE of all systems with manufacturing errors did not exceed λ/4 (maximum 0.248λ). This result illustrates the effectiveness of the local surface shape tolerance model proposed by the embodiment of the present disclosure.

The radius R of an optical surface is a parameter that reflects the power of the surface. If the manufacturing error of the curved surface causes its radius R to deviate, it can be compensated by adjusting the position of the curved surface. Next, the surface shape tolerance of the surface after using position compensation is analyzed. Generally speaking, the error ΔR of the surface radius is very small, much smaller than its radius R. For a reflective surface, its focal length approximately satisfies f'=R/2. When there is a manufacturing error ΔR in the radius of the curved surface, there are a variety of position compensation methods to compensate for the degradation in imaging quality caused by radius deviation. Embodiments of the present disclosure realize that the conjugate distance of the object space and image space of the curved surface remains unchanged by moving the position of the reflective curved surface with a manufacturing error in its radius. Taking the Cassegrain system shown in Figure 9 above as an example, the positional movement amount of the curved surface, that is, the position compensation amount Δd, can be obtained by the following formula (12):

Among them, f ₁ ' is the focal length of the reflective surface, l ₁ and l ₁ ' are the object distance and image distance of the curved surface respectively. For the primary mirror of the Cassegrain system, an object at infinite distance is incident with parallel light, and the position compensation amount Δd=ΔR/2 can be known from the above formula (12). The surface radius R of the primary mirror is -1123.55mm. Assume that the manufacturing error ΔR of the primary mirror radius is 1mm, that is, the radius of the primary mirror is -1124.55mm. After position compensation of Δd=0.5mm (the primary mirror moves 0.5mm to the right along the Z-axis), the imaging quality of the system remains almost unchanged. At this time, the local surface tolerance of the primary mirror is recalculated. FIG. 13 shows a schematic diagram of the local surface tolerance distribution of the primary mirror after position compensation is performed on the coaxial two-reverse Cassegrain system shown in FIG. 10 according to an embodiment of the present disclosure. As shown in Figure 13, it includes the upper surface deviation distribution, the lower surface deviation distribution, and the local surface tolerance distribution of the main mirror.

Comparing Figure 13 with the local surface tolerance distribution of the primary mirror without radius error, it can be seen that overall, the upper surface deviation distribution, lower surface deviation distribution and surface tolerance distribution of the main mirror are highly similar. of. The tolerance change of each point on the primary mirror is very small, and the upper and lower deviation differences of each point do not exceed 2.9nm. This difference is negligible compared to the tolerance of the primary mirror. If the radius deviation ΔR of the primary mirror increases to 5mm (R=-1128.55mm), the compensation amount of the primary mirror is to move 2.5mm along the positive direction of the Z-axis, and its surface tolerance distribution is re-solved. At this time, the upper and lower deviation differences of each point on the primary mirror do not exceed 13.6nm. It is not difficult to know that as the error ΔR of the primary mirror radius increases, the local surface shape tolerance of the primary mirror changes greater.

If ΔR _max is the maximum manufacturing error allowed by the radius R of the optical surface. If the radius error ΔR is different, the surface tolerance distribution of the position-compensated surface will be different. For any curved surface with ΔR ≤ ΔR _max , as long as it meets the requirements of a certain tolerance distribution, the imaging quality of the system can be guaranteed through position compensation. This surface shape tolerance distribution is the intersection of the surface shape tolerances corresponding to the surface radius R+ΔR _max and R-ΔR _max position compensation. As the surface radius error tolerance ΔR _max increases, this surface tolerance will eventually become more stringent.

Local tolerance analysis of high-precision laser alignment systems.

The third system is a high-precision laser collimation optical system operating at 532nm wavelength. The system consists of a plano-convex lens with a refractive index of 1.519 at 532nm, in which the first surface of the lens is a 10th-order aspherical surface. The focal length of the system is 100mm, the numerical aperture NA of the system is 0.2, and the aperture stop is on the first surface of the lens. The system can achieve diffraction-limited imaging quality at the operating wavelength. Figure 14 shows an optical path diagram of a high-precision laser collimation system according to an embodiment of the present disclosure and a wave aberration pupil diagram of the system in the central field of view. The optical path diagram of the system is shown in Figure 14(a), and the wave aberration pupil diagram of the system in the central field of view is shown in Figure 14(b).

The aperture of the first face of the lens is 42.5 mm, and the first face is sampled in the form of a uniform rectangular grid with a sampling interval of 0.25 mm. Here, the desired W _Exp is set to λ/4 (λ = 532 nm). Next, the local tolerance of the non-curved surface of the lens can be calculated assuming the second surface to be the design value. FIG. 15 shows a schematic diagram of the local tolerance distribution of the first surface in the high-precision laser collimation optical system shown in FIG. 14 according to an embodiment of the present disclosure. As shown in Figure 15, (a) in Figure 15 is the upper surface deviation, (b) in Figure 15 is the lower surface deviation, and (c) in Figure 15 is the local surface tolerance. As can be seen from Figure 15, the tolerance at the center of the aspherical surface is looser than at the edge, with the strictest tolerance being 242nm and the loosest tolerance being 256nm.

In order to verify the correctness of the calculated local tolerance of the surface, 1000 surface shape errors that meet the local tolerance were randomly generated and superimposed on the non-curved surface respectively, thereby obtaining 1000 perturbation optical systems. The maximum value of the wave aberration PV value of these optical systems does not exceed λ/4, which shows that the calculated local tolerance is correct and effective. This example also demonstrates the suitability of the model for analyzing local tolerances of refractive elements.

Component quality analysis of coaxial two-reflection Cassegrain system primary mirror based on imaging quality.

Taking the above-mentioned coaxial two-reverse Cassegrain system as an example, the component quality analysis is discussed. The RWE in the element quality evaluation function proposed in the embodiment of the present disclosure is used to evaluate the quality of the primary mirror of the system, thereby distinguishing the performance differences of primary mirrors with different manufacturing surface shape errors.

25 uniformly sampled fields of view were selected for analysis. First, the initial wave aberration W ₀ ^(F) and incident angle θ ^(F) of the light rays at each sampling field point of the design system are obtained through ray tracing, as well as the normalized irradiance distribution of each field point on the primary mirror. ρ ^(F) . Then, six groups of random surface shape errors were constructed, each group including 3000 random surface shape errors, and superimposed on the primary mirror to simulate manufacturing errors. The PV values of three groups of surface shape errors are 0.1λ (λ = 3 μm), 0.08λ and 0.05λ respectively, and the RMS values of the other three groups of surface shape errors are 0.02λ, 0.016λ and 0.01λ respectively. Next, use formulas (7)-(10) to calculate the evaluation function RWE of the primary mirror with different surface shape errors.

In order to verify that the RWE evaluation function can accurately reflect the imaging quality of the component in the system, a group of 3000 primary mirrors with a PV value of 0.1λ and surface shape errors were sorted according to the RWE value. Then they are put into the design system respectively, their imaging quality is calculated through ray tracing and sorted according to the field average of the wave aberration RMS. The comparison shows that the two sorting results are the same, which shows the correctness of the RWE evaluation function.

Then, the RWE of each of these six groups of primary mirrors with surface shape errors was statistically analyzed. Figure 16 shows a schematic diagram of RWE statistics of a primary mirror with surface shape error according to an embodiment of the present disclosure. It can be seen from (a)-(f) in Figure 16 that even if the surface shape errors with the same PV value or RMS value of the primary mirror are superimposed, their RWE values are different. This shows that the performance of primary mirrors with the same PV value or RMS value in the Cassegrain system is different, which will ultimately lead to different imaging qualities of the actual system. Comparing (a)-(c) in Figure 16, when the surface shape error PV values of the primary mirror are 0.1λ, 0.08λ, and 0.05λ respectively, the quantitative distribution forms of RWE of these three groups of primary mirrors are similar. In addition, as the PV value of the surface shape error decreases, the RWE statistical chart of the primary mirror moves in the direction of smaller RWE, which means that the overall imaging quality of these systems becomes better. At the same time, the width of the RWE statistical chart of the primary mirror is getting narrower and narrower, that is to say, the quality difference between the primary mirrors is getting smaller and smaller, and the difference in imaging quality of the actual system is gradually shrinking. Comparing (d)-(f) in Figure 16, the three sets of primary mirrors with surface error RMS values of 0.02λ, 0.016λ and 0.01λ also have similar rules. In Table 2, the maximum value, minimum value and distribution range of RWE values of each group are given. It can be seen from Table 2 that for a system with a smaller PV value or RMS value of the surface shape error, the maximum value, minimum value and distribution range of the RWE of the primary mirror will also be smaller.

Combining Figure 16 and Table 2, it can be seen that a primary mirror with a smaller surface error PV value or RMS value is more likely to be of good quality, and it has a greater probability of achieving higher imaging quality in the Cassegrain system. In other words, continuously improving component manufacturing accuracy can ensure that the system imaging quality meets the requirements to a certain extent, which is consistent with everyone's traditional understanding. However, according to Figure 16, the RWE distribution ranges of the primary mirrors of the 0.1λ group, 0.08λ group and 0.05λ group with surface error PV values all have overlapping intervals. In other words, the RWE of a primary mirror with a surface error PV value of 0.1λ may be smaller than that of a primary mirror with a PV value of 0.08λ. According to the previous evaluation of the PV value of surface error, it is considered that two primary mirrors with the same PV value of surface error are the same, and a primary mirror with a PV value of 0.08λ will be better than a primary mirror with a PV value of 0.1λ. However, in fact, Even if the surface shape error PV of the components is the same, the final imaging quality is different. In addition, the primary mirror with a small surface shape error PV value may have a worse imaging quality of the final system. There are similar rules for the evaluation of the RMS value of surface shape error.

Table 2

In order to further illustrate the above conclusion, several primary mirrors with different surface shape errors were selected from the above six groups of primary mirrors. FIG. 17 shows a schematic diagram of surface shape error distribution of a primary mirror according to an embodiment of the present disclosure. Comparing (a) and (b) in Figure 17, their surface shape error PV values are both 0.1λ. However, the RWE of the latter is smaller than that of the former, which means that the latter will have better performance in the Cassegrain system used for design. Imaging quality. Comparing (b) and (c) in Figure 17, the primary mirror with a smaller surface error PV value will have a larger RWE and better imaging quality. In other words, the traditional evaluation based on PV value is opposite to the imaging quality performance of these two primary mirrors in the designed system. Comparing (d)-(f) in Figure 17, it can be found that the evaluation based on the RMS value also has similar problems. It can be seen from Figure 17 that the error distributions of these six types of surface shapes are quite different. In the design system, the wave aberration of light at different fields of view and different apertures is different, and the same surface shape error changes the optical path of light at different incident angles differently, and the normalization of different areas on the curved surface Chemical irradiance is not the same. However, the evaluation of PV or RMS does not take into account the various localities mentioned above, which ultimately leads to such evaluation being inconsistent with imaging quality. This is exactly the flaw of this type of evaluation of the geometric accuracy of the overall manufacturing surface based on curved surfaces.

To sum up, putting forward more stringent requirements on the PV value or RMS value of the surface shape error can ensure the imaging quality of the final system to a certain extent. However, the PV value or RMS value of the entire surface shape error cannot accurately reflect the impact of optical elements in the system on the actual imaging quality. The evaluation function based on imaging quality proposed in the embodiment of the present disclosure can distinguish differences in imaging quality of components with different surface error distributions, thereby avoiding the requirement to blindly improve manufacturing accuracy.

In related technologies, surface shape errors of optical surfaces are considered harmful and will lead to a decrease in the imaging quality of the optical system. However, research in embodiments of the present disclosure has found that surface shape errors do not necessarily lead to a decrease in the imaging quality of the system, and some forms of surface shape errors can even improve the imaging quality of the system. If the surface shape error of the curved surface meets the optimization tolerance requirements, it will be possible to manufacture a series of systems with imaging quality that is better than the imaging quality of the designed system. This is unimaginable and impossible to achieve using traditional methods. Optimizing tolerances provides new ideas for manufacturing extremely high-precision systems.

The local surface shape tolerances of various curved surfaces of the optical system have an impact on each other. From the perspective of the local tolerance distribution shape of the surface, if the local tolerance of a certain surface changes, it will also change the local tolerance distribution of the other surfaces.

In the field of optical processing, related technologies use the PV or RMS value of the surface shape error of the entire surface to evaluate the quality of components. It describes the surface geometric accuracy of component manufacturing and cannot distinguish surfaces with the same PV value or RMS value. The difference in imaging quality of shape error components. In addition, this evaluation parameter cannot evaluate the impact of a single optical element on the imaging quality of the system after it is manufactured. The manufacturing quality of components can often be evaluated through the final system imaging quality after all components are manufactured. Based on the local tolerance model proposed in the embodiment of the present disclosure, an evaluation function for evaluating component quality from the perspective of imaging performance is further proposed. This evaluation function can reflect the imaging performance of the component in the optical system. Since different systems have different characteristics such as initial wave aberration, surface shape sensitivity, and normalized irradiance, the evaluation function RWE value of the same component in different systems is different. Although this evaluation function can reflect the quality of the component's imaging quality in the design system, it does not require all the information of the entire system and only requires some feature parameters extracted from the design system.

The component quality evaluation function of the embodiment of the present disclosure has many foreseeable benefits. For example, first, the RWE ^(F) value of the component can reflect the impact of the component on the imaging quality of different fields of view in the system. The surface shape error of the curved surface will cause changes in the imaging quality of each field of view in the system, and the changes in imaging quality in different fields of view are different. By detecting the manufacturing errors at each point on the curved surface, the RWE ^(F) values of the component in different fields of view can be calculated. They reflect the difference in imaging quality in different fields of view when the component is used in the system. Second, the evaluation function RWE can accurately distinguish the quality of components with different surface shape errors. In the aforementioned example analysis, when the manufactured components have surface shape errors with the same PV value or RMS value, their imaging performance in the system is different. In addition, components with larger surface error PV or RMS values may have smaller RWE values and better imaging quality. This is beyond the scope of traditional evaluation based on surface geometry accuracy. Third, the development process of high-performance optical systems requires in-depth collaboration in design, manufacturing, and testing. Using the component quality evaluation function proposed in this article, the manufacturing and inspection side only needs to design some characteristic parameters of the system to evaluate the quality of a single component, which is conducive to the coordination and cooperation of the design, manufacturing, and inspection of complex high-performance systems.

The local tolerance model and evaluation function proposed in the embodiment of the present disclosure are exemplified by reflective elements and refractive elements, but are not limited to refractive and reflective elements. It can be applied to diffractive elements, phase elements, and metasurface elements through simple adjustments. That is, by replacing the relationship between the surface shape error of the reflective or refractive surface and the change of the wave aberration of the corresponding light rays with the relationship of the corresponding elements, it can be analyzed Diffractive elements, phase elements, metasurfaces and other elements are not specifically limited in this disclosure.

It should be noted that although the local surface shape tolerance analysis of optical curved surfaces is introduced above using three optical systems as examples, those skilled in the art can understand that the present disclosure should not be limited thereto. In fact, users can flexibly set the optical system according to personal preferences and/or actual application scenarios.

In some embodiments, the functions or modules provided by the device provided by the embodiments of the present disclosure can be used to execute the methods described in the above method embodiments. For specific implementation, refer to the description of the above method embodiments. For the sake of brevity, here No longer.

FIG. 18 shows a block diagram of an element tolerance analysis device of an optical system according to an embodiment of the present disclosure. As shown in Figure 18, device 180 includes:

The wave aberration tolerance allocation module 181 is used to determine the wave aberration tolerance corresponding to the optical curved surface of the optical element to be analyzed for the optical element to be analyzed in the optical system;

The local surface shape tolerance determination module 182 determines the local surface shape tolerance distribution of the optical element to be analyzed according to the wave aberration tolerance corresponding to the optical surface of the optical element to be analyzed, wherein the local surface shape tolerance of the optical element to be analyzed is The distribution includes surface tolerances at different points on the optical surface of the optical element to be analyzed.

In a possible implementation, the wave aberration tolerance allocation module 181 is used for:

Determine at least one sampling field corresponding to the optical system;

For any sampling field of view, according to the wave aberration design peak value and wave aberration design valley value corresponding to the sampling field of view, determine the corresponding wave aberration tolerance of the optical surface of the optical element to be analyzed in the sampling field of view.

In a possible implementation, the local surface shape tolerance determination module 182 is used to:

For any sampling field of view, determine the local surface shape tolerance distribution of the optical element to be analyzed under the sampling field of view based on the wave aberration tolerance corresponding to the optical surface of the optical element to be analyzed under the sampling field of view;

The intersection of the local surface shape tolerance distribution of the optical element to be analyzed under at least one sampling field of view is obtained to obtain the local surface shape tolerance distribution of the optical element to be analyzed.

In a possible implementation, the local surface shape tolerance determination module 182 is used to:

According to the corresponding wave aberration tolerance of the optical surface of the optical element to be analyzed under the sampling field of view, determine the upper limit and lower limit of wave aberration of the optical surface of the optical element to be analyzed under the sampling field of view;

Determine multiple sampling points on the optical surface of the optical element to be analyzed;

According to the upper limit and lower limit of wave aberration of the optical surface of the optical element to be analyzed under the sampling field of view, determine the surface shape tolerance at each sampling point on the optical surface of the optical element to be analyzed under the sampling field of view;

According to the surface shape tolerance at multiple sampling points on the optical surface of the optical element to be analyzed under the sampling field of view, the local surface shape tolerance distribution of the optical element to be analyzed under the sampling field of view is determined.

In a possible implementation, the local surface shape tolerance determination module 182 is used to:

For any one of the multiple sampling points, according to the upper limit of wave aberration of the optical surface of the optical element to be analyzed under the sampling field of view, determine the surface shape at the sampling point on the optical surface of the optical element to be analyzed under the sampling field of view. upper deviation;

According to the lower limit of the wave aberration of the optical surface of the optical element to be analyzed under the sampling field of view, determine the surface deviation at the sampling point on the optical surface of the optical element to be analyzed under the sampling field of view;

The difference between the upper surface deviation and the lower surface deviation at the sampling point on the optical surface of the optical element to be analyzed under the sampling field of view is determined as the surface shape at the sampling point on the optical surface of the optical element to be analyzed under the sampling field of view. tolerance.

In a possible implementation, the optical system includes multiple optical elements to be analyzed;

Wave aberration tolerance allocation module 181, used for:

According to the wave aberration design peak value and wave aberration design valley value corresponding to the sampling field of view, as well as the first allocation condition and the second allocation condition, the corresponding wave aberration in the sampling field of view is assigned to the optical surface of each optical element to be analyzed. Tolerance, where the first distribution condition is that the wave aberration variation caused by the surface shape error of the optical surfaces of the multiple optical elements to be analyzed satisfies the linear superposition relationship, and the second distribution condition is that the optical curved surfaces of the multiple optical elements to be analyzed correspond to The sum of the wave aberrations is greater than or equal to the wave aberration tolerance valley value corresponding to the sampling field of view and is less than or equal to the wave aberration tolerance peak value corresponding to the sampling field of view.

In a possible implementation, device 180 also includes:

The manufacturing module is used to manufacture the optical element to be analyzed according to the local surface shape tolerance distribution of the optical element to be analyzed, wherein the manufacturing error of the optical element to be analyzed satisfies the local surface shape tolerance distribution of the optical element to be analyzed.

In a possible implementation, device 180 also includes:

A compensation module for compensating by moving the position of the optical element to be analyzed according to the radius deviation of the optical surface radius of the optical element to be analyzed when the manufacturing error of the optical element to be analyzed results in a radius deviation in the radius of the optical surface;

The local surface shape tolerance determination module 182 is used to re-determine the local surface shape tolerance distribution of the optical element to be analyzed based on the wave aberration tolerance corresponding to the optical curved surface of the optical element to be analyzed for the compensated optical element to be analyzed.

FIG. 19 shows a block diagram of an element quality evaluation device of an optical system according to an embodiment of the present disclosure. As shown in Figure 19, device 190 includes:

The function determination module 191 is used to determine the quality evaluation function of the optical surface of the optical element to be evaluated for the optical element to be evaluated in the optical system;

The quality evaluation module 192 is used to determine the quality evaluation function value corresponding to the optical element to be evaluated according to the quality evaluation function, where the quality evaluation function value is used to perform quality evaluation of the optical element to be evaluated.

In a possible implementation, the quality evaluation module 192 is used to:

Determine at least one sampling field corresponding to the optical system;

According to the manufacturing errors at different points on the optical surface of the optical element to be evaluated, the initial wave aberration at different points on the optical surface of the optical element to be evaluated in each sampling field of view, and the different points on the optical surface of the optical element to be evaluated in each sampling field. The irradiance under each sampling field of view is determined to determine the root mean square of the wave aberration corresponding to the optical element to be evaluated in each sampling field of view;

According to the root mean square of wave aberration corresponding to the optical element to be evaluated in at least one sampling field of view, the quality evaluation function value corresponding to the optical element to be evaluated is determined.

In a possible implementation, the quality evaluation module 192 is used to:

According to the root mean square of wave aberration corresponding to the optical element to be evaluated in at least one sampling field of view and the weight corresponding to each sampling field of view, the quality evaluation function value corresponding to the optical element to be evaluated is determined.

The embodiments of the present disclosure have been described above. The above description is illustrative, 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 chosen to best explain the principles, practical applications, or technical improvements in the market of the embodiments, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims (13)

1. A component tolerance analysis method of an optical system, which is characterized by including:

   For the optical element to be analyzed in the optical system, determine the wave aberration tolerance corresponding to the optical curved surface of the optical element to be analyzed;

   According to the wave aberration tolerance corresponding to the optical surface of the optical element to be analyzed, the local surface shape tolerance distribution of the optical element to be analyzed is determined, wherein the local surface shape tolerance distribution of the optical element to be analyzed includes The surface shape tolerance at different points on the optical curved surface of the optical element to be analyzed.
2. The method according to claim 1, characterized in that, for the optical element to be analyzed in the optical system, determining the wave aberration tolerance corresponding to the optical curved surface of the optical element to be analyzed includes:

   Determine at least one sampling field of view corresponding to the optical system;

   For any of the sampling fields of view, according to the wave aberration design peak value and the wave aberration design valley value corresponding to the sampling field of view, determine the wave aberration corresponding to the optical curved surface of the optical element to be analyzed in the sampling field of view. Aberration tolerance.
3. The method of claim 2, wherein determining the local surface shape tolerance distribution of the optical element to be analyzed based on the wave aberration tolerance corresponding to the optical curved surface of the optical element to be analyzed includes:

   For any of the sampling fields of view, the local distortion of the optical element to be analyzed under the sampling field of view is determined based on the wave aberration tolerance corresponding to the optical curved surface of the optical element to be analyzed under the sampling field of view. Domain surface shape tolerance distribution;

   The intersection of the local surface shape tolerance distribution of the optical element to be analyzed under the at least one sampling field of view is obtained to obtain the local surface shape tolerance distribution of the optical element to be analyzed.
4. The method according to claim 3, characterized in that, based on the wave aberration tolerance corresponding to the optical curved surface of the optical element to be analyzed in the sampling field of view, it is determined that the optical element to be analyzed is in the The local surface shape tolerance distribution under the sampling field of view includes:

   According to the corresponding wave aberration tolerance of the optical curved surface of the optical element to be analyzed under the sampling field of view, the upper limit of wave aberration and wave image of the optical curved surface of the optical element to be analyzed under the sampling field of view are determined. difference lower limit;

   Determine multiple sampling points on the optical surface of the optical element to be analyzed;

   According to the upper limit and lower limit of wave aberration of the optical curved surface of the optical element to be analyzed under the sampling field of view, determine each sample on the optical curved surface of the optical element to be analyzed under the sampling field of view. Surface tolerance at points;

   Determine the local surface shape tolerance distribution of the optical element to be analyzed under the sampling field of view according to the surface shape tolerance at the plurality of sampling points on the optical curved surface of the optical element to be analyzed under the sampling field of view. .
5. The method according to claim 4, characterized in that, based on the upper limit of the wave aberration and the lower limit of the wave aberration of the optical curved surface of the optical element to be analyzed in the sampling field of view, determining the lower limit of the wave aberration in the sampling field of view. The surface tolerance at each sampling point on the optical surface of the optical element to be analyzed includes:

   For any one of the plurality of sampling points, the optical element to be analyzed under the sampling field of view is determined according to the upper limit of the wave aberration of the optical curved surface of the optical element to be analyzed under the sampling field of view. The surface shape deviation at the sampling point on the optical surface;

   According to the lower limit of the wave aberration of the optical surface of the optical element to be analyzed under the sampling field of view, the lower surface deviation at the sampling point on the optical surface of the optical element to be analyzed is determined under the sampling field of view. ;

   The difference between the upper surface deviation and the lower surface deviation at the sampling point on the optical curved surface of the optical element to be analyzed under the sampling field of view is determined as the optical element to be analyzed under the sampling field of view. The surface shape tolerance at the sampling point on the optical surface.
6. The method according to claim 2, characterized in that the optical system includes a plurality of optical elements to be analyzed;

   For any of the sampling fields of view, according to the wave aberration design peak value and the wave aberration design valley value corresponding to the sampling field of view, it is determined that the optical curved surface of the optical element to be analyzed corresponds to the sampling field of view. Wave aberration tolerance, including:

   According to the wave aberration design peak value and wave aberration design valley value corresponding to the sampling field of view, as well as the first allocation condition and the second allocation condition, the sampling field of view is allocated to the optical curved surface of each optical element to be analyzed. The corresponding wave aberration tolerance is below, wherein the first allocation condition is that the wave aberration variation caused by the surface shape error of the optical surfaces of the plurality of optical elements to be analyzed satisfies a linear superposition relationship, and the second allocation condition The condition is that the sum of the wave aberrations corresponding to the optical surfaces of the plurality of optical elements to be analyzed is greater than or equal to the wave aberration tolerance valley value corresponding to the sampling field of view and is less than or equal to the wave aberration tolerance corresponding to the sampling field of view. Limit the peak value.
7. The method according to any one of claims 1 to 6, characterized in that the method further includes:

   The optical element to be analyzed is manufactured according to the local surface shape tolerance distribution of the optical element to be analyzed, wherein the manufacturing error of the optical element to be analyzed satisfies the local surface shape tolerance distribution of the optical element to be analyzed.
8. The method of claim 7, further comprising:

   In the case where the manufacturing error of the optical element to be analyzed results in a radius deviation in the radius of the optical curved surface, compensation is made by moving the position of the optical element to be analyzed according to the radius deviation of the radius of the optical curved surface of the optical element to be analyzed;

   For the compensated optical element to be analyzed, the local surface shape tolerance distribution of the optical element to be analyzed is redetermined according to the wave aberration tolerance corresponding to the optical curved surface of the optical element to be analyzed.
9. An optical system component quality evaluation method, which is characterized by including:

   For the optical element to be evaluated in the optical system, determine the quality evaluation function of the optical surface of the optical element to be evaluated;

   According to the quality evaluation function, a quality evaluation function value corresponding to the optical element to be evaluated is determined, wherein the quality evaluation function value is used to evaluate the quality of the optical element to be evaluated.
10. The method of claim 9, wherein determining the quality evaluation function value corresponding to the optical element to be evaluated according to the quality evaluation function includes:

    Determine at least one sampling field of view corresponding to the optical system;

    According to the manufacturing errors at different points on the optical surface of the optical element to be evaluated, the initial wave aberrations at different points on the optical surface of the optical element to be evaluated in each of the sampling fields, the optical element to be evaluated The irradiance of different points on the optical surface under each of the sampling fields of view is determined to determine the root mean square of the wave aberration corresponding to the optical element to be evaluated in each of the sampling fields of view;

    The quality evaluation function is used to determine the quality evaluation function value corresponding to the optical element to be evaluated based on the root mean square of wave aberration corresponding to the optical element to be evaluated in the at least one sampling field of view.
11. The method according to claim 10, characterized in that the quality evaluation function is used to determine the root mean square of wave aberration corresponding to the optical element to be evaluated in the at least one sampling field of view. The quality evaluation function values corresponding to the optical components to be evaluated include:

    Using the quality evaluation function, the optical element to be evaluated is determined according to the root mean square of wave aberration corresponding to the optical element to be evaluated in the at least one sampling field of view, and the weight corresponding to each of the sampling fields of view. The quality evaluation function value corresponding to the component.
12. An optical system component tolerance analysis device, characterized by including:

    A wave aberration tolerance allocation module, used for determining the wave aberration tolerance corresponding to the optical surface of the optical element to be analyzed for the optical element to be analyzed in the optical system;

    The local surface shape tolerance determination module determines the local surface shape tolerance distribution of the optical element to be analyzed according to the wave aberration tolerance corresponding to the optical curved surface of the optical element to be analyzed, wherein the local surface shape tolerance distribution of the optical element to be analyzed is The local surface tolerance distribution includes surface tolerances at different points on the optical curved surface of the optical element to be analyzed.
13. An optical system component quality evaluation device, characterized by including:

    A function determination module, configured to determine the quality evaluation function of the optical surface of the optical element to be evaluated for the optical element to be evaluated in the optical system;

    A quality evaluation module, configured to determine a quality evaluation function value corresponding to the optical element to be evaluated according to the quality evaluation function, where the quality evaluation function value is used to perform quality evaluation of the optical element to be evaluated.