Optical system parameter determination method

Abstract

The application discloses an optical system parameter determination method; the method first acquires performance index parameters and constraint conditions of a to-be-output optical system, generates a plurality of plane reflection systems according to the performance index parameters and the constraint conditions, then generates a plurality of spherical reflection systems according to object-image relationships and the plurality of plane reflection systems, finally performs fitting processing on reflection spherical surfaces in each of the spherical reflection systems and searches system surface position parameters according to surface type sequence combination parameters of the to-be-output optical system, and determines optical system parameters of the to-be-output optical system; since the method can automatically output a series of optical system parameters of off-axis reflection systems with different surface type combinations after a user inputs performance index parameters and constraint conditions, full-automatic design of the optical system is realized, and dependence on manual work is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical system design, in particular to an optical system parameter determination method. BACKGROUND

[0002] From the glasses that have existed for hundreds of years to the AR headsets that are gradually emerging at present, from the microscopes for observing the microscopic world to the astronomical telescopes for looking into the space, from the cameras for recording the static images of objects to the spectrometers for analyzing the spectral components, various optical instruments have wide applications in various fields of human life such as industry, agriculture, medicine and scientific research, and these optical instruments cannot be designed without the optical system design.

[0003] At present, the optical system design needs to be tried and tested for a long time by the designer to obtain a small number of solutions, and how to reasonably determine the number of various curved surface types (spherical surface, aspherical surface, free curved surface) required by the optical system and the order thereof in the system is highly dependent on the experience of the designer.

[0004] SUMMARY

[0005] The embodiments of the present application provide an optical system parameter determination method to alleviate the technical problem that the current optical system design technology is too dependent on manual participation and design experience.

[0006] To solve the above technical problem, the embodiments of the present application provide the following technical solutions:

[0007] In one embodiment, the present application provides an optical system parameter determination method, which comprises:

[0008] obtaining a performance index parameter and a constraint condition of a to-be-output optical system;

[0009] generating a plurality of plane reflection systems according to the performance index parameter and the constraint condition; the geometric control parameters of different plane reflection systems are different, and the geometric control parameters comprise a first position parameter of each reflection plane in the plane reflection system and a second position parameter of an image plane;

[0010] generating a plurality of spherical surface reflection systems according to the object-image relationship and the plurality of plane reflection systems; the spherical surface parameters of different spherical surface reflection systems are different, and the spherical surface parameters comprise a refractive power distribution parameter and a spherical surface position parameter of each reflection spherical surface in the spherical surface reflection system;

[0011] performing fitting processing on the reflection spherical surfaces in each spherical surface reflection system and searching the system surface position parameters according to the curved surface type order combination parameter of the to-be-output optical system, to determine the optical system parameters of the to-be-output optical system; the optical system parameters comprise a wavefront error parameter of the to-be-output optical system and the curved surface type, the refractive power distribution parameter, the position parameter and the size parameter of each reflection curved surface.

[0012] In an embodiment, the performance index parameters in the above embodiments include a field of view, an entrance pupil diameter, and a focal length; and the step of generating a plurality of planar reflective systems according to the performance index parameters and the constraints comprises:

[0013] determining a range of values for each of the geometric control parameters according to a requirement for compactness;

[0014] determining a relative relationship of first position parameters of each reflective plane in the planar reflective system according to the unobstructed configuration requirement and the field of view;

[0015] determining a plurality of first position parameters of each reflective plane according to the range of values and the relative relationship;

[0016] determining a plurality of second position parameters of the image plane based on the unobstructed configuration requirement and the plurality of first position parameters of each reflective plane.

[0017] In an embodiment, the step of determining a plurality of first position parameters of each reflective plane according to the range of values and the relative relationship in the above embodiments comprises:

[0018] determining a plurality of random numbers as a plurality of first position parameters of a reference reflective plane in the planar reflective system according to the range of values for each of the geometric control parameters;

[0019] determining a plurality of first position parameters of a non-reference reflective plane in the planar reflective system according to the range of values for each of the geometric control parameters and the plurality of first position parameters of the reference reflective plane.

[0020] In an embodiment, the step of generating a plurality of spherical reflective systems according to the object-image relationship and the plurality of planar reflective systems in the above embodiments comprises:

[0021] generating a plurality of candidate spherical reflective systems corresponding to each of the planar reflective systems and different in a plurality of optical power distribution parameters based on the object-image relationship;

[0022] screening the plurality of candidate spherical reflective systems according to a preset spherical reflective system screening manner to obtain the plurality of spherical reflective systems.

[0023] In an embodiment, the step of screening the plurality of candidate spherical reflective systems according to the preset spherical reflective system screening manner in the above embodiments comprises:

[0024] evolve each of the candidate spherical reflective systems into a corresponding candidate free-form reflective system, wherein all reflective surfaces in the free-form reflective system are free-form surfaces;

[0025] obtain imaging quality parameters of each of the candidate free-form reflective systems;

[0026] from the candidate spherical reflective systems, eliminate a candidate spherical reflective system corresponding to a candidate target free-form reflective system whose imaging quality parameter does not satisfy a preset condition.

[0027] In an embodiment, the method in the above embodiments further comprises, before the step of fitting each reflective surface in each of the spherical reflective systems according to the surface type sequential combination parameter of the optical system to be output:

[0028] obtain a surface type sequential combination parameter ranking;

[0029] determine the surface type sequential combination parameter of the to-be-generated curved reflective system according to the surface type sequential combination parameter ranking.

[0030] In an embodiment, the step of obtaining the surface type sequential combination parameter ranking in the above embodiments comprises:

[0031] obtain a number of reflective surfaces of the optical system to be output;

[0032] generate a plurality of surface type sequential combination parameters according to the number of reflective surfaces and the surface type;

[0033] generate the surface type sequential combination parameter ranking according to an aberration correction ability of each surface type in each surface type sequential combination parameter.

[0034] In an embodiment, the step of generating the surface type sequential combination parameter ranking according to the aberration correction ability of each surface type in each surface type sequential combination parameter in the above embodiments comprises:

[0035] sort the surface type sequential combination parameters according to the aberration correction ability of each surface type in each surface type sequential combination parameter to obtain a surface type sequential combination parameter initial ranking;

[0036] obtain a surface type sequential combination parameter elimination manner;

[0037] in a design process, eliminate the surface type sequential combination parameter ranking according to the surface type sequential combination parameter elimination manner to obtain a new surface type sequential combination parameter ranking.

[0038] In an embodiment, the step of fitting the reflective surfaces in the curved surface reflection system and searching the surface position parameters of the system according to the sequential combination parameters of the types of the curved surfaces in the curved surface reflection system to determine the optical system parameters of the optical system to be outputted in the above-mentioned embodiments comprises:

[0039] According to the equal optical path correction mode, the data point positions of each reflective surface in the curved surface reflection system are corrected;

[0040] According to the sequential combination parameters of the types of the curved surfaces in the curved surface reflection system, the types of the curved surfaces of each reflective surface in the curved surface reflection system are determined;

[0041] According to the fitting mode of the curved surface corresponding to the type of each reflective surface, the corrected data point positions of each reflective surface are fitted to obtain the shape of each reflective surface;

[0042] The surface position parameters are searched to further improve the imaging quality.

[0043] Meanwhile, in an embodiment, the present application also provides an optical system parameter determination device, which comprises:

[0044] An acquisition module is configured to acquire the performance index parameters and constraint conditions of an optical system to be outputted;

[0045] A plane reflection system determination module is configured to generate a plurality of plane reflection systems according to the performance index parameters and the constraint conditions; the geometric control parameters of different plane reflection systems are different, and the geometric control parameters comprise the first position parameters of each reflective plane in the plane reflection system and the second position parameters of the image plane;

[0046] A spherical surface reflection system determination module is configured to generate a plurality of spherical surface reflection systems according to the object-image relationship and the plurality of plane reflection systems; the spherical surface parameters of different spherical surface reflection systems are different, and the spherical surface parameters comprise the focal power distribution parameters and the spherical surface position parameters of each reflective surface in the spherical surface reflection system;

[0047] A curved surface reflection system determination module is configured to fit the reflective surfaces in each spherical surface reflection system and search the surface position parameters of the system according to the sequential combination parameters of the types of the curved surfaces in the curved surface reflection system to determine the optical system parameters of the optical system to be outputted; the optical system parameters comprise the wavefront error parameters of the optical system to be outputted and the types, focal power distribution parameters, position parameters and size parameters of each reflective surface.

[0048] The embodiment of the present application provides a new optical system parameter determination method; the method first acquires performance index parameters and constraint conditions of a to-be-output optical system, generates a plurality of plane reflection systems according to the performance index parameters and the constraint conditions, then generates a plurality of spherical reflection systems according to an object-image relationship and the plurality of plane reflection systems, finally performs fitting processing on reflection spherical surfaces in the spherical reflection systems and searches the system surface position parameters according to the curve type sequence combination parameters of the to-be-output optical system, and determines the optical system parameters of the to-be-output optical system; since the method can automatically output a series of optical system parameters of off-axis reflection systems with different curve type combinations after the user inputs the performance index parameters and the constraint conditions, the full-automatic design of the optical system is realized, the dependence on artificial is reduced, the design efficiency of the optical system is improved, and the number and sequence of different types of curves required by the optical system can be reasonably determined, and the long-term problem that plagues designers is solved. BRIEF DESCRIPTION OF DRAWINGS

[0049] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0050] Figure 1 Fig. 1 is a first flowchart of the optical system parameter determination method provided by the embodiment of the present application.

[0051] Figure 2 Fig. 2 is a second flowchart of the optical system parameter determination method provided by the embodiment of the present application.

[0052] Figure 3 Fig. 3 is a structural diagram of the optical system parameter determination device provided by the embodiment of the present application.

[0053] Figure 4 Fig. 4 is a design diagram of the plane reflection system related to the embodiment of the present application. Figure 5

[0054] Fig. 5 is a data point correction diagram related to the embodiment of the present application. Figure 6

[0055] Fig. 6 is a diagram of the to-be-output optical system related to the embodiment of the present application. Figure 7

[0056] Fig. 7 is a diagram of the optical system parameters related to the embodiment of the present application. Figure 8 DETAILED DESCRIPTION

[0057] ​With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the scope of the present application.

[0058] Figure 1 is a first flowchart of the optical system parameter determination method provided by the embodiments of the present application. Please refer to Figure 1 The optical system parameter determination method comprises the following steps.

[0059] 201: Obtain performance index parameters and constraint conditions of an optical system to be output.

[0060] In an embodiment, the server 12 first obtains performance index parameters and constraint condition parameters such as constraint conditions from the terminal 11.

[0061] In an embodiment, the performance index parameters can be parameters such as the number of reflecting surfaces, the field of view angle, the F number, the entrance pupil diameter, and the wavelength of the optical system to be output, and the constraint condition parameters can include parameters such as the compactness degree parameters of the spacing / volume between adjacent reflecting surfaces and the search density.

[0062] 202: Generate a plurality of plane reflecting systems according to the performance index parameters and the constraint conditions.

[0063] In an embodiment, the plane reflecting system refers to an optical system in which all the reflecting surfaces are planes.

[0064] In an embodiment, the geometric control parameters of different plane reflecting systems are different, and the geometric control parameters include first position parameters of each reflecting plane in the plane reflecting system and second position parameters of an image plane.

[0065] In an embodiment, the performance index parameters include the field of view angle; this step 202 comprises: determining the value range of each parameter in the geometric control parameters according to the requirement for the compactness degree; determining the relative relationship of the first position parameters of each reflecting plane in the plane reflecting system according to the unobstructed configuration requirement and the field of view angle; determining a plurality of first position parameters of each reflecting plane according to the value range and the relative relationship; and determining a plurality of second position parameters of the image plane based on the unobstructed configuration requirement and the plurality of first position parameters of each reflecting plane.

[0066] In an embodiment, the step of determining the first position parameters of each reflection plane according to the value range and the relative relationship in the previous embodiment comprises: determining a plurality of random numbers as the first position parameters of a reference reflection plane in the plane reflection system according to the value range of each parameter in the geometric control parameter; and determining the first position parameters of a non-reference reflection plane in the plane reflection system according to the value range of each parameter in the geometric control parameter and the first position parameters of the reference reflection plane.

[0067] The plane reflection system involved in this step will be described in detail below.

[0068] 203: generating a plurality of spherical reflection systems according to the object-image relationship and the plurality of plane reflection systems.

[0069] In an embodiment, the spherical reflection system refers to an optical system in which all reflection surfaces are spherical.

[0070] In an embodiment, the spherical parameters of different spherical reflection systems are different, and the spherical parameters include the power distribution parameters and the position parameters of each reflection surface in the spherical reflection system.

[0071] In an embodiment, the step 203 comprises: generating a plurality of spherical reflection systems corresponding to each plane reflection system, in which the power distribution parameters of the spherical reflection systems are different and all reflection surfaces are spherical, based on the object-image relationship, and determining a plurality of candidate spherical reflection systems; and screening the plurality of candidate spherical reflection systems according to a preset spherical reflection system screening manner to obtain the plurality of spherical reflection systems.

[0072] In an embodiment, the step of screening the plurality of candidate spherical reflection systems according to the preset spherical reflection system screening manner in the previous embodiment comprises: evolving each candidate spherical reflection system into a corresponding candidate free-form surface reflection system; the surface type of all reflection surfaces in the free-form surface reflection system is free-form surface; obtaining an imaging quality parameter of each candidate free-form surface reflection system; and eliminating, from the candidate spherical reflection systems, a candidate spherical reflection system corresponding to a candidate target free-form surface reflection system whose imaging quality parameter does not satisfy a preset condition.

[0073] The spherical reflection system involved in this step will be described in detail below.

[0074] 204: fitting and searching the reflection surfaces in each spherical reflection system and the system surface position parameters according to the surface type order combination parameters of the to-be-output optical system to determine the optical system parameters of the to-be-output optical system.

[0075] In an embodiment, the optical system parameters include wavefront error parameters of the optical system to be output and surface type, power distribution parameters, position parameters and size parameters of each reflective surface.

[0076] In an embodiment, the surface type sequential combination parameters are combination parameters obtained by arranging surface types of all reflective surfaces in the optical system in sequence of reflective surfaces. These parameters will be described below.

[0077] In an embodiment, in order to improve data accuracy, the step 204 includes: correcting data point positions of each reflective surface in the curved reflective system according to an equal optical path correction method; determining surface types of each reflective surface in the curved reflective system according to the surface type sequential combination parameters of the curved reflective system; and fitting the corrected data point positions of each reflective surface according to a surface fitting method corresponding to the surface type of each reflective surface, to obtain the shape of each reflective surface.

[0078] In an embodiment, in order to improve design efficiency, the present application can prioritize the design of optical systems with good aberration correction capability, and provides surface type sequential combination parameter sorting. Specifically, Figure 1 The method shown further includes, before the step 204: obtaining surface type sequential combination parameter sorting; and determining surface type sequential combination parameters of the curved reflective system to be generated according to the surface type sequential combination parameter sorting.

[0079] In an embodiment, the step of obtaining the surface type sequential combination parameter sorting in the previous embodiment includes: obtaining the number of reflective surfaces of the optical system to be output; generating a plurality of surface type sequential combination parameters according to the number of reflective surfaces and surface types; and generating the surface type sequential combination parameter sorting according to aberration correction capability of each surface type in each surface type sequential combination parameter.

[0080] In an embodiment, the step of generating the surface type sequential combination parameter sorting according to aberration correction capability of each surface type in each surface type sequential combination parameter in the previous embodiment includes: sorting the surface type sequential combination parameters according to aberration correction capability of each surface type in each surface type sequential combination parameter to obtain surface type sequential combination parameter initial sorting; obtaining a surface type sequential combination parameter elimination method; and eliminating the surface type sequential combination parameter initial sorting according to the surface type sequential combination parameter elimination method during the design process to obtain the surface type sequential combination parameter sorting.

[0081] The fitting method of the optical system to be output involved in this step will be described below.

[0082] The embodiment provides a new optical system parameter determination method; the method first acquires performance index parameters and constraint conditions of a to-be-output optical system, generates a plurality of plane reflection systems according to the performance index parameters and the constraint conditions, then generates a plurality of spherical reflection systems according to object-image relationships and the plurality of plane reflection systems, finally performs fitting processing on reflection spherical surfaces in each spherical reflection system and searches for system surface position parameters according to surface type sequence combination parameters of the to-be-output optical system, and determines optical system parameters of the to-be-output optical system; since the method can automatically output a series of optical system parameters of off-axis reflection systems with different surface type combinations after a user inputs performance index parameters and constraint conditions, realizes full-automatic design of the optical system, reduces dependence on manpower, improves the design efficiency of the optical system, and can reasonably determine the number and sequence of different types of surfaces required by the optical system, and solves a long-term problem that has puzzled designers.

[0083] The present application is further described in the light of the research background and Figure 2 The present application is further described in the light of the research background and

[0084] In recent decades, researchers have carried out a series of researches on the design method of optical systems based on computer-aided design. These researches not only promote the development of traditional optical design methods, but also promote the rapid development of related technologies in the fields of optical manufacturing, optical detection and the like. However, the traditional optical design method is essentially a computer-aided design which seriously depends on the participation and experience of designers, and there are still some public problems hindering its further development. The inventors believe that the real full-automatic optical system design service should have the following effects:

[0085] Effect 1: The design process almost does not need human participation, and has the ability to directly design a system with imaging quality close to the diffraction limit. At present, almost every step of the traditional optical design needs the participation of the designer, which is a trial-and-error process with high requirements for design experience. The designer generally needs to select an initial structure according to his own experience, determine the next optimization strategy according to the current state of the optical system and design experience, and obtain the optimized design result through progressive optimization. However, the selected initial structure and optimization strategy may not be optimal, or even may be wrong, so the designer may need to repeat the previous process several times to obtain a design result that meets the requirements.

[0086] Effect 2, can automatically output diversified design results. Traditional optical design lacks diversity. Due to the existence of tedious manual design process in traditional optical design method, designers can only get a small number of design results (often only one solution) each time. For a specific design index, there should be a series of solutions that meet the requirements. If a series of solutions that meet the requirements can be obtained through a single design, multiple factors can be considered to choose the most suitable design result.

[0087] Effect 3, suitable for the design of optical systems of multiple curved surface types (spherical surface, aspherical surface, free-form surface). With the advancement of processing technology, optical system surfaces have more choices. Currently, spherical and aspherical surfaces have been widely used in optical systems. In recent years, with the emergence and development of super-precision machining technology, free-form surfaces have been successfully applied to telescopes, helmet display systems, spectrometers, and lithography systems. A general automatic optical system design method should cover the design of systems of different curved surface types.

[0088] Effect 4, has the ability to reasonably select the types of each reflecting surface of the system after giving the performance index. In the process of optical design, how to reasonably select the types of each reflecting surface of the system has always been a difficult problem. Generally, low-degree-of-freedom curved surfaces are preferred as much as possible under the premise of meeting the design requirements. In the application, the combination of the types of each reflecting surface in the optical system in a given order is used to describe the types of all reflecting surfaces in the optical system, which is abbreviated as RSTC. For the selection of RSTC, current technology cannot accurately predict the number of each type of curved surface required for complex systems according to existing theories or methods. Designers can determine the RSTC of the system according to existing patents and literature, but may not be able to find a suitable initial structure. Designers can also give a series of possible RSTCs of the system through permutation and combination, select one according to experience, and obtain the design result of the corresponding RSTC through optimization of the initial structure. If the design result meets the design index, the designer will generally design another RSTC system with fewer aspherical surfaces. If the design result does not meet the design requirements, the designer needs to replace the RSTC or even the initial structure according to experience and re-optical design through tedious manual optimization. Therefore, currently designing a reasonable optical system with RSTC is a very complex and tedious process.

[0089] In the research of optical design, there are a lot of researches on the initial structure solving and a lot of researches on the optimization method, but these design methods cannot realize the full-automatic design of the optical system. Although the automatic design method of the free-form surface optical system which integrates the initial structure solving and the optimization is appeared, these methods are only suitable for the system in which each reflecting surface is a free-form surface. Therefore, these methods cannot meet the above four requirements at the same time.

[0090] In order to obtain the design method which meets the above four requirements at the same time, the present application provides a full-automatic design method of the off-axis reflecting system with universality, which can automatically obtain a series of design results of RSTC. The method only needs to input the design index and the constraint condition of the optical system, and does not need the designer to participate in the determination of the RSTC and the rest of the system, so that a series of selectable design results can be automatically established, and the imaging quality of these design results is excellent, and there are differences in the RSTC and the size of the system. In the method: in order to obtain diversified design results with high imaging quality, the plane system establishment method based on the geometric shape control parameter is proposed; in order to screen the spherical surface system with reasonable power distribution and reflecting surface position from a large number of established spherical surface systems, the screening principle of the spherical surface system is proposed; in order to improve the solving accuracy of the data point position, the data point position calculation method based on the equal optical path principle is proposed; in order to directly obtain the system with imaging quality close to the diffraction limit through the point-by-point calculation method, the high-precision aspheric surface and free-form surface fitting method is proposed; in order to improve the design efficiency, the elimination principle of the RSTC type is proposed.

[0091] And finally, the full-automatic design of the off-axis three-reflecting system is taken as an example to show the effectiveness of the method. With the help of the full-automatic design method, 90 design results with imaging quality close to the diffraction limit are obtained, and these systems have 17 kinds of RSTC; the designer can select the design result which meets the requirements most according to the design requirements.

[0092] Figure 2 is the second flowchart of the optical system parameter determination method provided by the embodiment of the present application, please refer to Figure 2 The optical system parameter determination method comprises the following steps:

[0093] 301: a series of plane systems with different surface positions are established.

[0094] This step is to establish a series of plane systems with different surface positions according to the plane system establishment method based on the geometric shape control parameter proposed by the present application.

[0095] In this application, the positions of the surfaces of the planar system significantly impact the imaging quality of the final design results. To achieve solution diversity, it is necessary to automatically establish a large number of planar systems with different positional parameters. This application introduces a method for establishing planar systems based on geometric control parameters.

[0096] Let Ω be the s-th reflecting surface of the plane reflection system. s This is the aperture stop, and it serves as the reference plane. For example... Figure 4 As shown in (a), the aperture Ω s Let A be the upper endpoint and B be the lower endpoint. ω1 and ω2 are the edge fields of view within the meridional plane, and the angle between them is equal to the field of view angle within the meridional plane. The incident angle of the ray from field of view ω1 at the aperture stop is smaller, θ. s Ω, the reflecting surface s The lower ray of the incident light and the upper ray of the outgoing light intersect at point C, given θ. s Once the value is set, the directions of incident and outgoing light in all fields of view at the aperture stop are determined.

[0097] The reflective plane Ω is determined based on the unobstructed requirement. s-1 The position and the direction of the incident light. For example... Figure 4 As shown in (b), to avoid light occlusion, the reflecting plane Ω s-1 The lower endpoint D should be located above the light emitted from the aperture. Reflecting surface Ω s-1 In the incident light, the intersection point E of the lower ray of field of view ω1 and the extension of line segment AB is given. To avoid ray occlusion, point E should be above point A. After selecting the lengths of line segments CD and AE, the reflecting surface Ω... s-1 The position and direction of the incident light are thus determined. In this application, the length l1 of line segment CD is defined. (s-1) and the length l2 of AE (s-1) Called the reflecting surface Ω s-1 Position control parameters.

[0098] like Figure 4 (c) refers to the reflecting plane Ω. s+1 Using the same method, select the length l1 of line segment CF. (s+1) And BG's length l2 (s+1) Afterwards, the reflecting plane Ω s+1 The location was then determined.

[0099] The position of each reflecting plane can be determined by such unobstructed parameters. Once the positions of all reflecting planes in front of the aperture are determined, the direction of incident light on the first reflecting plane of the system for each field of view is also determined.

[0100] After determining the positions of all reflecting planes in the optical system, the position of the image plane needs to be determined based on the requirement of no obstruction. For example... Figure 5The reflection surface adjacent to the image plane is Ω s , whose upper end is K, and the reflection surface Ω s-1 , whose upper end is H and lower end is J. A point L is selected on the extension of the line segment HJ, and the line segment KL is parallel to the reflection surface Ω S-1 , and the lower light ray of the outgoing light intersects at point M. In order to avoid occlusion of light rays, the point L should be below the point J, and the point N should be on the extension of the line segment KM. The length of the line segment JL is selected as l1 (S+1) , and the length of the line segment MN is selected as l2 (S+1) . After the position of the point N is determined, the angle between the image plane and the vertical direction is selected as α S+1 . After the position of the image plane is determined, the values of l1 (S+1) , l2 (S+1) , and α S+1 are called the position parameters of the image plane. By controlling the inclination angle of the image plane, the incident angle of the chief ray on the image plane can be controlled.

[0101] The parameters used to determine the positions of all the reflection surfaces and the image plane are called the geometric control parameters of the plane system. The value range of the geometric control parameters of the plane system is determined according to the requirement of the compactness of the system, a series of random numbers are taken in the value range of each geometric control parameter, and a series of plane reflection systems are automatically established by using the above method.

[0102] 302: Construct a spherical reflection system.

[0103] This step is used to establish a large number of spherical systems with different power distribution or surface positions, and to perform rough screening on the power distribution and surface positions according to the proposed spherical system screening principle, and to select potential spherical systems. These systems will be the starting point for the next process.

[0104] For how to obtain a spherical system with reasonable surface positions and power distribution, including how to establish a series of spherical systems that differ in power distribution or surface positions, and then how to obtain a spherical system with reasonable surface positions and power distribution by using the proposed spherical system screening principle.

[0105] The process of establishing a series of spherical systems with different power distributions from a plane reflection system is as follows:

[0106] (1) A certain number of characteristic light rays are selected, and the positions of the ideal image points corresponding to each characteristic light ray are calculated according to the object-image relationship.

[0107] (2) The s-th reflection plane Ω s is constructed as a spherical surface. Specifically, a characteristic light ray is selected, and the light ray and the reflection plane Ω sthe intersection of the chief ray and the plane Ω as the first data point, then according to the Fermat principle and the object-image relationship, the reflection plane Ω s the ideal normal vector at the data point. Next, according to the principle of the nearest ray, the object-image relationship, and the Fermat principle, the reflection plane Ω s is determined in turn, and then the positions of the remaining data points are fitted to a spherical surface.

[0108] (3) The remaining reflection planes are sequentially constructed into reflection spherical surfaces using the same method.

[0109] (4) Through an iterative process, a series of reflection spherical surface systems with different power distributions are obtained.

[0110] Starting from the series of reflection plane systems established in step 301, a series of reflection spherical surface systems with different power distributions or surface positions can be established using the above method. Starting from the spherical surface system, through an evolutionary process, a selected RSTC system can be obtained. The positions of the reflection surfaces and the power distribution of the spherical surface system will have an important impact on the imaging quality of the system obtained through subsequent evolution. In order to obtain a potential starting point for the evolutionary process, the present application proposes a spherical surface system screening principle for judging whether the power distribution and surface position of the spherical surface system are reasonable: evolve a large number of established spherical surface systems into systems with each reflection surface being a free-form surface, and then select the spherical surface systems corresponding to the free-form surface systems with better imaging quality. These spherical surface systems are referred to as potential spherical surface systems, and the remaining spherical surface systems are discarded.

[0111] 303: Determine the selection range of RSTC.

[0112] In the present application, these RSTCs are sorted according to the proposed principle to obtain an RSTC arrangement: [RSTC1, RSTC2, RSTC3,...]. The fully automatic design method will sequentially design the system corresponding to each possible RSTC of the system according to the order determined by the arrangement.

[0113] In order to improve design efficiency, the present application needs to reasonably select the design order of systems with different RSTCs and eliminate unreasonable RSTC categories. Next, the RSTC arrangement method and elimination method proposed in the present application are described.

[0114] First, determine the types of RSTC that can be selected. There are three possible types of a reflection surface: spherical surface, aspherical surface, and free-form surface. Therefore, a system with S reflection surfaces has 3 S RSTCs. If the designer does not provide any experience guidance, the RSTCs that can be selected should include these 3 SRSTC. If the number of each type of reflecting surface needed by the system can be roughly estimated, the range of RSTC selection can be further reduced.

[0115] Then, the RSTCs are sorted according to the strength of their aberration correction ability. Since the RSTC with stronger aberration correction ability has a higher probability of successful system design, the full-automatic design method proposed in this application prioritizes the design of such systems.

[0116] The strength of the aberration correction ability of an RSTC is determined by the following method. If the aberration correction ability of each type of reflecting surface of the t1th RSTC is not weaker than that of the corresponding reflecting surface of the t2th RSTC, the aberration correction ability of the t1th RSTC is recorded as stronger than that of the t2th RSTC. According to the aberration correction ability, the RSTCs can be arranged in the order [RSTC1, RSTC2, RSTC3, …]. The full-automatic design framework designs the systems corresponding to each RSTC in the order determined by the RSTC arrangement.

[0117] Next, the RSTC elimination principle proposed in this application is introduced. In order to improve the design efficiency, some unreasonable RSTCs will be eliminated from the RSTC arrangement; if the design results of a certain RSTC obtained by the full-automatic design method do not meet the requirements, the RSTC with weaker aberration correction ability will be eliminated from the RSTC arrangement.

[0118] 304: Design of the optical reflecting system of the tth RSTC.

[0119] In this step, the system of the tth RSTC is designed according to the given design order. Through the search starting point elimination method proposed in this application, a series of good starting points of the tth RSTC are obtained. By searching the position parameters, the design results of the tth RSTC with good imaging quality are obtained.

[0120] Now, how to obtain a series of design results of the same RSTC with good imaging quality is described. Starting from the potential spherical reflecting system obtained in step 302, the potential search starting points are obtained through evolution and the elimination principle of search starting points proposed in this application. Then, using the data point position calculation method based on the equal path length principle proposed in this application and the data point fitting method based on the best quadric surface, the imaging quality of the system is improved by the method of single degree of freedom search of the surface position parameters.

[0121] Compared with free-form surface system, the design freedom of optical system containing spherical surface and aspherical surface is less, and the solution is less. If the single freedom search method of imposing perturbation on the position parameters of optical system is used to obtain the system containing spherical surface and aspherical surface with imaging quality close to the diffraction limit, a system with relatively good imaging quality is needed as the search starting point; the following two-step cooperation is used to obtain a good search starting point: first, the rough screening of optical power and surface position is completed by the spherical surface system screening principle of step 302, and a series of potential spherical surface systems are obtained; second, the more detailed screening of optical power and surface position is completed by the search starting point elimination principle proposed in this section, and a better search starting point is obtained.

[0122] Next, how to obtain the search starting point is described. A series of potential spherical surface systems obtained by step 302 are used as the starting point, and a series of systems of selected RSTC are established by the point-by-point construction and iteration method and the fitting method proposed in this application. A certain number of systems with good imaging quality are selected from these RSTC systems, and these systems will be used as the starting point of the search process.

[0123] Now the data point calculation method based on the equal optical path principle proposed in this application is introduced. First, select the characteristic field of view, and define the characteristic light rays of each characteristic field of view, such as Figure 6 As described above, R f (0) and R f (k) are the chief ray and the kth characteristic light ray of the fth characteristic field of view, respectively, and D f (k) is the intersection of the light ray R f (k) and the surface Ω s . For a system with aberration, the optical path from the object point to the intersection of the light ray and the image plane is not the same for different characteristic light rays of the same characteristic field of view. In order to improve the calculation accuracy of the data point position, the chief ray is used as the reference light ray, and the position of the data point on the surface Ω s is corrected according to the equal optical path principle.

[0124] The chief ray R f (0) is denoted as OL f , and it is used as the reference optical path of the fth characteristic field of view. If the optical path of the light ray R f (k) is not the same as OL f , the light ray R f (k) corresponding to the data point D f (k) needs to be changed. The data point D f(k) , k, P) is the error function of the data points, which is defined as the sum of the square of the difference between the normal vector of the data points and the normal vector of the aspheric surface. The position of the data points is modified so that the optical path of the light ray passing through the data point is equal to the reference optical path OL f . The same method is used to modify the position of all data points on the surface Ω s . Next, the calculation accuracy of the data point position is further improved by searching the reference optical path of each feature field.

[0125] Solving the system with good imaging quality requires a high-precision data point fitting method. In order to improve the imaging quality of the system, the coordinates and normal vectors of the data points need to be fitted simultaneously. Next, the fitting method of aspheric surface and free-form surface proposed in this application is introduced.

[0126] First, given the position of the local coordinate system of the aspheric surface, it is shown how to fit the data points to the aspheric surface. The expression of the aspheric surface is as formula (1), where c is the curvature radius, k is the quadratic surface constant, P a is the vector composed of the 2nd (o+1) order coefficients of the aspheric surface (o=1, 2, 3, …), z c (x, y; c, k) is the quadratic surface term, z r (x, y; P a ) is the residual term.

[0127]

[0128] The method proposed in this application finds the best aspheric surface by first calculating the quadratic surface term parameters and then calculating the high-order term coefficients. The total number of data points on the aspheric surface is NumD, the coordinates of the dth data point are (x d , y d , z d ), and the corresponding normal vector is (u d , v d , -1). The fitting error of the aspheric surface is evaluated by the error function e a (c, k, P a ), as formula (2). Where W is the weight of the normal vector fitting error.

[0129] First, fit the data points to the quadratic surface C1. Next, fit the data points to the aspheric surface with C1 as the base and the function ea as the evaluation function, and calculate the value of the function e a at this time. By searching the parameters c and k, the value of the error function e a is further reduced.

[0130]

[0131] If the position of the local coordinate system of the selected aspheric surface changes, the error function ea(c, k, Pa ) will also change. The position of the best aspheric local coordinate system needs to be determined by searching the position of the aspheric local coordinate system. In order to determine the search range of the origin of the aspheric local coordinate system, the data points are first fitted to a surface, and then the position of the origin of the aspheric local coordinate system is searched along the intersection line of the surface and the YOZ plane of the global coordinate system. In this process, the angle between the global coordinate system and the local coordinate system of the asphere also needs to be searched.

[0132] Next, the proposed free-form surface fitting method based on optimal base optimization is introduced. In the local coordinate system of the free-form surface, the free-form surface can be represented by equation (3). Where f c (x,y; c, k) is the quadratic surface term, f r (x,y; P f ) is the residual term composed of XY polynomials, and the vector P f = (A 10 ,A 01 ,....,A MN ) T In the local coordinate system of the free-form surface, the coordinates of the dth data point are (x d ,y d ,z d ), the corresponding normal vector is (u d ,v d ,-1), and the total number of data points is NumD.

[0133]

[0134] The application uses the function e f (c, k, P f ) to evaluate the fitting error of the free-form surface, as shown in equation (4). Where WP d is the weight of the fitting error of the dth data point, and W is the weight of the normal vector error. First, the data points are fitted to a quadratic surface. With the quadratic surface as the base, the data points are fitted to a free-form surface, and the value of the function ef is calculated. Next, by searching the parameters c and k, the value of the error function e f is further reduced.

[0135]

[0136] When the imaging quality of the system is low, in order to reduce the average value of the RMS wavefront error of the system, the weight WP d of each data point fitting error in the community is set to 1. When the imaging quality of the system approaches the diffraction limit, the maximum value of the wavefront error of the system is reduced by adjusting the weight WP d .

[0137] 305: According to the proposed RSTC elimination principle, it is judged whether part of the unreasonable RSTCs in the arrangement of RSTCs need to be eliminated.

[0138] And repeat steps 304 to 305 until the design of all RSTCs corresponding to the system in the RSTC arrangement is completed.

[0139] Specifically, the present application takes the off-axis three-mirror system with performance indicators as shown in Table 1 as an example to demonstrate the effectiveness of the full-automatic design method.

[0140] Parameter Specification Field of view 3°×4° F number 7 Entrance pupil diameter 20 mm Wavelength 380 ~ 750 nm

[0141] Table 1

[0142] After inputting the performance indicators and constraint conditions, the full-automatic design method automatically outputs 228 design results. There are 90 design results with the maximum value of wavefront error less than 0.085λ(λ=587nm), and their optical path diagrams are shown in Figure 7 . The name of each system is marked above the system. The type of each reflective surface is marked near the corresponding reflective surface, where "S" represents a spherical surface, "A" represents an aspherical surface, and "F" represents a free-form surface. In this paper, the combination of the types of three reflective surfaces is used to describe the RSTC of each optical system in the design examples. For example, "ASF" means that the primary mirror of the system is aspherical, the secondary mirror is spherical, and the tertiary mirror is free-form.

[0143] The main parameters of each optical system are shown in Figure 8 , in which the unit is mm, the optical system is symmetric about the YOZ plane, and the x coordinate of all mirror positions is 0. Figure 8

[0144] According to the above description, it can be known that:

[0145] ​The design method proposed in the present application is suitable for full-automatic and multi-solution design of multi-surface optical systems, and can determine the minimum number of high-degree-of-freedom surfaces and the types of RSTC that can meet the design requirements. In the traditional design method, the determination of RSTC has always been a time-consuming and blind process. The method proposed in the present application can provide the designer with a series of design results with different RSTC, so that the designer can quickly select the design result that best meets the actual needs according to the needs, and solve the long-standing problem of how to reasonably determine the RSTC of the system. In the design example, 19 RSTC design results are obtained by the method proposed in the present application. Among them, there are 17 RSTC design results with imaging quality close to the diffraction limit. In this design example, the imaging quality of the design result using two aspheric surfaces and one spherical surface is already close to the diffraction limit. In addition, the order of different types of surfaces in the system can also have a great influence on the imaging quality of the system. If the number of each type of surface used in the system has been given, the designer can use the framework proposed in this paper to select the optimal order of the surface type. In the design example, "SAA" and "ASA" have an advantage in imaging quality compared to "AAS".

[0146] After the completion of a single full-automatic design process, if more design results of a certain RSTC are desired, the designer can use the obtained series of design results of this RSTC as a starting point to search for more precise optical power distribution and surface positions. The designer can also use the proposed full-automatic framework to expand the search range of the plane system geometry control parameters and improve the search density to obtain a series of systems with this RSTC.

[0147] Unlike traditional optical design methods that usually require a long time to obtain a local optimal solution, the proposed framework can automatically output a series of design results with different RSTC by only inputting performance indicators and constraints. In the design method of the present application, 228 design results are obtained by the method proposed in the present application; among them, there are 31 design results with a wavefront aberration maximum value less than 0.06λ, 59 design results between 0.06λ and 0.081λ, 122 design results between 0.081λ and 0.15λ, and 16 design results greater than 0.15λ. The designer can select the most suitable solution from the obtained design results according to the existing manufacturing process and actual needs. Unlike traditional optical design methods that can only obtain one or a few solutions, the proposed framework can obtain a large number of solutions. With the help of the framework in this paper, the designer does not need to spend a lot of time on improving the imaging quality of the optical system, but can devote more effort to the evaluation and selection of the design results.

[0148] By changing the geometric shape control parameters and the unobstructed constraint condition of the plane system, the application can design other off-axis reflective optical systems with other optical path structures.

[0149] In summary, the embodiment provides a framework that can be used for full-automatic design of reflective optical systems containing spherical aspherical surfaces and free-form surfaces, and the full-automatic design of such systems is realized for the first time. Unlike traditional design methods that heavily rely on the participation and design experience of designers and can only obtain a small number of solutions, the application only needs to input performance indicators and constraint conditions, does not require an initial structure, does not require the participation of designers in the tedious RSTC trial-and-error process and optimization process, and automatically outputs a series of design results with different RSTCs and good imaging quality. The method can reasonably determine the number and order of different types of surfaces required by the optical system, and solves the long-standing problem that has plagued designers. By changing the geometric shape control parameters and the constraint condition, the method is also applicable to the full-automatic design of other reflective off-axis optical systems with optical path structures different from the examples. By adding constraint conditions and screening principles that are conducive to manufacturing and detection in the method, the optical system with lower manufacturing and detection difficulty can be more efficiently obtained. The method expands the group of people who can participate in optical design, so that engineers with rich experience in optical system manufacturing and detection can also participate in the optical design process, which is conducive to obtaining design results that meet actual needs.

[0150] Correspondingly, Figure 3 is a structural schematic diagram of an optical system parameter determination device provided by the embodiment of the application, please refer to Figure 3 The optical system parameter determination device includes the following modules:

[0151] The acquisition module 401 is configured to acquire performance indicator parameters and constraint conditions of an optical system to be output.

[0152] The plane reflective system determination module 402 is configured to generate a plurality of plane reflective systems according to the performance indicator parameters and the constraint conditions. The geometric control parameters of different plane reflective systems are different, and the geometric control parameters include first position parameters of reflective planes in the plane reflective systems and second position parameters of image planes.

[0153] The spherical reflective system determination module 403 is configured to generate a plurality of spherical reflective systems according to an object-image relationship and the plurality of plane reflective systems. The spherical parameters of different spherical reflective systems are different, and the spherical parameters include power distribution parameters and spherical position parameters of reflective spherical surfaces in the spherical reflective systems.

[0154] The curved surface reflection system determining module 404 is configured to perform fitting processing on the reflection curved surface in each of the spherical reflection systems and search the system surface position parameters according to the curved surface type sequence combination parameters of the optical system to be output, so as to determine the optical system parameters of the optical system to be output, wherein the optical system parameters include the wavefront error parameters of the optical system to be output and the curved surface type, the optical power distribution parameters, the position parameters and the size parameters of each reflection curved surface.

[0155] The above describes in detail the optical system parameter determination method provided by the embodiments of the present application. The principles and implementation manners of the present application are described by using specific examples. The above embodiment descriptions are only used to help understand the method of the present application and the core idea thereof. Meanwhile, for those skilled in the art, the specific implementation manners and application ranges can be changed according to the idea of the present application. In conclusion, the content of the present description should not be understood as a limitation of the present application.

Claims

1. A method for determining the parameters of an optical system, characterized in that, include: Obtain the performance parameters and constraints of the optical system to be output; Multiple planar reflection systems are generated based on the performance index parameters and the constraints. The geometric control parameters of different planar reflection systems are different. The geometric control parameters include the first position parameters of each reflection plane in the planar reflection system and the second position parameters of the image plane. The performance index parameters include the field of view, entrance pupil diameter, and focal length. Multiple spherical reflection systems are generated based on the object-image relationship and the multiple planar reflection systems; the spherical parameters of different spherical reflection systems are different, and the spherical parameters include the optical power distribution parameters and spherical position parameters of each reflecting spherical surface in the spherical reflection system; Based on the surface type sequence combination parameters of the optical system to be output, the reflecting spherical surfaces in each of the spherical reflection systems are fitted and the system surface position parameters are searched to determine the optical system parameters of the optical system to be output. The optical system parameters include the wavefront error parameters of the optical system to be output, as well as the surface type, optical power distribution parameters, position parameters, and size parameters of each reflecting surface. The surface type sequence combination parameters are the combination parameters obtained by arranging the surface types of all reflecting surfaces in the optical system according to the order of the reflecting surfaces.

2. The method for determining optical system parameters according to claim 1, characterized in that, The step of generating multiple planar reflection systems based on the performance index parameters and the constraints includes: The value range of each parameter in the geometric control parameters is determined according to the requirements for compactness; Based on the unobstructed configuration requirements and the field of view, the relative relationships of the first position parameters of each reflecting plane in the planar reflection system are determined; Based on the value range and the relative relationship, multiple first position parameters of each reflecting plane are determined; Based on the unobstructed configuration requirement and the multiple first position parameters of each reflective plane, multiple second position parameters of the image plane are determined.

3. The method for determining optical system parameters according to claim 2, characterized in that, The step of determining multiple first position parameters of each reflecting plane based on the value range and the relative relationship includes: Based on the value range of each parameter in the geometric control parameters, multiple random numbers are determined as multiple first position parameters of the reference reflection plane in the planar reflection system; Based on the value range of each parameter in the geometric control parameters and the multiple first position parameters of the reference reflection plane, the multiple first position parameters of the non-reference reflection plane in the planar reflection system are determined.

4. The method for determining optical system parameters according to claim 1, characterized in that, The step of generating multiple spherical reflection systems based on the object-image relationship and the multiple planar reflection systems includes: Based on the object-image relationship, multiple spherical reflection systems with different optical power allocation parameters and all reflective surfaces having a surface type of only sphere are generated for each of the planar reflection systems, and these are identified as multiple candidate spherical reflection systems. According to the preset spherical reflection system screening method, the multiple candidate spherical reflection systems are screened to obtain the multiple spherical reflection systems.

5. The method for determining optical system parameters according to claim 4, characterized in that, The step of screening the multiple candidate spherical reflection systems according to a preset spherical reflection system screening method includes: Each of the candidate spherical reflection systems is transformed into a corresponding candidate freeform surface reflection system; the surface type of all reflection surfaces in the freeform surface reflection system is a freeform surface; Obtain the imaging quality parameters of each candidate freeform surface reflection system; From the candidate spherical reflection systems, candidate target freeform surface reflection systems that do not meet the preset conditions in terms of imaging quality parameters are eliminated.

6. The method for determining optical system parameters according to claim 1, characterized in that, Before the step of fitting each reflecting spherical surface in each of the spherical reflection systems to the parameters according to the order of the surface types of the optical system to be output, the method further includes: Obtain the sorting order of surface type combination parameters; Based on the sorting of the surface type sequence combination parameters, the surface type sequence combination parameters of the surface reflection system to be generated are determined.

7. The method for determining optical system parameters according to claim 6, characterized in that, The step of obtaining the sorted combination parameters of surface type includes: Obtain the number of reflecting surfaces of the optical system to be output; Based on the number of reflective surfaces and the surface type, generate multiple surface type sequential combination parameters; Based on the aberration correction capability of each surface type in the sequential combination parameters of each surface type, the sorting of the sequential combination parameters of the surface types is generated.

8. The method for determining optical system parameters according to claim 7, characterized in that, The step of generating the sorting of surface type sequential combination parameters based on the aberration correction capability of each surface type in the sequential combination parameters of each surface type includes: Based on the aberration correction capability of each surface type in the sequential combination parameters of each surface type, the sequential combination parameters of the surface types are sorted to obtain the initial sorting of the sequential combination parameters of the surface types; Obtain the elimination method for the sequential combination parameters of surface types; During the design process, the sorting of the surface type sequential combination parameters is eliminated according to the elimination method of the surface type sequential combination parameters to obtain a new sorting of the surface type sequential combination parameters.

9. The method for determining optical system parameters according to any one of claims 1 to 8, characterized in that, The step of combining parameters according to the surface type order of each of the curved surface reflection systems, fitting the reflecting spherical surface in the curved surface reflection system and searching the system surface position parameters to determine the optical system parameters of the optical system to be output includes: The positions of the data points on each reflecting spherical surface in the curved surface reflection system are corrected according to the equal optical path correction method. The surface type of each reflective surface in the curved surface reflection system is determined based on the sequential combination parameters of the surface type of the curved surface reflection system. Based on the surface fitting method corresponding to the surface type of each reflective surface, the positions of the corrected data points of each reflective sphere are fitted to obtain the shape of each reflective surface; The positional parameters of the curved surface are searched to further improve the imaging quality.

10. An optical system parameter determination device, characterized in that, include: The acquisition module is used to acquire the performance parameters and constraints of the optical system to be output. A planar reflection system determination module is used to generate multiple planar reflection systems based on the performance index parameters and the constraints. Different planar reflection systems have different geometric control parameters, which include the first position parameters of each reflection plane and the second position parameters of the image plane in the planar reflection system. The performance index parameters include the field of view, entrance pupil diameter, and focal length. A spherical reflection system determination module is used to generate multiple spherical reflection systems based on the object-image relationship and multiple planar reflection systems; different spherical reflection systems have different spherical parameters, including the optical power allocation parameters and spherical position parameters of each reflecting spherical surface in the spherical reflection system; The curved surface reflection system determination module is used to perform fitting processing on the reflecting spherical surfaces in each of the spherical reflection systems and search for the system surface position parameters according to the sequential combination parameters of the curved surface type of the optical system to be output, thereby determining the optical system parameters of the optical system to be output. The optical system parameters include the wavefront error parameters of the optical system to be output, as well as the curved surface type, optical power allocation parameters, position parameters, and size parameters of each reflecting surface. The sequential combination parameters of the curved surface type are combination parameters obtained by arranging the curved surface types of all reflecting surfaces in the optical system according to the order of the reflecting surfaces.

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