Miniaturized transmission-type optical system design method based on improved ray tracing model

Abstract

The invention belongs to the technical field of optical design, and particularly relates to a miniaturized transmission-type optical system design method based on an improved ray tracing model. Comprising the following steps: S1, establishing a transmission-type optical system by utilizing optical design software, and optimizing the transmission-type optical system according to a preset constraint condition to obtain an initial structure of the transmission-type optical system; s2, constructing an axial length constraint function of an initial structure of the transmission-type optical system based on an improved ray tracing model; and S3, performing axial length optimization on the initial structure of the transmission-type optical system by using the axial length constraint function to obtain the miniaturized transmission-type optical system. According to the invention, the calculation complexity of the miniaturized transmission-type optical system is reduced, and the imaging quality of the transmission-type optical system is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical design, and in particular relates to a design method for a miniaturized transmission optical system based on an improved ray tracing model. Background Art

[0002] With the rapid development of optical imaging systems in recent years, people have put forward more stringent requirements on the structural dimensions and imaging quality of optical imaging systems. Under the premise of meeting a certain imaging quality, reducing the structural dimensions of the optical imaging system to achieve miniaturization of the optical system is of great significance for improving the portability of the optical imaging system and expanding the application field of the optical imaging system. The miniaturization design of the transmissive optical system based on the means of geometric optical ray tracing can meet the compactness requirements of the transmissive imaging system without increasing the difficulty of processing and adjustment and the development cost.

[0003] However, the current miniaturization design of transmissive optical systems based on ray tracing starts with the system length evaluation function built into the optical design software, and solves the transmissive optical system face by face based on the optical path calculation formula and transition formula of Snell's law, which makes the calculation complexity high. Therefore, it is necessary to develop a miniaturization design method for transmissive optical systems that takes into account the imaging quality of the optical system, has low calculation complexity and is accurate.

[0004] The total length of the optical system is directly controlled by using the built-in evaluation function in the optical design software. This optimization method has high computational complexity and can easily cause the optimization variables to fall into the local minimum and escape the trap of the local optimal solution. It not only requires high design experience and optimization skills from the designer, but also takes a lot of time. Summary of the invention

[0005] In view of this, the present invention aims to provide a design method for a miniaturized transmissive optical system based on an improved ray tracing model, so as to solve the problems that the existing method requires a lot of optimization time, resulting in low optimization efficiency and easy to fall into local optimality. The present invention constructs a simplified axial length model of the transmissive optical system and forms a miniaturized design method for the transmissive optical system based on the model. The method can reduce the computational complexity of the miniaturized transmissive optical system while ensuring the imaging quality of the transmissive optical system.

[0006] To achieve the above object, the technical solution created by the present invention is implemented as follows: A design method for a miniaturized transmissive optical system based on an improved ray tracing model specifically comprises the following steps: S1: Establish a transmissive optical system using optical design software, and optimize the transmissive optical system according to preset constraints to obtain the initial structure of the transmissive optical system; S2: Construct the axial length constraint function of the initial structure of the transmissive optical system based on the improved ray tracing model; S3: The axial length constraint function is used to optimize the axial length of the initial structure of the transmissive optical system to obtain a miniaturized transmissive optical system.

[0007] Further, in step S1, the optical design software includes CODE V software.

[0008] Furthermore, in step S1, the preset constraints include the effective focal length of the transmissive optical system, the axial length of the transmissive optical system, the center thickness of each lens included in the transmissive optical system, and the like.

[0009] Further, in step S1, the optimization process includes correcting residual aberrations.

[0010] Furthermore, step S2 specifically includes the following steps: S21: Remove the aperture surface of the initial structure of the transmissive optical system, and calculate the axial length model of the initial structure of the transmissive optical system by the following formula: ; ; ; in, r i For the i The distance from the center of curvature of the surface lens to the incident light ray; TL m is the total axial length of the initial structure of the transmissive optical system; TL m,1 is the distance between the intersection of the outgoing light of the mth lens and the optical axis and the vertex of the first lens in the initial structure of the transmission optical system; m is the total number of optical surfaces of the transmission optical system; R i For the i The radius of curvature of the surface lens; n i For the i The lens and the i+ 1. The refractive index between the lenses; d i-1 For the i- 1 lens and the i The axial distance between the vertices of the facet lenses; h i For the i The incident height of the surface lens; h I For image height; u i-1The reference ray is i The incident aperture angle of the surface lens, i =1,2,… m ; S22: Construct the axial length constraint function of the initial structure of the transmissive optical system based on the axial length model: ; in, TL is the axial length constraint function of the initial structure of the transmissive optical system, is the total axial length of the initial structure of the transmissive optical system at the f-th field of view, f is the field number, f =1, 2, …, F .

[0011] Compared with the prior art, the invention can achieve the following beneficial effects: (1) The present invention creates a miniaturized transmissive optical system design method based on an improved ray tracing model. The distance r from the center of curvature to the incident light is used as a bridge to introduce the structural parameter information of the transmissive optical system into the light transmission process of the transmissive optical system, thereby improving the ray tracing method of the transmissive optical system and constructing a simplified axial length model of the transmissive optical system.

[0012] (2) The present invention creates a design method for a miniaturized transmissive optical system based on an improved ray tracing model, constructs an axial length constraint function based on the improved ray tracing model, and proposes a design process for a miniaturized transmissive optical system. Simulation results show that this method reduces the computational complexity of the transmissive optical system while satisfying the advantage of miniaturization of the transmissive optical system, thereby ensuring the imaging quality of the transmissive optical system. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings: Figure 1 A schematic flow chart of a method for designing a miniaturized transmissive optical system based on an improved ray tracing model according to an embodiment of the present invention; Figure 2 A schematic diagram of the structure of the optical initial structure described in the embodiment of the present invention; Figure 3 A schematic diagram of the structure of the optical system after being optimized by the system length evaluation function built into the optical design software according to the embodiment of the present invention; Figure 4A schematic diagram of the structure of an optical system after the axial length constraint function is optimized according to an embodiment of the present invention.

[0014] Description of reference numerals: 1. First meniscus convex lens; 2. Second meniscus convex lens; 3. First meniscus concave lens; 4. Second meniscus concave lens; 5. Aperture; 6. Double cemented lens; 7. First biconvex lens; 8. Second biconvex lens; 9. Biconcave lens; 10. Third biconvex lens; 11. Fourth biconvex lens; 12. Plano-concave lens. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solution and advantages of the invention more clear, the invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described here are only used to explain the invention and do not constitute a limitation of the invention.

[0016] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0017] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0018] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0019] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0020] like Figure 1 As shown, a design method for a miniaturized transmissive optical system based on an improved ray tracing model specifically includes the following steps: S1: Use optical design software to establish a transmissive optical system, and optimize the transmissive optical system according to preset constraints to obtain the initial structure of the transmissive optical system.

[0021] The initial structure of the transmissive optical system is searched from the built-in structure library of existing optical design software (such as CODE V software), the curvature radius of each lens surface of the transmissive optical system and the spacing position of each lens surface are set as variables, and the configuration constraints (i.e., preset constraints) are set before optimization. Various optimization methods such as bending radius, splitting lenses, adjusting intervals, and replacing glass pairs are used to correct residual aberrations, complete the lens optical design, and optimize the optical system to achieve the best imaging quality.

[0022] S2: Construct the axial length constraint function of the initial structure of the transmissive optical system based on the improved ray tracing model.

[0023] S21: Remove the aperture surface of the initial structure of the transmissive optical system, and calculate the axial length model of the initial structure of the transmissive optical system by the following formula: ; ; ; in, r i For the i The distance from the center of curvature of the surface lens to the incident light ray; TL m is the total axial length of the initial structure of the transmissive optical system; TL m,1 is the distance between the intersection of the outgoing light of the mth lens and the optical axis and the vertex of the first lens in the initial structure of the transmission optical system; m is the total number of optical surfaces of the transmission optical system; R i For the i The radius of curvature of the surface lens; n i For the i The lens and the i+ 1. The refractive index between the lenses; d i-1 For the i- 1 lens and the i The axial distance between the vertices of the facet lenses; h i For the iThe incident height of the surface lens; h I For image height; u i-1 The reference ray is i The incident aperture angle of the surface lens, i =1,2,… m ; S22: Construct the axial length constraint function of the initial structure of the transmissive optical system based on the axial length model: ; in, TL is the axial length constraint function of the initial structure of the transmissive optical system, is the total axial length of the initial structure of the transmissive optical system at the f-th field of view, f is the field number, f =1, 2, …, F .

[0024] S3: The axial length constraint function is used to optimize the axial length of the initial structure of the transmissive optical system to obtain a miniaturized transmissive optical system.

[0025] The axial length optimization uses the axial length constraint function as the optimization constraint condition and sets the interval step size to reduce the length of the transmissive optical system. Each round of calculation will reduce the length of the transmissive optical system by the corresponding step size. When the axial length constraint function of the transmissive optical system does not reach the limit value, the axial length is reduced and the imaging quality still meets the design requirements; when the axial length constraint function reaches the limit value, the axial length is reduced and the imaging quality no longer meets the design requirements. At this time, the output is a transmissive optical system with the shortest axial length and imaging quality that meets the design requirements.

[0026] In step S2, if the initial structure of the transmissive optical system is a single refractive spherical system, the axial length model of the single refractive spherical system is: ; ; ; in, r s,1 is the distance from the center of curvature of the first lens of the single refractive spherical system s to the incident light; TL s is the total axial length of a single refractive spherical system; TL s,1 is the distance between the intersection of the outgoing light ray and the optical axis and the vertex of the first lens; R is the radius of curvature of the first lens; n and n' are the object-side refractive index and image-side refractive index of the first lens respectively; h is the incident height of the first lens; u 0 is the object aperture angle; - h I For image height.

[0027] If the initial structure of the transmissive optical system is a birefringent spherical system, the axial length model of the birefringent spherical system is: ; ; ; ; in, r d,i is the first i The distance from the center of curvature of the surface lens to the incident light ray; TL d is the total axial length of the birefringent spherical system; TL d,1 is the distance between the vertex of the first lens and the intersection of the outgoing light of the second lens with the optical axis; R i For the i The radius of curvature of the surface; n i For the i The lens and the i+ 1. The refractive index between the lenses; d 1 is the axial distance between the two lens vertices; h i For the i The incident height of each lens; h I For image height; u i-1 The reference ray is i The incident aperture angle of the surface ( i =1, 2).

[0028] Example 1 For ease of understanding, this embodiment uses the design process of a transmissive optical system as technical support, aiming to demonstrate the feasibility and simplicity of the miniaturized design method of the transmissive optical system. The initial structure of the optical system selects a transmissive optical system with a focal length of 1.74mm, an effective aperture of 10mm, a diagonal field of view of 24°, and a working wavelength of visible light. The structure of the initial structure of the optical system is: a first meniscus convex lens 1, a second meniscus convex lens 2, a first meniscus concave lens 3, a second meniscus concave lens 4, an aperture 5, a double glued lens 6, a first biconvex lens 7, a second biconvex lens 8, a biconcave lens 9, a third biconvex lens 10, a fourth biconvex lens 11 and a plano-concave lens 12 arranged in sequence along the light path. The specific steps are as follows: Step 1: Construct the initial structure of the optical system and optimize the image quality of the initial structure of the optical system; The initial structure of the optical system is searched from the structure library built into the existing optical design software, and the curvature radius of each lens surface of the initial structure of the optical system and the spacing position of each lens surface are set as variables. The configuration constraints are set before optimization: the effective focal length EFFL of the optical system after image quality optimization is set to 17.4mm, the axial length TOTR<50mm, and the center thickness of each curved surface is set between 1~4mm. With the diffuse spot radius and MTF value as the main evaluation criteria, according to the design requirements, various optimization methods such as bending radius, splitting lenses, adjusting intervals and replacing glass pairs are used to correct residual aberrations and optimize the initial structure of the optical system to the best imaging quality. The resulting system layout diagram is shown below. Figure 1 As shown in Figure 1, the axial length of the initial structure of the optical system is 39 mm. After optimizing the initial structure of the optical system using the system length evaluation function built into the optical design software, the layout diagram of the optical system is obtained as shown in Figure 1. Figure 2 As shown, the total length of the optimized optical system is 33 mm.

[0029] Step 2: For the optimized optical system, construct the axial length constraint function of the optimized optical system based on the ray tracing model.

[0030] like Figure 2 As shown in the figure, after removing the aperture surface, the optical system has a total of 23 optical surfaces. d 1~ d 22 ,in d i-1 For the i- The vertex of lens 1 and the i The axial distance between the facet lens vertices; R 1~ R 23 ,in R i For the iThe radius of curvature of the surface; construct n 0~ n 23 ,in n 0=1, n i For the i Surface and i+ 1The refractive index between the surfaces; construct h1~h 23 ,in h i For the i The incident height of the surface lens, - h I Representative image height; construction u 0~ u 22 , u i-1 The reference ray is i The incident aperture angle of the surface ( i =1, 2, …23).

[0031] Here, five fields of view, 3°, 5°, 8°, 10°, and 12°, are selected to participate in the construction of the axial length constraint function. f is the field number ( f =1, 2, …5). d i , R i and n i is a quantity that is independent of the field of view. h i and u i is a quantity related to the field of view, so the axial length constraint function TL of the optical system is as follows: ; ; ; Step 3: Using the axial length constraint function as the optimization index, perform axial length optimization on the optimized optical system to obtain the final transmissive optical system.

[0032] In the optical design software, write a macro function of the axial length constraint function. Then, use the effective focal length, the center thickness of the element, and the constructed length model as constraints, and use the diffuse spot radius as the image quality evaluation standard to carry out the miniaturization design of the transmissive optical system. Optimize with a step size of 1mm, and the axial length constraint function is continuously reduced through multiple optimizations until the image performance of the optical system no longer meets the imaging requirements. Finally, output the optical system with the shortest axial length and imaging quality that meets the design requirements. The layout diagram is shown in the figure below. Figure 3 shown.

[0033] The final output optical system is compared with the optical system optimized by the system length evaluation function built into the optical design software. The comparison results are shown in Table 1: Table 1

[0034] It can be seen from Table 1 that the miniaturized transmission optical system design method based on the improved ray tracing model of the present invention has an excellent optimization effect.

[0035] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the disclosure of the present invention can be performed in parallel, sequentially or in different orders, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and this document does not limit this.

[0036] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A design method for a miniaturized transmissive optical system based on an improved ray tracing model, characterized in that: The specific steps include: S1: Establish a transmissive optical system using optical design software, and optimize the transmissive optical system according to preset constraints to obtain the initial structure of the transmissive optical system; S2: Construct the axial length constraint function of the initial structure of the transmissive optical system based on the improved ray tracing model; S3: Utilize the axial length constraint function to optimize the axial length of the initial structure of the transmissive optical system to obtain the final transmissive optical system.

2. The method for designing a miniaturized transmissive optical system based on an improved ray tracing model according to claim 1, characterized in that: In step S1, the optical design software includes CODE V software.

3. The method for designing a miniaturized transmissive optical system based on an improved ray tracing model according to claim 1, characterized in that: In step S1 , the preset constraints include the effective focal length of the transmissive optical system, the axial length of the transmissive optical system, and the center thickness of each lens included in the transmissive optical system.

4. The method for designing a miniaturized transmissive optical system based on an improved ray tracing model according to claim 1, characterized in that: In step S1 , the optimization process includes correcting residual aberrations.

5. The method for designing a miniaturized transmissive optical system based on an improved ray tracing model according to claim 1, characterized in that: Step S2 specifically includes the following steps: S21: Remove the aperture surface of the initial structure of the transmissive optical system, and calculate the axial length model of the initial structure of the transmissive optical system by the following formula: ； ； ； in, r i For the i The distance from the center of curvature of the surface lens to the incident light ray; TL m is the total axial length of the initial structure of the transmissive optical system; TL m,1 is the distance between the intersection of the outgoing light of the mth lens and the optical axis and the vertex of the first lens in the initial structure of the transmission optical system; m is the total number of optical surfaces of the transmission optical system; R i For the i The radius of curvature of the surface lens; n i For the i The lens and i+ 1. The refractive index between the lenses; d i-1 For the i- 1 lens and the i The axial distance between the vertices of the face lenses; h i For the i The incident height of the surface lens; h I For image height; u i-1 The reference ray is i The incident aperture angle of the surface lens, i =1,2,… m ; S22: Construct the axial length constraint function of the initial structure of the transmissive optical system based on the axial length model: ； in, TL is the axial length constraint function of the initial structure of the transmissive optical system, is the total axial length of the initial structure of the transmissive optical system at the f-th field of view, f is the field number, f =1, 2, …, F .

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