Method for designing initial structure of optical system based on first-order quantity

Abstract

The present invention relates to the field of optical design technology, and specifically provides a method for designing the initial structure of an optical system based on a first-order quantity, by randomly assigning values ​​to the focal lengths of other elements except the last element and the intervals between adjacent elements, calculating the focal length of the last element and the interval between it and a detection surface according to system design requirements, setting an objective function, and using a global algorithm to find the focal length and interval allocation data of the elements when the objective function value is optimal, and then modeling and optimizing through optical design software. The present invention simplifies the optimization variables in the optical design process, simplifies the traditional optical design process without reducing the accuracy of the initial structure design, reduces the design complexity, and effectively avoids the problems of low design efficiency and waste of computing resources in traditional design methods.

Description

Technical Field

[0001] The invention relates to the technical field of optical design, and specifically provides a method for designing an initial structure of an optical system based on a first-order quantity. Background Art

[0002] With the popularity of computers today, optical design has become much more convenient. You only need to find a suitable starting point and avoid complex calculations through software with optimization functions (such as codev, zemax, etc.). However, the prerequisite is that the initial structure must be found. The currently widely used method is the PWC method based on the theoretical balance of third-order aberrations. The PWC method is suitable for systems with relatively simple systems and fewer degrees of freedom. When the number of design variables is far greater than the number of aberrations, the role of this method is relatively limited. Therefore, this method has not become a commonly adopted method for optical design. Another way to obtain the initial structure is to query publicly published lens patents, select lenses with parameters close to the requirements, and slightly modify the parameters to obtain a set of starting structures. Although publicly published patents can provide references for the initial structure design, how to find patents that truly meet the requirements is a problem, which depends on luck to some extent.

[0003] Therefore, it is urgent to design a method to obtain the initial structure of optical design to fill the gap in the initial structure design. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a method for designing the initial structure of an optical system based on first-order quantities, uses the distributed optical focal length to find the initial lens structure, and through the reasonable distribution of the focal length of the optical lens, quickly generates the configuration of the optical system and meets the requirements of the optical system, greatly reducing the workload of designing the initial structure.

[0005] To achieve the above object, the technical solution created by the present invention is implemented as follows:

[0006] The method for designing the initial structure of an optical system based on a first-order quantity provided by the present invention comprises:

[0007] Define the number of elements of the optical system to be designed as N;

[0008] S1: Randomly assign the optical power or focal length of the first N-1 elements, as well as the interval between adjacent elements, and calculate the optical power or focal length of the Nth element, as well as the interval from the Nth element to the detection surface, in combination with the parameter requirements of the optical system;

[0009] S2: Set the objective function and calculate the objective function value of the initial solution obtained in S1;

[0010] S3: Update the optical power or focal length of the first N-1 elements and the interval between the N elements, and use a global algorithm to find the optical power or focal length of the N elements, the interval between adjacent elements, and the interval from the Nth element to the detection surface when the objective function value meets the set requirements.

[0011] Preferably, the parameter requirements of the optical system include one, two or three of the field of view angle, focal length and entrance pupil diameter.

[0012] Preferably, the optical power or focal length of the Nth element is calculated using the following equivalent optical power formula:

[0013] ;

[0014] in, is the focal length of the optical system, is the incident height of the light on the first element, For the The incident height of the light on the element is For the The focal length is the reciprocal of the focal length of each element. The focal length can be obtained by calculating the focal length of the Nth element.

[0015] Preferably, the objective function is any one of or a combination of at least two of the sum of the deflection angles of the principal rays and the marginal rays incident on all element surfaces, the total aberration sum of the optical system, and the total length of the optical system.

[0016] Preferably, when the objective function is the sum of the deflection angles of the main light and the edge light incident on all element surfaces, the objective function is expressed as:

[0017] ;

[0018] in, For the The optical power of each element, For the Components and The spacing of the elements, The main ray is The deflection angle on the surface of the element is hour, represents the deflection angle of the main light on the detection surface, For the edge ray The deflection angle on the surface of the element is hour, Indicates the deflection angle of the edge light on the detection surface.

[0019] Preferably, the requirement is set as follows: the objective function value calculated by the global algorithm is less than a set optimization threshold.

[0020] Preferably, the objective function also includes at least one of the following constraints:

[0021] The maximum focal length of the component is less than the set component focal length threshold;

[0022] The maximum distance between adjacent elements is less than the set distance threshold.

[0023] Preferably, it also includes:

[0024] S4: The optical power or focal length of N elements that meet the set requirements, the intervals between adjacent elements, and the interval from the Nth element to the detection surface obtained in S3 are imported into the optical design carrier for modeling.

[0025] Preferably, the curvature and material of each surface of the element are designed according to the optical power or focal length of each element obtained in S3.

[0026] Preferably, the light-receiving effect of the positive and negative design elements is designed according to the intervals between adjacent elements obtained in S3. Components and The interval between the elements is positive, indicating that the The orientation of the first element is related to the incident light If the propagation direction of the light rays of the first element is the same, then The first element is designed as a lens; when the Components and The interval between the elements is negative, indicating that the The orientation of the first element is related to the incident light The propagation direction of the light rays of the first element is opposite, then The first element is designed as a reflector.

[0027] Compared with the prior art, the invention can achieve the following beneficial effects:

[0028] In the traditional optical design process, the curvature, material, refractive index and spacing of the components are taken as variables to be optimized. The system design has too many degrees of freedom, resulting in a huge amount of calculation and a waste of computing resources. Compared with the traditional design method, the present invention only regards the optical power (or focal length) and the spacing between the components as variables, allocates the optical power and spacing through a global algorithm, and quickly finds the initial lens structure, which effectively reduces the amount of calculation, simplifies the traditional optical design process, and reduces the design complexity.

[0029] In addition, the method of the present invention can be integrated with existing optical design software to facilitate the automation of design, improve design efficiency, and further optimize the designed optical system in the software according to actual needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] 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:

[0031] Figure 1 is a design flow chart of an initial structure of an optical system provided according to an embodiment of the present invention;

[0032] Figure 2 is a graph showing a change trend of an objective function value provided according to an embodiment of the present invention;

[0033] Figure 3 is an initial structure diagram under ideal conditions provided by an embodiment of the present invention;

[0034] Figure 4 This is a lens structure after replacing the ideal lens provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the invention clearer, 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 herein are only used to explain the invention and do not constitute a limitation to the invention. Similar components in different embodiments use associated similar component numbers. In the following embodiments, many detailed descriptions are to enable the invention to be better understood. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other components, materials, and methods. In some cases, some operations related to the invention are not shown or described in the specification, in order to avoid the core part of the invention being overwhelmed by too much description, and for those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations according to the description in the specification and the general technical knowledge in the art.

[0036] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other to form various implementation methods. At the same time, the steps or actions in the method description can also be interchanged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the various sequences in the specification and the drawings are only for the purpose of clearly describing a certain embodiment and are not meant to be a necessary sequence, unless otherwise specified that a certain sequence must be followed.

[0037] In the description of the invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the 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 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. Therefore, the features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the invention, unless otherwise specified, the meaning of "multiple" is two or more.

[0038] 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.

[0039] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0040] See also Figure 1 In one embodiment of the present invention, a method for designing the initial structure of an optical system based on first-order quantities is provided. By reasonably allocating the optical power or focal length of the optical system to be designed, as well as the element spacing, the initial structure of the optical system that meets the design requirements is designed, or it is called an initial lens. It should be noted that the optical power and focal length of the element are reciprocals of each other and can be directly converted. Therefore, in the design process, the design data can be in the data format with the optical power as a variable or in the data format with the focal length as a variable, and the design process is exactly the same. The specific design process is as follows:

[0041] S1: First, extract the parameter requirements according to the optical system to be designed, that is, the initial structure of the design needs to meet the field of view angle ,focal length and entrance pupil diameter D. It can be understood that the field of view here is ,focal length And the entrance pupil diameter D refer to the parameters of the initial structure obtained by the final design, rather than the parameters of each component in the optical system.

[0042] Assuming that the number of elements in the optical system to be designed is N, the optical power data of N elements is recorded as … ,in, The subscript of represents the number of the element, which is sorted according to the transmission order of the incident light; the intervals between adjacent elements are sorted. In addition, it should be noted that the initial structure of the designed optical system needs to be able to obtain an image on the specified detection surface, so the interval between the last element and the detector CCD also needs to be designed. Therefore, the interval data should be recorded as … ,in, Represents the interval between the first element and the second element, Represents the interval between the second and third elements, and so on. Represents the distance between the Nth element and the CCD detection surface.

[0043] The optical power of the first N-1 elements … and the first N-1 intervals (i.e. the intervals between adjacent elements in N elements) … Set as a variable and … and … The initial value is randomly assigned. The initial value can be set arbitrarily. In the embodiment of the present invention, the design of an infinite conjugate focused transmission system is specifically taken as an example. Since all the components in the system are lenses and there are no reflectors, in order to satisfy the physical meaning, … The initial value assigned must be greater than 0. It is understood that all components are set in the order of transmission of the incident light, but in particular, in a system with a reflector, the interval When it is a negative value, it means that the setting direction of the element is opposite to the propagation direction of the incident light. The positive and negative signs indicate the setting direction of the component.

[0044] In order to make the field of view angle, focal length and entrance pupil diameter meet the parameter requirements of the optical system to be designed, the focal power data of the first N-1 elements after the initial value is assigned and the first N-1 intervals can be combined to use the equivalent focal power formula to calculate the focal power of the Nth element. The equivalent focal power formula is:

[0045] ;

[0046] in, is the focal length of the optical system, is the incident height of the light on the first element, For the The incident height of the light on the element is For the The focal length is the reciprocal of the focal length of each element. The focal length can be obtained by calculating the focal length of the Nth element.

[0047] The equivalent optical power formula can be expanded to calculate the optical power of the Nth element: , combined with the CCD imaging requirements, the distance from the Nth element to the CCD detection surface can be calculated At this point, the optical power and spacing of all components can be determined and meet the design requirements of the optical system. The obtained optical power and spacing data are called the initial solution.

[0048] S2: Based on S1, it is necessary to design an objective function to optimize the optical power and spacing of all elements. Specifically, when N is greater than 2, the optical power of the first N-1 elements and the values ​​of the spacing between adjacent elements change. Correspondingly, the optical power of the Nth element is calculated. , and the distance between N elements and the CCD detection surface , will also change accordingly. Therefore, there will be an infinite number of sets of data that can meet the design requirements, so it is necessary to design an objective function for optimization. The design of the objective function needs to be constructed according to the design expectations of the optical system. The design expectations usually include: reducing system aberrations, reducing system length, imaging quality, etc.

[0049] The refraction theorem is as follows:

[0050] ;

[0051] in, is the refractive index of the incident medium, represents the refractive index of the refracting medium, represents the angle of incidence, Represents the refraction angle.

[0052] When the sine value After Taylor series expansion:

[0053] ;

[0054] The expansion divides the behavior of light into different levels, each level represents a different optical effect, where the first term For a paraxial (ideal) optical system, the second term Corresponding to the third (primary) aberration, the third term Corresponding to the fifth (higher) order aberration. It can be seen that the large incident angle of light on the surface is the fundamental reason for the geometric aberration. Obviously, an optical system with a small relative aperture and a small field angle satisfies the conditions of a paraxial optical system, while an optical system with a large relative aperture and a large field angle has large aberrations. The aberration of the optical system originates from the behavior of light on the surface of a refracting or reflecting element. In order to ensure the excellent performance of the optical system, it is necessary to minimize the deflection of light on each surface so that the transmission of light from the object surface to the image plane is as smooth as possible. Therefore, in order to realize the automatic generation of the optical system under specific constraints, the present invention traces the marginal ray and the main ray, wherein the main ray is a ray passing through the center of the entrance pupil of the optical system and parallel to the optical axis. Ideally, this ray will propagate along the optical axis and pass through the focus of the optical system; the marginal ray is a ray passing through the edge of the entrance pupil of the optical system and perpendicular to the optical axis. The propagation path of this ray in the optical system represents the maximum field angle of the system. The objective function is selected to optimize the sum of the deflection angles of the main light and the marginal light incident on all the surfaces of the components. The designed optical system is evaluated and optimized according to the objective function value. The objective function is established as follows:

[0055] ;

[0056] in, For the The optical power of each element, For the Components and The spacing of the elements, The main ray is The deflection angle on the surface of the element is hour, represents the deflection angle of the main light on the detection surface, For the edge ray The deflection angle on the surface of the element is hour, Indicates the deflection angle of the edge light on the detection surface.

[0057] Then, based on the above objective function, the objective function value of the initial solution obtained in S1 is calculated.

[0058] As a preferred embodiment, the objective function in the embodiment of the present invention is not unique and fixed, and the objective function can be modified and limited according to the expectation of the optical system. In practical application, in addition to the sum of the deflection angles of the main light and the marginal light as the objective function adopted in the embodiment of the present invention, the total aberration sum of the optical system can also be used as the objective function, or the total length of the optical system can be used as the objective function. In addition, the above-mentioned objective functions can not only be used alone, but also at least two of them can be selected to be combined.

[0059] Furthermore, one or more constraints may be added to the objective function. Common constraints include: requiring that the maximum focal length of any element among all elements is less than a set element focal length threshold. This threshold is designed and adjusted according to actual needs and has no specific value; requiring that the maximum interval between adjacent elements is less than a set interval threshold. This threshold also needs to be designed and adjusted according to actual needs and has no specific value.

[0060] S3: Through S2, the design of the initial structure of the optical system has been transformed into a constrained optimization problem. Under known constraints, the optical power or focal length of the first N-1 elements and the spacing between N elements can be updated to generate different optical structures, optimize the objective function, and then obtain the objective function value based on the deflection angle of the main light and the edge light. Through the search of the global algorithm, the objective function value that meets the set requirements is obtained. The optical power and spacing data corresponding to the objective function value are the data that are finally used as the initial structure design parameters, that is, the optical power or focal length of N elements, the spacing between adjacent elements, and the spacing from the Nth element to the detection surface when the objective function of the optical system converges to the minimum value.

[0061] As a preferred embodiment, the above global algorithm optimization process can be performed in MATLAB.

[0062] As a preferred embodiment, the global algorithms that can be used include but are not limited to particle swarm algorithm, genetic algorithm and ant colony algorithm.

[0063] S4: Import the optimal initial structural design parameter data obtained in S3 into optical software such as the commonly used CODE V. Specifically, establish communication between CODE V and MATLAB, import the optimal initial structural design parameter data obtained in S3 from MATLAB into the optical software, and change these data into actual component models. At this time, each component model needs to be further designed. For each lens model, it has two surfaces, so the curvature and material of each surface need to be allocated, and the image quality of the system is optimized by controlling the point diagram in CODE V.

[0064] It should be noted that the embodiment of the present invention is directed to an infinite conjugate focused transmission system. Since all the elements in the system are lenses, the calculated interval are all greater than 0. When modeling in the software, you can also manually Set to less than 0, but in this case the corresponding element needs to be changed into a reflector.

[0065] The design method provided by the embodiment of the present invention has been verified in practice and has achieved good results. It greatly reduces the amount of calculation and improves the design efficiency without reducing the system design accuracy. Taking the design of the Cooke three-piece classic lens as an example, the parameter requirements are a full field angle of 40°, a focal length of 50mm, and an aperture of 10mm. Using the method of the embodiment of the present invention, in the optimization process, the change of the objective function value is as follows: Figure 2 As shown, under the search of the global algorithm, the initial structure found is as follows Figure 3 As shown, the focal lengths of the three mirrors Lens1, Lens2, and Lens3 are 48.4788mm, -47.1116mm, and 48.4206mm, respectively. The interval between Lens1 and Lens2 is 2.8824mm, the interval between Lens2 and Lens3 is 6.4152mm, and the interval between Lens3 and the CCD detection surface is 46.8143mm. The above data is input into the software with optimization function for optimization. The obtained simple optimized lens data is shown in Table 1. The surface numbers in the table correspond to Figure 4 The two-dimensional lens structure in .

[0066] Table 1 Lens data

[0067]

[0068] At this point, the design and optimization of the initial structure are complete. Next, we can carefully optimize the lens thickness, replace the glass, or adjust the design to reduce the overall length of the entire system. This process is no different from the optimization of existing lenses and will not be repeated here.

[0069] As a preferred embodiment, the present invention can quickly generate multiple groups of design data with different parameters. Therefore, the method of the present invention can also provide a data set for training a lens optimization model based on deep learning. Multiple lenses are generated using the method of the present invention, and then input into a neural network for training to generate lenses that meet the requirements.

[0070] In short, the above description is only a preferred embodiment of this specification and is not intended to limit the protection scope of this specification. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this specification shall be included in the protection scope of this specification.

[0071] The systems, devices, modules or units described in one or more of the above embodiments may be implemented by a computer chip or entity, or by a product having a certain function. A typical implementation device is a computer. Specifically, the computer may be, for example, a personal computer, a laptop computer, a cellular phone, a camera phone, a smart phone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or a combination of any of these devices.

[0072] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0073] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0074] The above is a description of a specific embodiment of the specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recorded in the claims can be performed in an order different from that in the embodiments and still achieve the desired results. In addition, the processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

Claims

1. A method for designing the initial structure of an optical system based on first-order quantities, wherein the number of elements set in the optical system is N, characterized in that: include: S1: Randomly assign the optical power or focal length of the first N-1 elements and the interval between adjacent elements, and calculate the optical power or focal length of the Nth element and the interval from the Nth element to the detection surface in combination with the parameter requirements of the optical system; calculate the optical power or focal length of the Nth element using the following equivalent optical power formula: ； in, is the focal length of the optical system, is the incident height of the light on the first element, For the The incident height of the light on the element is For the The focal power of the Nth element. The focal power and focal length are reciprocals of each other. The focal length can be obtained by calculating the focal power of the Nth element. S2: setting an objective function, and calculating an objective function value of the initial solution obtained in S1; the objective function is: any one or a combination of at least two of the sum of the deflection angles of the principal rays and the marginal rays incident on all element surfaces, the total aberration sum of the optical system, and the total length of the optical system; S3: Update the optical power or focal length of the first N-1 elements and the interval between the N elements, and use a global algorithm to find the optical power or focal length of the N elements, the interval between adjacent elements, and the interval from the Nth element to the detection surface when the objective function value meets the set requirements.

2. The method for designing the initial structure of an optical system based on first-order quantities according to claim 1, characterized in that: The parameter requirements of the optical system include one, two or three of the field of view angle, focal length and entrance pupil diameter.

3. The method for designing the initial structure of an optical system based on first-order quantities according to claim 1, characterized in that: When the objective function is the sum of the deflection angles of the main light and the marginal light incident on all element surfaces, the expression of the objective function is: ； in, For the The optical power of each element, For the Components and The spacing of the elements, The main ray is The deflection angle on the surface of the element is hour, represents the deflection angle of the main light on the detection surface, For the edge ray The deflection angle on the surface of the element is hour, Indicates the deflection angle of the edge light on the detection surface.

4. The method for designing the initial structure of an optical system based on first-order quantities according to claim 1, characterized in that: The setting requirement is: the objective function value calculated by the global algorithm is less than the set optimization threshold.

5. The method for designing the initial structure of an optical system based on first-order quantities according to claim 1 or 3, characterized in that: The objective function also includes at least one of the following constraints: The maximum focal length of the component is less than the set component focal length threshold; The maximum distance between adjacent elements is less than the set distance threshold.

6. The method for designing the initial structure of an optical system based on first-order quantities according to claim 1, characterized in that: Also includes: S4: The optical power or focal length of the N elements that meet the set requirements, the intervals between adjacent elements, and the interval from the Nth element to the detection surface obtained in S3 are imported into the optical design carrier for modeling.

7. The method for designing the initial structure of an optical system based on first-order quantities according to claim 6, characterized in that: The curvature and material of each surface of the element are designed according to the optical power or focal length of each element obtained in S3.

8. The method for designing the initial structure of an optical system based on first-order quantities according to claim 6, characterized in that: According to the positive and negative design elements of the intervals between adjacent elements obtained in S3, when the first Components and The interval between the elements is positive, indicating that the The orientation of the first element is related to the incident light If the propagation direction of the light rays of the first element is the same, then The first element is designed as a lens; when the Components and The interval between the elements is negative, indicating that the The orientation of the first element is related to the incident light The propagation direction of the light rays of the first element is opposite, then The first element is designed as a reflector.

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