A method and system for optimizing design parameters of a long optical path gas cell

Abstract

The application is suitable for the technical field of optical design parameter optimization, and provides a design parameter optimization method and system for a long optical path gas absorption cell, which comprises the following steps: based on a theoretical model of a light propagation matrix, theoretically verifying the feasibility of mirror parameters of a spherical mirror, determining initial mirror parameters and a key design parameter range; establishing an optical cavity model composed of two spherical mirrors, and performing automatic light ray tracing simulation according to the initial mirror parameters, the key design parameter range and a preset step value; verifying simulation data, determining the number of light spots, and selecting an optimal key design parameter combination for maximizing the optical path according to the number of light spots. The method is mainly used for long optical path gas absorption cell design in an infrared absorption spectrum trace gas sensor detection, has practical significance, realizes verification of optimal design parameters, reduces development difficulty and improves development efficiency.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical design parameter optimization, and particularly relates to a design parameter optimization method and system for a long optical path gas absorption cell. BACKGROUND

[0002] An infrared absorption spectrum trace gas sensor mainly obtains component and content information of unknown gas molecules by capturing the infrared "fingerprint" of the unknown gas molecules. For example, detection of toxic and harmful gas, greenhouse gas, and component and concentration of plant and animal respiration gas at ppb or sub-ppm concentration. A high-efficiency compact long optical path gas absorption cell is a key component thereof. According to the Lambert-Beer law, the strength of absorbance is positively correlated with the effective action length between laser and gas. In order to enable gas molecules to absorb sufficient light, light needs to pass through a gas sample in a tiny optical cavity of a millimeter unit through a path of several kilometers or more. Optimal design parameters of the long optical path gas absorption cell determine the detection accuracy of the gas sensor.

[0003] The development of a long optical path gas absorption cell generally includes theoretical design, parameter optimization, simulation verification, and actual verification. Traditional gas absorption cell design mainly uses a large number of tedious and complex matrix operations and other mathematical theoretical calculations. After theoretical calculation, the theoretical range values of parameters such as the diameter and focal length of a concave mirror, the opening position of a light transmission aperture, the light incidence angle, and the distance between the centers of two concave mirrors are obtained. Then, the lenses are manufactured by a factory to meet the parameters. However, the cost of opening a mold for a new lens is high, and the performance of a gas absorption cell composed of different parameters is different, which makes the design process very complex and difficult to find the optimal design parameters. Moreover, it is extremely difficult to regulate the optical cavity in verification. If the optical cavity does not match the resonant mode in the cavity, the laser beam will be emitted. In this case, a large amount of time is still needed to repeatedly verify the accuracy of the lens parameters, which has great uncertainty. Therefore, an automatic optimization design method is urgently needed before experimental verification. After the design parameters are input, the light is automatically simulated from the light transmission aperture of the first concave mirror in the simulation environment. The light propagates along a straight line to the other concave mirror to form a reflection, and then the light returns to the first concave mirror. This process is repeated until the light is emitted from the light transmission aperture of the second concave mirror.

[0004] In the design of long optical path gas absorption cell, the diameter of concave mirror, focal length, aperture opening position, light incidence angle and the distance between the centers of two concave mirrors are the basis and key to realize the maximum optical path under the limit volume, and these parameters are usually determined by optical simulation. Since the traditional simulation method has complex simulation process and needs to spend a lot of time for trial, the parameters cannot be optimized, resulting in long development cycle and poor flexibility. Therefore, developing an automatic optimization method for long optical path gas absorption cell design plays an important role in improving the precision and rapid application of infrared absorption spectrum trace gas detection sensor. SUMMARY

[0005] The purpose of the present application is to provide a design parameter optimization method for long optical path gas absorption cell, aiming at solving the above technical problems.

[0006] The present application is implemented as follows: a design parameter optimization method for long optical path gas absorption cell, comprising the following steps:

[0007] Based on the theoretical model of light propagation matrix, according to the engineering volume requirement of the long optical path gas absorption cell to be designed, the feasibility of the lens parameters of the spherical mirror is theoretically verified, and the initial lens parameters and the range of key design parameters are determined;

[0008] An optical cavity model composed of two spherical mirrors is established, and based on the optical cavity model, according to the initial lens parameters and the range of key design parameters and the preset step value, an automatic light tracing simulation is carried out to obtain simulation data;

[0009] Based on the image processing algorithm, the simulation data is verified to determine the number of light spots, and the optimal key design parameter combination that maximizes the optical path is selected according to the number of light spots.

[0010] Further, the theoretical model of the light propagation matrix is as follows: according to the radii of curvature of the two spherical mirrors, the transformation matrix of the light rays in the two spherical mirrors is deduced; assuming that the light ray starts from the light transmission hole on one of the spherical mirrors and propagates to the direction of the other spherical mirror, the initial light ray angle parameter is Then, the total coordinate transformation of the light ray in the two spherical mirrors for one round trip is:

[0011] ;

[0012] ;

[0013] In the formula, is the light ray angle parameter after one round trip; L is the distance between the two mirrors; R1 and R2 are the radii of curvature of the two spherical mirrors; T is the round trip matrix, and A, B, C and D are the matrix elements.

[0014] Further, the key design parameters include the aperture position, the distance between the two mirrors, and the incident light angle.

[0015] Further, the method of ray tracing simulation is as follows: a first aperture is set on the first spherical mirror, and ray tracing is started at the initial distance between the two mirrors. The incident light angle range is adjusted to make the incident light enter the optical cavity. After the tracing verification of all incident light angles is completed, the distance between the two mirrors is adjusted step by step according to the preset step value. Each time the distance between the two mirrors changes, the tracing of all angle parameters needs to be repeated for the incident light angle. Until the distance between the two mirrors completes all parameter verifications in the set range. Then, a new aperture position is set on the first spherical mirror, and the above steps are repeated until the verification of all aperture positions in the first spherical mirror is completed, and the ray tracing simulation is completed.

[0016] Further, the verification of the aperture position is as follows: taking the center of the spherical mirror as the coordinate origin, the spherical mirror is divided into multiple regions. Through program control, the position of a cylinder that is the difference set of the spherical mirror is adjusted by a preset step value, thereby simulating the process of opening an aperture at different positions of the spherical mirror, until the entire aperture range of the spherical mirror is covered.

[0017] Further, the parameter tracing verification of the incident light angle is as follows: according to different aperture positions, the incident light angle range is set, and all incident light angles are simulated by a preset step value until the simulation is completed.

[0018] The simulation method of the incident light angle is as follows: the aperture position is taken as the initial coordinate value of the incident light angle. The aperture is circular. The incident light is adjusted through the first spherical mirror until the light cannot pass through the first spherical mirror. The intersection of the incident light and the first spherical mirror is a circle, and the value range is within the area of the circle. Let x, y, z be the coordinate values of the incident light, and r be the aperture radius of the spherical mirror, which is determined by the following formula:

[0019] ;

[0020] In the formula, x and y are the coordinates of the incident light on the plane of the spherical mirror; z is the coordinate of the plane where the spherical mirror is located; z0 is the initial coordinate of the plane where the spherical mirror is located.

[0021] The iteration formula of the incident light angle range is as follows:

[0022] ;

[0023] In the formula, is the polar angle of the light deviating from the optical axis. is the azimuth angle of the light ray around the optical axis; k, l are constants; , is a preset step value;

[0024] The determination condition is: if the incident light ray passes through the light hole of the first spherical mirror, the determination result is equal to 1; if the incident light ray is blocked or exceeds the light hole, the determination result is equal to 0;

[0025] The adaptive search termination condition is: if f(L) is equal to 0, stop the search of the angle direction of the incident light ray.

[0026] Further, the adjustment method of the distance between the two mirrors is: after the light hole position and the incident light ray angle range are set, the simulation step is completed by adjusting the distance between the two mirrors in the preset working condition requirement size range with a preset step value;

[0027] The simulation method of the distance between the two mirrors is as follows: the adjustment range of the distance between the two mirrors is that the light ray cannot intersect with the second spherical mirror after passing through the first spherical mirror; the distance between the two mirrors is adjusted adaptively by judging whether the light ray intersects with the second spherical mirror or not; let the distance between the two mirrors be L, and define the determination function f(L) as follows:

[0028] ;

[0029] Wherein, Q1 represents the effective reflection area of the first spherical mirror; Q2 represents the effective reflection area of the second spherical mirror; ∩ represents the set intersection symbol; represents an empty set; if the intersection of Q1 and Q2 is not empty, it means that the light ray can be transmitted from the first spherical mirror to the second spherical mirror;

[0030] On this basis, the maximum allowed distance L between the two mirrors is defined as: max

[0031] .

[0032] Further, the image processing algorithm is: by comparing the preset background image with the simulation image in the simulation data, specifically as follows:

[0033] ;

[0034] Wherein:

[0035] ;

[0036] ;

[0037] ​​​​ ;

[0038] ;

[0039] wherein, is the final spot number; is the connected domain set; is the i-th connected domain area; min is the minimum effective area threshold; is the binarization result; is the frame difference map; is the simulation image, is the preset background image; is the adaptive threshold, is the local mean, and k is a coefficient, is the local standard deviation.

[0040] Another object of the present application is to provide a design parameter optimization system for a long optical path gas absorption cell, which implements the design parameter optimization method described above, and which comprises:

[0041] A parameter feasibility verification module, configured to perform theoretical verification on the feasibility of the mirror parameters of the spherical mirror based on a theoretical model of light propagation matrix, according to the engineering volume requirement of the long optical path gas absorption cell to be designed, to determine the initial mirror parameters and the range of key design parameters.

[0042] An optical simulation module, configured to establish an optical cavity model composed of two spherical mirrors, and to perform automatic ray tracing simulation based on the optical cavity model, according to the initial mirror parameters and the range of key design parameters and a preset step value, to obtain simulation data.

[0043] A simulation data screening module, configured to verify the simulation data based on an image processing algorithm, to determine the spot number, and to screen out the optimal combination of key design parameters that maximizes the optical path based on the spot number.

[0044] This invention provides a method for optimizing the design parameters of a long-path gas absorption cell. This method verifies the theoretical parameters of a long-path gas absorption cell with the maximum optical path under extreme volume conditions. Simultaneously, it verifies the parameters of existing concave mirrors on the market. By inputting the mirror parameters, the method automatically verifies whether these parameters meet the design requirements of the long-path gas absorption cell. This allows for better and faster selection of mirrors suitable for the gas cell equipment parameters to meet different operating conditions. This method is mainly used for the design of long-path gas absorption cells in infrared absorption spectroscopy trace gas sensor detection. It has practical significance, maximizes equipment efficiency, and verifies the optimal design parameters. It not only verifies the accuracy of newly developed mirror parameters but also verifies whether existing mirrors on the market can be used for long-path gas absorption cell design, reducing development difficulty and improving development efficiency. Attached Figure Description

[0045] Figure 1 A flowchart illustrating the design parameter optimization method for a long optical path gas absorption cell provided in this embodiment of the invention.

[0046] Figure 2 This is a schematic diagram of the theoretical model of the light propagation matrix provided in an embodiment of the present invention.

[0047] Figure 3 A schematic diagram of the design parameter optimization system for the long optical path gas absorption cell provided in this embodiment of the invention. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0049] In the infrared absorption spectroscopy gas sensor detection technology, this invention addresses the problem of finding the optimal design parameters for long-path gas absorption cells.

[0050] Specifically, such as Figure 1 As shown, in one embodiment of the present invention, a method for optimizing the design parameters of a long optical path gas absorption cell is provided, comprising the following steps:

[0051] S100. Based on the theoretical model of the light propagation matrix, the feasibility of the lens parameters of the spherical mirror is theoretically verified according to the engineering volume requirements of the long optical path gas absorption cell to be designed, and the initial lens parameters and key design parameter ranges are determined.

[0052] S200, an optical cavity model composed of two spherical mirrors is established, and based on the optical cavity model, automatic ray tracing simulation is performed according to initial lens parameters and a key design parameter range and a preset step value, and simulation data is obtained;

[0053] S300, based on an image processing algorithm, the simulation data is verified to determine the number of light spots, and the optimal key design parameter combination that maximizes the optical path is selected according to the number of light spots.

[0054] It should be noted that the spherical mirror includes a concave mirror and a convex mirror, etc. In the embodiments of the present application, the concave mirror is taken as an example for illustrative description. Specifically, in the simulation of two concave mirrors, the optimal simulation parameter acquisition is mainly realized by the coupling optimization algorithm of Matlab and Tracepro. After the lens parameters are determined, the simulation and analysis are performed by adjusting three key design parameters, i.e. the light hole position (the opening position of the concave mirror), the distance between the two mirrors and the incident light angle. The three key design parameters are alternately changed according to the set step value in turn until the running is completed, and then a large amount of simulation results are saved in a folder named by the light hole position, the distance between the two mirrors and the incident light angle, to generate a simulation result database. Matlab reads and compares the large amount of simulation result database saved in the Tracepro file according to the specified address directory, automatically judges the long optical path gas absorption cell parameter information under the optimal lens, and realizes the verification of the optimal design parameters of the long optical path gas absorption cell.

[0055] In the actual design theory, the long optical path gas absorption cell involves multiple variables, and the results presented under different parameters are not the same. Generally, the optimal optical path design principle under the limit volume is followed, and when designing, the volume and related size parameter range under the engineering condition requirement are first determined, the theory model of the light propagation matrix and its improved form are followed, and the lens diameter, the curvature radius, the distance of the light hole relative to the mirror center, and the distance between the two mirrors are preliminarily determined through multiple iterations. After the above parameters are determined, the parameter information is input into Tracepro through DDE as a connection channel by Matlab through macro language, and a visual simulation model of the long optical path gas absorption cell parameters is established. Under the same lens parameters, the optical cavity model in Tracepro mainly adjusts the three key design parameters (light hole position, incident light angle, distance between two mirrors) automatically, and gradually performs simulation calculation. This process is repeated multiple times until all steps are completed.

[0056] For example, Figure 2As shown, in a preferred embodiment of the present invention, the theoretical model of the light propagation matrix is ​​as follows: Based on the radii of curvature of the two spherical mirrors, the transformation matrix for the light to travel back and forth once between the two spherical mirrors is derived; assuming that the light originates from the light aperture on one of the spherical mirrors M1 and propagates towards the other spherical mirror M2, its initial light angle parameter is... Then, the light ray completes one round trip between the two spherical mirrors (optical cavity), and its total coordinate transformation is:

[0057] ;

[0058] ;

[0059] In the formula, The angle parameters of the light rays after one round trip; L is the distance between the two mirrors; R1 and R2 are the radii of curvature of the two spherical mirrors, respectively; T is the round trip matrix, which is the total transformation matrix of the paraxial ray when it makes one round trip in the optical cavity, and A, B, C, and D are its matrix elements; T L , These are the matrices corresponding to each transformation process.

[0060] In a preferred embodiment of the present invention, after verifying the above-mentioned lens parameters, a lens model is established in a simulation environment, and an optical cavity model consisting of two spherical mirrors (such as concave mirrors) is constructed. Then, ray tracing simulation is performed. The ray tracing simulation method is as follows: a first light-transmitting hole is set on the first spherical mirror, and ray tracing begins at the initial distance between the two mirrors. The incident light angle is adjusted according to the range of incident light angles to allow the incident light to enter the optical cavity. After verifying the tracing of all incident light angles, the distance between the two mirrors is gradually adjusted according to a preset step value. Each time the distance between the two mirrors changes, the incident light angle must be tracing all angle parameters repeatedly until the distance between the two mirrors completes the verification of all parameters within the set range. Then, a new light-transmitting hole position is set on the first spherical mirror, and the above steps are repeated until the verification of all light-transmitting hole positions in the first spherical mirror is completed, and the ray tracing simulation ends.

[0061] In a preferred embodiment of the present invention, the verification of the position of the light-transmitting hole is as follows: taking the center of the spherical reflector as the origin of the coordinate system, the spherical reflector is divided into multiple regions. Through program control, the position of a cylinder that is the difference set with the spherical reflector is adjusted by a preset step value, thereby simulating the process of opening light-transmitting holes at different positions of the spherical reflector until the preset opening range of the entire spherical reflector is covered.

[0062] In practical applications, because the mirror surface of the spherical mirror can be opened with many light holes, and the light tracking results formed by the light holes at different positions on the mirror surface are different, the key opening data will provide a key basis for subsequent opening positions of the concave mirror. In actual development, in order to obtain the optimal light hole position parameters, simulation verification is usually required, and this process needs to be executed repeatedly in simulation verification. In the simulation verification, a plurality of holes are opened on the lens to simulate the condition that the incident light passes through the lens through different opening positions on the lens. The embodiment of the application sets the opening (light hole position) parameter range through Matlab, inputs the parameter information into Tracepro, simulates the light hole positions of the entire mirror surface, and obtains the related simulation results.

[0063] Specifically, the implementation steps of simulating the light hole position of the concave mirror are as follows: the macro language of Matlab coordinates the interpolation of the concave mirror and the cylinder in Tracepro, so that the intersection part of the concave mirror and the cylinder is a difference set. By adjusting the X and Y coordinate values of the cylinder, such as setting a step of 0.01 mm on the X and Y axes, the simulation of the light hole diameter at different positions of the mirror surface is realized. The opening range of the mirror surface is set, mainly taking the center of the mirror surface as the origin, and dividing the entire mirror surface into four parts. First, the quarter circle of the XOY axis is set as the opening range of the first part of the light hole diameter according to the above steps, that is, the X and Y coordinate values of the opening are within the area of the quarter circle. The values are taken step by step until the end by using the exhaustion method. After completing the first part of the opening task, the lens is rotated 90° around the coordinate origin according to the symmetry principle, and the X and Y coordinate values of the cylinder change accordingly. After the simulation is completed, the above steps are repeated twice until the lens is rotated 360° around the coordinate origin. The simulation of the opening position of the entire mirror surface is completed. Assuming that the radius of the concave mirror is R and the center is at the origin (0, 0), the X and Y value formulas are as follows:

[0064] .

[0065] In a preferred embodiment of the application, the parameter tracking verification of the incident light angle is as follows: according to different light hole positions, the range of the incident light angle is set, and all incident light angles are simulated with a preset step value (such as 0.01 degrees) until the simulation is completed.

[0066] In the embodiment of the present application, the incident light angle range is selected by an adaptive threshold method; the simulation method of the incident light angle is as follows: since each opening position is different, the light transmission hole position is taken as the initial coordinate value of the incident light angle, the light transmission hole is circular, the incident light is adjusted through the first spherical mirror until the light cannot pass through the first spherical mirror, the intersection of the incident light and the first spherical mirror is a circle, and the value range is in the area of the circle, and there are various combination conditions which need to be simulated and verified one by one; let x, y and z be the coordinate values of the incident light, and r be the light transmission hole radius of the spherical mirror, which is determined by the following formula;

[0067] ;

[0068] In the formula, x and y are the coordinates of the incident light on the plane of the spherical mirror; z is the plane coordinate of the spherical mirror; z0 is the initial plane coordinate of the spherical mirror; the above formula is constrained to ensure that all incident lights pass through the light transmission hole.

[0069] The iteration formula of the incident light angle range is as follows:

[0070] ;

[0071] In the formula, is the polar angle of the light deviating from the optical axis; is the azimuth angle of the light around the optical axis; k and l are constants; , is a preset step value, generally 0.01°;

[0072] The determination condition is: if the incident light passes through the light transmission hole of the first spherical mirror, the determination result is equal to 1; if the incident light is blocked or exceeds the light transmission hole, the determination result is equal to 0;

[0073] The adaptive search termination condition is: if is equal to 0, the search of the incident light angle direction is stopped.

[0074] In a preferred embodiment of the present application, the mirror spacing is taken as the main base length of the long optical path gas absorption cell, and is also an important parameter for determining the optical path, mainly referring to the center distance of the two spherical mirrors; the adjustment method of the mirror spacing is: after the light transmission hole position and the incident light angle range are set, the simulation step is completed by adjusting the mirror spacing in the preset working condition requirement size range with a preset step value (such as 0.01 mm);

[0075] The simulation method of the distance between the two mirrors is as follows: the adjustment range of the distance between the two mirrors is that the light cannot intersect with the second spherical mirror after passing through the first spherical mirror; the distance between the two mirrors is adjusted adaptively by judging whether the light intersects with the second spherical mirror or not; and the actual process is that Matlab reads the data information in Tracepro to judge whether there is light flux on the second spherical mirror.

[0076] Specifically, first, the distance between the two mirrors is L, and the judgment function f(L) is defined as follows:

[0077] ;

[0078] Wherein Q1 represents the effective reflection area of the first spherical mirror; Q2 represents the effective reflection area of the second spherical mirror; and ∩ represents a set intersection symbol; Indicates an empty set; if the intersection of Q1 and Q2 is not empty, it means that the light can be transmitted from the first spherical mirror to the second spherical mirror;

[0079] On this basis, the maximum allowed distance between the two mirrors L max is defined as:

[0080] ;

[0081] That is, among all the distances between the two mirrors that satisfy the condition that the light can hit the second spherical mirror, the maximum value is taken as the allowed base length.

[0082] In a preferred embodiment of the present application, after a large amount of simulation data is generated, the simulation results such as simulation images need to be verified to determine the number of light spots in the simulation images; the verification method is mainly an image processing algorithm; the image processing algorithm is as follows:

[0083] ;

[0084] Wherein:

[0085] ;

[0086] ;

[0087] ;

[0088] ;

[0089] In the formula, is the final number of light spots; is a connected domain set; is the area of the ith connected domain; A minis a minimum effective area threshold value; is a binarization result; is a frame difference map; is a simulation image, is a preset background image; is an adaptive threshold value, is a local mean value, and k is a coefficient, is a local standard deviation.

[0090] As Figure 3 shown in another embodiment of the present application, a design parameter optimization system of a long optical path gas absorption cell is also provided for implementing the above design parameter optimization method, and specifically includes:

[0091] A parameter feasibility verification module 10 is configured to perform theoretical verification on the feasibility of the mirror parameters of the spherical mirror based on a theoretical model of light propagation matrix, according to the engineering volume requirement of the long optical path gas absorption cell to be designed, to determine the initial mirror parameters and the range of key design parameters.

[0092] An optical simulation module 20 is configured to establish an optical cavity model composed of two spherical mirrors, and perform automatic ray tracing simulation based on the optical cavity model, according to the initial mirror parameters and the range of key design parameters and a preset step value, to obtain simulation data.

[0093] A simulation data screening module 30 is configured to verify the simulation data based on an image processing algorithm, to determine the number of light spots, and to screen out the optimal combination of key design parameters that maximizes the optical path according to the number of light spots.

[0094] It should be noted that the above modules can be implemented in the form of a computer program, which can be run on a computer device, and the computer program composed of the modules can be stored in the memory of the computer device to enable the processor to execute the steps of the above method.

[0095] It should be understood that although each step in the flowchart of each embodiment of the present application is displayed in sequence according to the arrow, these steps are not necessarily executed in the order indicated by the arrow. Unless otherwise stated herein, the execution of these steps is not strictly limited in sequence, and these steps can be executed in other orders. Moreover, at least a part of the steps in each embodiment can include multiple sub-steps or multiple stages, which are not necessarily executed at the same time, but can be executed at different times, and the execution order of these sub-steps or stages is not necessarily sequential, but can be executed in rotation or alternation with at least a part of other steps or sub-steps or stages of other steps.

[0096] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program. The program can be stored in a non-volatile computer readable storage medium, and when the program is executed, the program can include the processes of the above-mentioned embodiments of each method. Any reference to memory, storage, database or other medium used in each embodiment provided by the present application can include non-volatile and / or volatile memory.

[0097] The above embodiments only express several implementation manners of the present application, which are described in a more specific and detailed manner, but cannot be understood as a limitation on the patent scope of the present application. It should be noted that, for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for optimizing the design parameters of a long optical path gas absorption cell, characterized in that, Includes the following steps: Based on the theoretical model of the light propagation matrix, and according to the engineering volume requirements of the long optical path gas absorption cell to be designed, the feasibility of the lens parameters of the spherical mirror is theoretically verified, and the initial lens parameters and the range of key design parameters are determined. An optical cavity model consisting of two spherical mirrors was established. Based on the optical cavity model, and according to the initial lens parameters, key design parameter ranges, and preset step values, automated ray tracing simulation was performed to obtain simulation data. Based on image processing algorithms, the simulation data is verified to determine the number of light spots, and the optimal combination of key design parameters that maximizes the optical path is selected based on the number of light spots. The theoretical model of the ray propagation matrix is ​​as follows: Based on the radii of curvature of the two spherical mirrors, the transformation matrix for a ray to travel back and forth once between the two spherical mirrors is derived; assuming the ray originates from the aperture on one of the spherical mirrors and propagates towards the other spherical mirror, its initial ray angle parameters are... Then, the light ray completes one round trip between the two spherical mirrors, and its total coordinate transformation is: ； ； In the formula, The angle parameters of the light rays after one round trip are given; L is the distance between the two mirrors; R1 and R2 are the radii of curvature of the two spherical mirrors, respectively; T is the round trip matrix, and A, B, C, and D are its matrix elements.

2. The method for optimizing the design parameters of a long optical path gas absorption cell according to claim 1, characterized in that, The key design parameters include the position of the light aperture, the distance between the two mirrors, and the angle of the incident light.

3. The method for optimizing the design parameters of a long optical path gas absorption cell according to claim 2, characterized in that, The method for ray tracing simulation is as follows: First, a light-transmitting aperture is set on the first spherical mirror. Ray tracing begins at the initial distance between the two mirrors. The incident light angle is adjusted according to the range of incident light angles to ensure the incident light enters the optical cavity. After verifying the tracing of all incident light angles, the distance between the two mirrors is gradually adjusted according to a preset step value. Each time the distance between the two mirrors changes, the incident light angle must be traced using all angle parameters repeatedly until the distance between the two mirrors completes the verification of all parameters within the set range. Then, a new light-transmitting aperture position is set on the first spherical mirror. The above steps are repeated until the verification of all light-transmitting aperture positions within the first spherical mirror is completed, and the ray tracing simulation ends.

4. The method for optimizing the design parameters of a long optical path gas absorption cell according to claim 3, characterized in that, The verification of the position of the light-transmitting hole is as follows: Taking the center of the spherical reflector as the origin of the coordinate system, the spherical reflector is divided into multiple regions. Through program control, the position of a cylinder that is the difference set with the spherical reflector is adjusted by a preset step value, thereby simulating the process of opening light-transmitting holes at different positions of the spherical reflector until the preset opening range of the entire spherical reflector is covered.

5. The method for optimizing the design parameters of a long optical path gas absorption cell according to claim 3, characterized in that, The parameter tracing verification of the incident light angle is as follows: Based on different light aperture positions, the incident light angle range is set, and all incident light angles are simulated with preset step values ​​until the simulation ends. The simulation method for the incident ray angle is as follows: The position of the light-transmitting aperture is taken as the initial coordinate value of the incident ray angle. The light-transmitting aperture is circular. The incident ray is adaptively adjusted to pass through the first spherical reflector until the ray cannot pass through the first spherical reflector. The intersection of the incident ray and the first spherical reflector is a circle, and its value range is within the area of ​​the circle. Let x, y, and z be the coordinate values ​​of the incident ray, and r be the radius of the light-transmitting aperture of the spherical reflector, which is determined by the following formula. ； In the formula, x and y are the coordinates of the incident ray on the plane of the spherical mirror; z is the coordinate of the plane where the spherical mirror is located; z0 is the initial coordinate of the plane where the spherical mirror is located. The iterative formula for the range of incident ray angles is as follows: ； In the formula, The polar angle at which the light ray deviates from the optical axis; Let be the azimuth angle of the light ray around the optical axis; k and l are both constants; , This is the preset step value; The determination condition is: if the incident light ray passes through the light aperture of the first spherical mirror, then the determination result is... The result is equal to 1; if the incident light is blocked or exceeds the light aperture, the result is determined as 1. Equal to 0; The adaptive search termination condition is: if If the value is 0, then stop searching for the angle and direction of the incident ray.

6. The method for optimizing the design parameters of a long optical path gas absorption cell according to claim 3, characterized in that, The method for adjusting the distance between the two mirrors is as follows: after setting the position of the light-transmitting aperture and the angle range of the incident light, the simulation steps are completed by adjusting the distance between the two mirrors within the preset working condition requirement size range using a preset step value. The simulation method for the distance between the two mirrors is as follows: the adjustment range of the distance between the two mirrors is until the light ray cannot intersect with the second spherical mirror after passing through the first spherical mirror; the distance between the two mirrors is adaptively adjusted by judging whether the light ray intersects with the second spherical mirror; let the distance between the two mirrors be L, and define the judgment function f(L) as follows: ； Where Q1 represents the effective reflection area of ​​the first spherical mirror; Q2 represents the effective reflection area of ​​the second spherical mirror; ∩ represents the intersection symbol of sets; This indicates an empty set; if the intersection of Q1 and Q2 is not empty, it means that light can be transmitted from the first spherical mirror to the second spherical mirror for reflection. Based on this, the maximum permissible distance between the two mirrors L max Defined as: 。 7. The method for optimizing the design parameters of a long optical path gas absorption cell according to claim 6, characterized in that, The image processing algorithm involves comparing a preset background image with a simulated image in the simulation data, as detailed below: ； in: ； ； ； ； In the formula, This represents the final number of light spots; It is a set of connected components; Let A be the area of ​​the i-th connected component; min The minimum effective area threshold; This is the binarized result; This is a frame difference map; For simulated images, The preset background image; For adaptive threshold, Let k be the local mean and k be the coefficient. This represents the local standard deviation.

8. A design parameter optimization system for a long optical path gas absorption cell, used to implement the design parameter optimization method according to any one of claims 1-7, characterized in that, include: The parameter feasibility verification module is used to theoretically verify the feasibility of the lens parameters of the spherical mirror based on the theoretical model of the light propagation matrix and the engineering volume requirements of the long optical path gas absorption cell to be designed, and to determine the initial lens parameters and the range of key design parameters. The optical simulation module is used to build an optical cavity model consisting of two spherical mirrors, and based on the optical cavity model, according to the initial lens parameters, key design parameter ranges and preset step values, to perform automated ray tracing simulation and obtain simulation data. The simulation data filtering module is used to verify the simulation data based on image processing algorithms, determine the number of light spots, and filter out the optimal combination of key design parameters that maximizes the optical path based on the number of light spots.

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