A hollow truncated cone-shaped multi-pass absorption tank

Abstract

The present invention proposes a hollow frustum-shaped multi-pass absorption cell, which relates to the field of gas measurement technology. The hollow frustum-shaped multi-pass absorption cell includes: a hollow circular plane mirror, a hollow circular concave spherical mirror, a hard plastic tube, two tripod mirror frames, three support rods, two window pieces, two pressing pieces, and a rubber ring. The hard plastic tube includes an inner circumference and an outer circumference. The hollow circular plane mirror and the hollow circular concave spherical mirror are respectively nested and fixed between the inner circumference and the outer circumference at both ends of the hard plastic tube and sealed with a rubber ring. The hollow frustum-shaped multi-pass absorption cell proposed by the present invention uses a special cutting method to obtain an inner diameter and an outer diameter of the hollow circular plane mirror that are smaller than the inner diameter and outer diameter of the hollow circular concave spherical mirror, thereby making high use of the mirror surface. At the same time, the hollow frustum-shaped absorption cell structure is formed by combining a specific hollow frustum-shaped hard plastic tube, so that a stable light field distribution is formed inside the absorption cell, thereby improving the mirror surface utilization rate and the gas exchange rate.

Description

Technical Field

[0001] The present invention relates to the field of gas measurement technology, and more particularly to a hollow frustum-shaped multi-pass absorption cell. Background Art

[0002] An optical multi-pass absorption cell uses mirrors or other optical elements to reflect a light beam multiple times within the cell, thereby increasing the interaction path length between the light and the gas sample, known as the effective optical path. This increased optical path length improves detection sensitivity, particularly for trace gas detection. Common absorption cell types include Herriott, White, Chernin, and annular cells. These cells utilize varying optical path structures to produce a variety of different spot distributions. Specifically, the curvature, coating quality, and arrangement of the core reflectors directly impact the detection performance of the multi-pass cell. The reflection path and spot distribution of the light beam within the multi-pass absorption cell are controlled by precisely adjusting the position and angle of the reflectors. During the detection process, the detection light within the absorption cell must be in full contact with the gas sample to ensure adequate absorption. Therefore, the design of the gas flow path is crucial for improving detection sensitivity. Currently, absorption cell design is evolving towards miniaturization and integration to accommodate the demands of portable detection equipment.

[0003] The existing absorption cells still have some problems that need to be solved. Among them, since the high-reflection mirrors used are limited by the reflectivity, the light will gradually consume the energy of the light spot when it reflects back and forth between the reflectors, resulting in the inability to complete subsequent reflections and the inability to achieve the ideal optical path. The traditional absorption cell structure mostly increases the base length of the cell itself to extend the single light transmission distance, and further extends the optical path by accumulating single distances. On the one hand, this method will increase the volume of the absorption cell and make it inconvenient to further integrate it with the system. On the other hand, it will increase the ineffective interaction space between light and gas during ventilation detection, thereby reducing the response rate of the absorption cell. In addition, because the traditional optical path structure uses concave spherical high-reflection mirrors with the same parameters, the light follows a symmetrical round-trip transmission equation when reflecting back and forth, resulting in distortion of the subsequent light spot. This increases the difficulty of the exit hole design and reduces the accuracy of the exit light spot detection, thereby affecting the entire subsequent gas concentration inversion part.

[0004] Therefore, a new multi-pass absorption cell structure is urgently needed to effectively solve the problems of spot detection accuracy, ensure the reaction rate of gas and light, and the weakening and distortion of spot energy due to multiple transmissions, so as to improve accuracy and stability and improve efficiency. Summary of the Invention

[0005] In response to the problems in the background technology, the present invention provides a hollow frustum-shaped multi-pass absorption tank to solve the defects of the multi-pass absorption tank in the prior art.

[0006] The technical solution of the present invention to solve the above technical problems is as follows:

[0007] A hollow frustum-shaped multi-pass absorption tank, comprising:

[0008] Hollow circular plane mirror, hollow circular concave spherical mirror, hard plastic tube, two tripod mirror stands, two window pieces, two pressing pieces and rubber rings,

[0009] The hard plastic tube includes an inner circumferential surface and an outer circumferential surface. The hollow circular plane mirror and the hollow circular concave spherical mirror are respectively nested and fixed between the inner circumferential surface and the outer circumferential surface at both ends of the hard plastic tube and sealed by the rubber ring. The three sides of the two tripod mirror frames are respectively provided with grooves. The three tangent points of the hollow circular plane mirror and the hollow circular concave spherical mirror are respectively fixed in the corresponding grooves through the outer circumferential surface of the hard plastic tube. The two pressing pieces respectively fix the two window pieces to the two tripod mirror frames.

[0010] Among them, the hard plastic tube is a hollow frustum, and the outer circumferential surface of the hard plastic tube is provided with an air inlet and an air outlet; the hollow circular plane mirror and the hollow circular concave spherical mirror are obtained by cutting a circular plane mirror and a circular concave spherical mirror respectively, the inner diameter of the hollow circular plane mirror is smaller than the inner diameter of the hollow circular concave spherical mirror, and the outer diameter of the hollow circular plane mirror is smaller than the outer diameter of the hollow circular concave spherical mirror.

[0011] Preferably, the multi-pass absorption cell further comprises three support rods, and threaded holes are provided at the three vertices of the two tripod frames, and the three support rods are connected to the two tripod frames through the threaded holes.

[0012] Preferably, the hollow circular plane mirror is provided with an exit hole, and the hollow circular concave spherical mirror is provided with an entrance hole.

[0013] Preferably, the design steps of the multi-pass absorption cell are as follows:

[0014] Step S1: Determine the incident parameters according to the transmission law matrix of the light reflected by the asymmetric light path. for: , where R is the radius of curvature of the circular concave spherical mirror, and d is the distance between the circular plane mirror and the circular concave spherical mirror; performing concentric ring spot distribution type simulations under multiple sets of incident parameters, and saving multiple sets of incident parameters and simulation graphs that meet the needs of subsequent experimental debugging, wherein the incident parameters include the incident angle, the incident point relative to the mirror center, and the mirror spacing;

[0015] Step S2: performing actual concentric ring light spot debugging on the cage structure based on multiple groups of incident angles, incident point positions relative to the mirror center, and mirror spacing determined by simulation;

[0016] Step S3: comparing the concentric ring light spot distribution quality of the circular plane mirror and the circular concave spherical mirror under multiple groups of concentric ring light spot distributions to determine whether there is any light spot overlap or obstruction;

[0017] Step S4: comparing the number of reflections under the multiple groups of concentric ring spot distributions to determine whether the number of reflections meets the expected optical path;

[0018] Step S5: determining the optimal incident angle, optimal incident point, and optimal mirror spacing for constructing the multi-pass absorption cell according to the light spot state and optical path of the circular plane mirror;

[0019] Step S6: cutting the circular plane mirror and the circular concave spherical mirror according to the concentric ring light spot distribution of the circular plane mirror and the circular concave spherical mirror, determining the mirror cutting size of the circular plane mirror and the circular concave spherical mirror, and removing the maximum mirror range of the circular plane mirror and the circular concave spherical mirror without affecting the light transmission and the inner edge light spot distribution to obtain the inner diameter and outer diameter of the hollow circular plane mirror, and the inner diameter and outer diameter of the hollow circular concave spherical mirror;

[0020] Step S7: designing the multi-pass absorption cell according to the optimal incident angle, the optimal incident point, the optimal mirror spacing, and the mirror cutting dimensions of the circular plane mirror and the circular concave spherical mirror.

[0021] Preferably, the specific steps of cutting the circular plane mirror and the circular concave spherical mirror according to the concentric ring spot distribution of the circular plane mirror and the circular concave spherical mirror are as follows:

[0022] Step S61: calculating the total energy of each light spot based on the concentric ring light spots from the innermost circle to the outermost circle on the circular plane mirror and the circular concave spherical mirror, and comparing the light spots with high energy;

[0023] Step S62: Record the polar coordinates of all the strong energy light spots on the circular plane mirror relative to the mirror surface distribution points. The polar coordinate corresponding to the m-th strong energy light spot is marked as (r, θ m ), where the radial distance r in the polar coordinates is a fixed value, θ m The polar angle of the mth strong energy light spot relative to the mirror distribution point is represented by m, which is a positive integer greater than or equal to 1. The polar coordinates of the first fixed reference point are set to (0, θ0). The distribution distance L between all the strong energy light spots on the circular plane mirror relative to the first fixed reference point is calculated. m , ;

[0024] Step S63: Record the polar coordinates (ri ,θ i ), where i is a positive integer greater than or equal to 1, r i Indicates the radial distance of the i-th strong energy light spot relative to the mirror distribution point, θ i The polar angle of the i-th strong energy light spot relative to the mirror distribution point is expressed. The polar coordinates of the second fixed reference point are set to (r0, θ0). The distribution distance L between all the strong energy light spots on the circular concave spherical mirror and the second fixed reference point is calculated. i , ;

[0025] Step S64: The distribution distance L m and the distribution distance L i Compare and sort out the distribution positions of the innermost circle and the outermost circle, and select the distribution distance L m The minimum value L m-min , the distribution distance L i The minimum value L i-min and the distribution distance L m The maximum value L m-max , the distribution distance L i The maximum value L i-max ;

[0026] Step S65: L m-min Determined as the inner diameter of the hollow circular plane mirror, L m-max Determine the outer diameter of the hollow circular plane mirror, and set L i-min Determine the inner diameter of the hollow circular concave spherical mirror, L i-max Determined as the outer diameter of the hollow circular concave spherical mirror.

[0027] The beneficial effects of the present invention are:

[0028] (1) The concave spherical mirror and the plane mirror form an asymmetric optical path structure. A complete round trip of the optical path in the multi-pass absorption cell includes: from the concave spherical mirror to the plane mirror, and then to the concave spherical mirror. After the light spot is reflected by the concave spherical mirror, a special convergence effect is produced on the plane mirror, thereby increasing the light spot energy and improving the optical path.

[0029] (2) The special asymmetric optical path structure makes each independent light spot produce a convergent light spot with inconsistent light spot distribution range on the plane mirror and the concave spherical mirror. Through the different types of concentric ring light spot distribution on the plane mirror and the concave spherical mirror, the special characteristics of the reflected light trajectory are utilized to cut the range without light spot distribution and without affecting the path of the reflected light trajectory in the center of the two mirrors, eliminating the ineffective interaction space between light and gas, so that the reflected light can fully interact with the gas to be measured, thereby improving the response rate of the absorption cell;

[0030] (3) The inner and outer diameters of the hollow circular plane mirror obtained by a special cutting method are both smaller than those of the hollow circular concave spherical mirror, which makes full use of the mirror surface. At the same time, a hollow frustum-shaped multi-pass absorption pool structure is formed by combining a specific hollow frustum-shaped hard plastic tube, so that a stable light field distribution is formed inside the multi-pass absorption pool, thereby improving the mirror surface utilization rate and gas exchange rate.

[0031] (4) The hollow circular plane mirror and the hollow circular concave spherical mirror are respectively nested and fixed between the inner and outer circumferences of the two ends of the hard plastic tube and sealed with rubber rings, which improves the sealing effect and sensitivity;

[0032] (5) Two different fixed reference points are set, and the distribution distances between multiple groups of strong energy light spots from the innermost circle to the outermost circle on the circular plane mirror and the circular concave spherical mirror and the two different fixed reference points are calculated respectively. The minimum distance value is determined as the inner diameter, and the maximum distance value is determined as the outer diameter. The maximum degree of invalid mirror cutting is performed without affecting the emission range of the selected strong energy light spots, thereby improving the cutting accuracy and efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to make the present invention more easily understood, the present invention will be described in more detail with reference to the specific embodiments shown in the accompanying drawings. These drawings only depict typical embodiments of the present invention and should not be considered as limiting the scope of protection of the present invention.

[0034] Figure 1 It is a structural schematic diagram of a hollow frustum-shaped multi-pass absorption tank provided by an embodiment of the present invention.

[0035] Reference numerals:

[0036] 1-Hollow circular plane mirror, 2-Hollow circular concave spherical mirror, 3-Input hole, 4-Output hole, 5-Hard plastic tube, 6-Air inlet, 7-Air outlet, 8-Rubber ring, 9-Triangular mirror frame, 10-Support rod, 11-Groove, 12-Window piece, 13-Pressure piece, 14-Threaded hole. DETAILED DESCRIPTION

[0037] The following describes the embodiments of the present invention with reference to the accompanying drawings so that those skilled in the art can better understand the present invention and implement it. However, the enumerated embodiments do not limit the present invention. In the absence of conflict, the following embodiments and technical features of the embodiments may be combined with each other, wherein the same components are represented by the same reference numerals. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0038] The present invention proposes a hollow truncated cone-shaped multi-pass absorption tank. Figure 1 , Figure 1It is a structural schematic diagram of a hollow frustum-shaped multi-pass absorption tank provided by an embodiment of the present invention.

[0039] See also Figure 1 In the embodiment of the present invention, the hollow frustum-shaped multi-pass absorption cell includes: a hollow circular plane mirror 1, a hollow circular concave spherical mirror 2, a hard plastic tube 5, two tripod mirror frames 9, three support rods 10, two window pieces 12, two pressing pieces 13 and a rubber ring 8.

[0040] The hard plastic tube 5 includes an inner circumference and an outer circumference. The hollow circular plane mirror 1 and the hollow circular concave spherical mirror 2 are respectively nested and fixed between the inner circumference and the outer circumference at both ends of the hard plastic tube 5 and sealed with a rubber ring 8. The three sides of the two tripod frames 9 are each provided with a groove 11. The contact parts of the outer circumference of the hard plastic tube 5 and the hollow circular plane mirror 1 and the hollow circular concave spherical mirror 2 are respectively fixed in the corresponding grooves 11 along the tangential direction. The three vertices of the two tripod frames 9 are each provided with a threaded hole 14. The three support rods 10 are connected to the two tripod frames 9 through the threaded holes. Two pressing pieces 13 respectively fix the two window pieces 12 to the two tripod frames 9.

[0041] Among them, the hard plastic tube 5 is a hollow frustum, and the outer surface of the hard plastic tube 5 is provided with an air inlet 6 and an air outlet 7; the hollow circular plane mirror 1 and the hollow circular concave spherical mirror 2 are cut from a circular plane mirror and a circular concave spherical mirror respectively, the inner diameter of the hollow circular plane mirror 1 is smaller than the inner diameter of the hollow circular concave spherical mirror 2, and the outer diameter of the hollow circular plane mirror 1 is smaller than the outer diameter of the hollow circular concave spherical mirror 2.

[0042] The triangular mirror frame 9 and support rods 10 are used to secure the entire absorption cell structure, ensuring a stable optical path. A window 12 is placed outside the two mirrors and at a specific angle to ensure that incoming light is not affected by reflections from the window 12. A plurality of threaded holes 14 are provided on the pressing plate 13 to secure the window 12 to the triangular mirror frame 9, further ensuring a tight seal.

[0043] It is worth noting that most of the existing multi-pass absorption pools are cylindrical structures with a low gas exchange rate; in the embodiments of the present invention, the multi-pass absorption pool is hollow frustum-shaped, and the hollow circular plane mirror and the hollow circular concave spherical mirror are respectively nested and fixed between the inner circumference and outer circumference of the two ends of the hard plastic tube and sealed with rubber rings. The inner diameter and outer diameter of the hollow circular plane mirror obtained by a special cutting method are both smaller than the inner diameter and outer diameter of the hollow circular concave spherical mirror, which makes high use of the mirror surface. At the same time, combined with a specific hollow frustum-shaped hard plastic tube, a hollow frustum-shaped multi-pass absorption pool structure is formed, so that a stable light field distribution is formed inside the absorption pool, thereby improving the mirror surface utilization and gas exchange rate.

[0044] In another embodiment of the present invention, the design steps of the multi-pass absorption cell are as follows:

[0045] Step S1: Determine the incident parameters according to the transmission law matrix of the light reflected by the asymmetric light path. for: , where R is the radius of curvature of the circular concave spherical mirror, and d is the distance between the circular plane mirror and the circular concave spherical mirror; perform concentric ring spot distribution type simulation under multiple sets of incident parameters, and save multiple sets of incident parameters and simulation diagrams that meet the needs of subsequent experimental debugging. The incident parameters include the incident angle, the incident point relative to the mirror center, and the mirror spacing;

[0046] In step S1, the derivation process of the transmission matrix equation of the reflected light of the asymmetric optical path is as follows: Assume that the radius of curvature of the circular concave spherical mirror is R, and the vertex, that is, the center point of the mirror surface, is located at a certain point on the optical axis. The circular plane mirror can be regarded as a mirror with an infinite radius of curvature and an infinite focal length. Assume that the circular plane mirror and the circular concave spherical mirror are placed parallel to each other, and the distance between the two is d. When propagating from the circular concave spherical mirror to the circular plane mirror, the light starts from the circular concave spherical mirror and propagates a distance d to the circular plane mirror. The reflection matrix of the circular plane mirror can be regarded as a "plane" reflection. A complete round trip includes: from the concave spherical mirror to the plane mirror, and then to the concave spherical mirror. In this way, the total transmission law matrix can be obtained.

[0047] Step S2: performing actual concentric ring light spot debugging on the cage structure based on multiple groups of incident angles, incident point positions relative to the mirror center, and mirror spacing determined by simulation;

[0048] Step S3: comparing the concentric ring light spot distribution quality of the circular plane mirror and the circular concave spherical mirror under multiple sets of concentric ring light spot distribution to determine whether there is any light spot overlap or obstruction;

[0049] Step S4: comparing the number of reflections under the multiple groups of concentric ring spot distributions to determine whether the number of reflections meets the expected optical path;

[0050] Step S5: Determine the optimal incident angle, optimal incident point, and optimal mirror spacing for constructing the absorption cell based on the light spot state and optical path of the circular plane mirror;

[0051] Step S6: Cutting the circular plane mirror and the circular concave spherical mirror according to their concentric ring spot distributions, determining the mirror cutting sizes of the circular plane mirror and the circular concave spherical mirror, and removing the maximum mirror surface range of the circular plane mirror and the circular concave spherical mirror without affecting light transmission and inner edge spot distribution to obtain the inner diameter and outer diameter of the hollow circular plane mirror 1, and the inner diameter and outer diameter of the hollow circular concave spherical mirror 2;

[0052] Step S7: Design a multi-pass absorption cell based on the optimal incident angle, the optimal incident point, the optimal mirror spacing, and the mirror cutting dimensions of the circular plane mirror and the circular concave spherical mirror.

[0053] The specific steps of cutting the circular plane mirror and the circular concave spherical mirror according to the concentric ring spot distribution of the circular plane mirror and the circular concave spherical mirror are as follows:

[0054] Step S61: Calculate the total energy of each light spot based on the concentric ring light spots from the innermost circle to the outermost circle on the circular plane mirror and the circular concave spherical mirror, and compare the light spots with high energy;

[0055] The concentric rings of light have multiple high-energy spots from the innermost to the outermost rings. The total energy of each spot is calculated based on the spot radius and the initial spot intensity or the peak intensity at the center of the spot. The initial spot intensity or the peak intensity at the center of the spot can be measured by a power meter. High-energy spots are determined by setting an energy threshold, such as those with a peak energy greater than 50%. Determining high-energy spots based on the total energy of each spot is a prior art method and will not be further described.

[0056] Step S62: Record the polar coordinates of all the strong energy light spots on the circular plane mirror relative to the mirror surface distribution points. The polar coordinate corresponding to the m-th strong energy light spot is marked as (r, θ m ), where the radial distance r in polar coordinates is a fixed value, θ m It represents the polar angle of the mth strong energy light spot relative to the mirror distribution point, where m is a positive integer greater than or equal to 1, m=1,2,3..., the polar coordinates of the first fixed reference point are set to (0, θ0), and the distribution distance L between all the strong energy light spots on the circular plane mirror relative to the first fixed reference point is calculated. m , ;

[0057] Step S63: Record the polar coordinates (r i ,θ i ), where i is a positive integer greater than or equal to 1, i=1,2,3……, r i Indicates the radial distance of the i-th strong energy light spot relative to the mirror distribution point, θ i Represents the polar angle of the i-th strong energy light spot relative to the mirror distribution point. The polar coordinates of the second fixed reference point are set to (r0, θ0). The distribution distance L between all the strong energy light spots on the circular concave spherical mirror relative to the second fixed reference point is calculated. i , ;

[0058] Step S64: Set the distribution distance L mand distribution distance L i Compare and sort the distribution positions of the innermost circle and the outermost circle, and select the distribution distance L m The minimum value L m-min , distribution distance L i The minimum value L i-min and distribution distance L m The maximum value L m-max , distribution distance L i The maximum value L i-max ;

[0059] Step S65: L m-min Determine the inner diameter of the hollow circular plane mirror 1, L m-max Determine the outer diameter of the hollow circular plane mirror 1, and set L i-min Determine the inner diameter of the hollow circular concave spherical mirror 2, L i-max Determined as the outer diameter of the hollow circular concave spherical mirror 2.

[0060] In another embodiment of the present invention, the uncut hollow circular concave spherical mirror 2 has a diameter of 50.8 mm and a focal length of 100. The uncut hollow circular plane mirror 1 also has a diameter of 50.8 mm. An entrance aperture 3 is provided on the hollow circular concave spherical mirror 2, measuring 1.5 mm and located 18 mm from the center of the reflector. An exit aperture 4 is provided on the hollow circular plane mirror 1.

[0061] The present invention adopts a concave spherical mirror and a plane mirror to form an asymmetric optical path structure. A complete round trip of the optical path in the absorption pool includes: from the concave spherical mirror to the plane mirror, and then to the concave spherical mirror, so that the light spot produces a special convergence effect on the plane mirror after being reflected by the concave spherical mirror, thereby increasing the light spot energy and improving the optical path; the special asymmetric optical path structure enables each independent light spot to produce a convergent light spot with inconsistent light spot distribution range on the plane mirror and the concave spherical mirror, through the different types of concentric ring light spot distribution on the plane mirror and the concave spherical mirror, using the particularity of the reflected light trajectory, cutting the center of the two mirrors without light spot distribution and without affecting the reflection The range of the light trajectory path eliminates the ineffective interaction space between light and gas, allowing the reflected light to fully interact with the gas to be measured, thereby improving the response rate of the absorption cell; in particular, the present invention sets two different fixed reference points, and respectively calculates the distribution distances between multiple groups of strong energy light spots from the innermost circle to the outermost circle on the circular plane mirror and the circular concave spherical mirror and the two different fixed reference points, and respectively determines the minimum distance value as the inner diameter and the maximum distance value as the outer diameter, thereby performing the maximum degree of ineffective mirror cutting without affecting the emission range of the selected strong energy light spot, thereby improving the cutting accuracy and efficiency.

[0062] The various embodiments of the present invention are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0063] The embodiments described above are merely preferred embodiments of the present invention. The phrases "in one embodiment," "in another embodiment," "in yet another embodiment," or "in other embodiments" used in this specification may refer to one or more of the same or different embodiments of the present disclosure. Any common changes and substitutions made by those skilled in the art within the scope of the present invention are intended to be encompassed within the scope of protection of the present invention.

Claims

1. A hollow truncated cone-shaped multi-pass absorption tank, characterized in that: include: Hollow circular plane mirror, hollow circular concave spherical mirror, hard plastic tube, two tripod mirror stands, two window pieces, two pressing pieces and rubber rings, The hard plastic tube includes an inner circumferential surface and an outer circumferential surface. The hollow circular plane mirror and the hollow circular concave spherical mirror are respectively nested and fixed between the inner circumferential surface and the outer circumferential surface at both ends of the hard plastic tube and sealed by the rubber ring. The three sides of the two tripod mirror frames are respectively provided with grooves. The three tangent points of the hollow circular plane mirror and the hollow circular concave spherical mirror are respectively fixed in the corresponding grooves through the outer circumferential surface of the hard plastic tube. The two pressing pieces respectively fix the two window pieces to the two tripod mirror frames. In which, the hard plastic tube is a hollow frustum, and an air inlet and an air outlet are provided on the outer circumference of the hard plastic tube; the hollow circular plane mirror and the hollow circular concave spherical mirror are obtained by cutting a circular plane mirror and a circular concave spherical mirror respectively, and the circular plane mirror and the circular concave spherical mirror are cut according to the concentric ring light spot distribution of the circular plane mirror and the circular concave spherical mirror. The inner diameter of the hollow circular plane mirror is smaller than the inner diameter of the hollow circular concave spherical mirror, and the outer diameter of the hollow circular plane mirror is smaller than the outer diameter of the hollow circular concave spherical mirror.

2. The hollow truncated cone-shaped multi-pass absorption tank according to claim 1, characterized in that: The multi-pass absorption cell further comprises three support rods. Threaded holes are provided at the three vertices of the two tripod frames, and the three support rods are connected to the two tripod frames via the threaded holes.

3. The hollow truncated cone-shaped multi-pass absorption tank according to claim 2, characterized in that: The hollow circular plane mirror is provided with an exit hole, and the hollow circular concave spherical mirror is provided with an entrance hole.

4. The hollow truncated cone-shaped multi-pass absorption tank according to any one of claims 1 to 3, characterized in that: The design steps of the multi-pass absorption cell are as follows: Step S1: Determine the incident parameters according to the transmission law matrix of the light reflected by the asymmetric light path. for: , where R is the radius of curvature of the circular concave spherical mirror, and d is the distance between the circular plane mirror and the circular concave spherical mirror; performing concentric ring spot distribution type simulations under multiple sets of incident parameters, and saving multiple sets of incident parameters and simulation graphs that meet the needs of subsequent experimental debugging, wherein the incident parameters include the incident angle, the incident point relative to the mirror center, and the mirror spacing; Step S2: performing actual concentric ring light spot debugging on the cage structure based on multiple groups of incident angles, incident point positions relative to the mirror center, and mirror spacing determined by simulation; Step S3: comparing the concentric ring light spot distribution quality of the circular plane mirror and the circular concave spherical mirror under multiple groups of concentric ring light spot distributions to determine whether there is any light spot overlap or obstruction; Step S4: comparing the number of reflections under the multiple groups of concentric ring spot distributions to determine whether the number of reflections meets the expected optical path; Step S5: determining the optimal incident angle, optimal incident point, and optimal mirror spacing for constructing the multi-pass absorption cell according to the light spot state and optical path of the circular plane mirror; Step S6: cutting the circular plane mirror and the circular concave spherical mirror according to the concentric ring light spot distribution of the circular plane mirror and the circular concave spherical mirror, determining the mirror cutting size of the circular plane mirror and the circular concave spherical mirror, and removing the maximum mirror range of the circular plane mirror and the circular concave spherical mirror without affecting the light transmission and the inner edge light spot distribution to obtain the inner diameter and outer diameter of the hollow circular plane mirror, and the inner diameter and outer diameter of the hollow circular concave spherical mirror; Step S7: designing the multi-pass absorption cell according to the optimal incident angle, the optimal incident point, the optimal mirror spacing, and the mirror cutting dimensions of the circular plane mirror and the circular concave spherical mirror.

5. The hollow truncated cone-shaped multi-pass absorption tank according to claim 4, characterized in that: The specific steps of cutting the circular plane mirror and the circular concave spherical mirror according to the concentric ring spot distribution of the circular plane mirror and the circular concave spherical mirror are as follows: Step S61: calculating the total energy of each light spot based on the concentric ring light spots from the innermost circle to the outermost circle on the circular plane mirror and the circular concave spherical mirror, and comparing the light spots with high energy; Step S62: Record the polar coordinates of all the strong energy light spots on the circular plane mirror relative to the mirror surface distribution points. The polar coordinate corresponding to the m-th strong energy light spot is marked as (r, θ m ), where the radial distance r in the polar coordinates is a fixed value, θ m The polar angle of the mth strong energy light spot relative to the mirror distribution point is represented by m, which is a positive integer greater than or equal to 1. The polar coordinates of the first fixed reference point are set to (0, θ0). The distribution distance L between all the strong energy light spots on the circular plane mirror relative to the first fixed reference point is calculated. m , ; Step S63: Record the polar coordinates (r i ,θ i ), where i is a positive integer greater than or equal to 1, r i Indicates the radial distance of the i-th strong energy light spot relative to the mirror distribution point, θ i The polar angle of the i-th strong energy light spot relative to the mirror distribution point is expressed. The polar coordinates of the second fixed reference point are set to (r0, θ0). The distribution distance L between all the strong energy light spots on the circular concave spherical mirror and the second fixed reference point is calculated. i , L i = ; Step S64: The distribution distance L m and the distribution distance L i Compare and sort out the distribution positions of the innermost circle and the outermost circle, and select the distribution distance L m The minimum value L m-min , the distribution distance L i The minimum value L i-min and the distribution distance L m The maximum value L m-max , the distribution distance L i The maximum value L i-max ; Step S65: L m-min Determined as the inner diameter of the hollow circular plane mirror, L m-max Determine the outer diameter of the hollow circular plane mirror, and set L i-min Determine the inner diameter of the hollow circular concave spherical mirror, L i-max Determined as the outer diameter of the hollow circular concave spherical mirror.

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