CN117740682A - W-shaped foldback type multi-way absorption tank and manufacturing method thereof - Google Patents
W-shaped foldback type multi-way absorption tank and manufacturing method thereof Download PDFInfo
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Abstract
The invention discloses a W-shaped foldback type multi-way absorption tank and a manufacturing method thereof, and belongs to the technical field of underground pipeline searching. Comprises a first concave mirror, a second concave mirror and a reflecting mirror. The concave inclination angle of the concave mirror is used for cutting and splicing to form a three-mirror system, the ratio of the major axis to the minor axis of an elliptical light spot falling on the reflecting mirror for the first time is changed by adjusting the distance between an input light source and the reflecting mirror, 3 elliptical light spots distributed on the periphery of the reflecting mirror can be generated, the ratio of the major axis to the minor axis of the elliptical light spot is more than 3, the utilization rate of the mirror surface is high, the total optical path length is long, and the detection sensitivity is high; the W-shaped foldback light path can be debugged through the fixed diaphragm, the debugging and the assembly are simple, the stability is strong, the light path is longer, and the volume is smaller under the same detection precision; in addition, the absorption tank does not need to be added with a corner mirror, and the structure is simpler.
Description
Technical Field
The invention relates to the technical field of laser absorption spectrum, in particular to a W-shaped foldback type multi-pass absorption tank and a manufacturing method thereof.
Background
The laser absorption spectrum technology has the advantages of high sensitivity, high resolution, non-contact and real-time performance, has important application value in the aspect of atmospheric trace gas monitoring as an advanced means of gas detection, and when the absorption spectrum technology is applied to trace gas detection, the absorption spectrum of molecules on a given optical path is measured to identify the molecules and determine the concentration of absorbing substances. At present, an optical multipass cell is widely applied to a tunable diode laser absorption spectrum technology, and can realize a longer optical path in a relatively smaller volume, the optical multipass cell generally consists of two or more high-reflectivity reflectors and corresponding mechanical fixing structures, and the reflectors in the multipass cell need to be adjusted to ensure that a light beam enters the multipass cell through a hole on one reflector and exits from an incident hole or another hole after a specific back and forth reflection times.
The common multi-way pool at present comprises a traditional Hospital pool, a white pool with an angle mirror, a Herriott pool and an astigmatic mirror pool. The traditional white type multi-way pool consists of three reflecting mirrors, and can realize multiple reflection in the multi-way pool and form two rows of light spot distribution on the mirror surface of the field mirror at most, but the design has certain defects such as large volume, low effective utilization rate of the mirror surface and the like, and limits the application range of the white pool. The light rays can meet the back and forth reflection condition of the white pool again by adding the angle mirrors, so that the light spot distribution of the multiple of the traditional white pool is generated, the mirror surface area is further utilized, but the increased light spot row number is related to the number of the angle mirrors, and the problems of difficult assembly, complex light path adjustment and the like of the angle mirrors are caused under the condition of the angle mirrors.
The Herriott type multi-way pool consists of two spherical reflectors, the optical system is compact in structure, elliptical light spot distribution can be formed on the mirror surface, but no light spot distribution exists in the middle range of the mirror surface, so that the cavity mirror area is not effectively utilized. The discrete mirror multipass cell overcomes the defects of the traditional Herriott multipass cell, effectively utilizes the cavity mirror area, can form the light spot distribution of Lissajous figures on the mirror surface, but the focal length of the discrete mirror lens in the x and y directions is different, and the discrete mirror lens does not belong to the traditional spherical mirror processing, so the cost is high, and the consistency is lower.
Aiming at the defects, the invention mainly provides a W-shaped foldback type multi-way absorption tank and a manufacturing method thereof. The concave inclination angle of the concave mirror is used for cutting and splicing to form a three-mirror system, the ratio of the major axis to the minor axis of an elliptical light spot falling on the reflecting mirror for the first time is changed by adjusting the distance between an input light source and the reflecting mirror, 3 elliptical light spots distributed on the periphery of the reflecting mirror can be generated, the ratio of the major axis to the minor axis of the elliptical light spot is more than 3, the utilization rate of the mirror surface is high, the total optical path length is long, and the detection sensitivity is high; the W-shaped foldback light path can be debugged through the fixed diaphragm, so that the debugging and the assembly are simple, and the stability is strong; by the design of the W-shaped foldback light path, the light path is longer, and the volume is smaller under the same detection precision; the angle mirror is not required to be added, and the structure is simple; in addition, the absorption tank is rectangular in shape, is better fixed in the detection instrument and has high space utilization rate.
Disclosure of Invention
In order to solve the above problems, a W-shaped foldback type multi-pass absorption cell and a method for manufacturing the same are provided. Comprises a first concave mirror, a second concave mirror and a reflecting mirror. The concave inclination angle of the concave mirror is used for cutting and splicing to form a three-mirror system, the ratio of the major axis to the minor axis of an elliptical light spot falling on the reflecting mirror for the first time is changed by adjusting the distance between an input light source and the reflecting mirror, 3 elliptical light spots distributed on the periphery of the reflecting mirror can be generated, the ratio of the major axis to the minor axis of the elliptical light spot is more than 3, the utilization rate of the mirror surface is high, the total optical path length is long, and the detection sensitivity is high; the W-shaped foldback light path can be debugged through the fixed diaphragm, the debugging and the assembly are simple, the stability is strong, the light path is longer, and the volume is smaller under the same detection precision; the angle mirror is not required to be added, and the structure is simple.
A W-shaped foldback type multi-pass absorption tank comprises a multi-pass absorption tank; the multi-way absorption tank comprises a first concave mirror, a second concave mirror and a reflecting mirror; the concave mirror I is provided with a round hole for inputting and outputting light; the first concave mirror, the second concave mirror and the reflecting mirror have the same curvature; the first concave mirror and the second concave mirror are spliced on the same plane in a double-combined way and are parallel to the rectangular base on the right side of the reflecting mirror; the distance D between the first concave mirror, the second concave mirror and the reflecting mirror and the specific incidence angle of the light are determined through light matrix transmission calculation.
Preferably, the light enters the multipass absorption tank through a round hole on the first concave mirror after being collimated according to a specific incident angle, and combines with a tiny inclination angle of the first concave mirror to enable a light spot falling on the reflecting mirror for the first time to be elliptical, and at the moment, the distance between the first concave mirror, the second concave mirror and the reflecting mirror is adjusted to be D, so that a long axis of the elliptical light spot of the first falling point on the reflecting mirror is formed: short axis >3; after being reflected for several times by the first concave mirror and the second concave mirror, the elliptical light spots generate 3 uniform and staggered elliptical light spots on the reflecting mirror to form a W-shaped foldback type multi-pass absorption pool, and finally, the light after being reflected for several times is output to the photoelectric detector through a round hole on the first concave mirror, thereby realizing high-sensitivity detection of the concentration of the gas to be detected.
Preferably, the first concave mirror, the second concave mirror and the reflecting mirror are all made of K9 glass with concave surfaces coated with a high-reflectivity film with the reflectivity of more than 99.5%.
Preferably, the first concave mirror, the second concave mirror and the reflecting mirror are made of traditional spherical concave reflecting mirrors.
Preferably, the spacing between the 3 elliptical light spots on the reflector is 10-40mm.
Preferably, the steps of the ray matrix transmission calculation are as follows:
step S1: in free space, light is transmitted along a straight line, and the coordinates of the point A are assumed to be%x1, θ1) The coordinates of the point B are%x2, θ2) R is the spherical curvature radius of the concave mirror; the number of the components in the x1,θ1 and 1x2，θ2 is:
；
step S2: the relation in the first step is arranged into a matrix form:
step S3: light rayThe propagation process in the reflecting cavity is regarded as a beam of lightx0、y0、x0′、y0') state from first incidence of concave mirror to first incidence of concave mirrornWhen the secondary reflector is used, the position of the light ray is #x n 、y n ) The same as when first incident; namely to achievex0、y0、x0′、yThe light in 0') state enters the multipass absorption tank and is reflected by the spherical surfaces of the first concave mirror, the second concave mirror and the reflecting mirror to obtain output light rays [ ]x n 、y n 、x n ′、y n ') expressed as a matrix:
step S4: solving the equation in the step 3 to obtain:
wherein,；
step S5: forming a closed elliptic light spot to be output from a round hole on the concave mirror I, meeting the requirement of 2μπ=NθLet n=2 (2μ+1), simultaneous determination:
wherein,θthe incidence angle is the incidence angle when light enters the multi-pass absorption cell through the round hole of the concave mirror I;
step S6: the distance D=d between the cut concave mirror I, the cut concave mirror II and the reflecting mirrord 2 /d 1 ) Whereind 2 ：d 1 To cut ratio ofExamples are shown.
Preferably, the concave mirror one and the concave mirror two are pressed along the long side by 1:2 proportion cutting.
Preferably, the bases of the first concave mirror, the second concave mirror and the reflecting mirror are rectangular.
Preferably, the multi-pass absorption cell is in a cuboid shape of 8 x 10 x 30cm, and the total optical path of the light after multiple reflections in the multi-pass absorption cell is 100m.
Preferably, the manufacturing method of the W-shaped foldback type multi-way absorption tank comprises the following steps:
step 1: grinding and polishing a concave mirror with a rectangular base, and pressing 1 along the long side: 2, cutting the light beam into a first rectangular concave mirror and a second rectangular concave mirror in proportion, and forming a round hole for inputting and outputting light at the center of the first concave mirror;
step 2: plating high-reflectivity films with reflectivity of more than 99.5% on the concave surfaces of the first concave mirror and the second concave mirror in the step 1 to finish the manufacturing of the first concave mirror and the second concave mirror;
step 3: manufacturing a reflecting mirror with the same curvature as the first concave mirror and the second concave mirror and the area similar to the sum of the first concave mirror and the second concave mirror according to the steps 1 and 2;
step 4: determining the distance D between the first concave mirror, the second concave mirror and the reflecting mirror through light matrix transmission calculation;
step 5: the first concave mirror and the second concave mirror are spliced on the same plane in a double mode, are parallel to the rectangular base on the right side of the reflecting mirror, and are fixed on a sliding rail perpendicular to the rectangular base of the reflecting mirror through glue or welding means, the reflecting mirror can move linearly along the sliding rail, and the first concave mirror and the second concave mirror are fixed through a fixed diaphragm;
step 6: 4 planes between the first concave mirror, the second concave mirror and the reflecting mirror are arranged and supplemented to form the multi-way absorption pool with the openable cover.
Preferably, the method for debugging and spectrum detection of the W-shaped foldback type multi-pass absorption tank comprises the following steps:
step 1: the light enters the multi-way absorption tank through the round hole of the first concave mirror according to a specific incident angle, and the light spots falling on the reflecting mirror for the first time are elliptical by combining the tiny inclination angle of the concave mirror;
step 2: and adjusting the distance between the first concave mirror, the second concave mirror and the reflecting mirror to be D, so that the long axis of the elliptical light spot at the first falling point on the reflecting mirror is formed: short axis >3;
step 3: after the elliptic light spots are reflected for a plurality of times by the first concave mirror and the second concave mirror, 3 uniform elliptic light spots which are staggered are generated on the reflecting mirror to form a W-shaped foldback type multi-pass absorption pool, and finally, the light rays after the repeated reflection are output to the photoelectric detector through the round hole on the first concave mirror;
step 4: the photoelectric detector converts the collected optical signals into electric signals and outputs the electric signals to the signal processing module, and the concentration of the gas to be detected is demodulated by the signal processing module.
By adopting the technical scheme, the invention has the following beneficial effects.
(1) The invention uses the concave dip angle of the concave mirror itself to cut and splice into a three-mirror system, can produce 3 elliptical light spots distributed on the periphery of the reflecting mirror, and forms a W-shaped light path for the light to turn back and forth in the cavity of the absorption cell, the utilization rate of the lens is high, a longer light path can be realized in the same space, and the detection sensitivity is higher.
(2) The invention is based on the principle of a Herriott absorption cell, the larger the ratio of the long axis to the short axis is, the higher the mirror surface utilization rate is, the longer the total optical path is, and the higher the detection sensitivity is. The invention changes the ratio of the major axis to the minor axis of the elliptical light spot falling on the reflecting mirror for the first time by adjusting the distance between the input light source and the reflecting mirror, the ratio of the major axis to the minor axis of the elliptical light spot is more than 3, the mirror surface utilization rate is high, the total optical path length is long, and the detection sensitivity is high.
(3) The three-mirror system of the invention uses the traditional spherical concave reflecting mirror with the same focal length, the manufacturing process is mature, and compared with an image scattering pool, the three-mirror system has low processing cost and high manufacturing precision.
(4) Compared with a white absorption tank, the invention has the advantages that the W-shaped foldback light path can be debugged through the fixed diaphragm, the debugging difficulty is low, the stability is strong, and the debugging and the assembly are simple.
(5) The absorption tank is rectangular in shape, is better fixed in a detection instrument, and has high space utilization rate; the design of the W-shaped foldback light path has longer light path and smaller volume under the same detection precision; the angle mirror is not required to be added, and the structure is simple.
Drawings
The making and using of the preferred embodiments of the present invention are discussed in detail below. It should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are provided to illustrate the manner of making and using the invention and are not intended to limit the scope of the invention, as other figures can be made from these figures by one of ordinary skill in the art without undue burden.
Fig. 1 is a schematic structural view of the present invention.
FIG. 2 is a diagram of simulation results of a W-type folded optical path of the present invention.
FIG. 3 is a light matrix transmission diagram of the present invention.
Fig. 4 is a schematic diagram of an elliptical spot distribution simulation of the present invention.
Wherein, the first 101-concave mirror, the second 102-concave mirror and the 201-reflecting mirror.
Detailed Description
The making and using of the preferred embodiments of the present invention are discussed in detail below. It should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not limit the scope of the invention.
A W-shaped foldback type multi-pass absorption tank and a manufacturing method thereof are provided, wherein the W-shaped foldback type multi-pass absorption tank comprises a multi-pass absorption tank; the multi-pass absorption cell comprises a first concave mirror 101, a second concave mirror 102 and a reflecting mirror 201; the concave mirror I101 is provided with a round hole for light input and output; the first concave mirror 101, the second concave mirror 102 and the reflecting mirror 201 have the same curvature; the first concave mirror 101 and the second concave mirror 102 are overlapped and spliced on the same plane and are parallel to the rectangular base on the right side of the reflecting mirror 201; the distance D between the concave mirror one 101, the concave mirror two 102 and the reflecting mirror 201 and the specific incident angle of the light are determined by the light matrix transmission calculation.
The light enters the multipass absorption tank through a round hole on the first concave mirror 101 after being collimated according to a specific incident angle, and combines with the tiny inclination angle of the first concave mirror to enable the light spot falling on the reflecting mirror 201 for the first time to be elliptical, and at the moment, the distance between the first concave mirror 101, the second concave mirror 102 and the reflecting mirror 201 is adjusted to be D, so that the long axis of the elliptical light spot falling on the reflecting mirror 201 for the first time is: short axis >3; after the elliptical light spots are reflected for several times by the first concave mirror 101 and the second concave mirror 102, 3 uniform elliptical light spots which are staggered are generated on the reflecting mirror 201 to form a W-shaped foldback type multi-pass absorption pool, and finally, the light rays after multiple reflections are output to a photoelectric detector through a round hole on the first concave mirror 101, so that the high-sensitivity detection of the concentration of the gas to be detected is realized.
The first concave mirror 101, the second concave mirror 102 and the reflecting mirror 201 are all made of K9 glass with concave surfaces coated with a high-reflectivity film with the reflectivity of more than 99.5%. The first concave mirror 101, the second concave mirror 102 and the reflecting mirror 201 are made of a conventional spherical concave reflecting mirror 201. The spacing between the 3 elliptical spots on the mirror 201 is 10-40mm.
The light matrix transmission calculation is as follows.
Step S1: in free space, light is transmitted along a straight line, and the coordinates of the point A are assumed to be%x1, θ1) The coordinates of the point B are%x2, θ2) R is the spherical curvature radius of the concave mirror; the number of the components in the x1,θ1 and 1x2，θ2 is:
。
step S2: the relation in the first step is arranged into a matrix form:
。
step S3:the light beam is regarded as a beam of light during the transmission process of the reflecting cavityx0、y0、x0′、y0') state from concave mirror one 101 to the firstnThe position of the light ray is as shown in the sub-mirror 201x n 、y n ) The same as when first incident; namely to achievex0、y0、x0′、y0') light enters the multipass absorption tank, and is reflected by the spherical surfaces of the first concave mirror 101, the second concave mirror 102 and the reflecting mirror 201 to obtain output light rays [x n 、y n 、x n ′、y n ') expressed as a matrix:
。
step S4: solving the equation in the step 3 to obtain:
wherein,。
step S5: form a closed elliptical light spot to be output from a round hole on the concave mirror one 101, which satisfies 2μπ=NθLet n=2 (2μ+1), simultaneous determination:
wherein,θis the incident angle of light rays entering the multi-pass absorption cell through the round hole of the concave mirror one 101.
Step S6: the distance d=d between the cut concave mirror one 101, the concave mirror two 102 and the reflecting mirror 201d 2 /d 1 ) Whereind 2 ：d 1 Is the cutting ratio.
The concave mirror one 101 and the concave mirror two 102 are pressed along the long side by 1:2 proportion cutting. The bases of the first concave mirror 101, the second concave mirror 102 and the reflecting mirror 201 are rectangular. The multi-pass absorption cell is in a cuboid shape of 8 x 10 x 30cm, and the total optical path of the light rays after multiple reflections in the multi-pass absorption cell is 100m.
A manufacturing method of a W-shaped foldback type multi-way absorption tank comprises the following steps.
Step 1: grinding and polishing a concave mirror with a rectangular base, and pressing 1 along the long side: 2 is cut into a first rectangular concave mirror 101 and a second rectangular concave mirror 102 in proportion, and a round hole for light input and output is formed in the center of the first concave mirror 101.
Step 2: the concave surfaces of the concave mirror one 101 and the concave mirror two 102 in the step 1 are coated with a high-reflection film with the reflectivity of more than 99.5%, so that the manufacturing of the concave mirror one 101 and the concave mirror two 102 is completed.
Step 3: the mirror 201 having the same curvature as the first concave mirror 101 and the second concave mirror 102 and an area similar to the sum of the first concave mirror 101 and the second concave mirror 102 is manufactured according to steps 1 and 2.
Step 4: the distance D between the concave mirror one 101, the concave mirror two 102 and the reflecting mirror 201 is determined by the light matrix transmission calculation.
Step 5: the first concave mirror 101 and the second concave mirror 102 are overlapped and spliced on the same plane and are parallel to the right rectangular base of the reflecting mirror 201, the reflecting mirror 201 is fixed on a sliding rail perpendicular to the rectangular base of the reflecting mirror 201 through glue or welding means, the reflecting mirror 201 can move linearly along the sliding rail, and the first concave mirror 101 and the second concave mirror 102 are fixed through a fixed diaphragm.
Step 6: 4 planes between the first concave mirror 101, the second concave mirror 102 and the reflecting mirror 201 are arranged and supplemented, so that the openable multi-pass absorption cell is formed.
A debugging and spectrum detection method of a W-shaped foldback type multi-pass absorption tank comprises the following steps.
Step 1: the light enters the multi-way absorption cell through the round hole of the first concave mirror 101 according to a specific incident angle, and combines with the tiny inclination angle of the concave mirror, so that the light spot falling on the reflecting mirror 201 for the first time is elliptical.
Step 2: the distance between the first concave mirror 101, the second concave mirror 102 and the reflecting mirror 201 is adjusted to D, so that the long axis of the elliptical light spot at the first falling point on the reflecting mirror 201: short axis >3.
Step 3: after the elliptic light spots are reflected for several times by the concave mirror I101 and the concave mirror II 102, 3 uniform elliptic light spots which are staggered are generated on the reflecting mirror 201 to form a W-shaped foldback type multi-pass absorption pool, and finally, the light rays after multiple reflections are output to the photoelectric detector through the round hole on the concave mirror I101.
Step 4: the photoelectric detector converts the collected optical signals into electric signals and outputs the electric signals to the signal processing module, and the concentration of the gas to be detected is demodulated by the signal processing module.
The invention is described in further detail below with reference to fig. 1-4.
Example 1
A W-type turn-back type multi-pass absorption cell as shown in fig. 1. Comprises a first concave mirror 101, a second concave mirror 102 and a reflecting mirror 201; the concave mirror one 101 is provided with a round hole for light input and output, as shown in fig. 2. The first concave mirror 101, the second concave mirror 102 and the reflecting mirror 201 have the same curvature; the first concave mirror 101, the second concave mirror 102 and the reflecting mirror 201 are all made of K9 glass with concave surfaces coated with a high-reflectivity film with the reflectivity of more than 99.5%; the first concave mirror 101, the second concave mirror 102 and the reflecting mirror 201 are made of a traditional spherical concave reflecting mirror 201; the bases of the first concave mirror 101, the second concave mirror 102 and the reflecting mirror 201 are rectangular. The first concave mirror 101 and the second concave mirror 102 are overlapped and spliced on the same plane and are parallel to the rectangular base on the right side of the reflecting mirror 201; the concave mirror one 101 and the concave mirror two 102 are pressed along the long side by 1:2 proportion cutting. The distance D between the concave mirror one 101, the concave mirror two 102 and the reflecting mirror 201 and the specific incident angle of the light are determined by the light matrix transmission calculation.
As shown in fig. 3, the steps of the ray matrix transmission calculation are as follows.
Step S1: in free space, light is transmitted along a straight line, and the coordinates of the point A are assumed to be%x1, θ1) The coordinates of the point B are%x2, θ2) R is the spherical curvature radius of the concave mirror; the number of the components in the x1,θ1 and 1x2，θ2 is:
。
step S2: the relation in the first step is arranged into a matrix form:
。
step S3: the light beam is regarded as a beam of light during the transmission process of the reflecting cavityx0、y0、x0′、y0') state from concave mirror one 101 to the firstnThe position of the light ray is as shown in the sub-mirror 201x n 、y n ) The same as when first incident; namely to achievex0、y0、x0′、y0') light enters the multipass absorption tank, and is reflected by the spherical surfaces of the first concave mirror 101, the second concave mirror 102 and the reflecting mirror 201 to obtain output light rays [x n 、y n 、x n ′、y n ') expressed as a matrix:
step S4: solving the equation in the step 3 to obtain:
wherein,。
step S5: form a closed elliptical light spot to be output from a round hole on the concave mirror one 101, which satisfies 2μπ=NθLet n=2 (2μ+1), simultaneous determination:
wherein,θis the incident angle of light rays entering the multi-pass absorption cell through the round hole of the concave mirror one 101.
Step S6: the distance d=d between the cut concave mirror one 101, the concave mirror two 102 and the reflecting mirror 201d 2 /d 1 ) Whereind 2 ：d 1 Is the cutting ratio.
The light enters the multi-pass absorption cell through a round hole on the concave mirror one 101 according to a specific incidence angle after being collimated, the multi-pass absorption cell is in a cuboid shape of 8 x 10 x 30cm, and the total optical path length of the light in the multi-pass absorption cell after being reflected for many times is 100m. In combination with the small inclination angle of the concave mirror, the light spot falling on the reflecting mirror 201 for the first time is elliptical, and at this time, the distance between the concave mirror one 101, the concave mirror two 102 and the reflecting mirror 201 is adjusted to be D, so that the long axis of the elliptical light spot falling on the reflecting mirror 201 for the first time: short axis >3; after the elliptical light spots are reflected for several times by the first concave mirror 101 and the second concave mirror 102, 3 uniform elliptical light spots which are staggered are generated on the reflecting mirror 201 to form a W-shaped foldback type multi-pass absorption pool, and the distance between the 3 elliptical light spots on the reflecting mirror 201 is 10-40mm, as shown in fig. 4. Finally, the light after multiple reflections is output to the photoelectric detector through the round hole on the concave mirror one 101, so that high-sensitivity detection of the concentration of the gas to be detected is realized.
As described in further detail below in connection with fig. 1-4.
As shown in fig. 1, the multi-way absorption cell of the present invention is a cuboid of 8×10×30cm, and comprises a first concave mirror 101, a second concave mirror 102 and a reflecting mirror 201, wherein a circular opening for light input and output is formed in the center of the first concave mirror 101. The first concave mirror 101, the second concave mirror 102 and the reflecting mirror 201 are all made of K9 glass, and the concave surfaces of the first concave mirror 101, the second concave mirror 102 and the reflecting mirror 201 are plated with high-reflection films with the reflectivity of more than 99.5%. The present invention determines the distance D between the concave mirror 101, the concave mirror 102 and the reflecting mirror 201 and the specific incident angle of the light through the light matrix transmission calculation.
The basic principle of the scheme is based on the deformation modification of the Herriott cell, light matrix transmission calculation is utilized, and light is transmitted along a straight line in a free space. As shown in FIG. 3, the coordinates at point A are [ ]x0,θ0) The coordinates of the point B are%x1,θ1). Using the mathematical relationship in the graph, one can obtainx0，θ0 and 0x1，θThe relationship between 1 is:x1 = x0 +dθ，θ1=θ0, arranging them into a matrix form to obtain
The ray matrix substituted into the available free space region is:
according to FIG. 3, it is assumed that the point A coordinates are [ ]x1, θ1) The coordinates of the point B are%x2, θ2) R is the spherical curvature radius of the concave mirror; the number of the components in the x1,θ1 and 1x2，θ2 is:
。
the relation in the above formula is arranged into a matrix form:
。
the light ray is regarded as a beam of light ray in the transmission process of the reflecting cavityx0、y0、x0′、y0') state from concave mirror one 101 to the firstnThe position of the light ray is as shown in the sub-mirror 201x n 、y n ) The same as when first incident; namely to achievex0、y0、x0′、y0') light enters the multipass absorption tank, and is reflected by the spherical surfaces of the first concave mirror 101, the second concave mirror 102 and the reflecting mirror 201 to obtain output light rays [x n 、y n 、x n ′、y n ') expressed as a matrix:
the formula is as follows:
wherein,。
when the formed closed elliptic light spot is output from the round hole on the concave mirror one 101, the requirement of 2 is satisfiedμπ=NθLet n=2 (2μ+1), simultaneous determination:
where θ is the incident angle of light entering the multipass absorption cell through the circular hole of the concave mirror one 101.
And the distance D=d between the first concave mirror 101, the second concave mirror 102 and the reflecting mirror 201 after cuttingd 2 /d 1 ) Whereind 2 ：d 1 Is the cutting ratio.
Therefore, by utilizing the cutting and splicing combination of the concave mirrors, the original circular light spots become elliptical and the light in the cavity is repeatedly turned back to form a W-shaped turning back light path, the problems of low utilization rate of Herriott Chi Jingmian, complex debugging of a white absorption tank, high manufacturing cost of an astigmatic mirror and the like of the existing absorption tank are solved, the technical effect of realizing a longer light path in the same volume is achieved, and the detection limit of an instrument is higher.
The basic idea of the invention is that the angle of the concave mirror is utilized, the concave mirrors are arranged and combined after being cut, the incident light angle is matched with the concave mirror angle, the light spots on the reflecting mirror 201 are arranged to be elliptical, meanwhile, the light falling points reflected back for the second time are arranged in a staggered way at the position 20mm below the first ellipse, the subsequent reflection is sequentially carried out until 4 elliptical area falling points are generated on the concave mirror I101 and the concave mirror II 102, 3 elliptical area falling points are generated on the reflecting mirror 201, and finally the light falling points are emitted from the opening of the concave mirror I101 after multiple reflection.
In actual manufacturing, the concave reflector base is set to be rectangular, and after grinding and polishing, the long side is subjected to the following steps: 2, cutting into a first rectangular concave mirror 101 and a second rectangular concave mirror 102 in proportion, then performing subsequent coating operation, taking the first rectangular concave mirror 101 and the second rectangular concave mirror 102 after finishing lens manufacturing, performing hole forming treatment on the center of one of the first rectangular concave mirror 101 and the second rectangular concave mirror 102, splicing the two rectangular concave mirrors, taking a rectangular concave mirror similar to the sum of the surface areas of the first concave mirror 101 and the second concave mirror 102 as a reflecting mirror 201, and forming a three-mirror reflecting cavity by the reflecting mirror 201, the first concave mirror 101 and the second concave mirror 102.
After being collimated by the collimating lens, the incident light enters the concave mirror I101 from the opening according to a specific angle, is reflected for a plurality of times, finally exits from the opening of the concave mirror I101, and is connected to the photoelectric detector. Wherein the concave mirror one 101, the concave mirror two 102 and the reflecting mirror 201 all have the same focal length f 1 The first concave mirror 101 is precisely matched with the second concave mirror 102, so that the plane of the first concave mirror 101 and the plane of the second concave mirror 102 are positioned on the same plane, the plane is in parallel relation with the rectangular base plane of the reflecting mirror 201, the fixing effects are realized by virtue of a mechanical structure, the distance between the first concave mirror 101, the second concave mirror 102 and the plane of the reflecting mirror 201 is D, and light rays are emitted from the round hole after being incident from the round hole for a plurality of times and reflected, and the period is thatThe total optical path is L, and the total optical path approaching 100m can be realized in 2400ml volume, so that the trace detection instrument has smaller volume and higher detection sensitivity.
Example 2
A manufacturing method of a W-shaped foldback type multi-way absorption tank comprises the following steps.
Step 1: grinding and polishing a concave mirror with a rectangular base, and pressing 1 along the long side: 2 is cut into a first rectangular concave mirror 101 and a second rectangular concave mirror 102 in proportion, and a round hole for light input and output is formed in the center of the first concave mirror 101.
Step 2: the concave surfaces of the concave mirror one 101 and the concave mirror two 102 in the step 1 are coated with a high-reflection film with the reflectivity of more than 99.5%, so that the manufacturing of the concave mirror one 101 and the concave mirror two 102 is completed.
Step 3: the mirror 201 having the same curvature as the first concave mirror 101 and the second concave mirror 102 and an area similar to the sum of the first concave mirror 101 and the second concave mirror 102 is manufactured according to steps 1 and 2.
Step 4: the distance D between the concave mirror one 101, the concave mirror two 102 and the reflecting mirror 201 is determined by the light matrix transmission calculation.
Step 5: the first concave mirror 101 and the second concave mirror 102 are overlapped and spliced on the same plane and are parallel to the right rectangular base of the reflecting mirror 201, the reflecting mirror 201 is fixed on a sliding rail perpendicular to the rectangular base of the reflecting mirror 201 through glue or welding means, the reflecting mirror 201 can move linearly along the sliding rail, and the first concave mirror 101 and the second concave mirror 102 are fixed through a fixed diaphragm.
Step 6: 4 planes between the first concave mirror 101, the second concave mirror 102 and the reflecting mirror 201 are arranged and supplemented, so that the openable multi-pass absorption cell is formed.
Example 3
A debugging and spectrum detection method of a W-shaped foldback type multi-pass absorption tank comprises the following steps.
Step 1: the light enters the multi-way absorption cell through the round hole of the first concave mirror 101 according to a specific incident angle, and combines with the tiny inclination angle of the concave mirror, so that the light spot falling on the reflecting mirror 201 for the first time is elliptical.
Step 2: the distance between the first concave mirror 101, the second concave mirror 102 and the reflecting mirror 201 is adjusted to D, so that the long axis of the elliptical light spot at the first falling point on the reflecting mirror 201: short axis >3.
Step 3: after the elliptic light spots are reflected for several times by the concave mirror I101 and the concave mirror II 102, 3 uniform elliptic light spots which are staggered are generated on the reflecting mirror 201 to form a W-shaped foldback type multi-pass absorption pool, and finally, the light rays after multiple reflections are output to the photoelectric detector through the round hole on the concave mirror I101.
Step 4: the photoelectric detector converts the collected optical signals into electric signals and outputs the electric signals to the signal processing module, and the concentration of the gas to be detected is demodulated by the signal processing module.
The invention is based on the principle of a Herriott absorption cell, the larger the ratio of the long axis to the short axis is, the higher the mirror surface utilization rate is, the longer the total optical path is, and the higher the detection sensitivity is. The invention changes the ratio of the major axis to the minor axis of the elliptical light spot falling on the reflecting mirror 201 for the first time by adjusting the distance between the input light source and the reflecting mirror 201, the ratio of the major axis to the minor axis of the elliptical light spot is more than 3, the mirror surface utilization rate is high, the total optical path length is long, and the detection sensitivity is high.
The invention uses the concave inclination angle of the concave mirror itself to cut and splice into a three-mirror system, can generate 3 elliptical light spots distributed on the periphery of the reflecting mirror 201, and forms a W-shaped light path for the light to turn back and forth in the cavity of the absorption cell, the utilization rate of the lens is high, a longer light path can be realized in the same space, and the detection sensitivity is higher.
Compared with a white absorption tank, the invention has the advantages that the W-shaped foldback light path can be debugged through the fixed diaphragm, the debugging difficulty is low, the stability is strong, and the debugging and the assembly are simple. The absorption tank is rectangular in shape, is better fixed in the detection instrument, and has high space utilization rate; the design of the W-shaped foldback light path has longer light path and smaller volume under the same detection precision; the angle mirror is not required to be added, and the structure is simple. In addition, the three-mirror system of the invention uses the traditional spherical concave reflecting mirror 201 with the same focal length, the manufacturing process is mature, and compared with an image scattering pool, the three-mirror system has the advantages of low processing cost and high manufacturing precision.
Although the specification has been described in detail, it should be understood that various changes, substitutions and alterations can be made hereto without departing from the spirit and scope of the invention as defined by the appended claims. Furthermore, the particular embodiments described are not intended to limit the scope of the invention, as one of ordinary skill in the art will readily appreciate from the disclosure that processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, may perform substantially the same function or achieve substantially the same result as the embodiments of the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
Claims (10)
1. A W-shaped foldback type multi-way absorption tank is characterized in that: comprises a multi-way absorption tank; the multi-way absorption tank comprises a first concave mirror, a second concave mirror and a reflecting mirror; the concave mirror I is provided with a round hole for inputting and outputting light; the first concave mirror, the second concave mirror and the reflecting mirror have the same curvature; the first concave mirror and the second concave mirror are spliced on the same plane in a double-combined way and are parallel to the rectangular base on the right side of the reflecting mirror; determining the distance D between the first concave mirror, the second concave mirror and the reflecting mirror and the specific incidence angle of the light through light matrix transmission calculation;
the light enters the multi-pass absorption tank through a round hole on the first concave mirror after being collimated according to a specific incidence angle, and combines with the tiny inclination angle of the first concave mirror, so that the light spot falling on the reflecting mirror for the first time is elliptical, and at the moment, the distance between the first concave mirror, the second concave mirror and the reflecting mirror is adjusted to D, so that the long axis of the elliptical light spot of the first falling point on the reflecting mirror is as follows: short axis >3; after being reflected for several times by the first concave mirror and the second concave mirror, the elliptical light spots generate 3 uniform and staggered elliptical light spots on the reflecting mirror to form a W-shaped foldback type multi-pass absorption pool, and finally, the light after being reflected for several times is output to the photoelectric detector through a round hole on the first concave mirror, thereby realizing high-sensitivity detection of the concentration of the gas to be detected.
2. A W-type turn-back type multi-pass absorption cell as defined in claim 1, wherein: the first concave mirror, the second concave mirror and the reflecting mirror are all made of K9 glass with concave surfaces plated with high-reflectivity films with reflectivity of more than 99.5%.
3. A W-type turn-back type multi-pass absorption cell as defined in claim 2, wherein: the first concave mirror, the second concave mirror and the reflecting mirror are made of traditional spherical concave reflecting mirrors.
4. A W-type turn-back type multi-pass absorption cell as claimed in claim 3, wherein: the spacing between the 3 elliptical light spots on the reflector is 10-40mm.
5. A W-type turn-back type multi-pass absorption cell as defined in claim 1, wherein: the light matrix transmission calculation comprises the following steps:
step S1: in free space, light is transmitted along a straight line, and the coordinates of the point A are assumed to be%x1, θ1) The coordinates of the point B are%x2, θ2) R is the spherical curvature radius of the concave mirror; the number of the components in the x1,θ1 and 1x2，θ2 is:
；
step S2: the relation in the first step is arranged into a matrix form:
step S3: the light beam is regarded as a beam of light during the transmission process of the reflecting cavityx0、y0、x0′、y0') state from first incidence of concave mirror to first incidence of concave mirrornWhen the secondary reflector is used, the position of the light ray is #x n 、y n ) The same as when first incident; namely to achievex0、y0、x0′、yThe light in 0') state enters the multipass absorption tank and is reflected by the spherical surfaces of the first concave mirror, the second concave mirror and the reflecting mirror to obtain output light rays [ ]x n 、y n 、x n ′、y n ') expressed as a matrix:
step S4: solving the equation in the step 3 to obtain:
wherein,；
step S5: forming a closed elliptic light spot to be output from a round hole on the concave mirror I, meeting the requirement of 2μπ=NθLet n=2 (2μ+1), simultaneous determination:
wherein θ is the incident angle of light entering the multi-pass absorption cell through the round hole of the concave mirror I;
step S6: the distance D=d between the cut concave mirror I, the cut concave mirror II and the reflecting mirrord 2 /d 1 ) Whereind 2 ：d 1 Is the cutting ratio.
6. A W-type turn-back type multi-pass absorption cell as defined in claim 5, wherein: the first concave mirror and the second concave mirror are pressed by 1 along the long side: 2 proportion cutting.
7. A W-type turn-back type multipass absorption cell as defined in claim 6, wherein: the bases of the first concave mirror, the second concave mirror and the reflecting mirror are rectangular.
8. A W-type turn-back type multi-pass absorption cell as defined in claim 1, wherein: the multi-pass absorption cell is in a cuboid shape of 8 x 10 x 30cm, and the total optical path of the light rays after multiple reflections in the multi-pass absorption cell is 100m.
9. A method for manufacturing a W-type turn-back type multi-way absorption cell according to any one of claims 1 to 8, characterized in that: the method comprises the following steps:
step 1: grinding and polishing a concave mirror with a rectangular base, and pressing 1 along the long side: 2, cutting the light beam into a first rectangular concave mirror and a second rectangular concave mirror in proportion, and forming a round hole for inputting and outputting light at the center of the first concave mirror;
step 2: plating high-reflectivity films with reflectivity of more than 99.5% on the concave surfaces of the first concave mirror and the second concave mirror in the step 1 to finish the manufacturing of the first concave mirror and the second concave mirror;
step 3: manufacturing a reflecting mirror with the same curvature as the first concave mirror and the second concave mirror and the area similar to the sum of the first concave mirror and the second concave mirror according to the steps 1 and 2;
step 4: determining the distance D between the first concave mirror, the second concave mirror and the reflecting mirror through light matrix transmission calculation;
step 5: the first concave mirror and the second concave mirror are spliced on the same plane in a double mode, are parallel to the rectangular base on the right side of the reflecting mirror, and are fixed on a sliding rail perpendicular to the rectangular base of the reflecting mirror through glue or welding means, the reflecting mirror can move linearly along the sliding rail, and the first concave mirror and the second concave mirror are fixed through a fixed diaphragm;
step 6: 4 planes between the first concave mirror, the second concave mirror and the reflecting mirror are arranged and supplemented to form the multi-way absorption pool with the openable cover.
10. The method for debugging and spectrum detection of a W-type foldback type multi-pass absorption cell according to claim 9, wherein the method comprises the steps of: the method comprises the following steps:
step 1: the light enters the multi-way absorption tank through the round hole of the first concave mirror according to a specific incident angle, and the light spots falling on the reflecting mirror for the first time are elliptical by combining the tiny inclination angle of the concave mirror;
step 2: and adjusting the distance between the first concave mirror, the second concave mirror and the reflecting mirror to be D, so that the long axis of the elliptical light spot at the first falling point on the reflecting mirror is formed: short axis >3;
step 3: after the elliptic light spots are reflected for a plurality of times by the first concave mirror and the second concave mirror, 3 uniform elliptic light spots which are staggered are generated on the reflecting mirror to form a W-shaped foldback type multi-pass absorption pool, and finally, the light rays after the repeated reflection are output to the photoelectric detector through the round hole on the first concave mirror;
step 4: the photoelectric detector converts the collected optical signals into electric signals and outputs the electric signals to the signal processing module, and the concentration of the gas to be detected is demodulated by the signal processing module.
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