Corrosion-resistant multi-reflection gas absorption cell

Abstract

The invention belongs to photoelectric detection, and particularly relates to a corrosion-resistant multi-reflection gas absorption cell which comprises a shell, and a first reflector and a second reflector which are arranged in the shell, the first reflector and the second reflector are plano-convex lenses, the plane of the first reflector and the plane of the second reflector are oppositely arranged and serve as transmission faces, and the convex face of the first reflector and the convex face of the second reflector are oppositely arranged and serve as reflection faces. The gas sensor has the advantages of strong anti-interference capability, long service life and the like, and is applied to low-concentration and ultra-low-concentration gas measurement.

Description

Technical Field

[0001] The invention relates to photoelectric detection, and in particular to a corrosion-resistant multiple-reflection gas absorption cell. Background Art

[0002] When the internal temperature or pressure changes, the structural parts of the traditional Herriott cavity that fix the two end mirrors are prone to deformation, causing the reflective surface connected to it to be affected by stress. The parallelism between the two reflective surfaces is very likely to change, affecting the position or angle of the emitted light, thereby causing a large change in the light intensity signal.

[0003] In addition, the reflection surface of the Herriott cavity is directly exposed to the measurement gas, and the corrosive gas components and dust may contaminate or damage the reflection surface of the reflector, causing the output light intensity to weaken or disappear, affecting the normal use of the gas chamber. Summary of the invention

[0004] In order to solve the deficiencies in the above-mentioned prior art solutions, the present invention provides a corrosion-resistant multiple-reflection gas absorption cell.

[0005] The objective of the present invention is achieved through the following technical solutions: A corrosion-resistant multiple-reflection gas absorption cell comprises a shell and a first reflector and a second reflector arranged in the shell; the first reflector and the second reflector are plano-convex lenses, the plane of the first reflector and the plane of the second reflector are arranged opposite to each other and serve as transmission surfaces, and the convex surface of the first reflector and the convex surface of the second reflector are arranged back to back and serve as reflection surfaces.

[0006] Compared with the prior art, the present invention has the following beneficial effects: 1. Strong anti-interference ability; A pressure ring is arranged on the plane of the reflector in contact with the gas, so as to fix the reflector, and the gas to be measured does not contact the reflective surface, thereby improving the anti-interference ability of the multiple reflection gas absorption cell in complex application environments, and reducing the structural stress influence on the cavity mirror (i.e., the first reflector and the second reflector) when the temperature and pressure in the gas chamber change rapidly, which is conducive to expanding the application range of the multiple reflection gas absorption cell; The gas to be measured does not contact the reflective surface, and the reflective mirror is corrosion-resistant, which reduces the probability of cleaning or replacing the cavity mirror due to sample gas or dust, increases the service life of the gas absorption cell, and is more suitable for long-term continuous use; 2. Wide range of applications; For open cavities, this new optical gas absorption cell can be equipped with equipment such as drones for outdoor work. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The disclosure of the present invention will become easier to understand with reference to the accompanying drawings. It is easy for those skilled in the art to understand that these drawings are only used to illustrate the technical solution of the present invention and are not intended to limit the scope of protection of the present invention. In the drawings: Figure 1 It is a schematic structural diagram of a multiple reflection gas absorption cell of the present invention; Figure 2 Schematic diagram of the incident position and incident angle of the present invention; Figure 3 Schematic diagram of the emission position and emission angle of the present invention; Figure 4 is a schematic diagram of light spot distribution on the reflective convex surface in Example 2 of the present invention; Figure 5 Schematic diagram of light spot distribution on the reflective convex surface in Example 3 of the present invention.

[0008] In the accompanying drawings, 1-shell, 11-first reflector, 12-second reflector, 21-pressure ring, 111-first transmission plane, 112-first reflection convex surface, 121-second transmission plane, 122-second reflection convex surface, 123-light hole. DETAILED DESCRIPTION

[0009] Figure 1-Figure 5 The following description describes optional specific embodiments of the present invention to teach those skilled in the art how to implement and reproduce the present invention. In order to teach the technical solution of the present invention, some conventional aspects have been simplified or omitted. Those skilled in the art will understand that variations or replacements derived from these specific embodiments will be within the scope of the present invention. Those skilled in the art will understand that the following features can be combined in various ways to form multiple variations of the present invention. Thus, the present invention is not limited to the following optional specific embodiments, but is only limited by the claims and their equivalents.

[0010] Example 1.

[0011] A corrosion-resistant multiple-reflection gas absorption cell of this embodiment, such as Figure 1 As shown, including: The housing 1 has an air inlet and an air outlet.

[0012] The first reflector 11 and the second reflector 12 are arranged in the housing 1; the first reflector 11 and the second reflector 12 are plano-convex lenses, and the first transmission plane 111 of the first reflector 11 and the second transmission plane 121 of the second reflector are arranged opposite to each other. The first reflection convex surface 112 of the first reflector 11 and the second reflection convex surface 122 of the second reflector are arranged back to back. The second reflector 12 has a light hole 123 that allows incident light and outgoing light to pass through.

[0013] In order to increase the number of reflections to improve the optical path, further, an anti-reflection film layer is provided on the first transmission plane 111 and the second transmission plane 121, and a reflective film layer is provided on the first reflection convex surface 112 and the second reflection convex surface 122, so that the transmittance of the first transmission plane 111 and the second transmission plane 121 is greater than 99%, and the reflectivity of the first reflection convex surface 112 and the second reflection convex surface 122 is greater than 99%.

[0014] In order to conveniently couple incident light of different wavelengths into the gas absorption cell, the incident light position and angle and the position and angle of the emitted light satisfy: , ; , , , .

[0015] like Figure 2 As shown, r0 is the distance between the incident point of the incident light on the second reflecting convex surface 122 and the system optical axis z, and θ0 is the angle between the incident light and the system optical axis z.

[0016] like Figure 3 As shown, r n is the distance between the exit point of the exit light on the second reflecting convex surface 122 and the system optical axis z, θ n is the angle between the outgoing light and the system optical axis z. The system optical axis z is collinear with the two central axes of the first reflector 11 and the second reflector 12.

[0017] R is the radius of curvature of the convex surface of the first reflector 11 and the second reflector 12, L is the mirror distance between the first reflector 11 and the second reflector 12, n1 is the refractive index of the gas between the first reflector 11 and the second reflector 12, n2 is the refractive index of the first reflector 11 and the second reflector 12, and n is the number of round trips of the incident light in the first reflector 11 and the second reflector 12. All parameters are in international units.

[0018] In order to fix the first reflector 11 and the second reflector 12 and reduce the influence of the measured gas on the reflective surface, a pressure ring 21 is further provided on the plane side of the first reflector 11 and the second reflector 12 .

[0019] Example 2.

[0020] An application example of the corrosion-resistant multiple-reflection gas absorption cell in Example 1 of the present invention.

[0021] In this application example, Figure 1As shown, in the housing 1 , the first transmission plane 111 of the first reflector 11 is opposite to the second transmission plane 121 of the second reflector 12 , and the first reflection convex surface 112 of the first reflector 11 is opposite to the second reflection convex surface 122 of the second reflector 12 .

[0022] The first reflector 11 and the second reflector 12 use the same plano-convex lens, that is, the reflective convex surface has the same curvature radius, and the mirror distance is similar to the curvature radius. According to the wavelength of the incident light beam, an internal reflection dielectric film is plated on the first reflective convex surface 112 and the second reflective convex surface 122, and the reflectivity is greater than 99%; an anti-reflection film is plated on the first transmission plane 111 and the second transmission plane 121, and the transmittance is greater than 99.6%.

[0023] A pressure ring 21 is provided on the plane side of the first reflecting mirror 11 and the second reflecting mirror 12 to fix the first reflecting mirror 11 and the second reflecting mirror 12 .

[0024] The second reflector 12 has a light hole 123. The incident light beam passes through the light hole 123, then passes through the gas to be measured, is transmitted through the first transmission plane 111, and then is reflected on the first reflection convex surface 112. The light beam reflected by the first reflection convex surface 112 is transmitted through the first transmission plane 111 again, is incident on the second reflector 12, is transmitted through the second transmission plane 121, and is incident on the second reflection convex surface 122 to be reflected. The light beam is reflected multiple times between the first reflector 11 and the second reflector 12 until the light beam is emitted from the light hole 123 again and leaves the gas absorption cell.

[0025] The parameters of the gas absorption cell in this embodiment are as follows: The aperture of the first reflector 11 and the second reflector 12 are both 59 mm, the radius of curvature R are both 500 mm, the mirror distance (the distance between the two transmission planes) L=429 mm, and the central axes are collinear. The position of the light source in the xyz coordinate system is (-4.5, 31.5, -96), and the incident angle is (4.25°, 3°, 0).

[0026] like Figure 1 As shown, the xyz coordinate system is: the origin is the center point of the second reflective convex surface 122, the system optical axis is the z-axis (ie, the center axis of the first reflector 11 and the second reflector 12), the vertical upward direction is the y-axis, and the direction perpendicular to the paper surface is the x-axis.

[0027] The incident light beam is reflected 78 times in the absorption cell. Figure 4 As shown, the reflected light spots are distributed in a circular ring shape on the two reflecting convex surfaces, the number of light spots on the second reflecting convex surface 122 is 38, and the number of light spots on the first reflecting convex surface 112 is 39. The effective optical path of the system is 33 meters.

[0028] Under the premise of meeting the requirements of long optical path and high detection accuracy, the gas absorption cell can reduce the structural stress influence on the first reflector 11 and the second reflector 12, and prevent the detection gas from directly contacting the reflection surface, thereby greatly improving the stability and life of the gas chamber.

[0029] Example 3.

[0030] The application example of the corrosion-resistant multiple-reflection gas absorption cell in Example 1 of the present invention is different from that in Example 2 in that: The position of the light source in the xyz coordinate system is (-5.8, 32.4, -96), and the incident angle is (5°, 3.2°, 0). The apertures of the first reflector 11 and the second reflector 12 are 60 mm, respectively, the radius of curvature is 426.3 mm, and the mirror distance L is 402.75 mm.

[0031] The incident light beam is reflected 34 times in the absorption cell, and the effective optical path of the system is about 13.7 meters. Figure 5 As shown, the reflected light spots are distributed in a circular ring shape on the two reflecting convex surfaces.

Claims

1. A corrosion-resistant multiple-reflection gas absorption cell, comprising a shell and a first reflector and a second reflector arranged in the shell; characterized in that: The first reflector and the second reflector are plano-convex lenses. The plane of the first reflector and the plane of the second reflector are arranged opposite to each other and serve as transmission surfaces. The convex surface of the first reflector and the convex surface of the second reflector are arranged back to back and serve as reflection surfaces.

2. The multiple reflection gas absorption cell according to claim 1, characterized in that: An anti-reflection film layer is provided on the plane of the first reflector and the plane of the second reflector, and a reflective film layer is provided on the convex surface of the first reflector and the convex surface of the second reflector.

3. The multiple reflection gas absorption cell according to claim 2, characterized in that: The transmittance of the plane of the first reflector and the plane of the second reflector is greater than 99%, and the reflectance of the convex surface of the first reflector and the convex surface of the second reflector is greater than 99%.

4. The multiple reflection gas absorption cell according to claim 1, characterized in that: The first reflector has a light hole that allows incident light and outgoing light to pass through.

5. The multiple reflection gas absorption cell according to claim 1, characterized in that: Incident light position and the position of the emitted light satisfy: ， ； ， ， ， ； r0 is the distance between the incident light's point of incidence on the convex surface of the second reflector and the system optical axis, θ0 is the angle between the incident light and the system optical axis; r n is the distance between the exit point of the outgoing light on the convex surface of the second reflector and the optical axis of the system, θ n is the angle between the outgoing light and the system optical axis; the system optical axis is collinear with the central axes of the first reflector and the second reflector; R is the radius of curvature of the convex surface of the first reflector and the convex surface of the second reflector, L is the mirror distance between the first reflector and the second reflector, n1 is the refractive index of the gas between the first reflector and the second reflector, n2 is the refractive index of the first reflector and the second reflector, and n is the number of round trips of the incident light in the first reflector and the second reflector.

6. The multiple reflection gas absorption cell according to claim 1, characterized in that: Pressure rings are provided on the plane sides of the first reflector and the second reflector.

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