Self-focusing three-dimensional annular photoelectric gas sensor probe and sensor device

Abstract

The invention discloses a self-focusing three-dimensional annular photoelectric gas sensor probe and a sensor device, comprising a three-dimensional annular concave reflection ring, which is characterized in that a section of concave circular ring containing a central cross section is cut by taking the central cross section of a hollow sphere as a centrosymmetric plane reference, and the reflection ring is fixed on a base; the base is provided with two light beam inlet and outlet through holes, and the two light beam inlet and outlet through holes are respectively provided with a plane mirror forming a 45-degree angle with the central section; a laser and a detector are arranged below the two through holes respectively, and the optical axes of the laser and the detector are both perpendicular to the central section. According to the invention, a laser light source of a light cone-shaped light beam with a very small divergence angle is adopted, and the focusing characteristic of a three-dimensional annular concave mirror is utilized, so that the light beam which is reflected for multiple times is converged on light of a detector, and a self-focusing reflection system in which the light source and the detector are focuses mutually is formed. The difficulty of adjusting the light path is reduced; and the overall design reduces the complexity of the production process, improves the production yield and is beneficial to large-scale production.

Description

Technical Field

[0001] The invention relates to the technical field of laser spectrum gas sensors, in particular to a self-focusing three-dimensional annular photoelectric gas sensor probe capable of focusing a laser beam multiple times. Background Art

[0002] Tunable diode laser absorption spectroscopy (TDLAS) technology has the advantages of high sensitivity, high selectivity, and rapid detection. In practical applications, the size of the sensor needs to be as small as possible. In the case where the size of the absorption cell is limited, in order to increase the measurement optical path length, the measurement gas chamber usually uses multiple mirrors or reflectors to reflect the light path multiple times in the gas chamber. Therefore, the main technical challenge of gas sensors based on TDLAS detection principle is how to design a gas absorption cell with a longer optical path in a limited sensor size, and how to use it for a long time in actual application scenarios with relatively harsh detection environments.

[0003] In order to increase the optical path of the absorption cell, various novel designs have been proposed. In Chinese patent CN110632008A, a spiral optical path is formed in a circular cross-section sensor head by five plane reflectors; in Chinese patent CN113406001A, two parallel reflectors are used to make the optical path undergo four reflections to achieve the purpose of extending the optical path; in Chinese patent CN108931504B, an annular multi-point reflection type photoelectric gas sensor probe is disclosed, including a two-dimensional annular multi-point light reflection ring, which is a hollow cylindrical structure. This design structure maximizes the use of the space of the absorption cell to increase the optical path length.

[0004] However, since the design uses a cylindrical structure, theoretically, in a collimated laser beam, only a small portion of the light in the middle of the beam can meet the multiple reflection conditions and eventually reach the detector, which greatly reduces the utilization rate of the detection beam light energy.

[0005] In order to make up for the shortcomings of the cylindrical reflective structure, the present invention proposes a self-focusing three-dimensional annular photoelectric gas sensor probe and sensor device solution, which can effectively use the laser beam energy while maintaining a long optical path and increases the stability of the entire optical path. Summary of the invention

[0006] In order to solve the technical problems existing in the prior Chinese patent CN108931504B, the self-focusing three-dimensional annular photoelectric gas sensor probe and sensor device of the present invention adopts two 45° plane reflectors and a reflective element with a three-dimensional annular concave reflection ring structure, which overcomes the defects of multiple separate elements in the prior art, simplifies the optical path adjustment, and makes the detection optical path very stable, solves the problems in this technical field, and makes the gas sensor more compact and efficient.

[0007] The technical solution adopted by the present invention to solve the technical problem is:

[0008] A self-focusing three-dimensional annular photoelectric gas sensor probe comprises a three-dimensional annular concave reflection ring, wherein the three-dimensional annular concave reflection ring is obtained by cutting a concave circular ring including the central section of a hollow sphere with its central section as the central symmetry plane reference, wherein the central section is parallel to the two cut surfaces, and the central section is located at the center of the two cut surfaces; a cover plate is arranged on the upper part of the three-dimensional annular concave reflection ring, and the lower part of the three-dimensional annular concave reflection ring is arranged on a base, wherein the central section of the three-dimensional annular concave reflection ring is parallel to the bottom surface of the base; a cavity formed by the three-dimensional annular concave reflection ring, the cover plate and the base is a gas absorption pool for accommodating the gas to be measured; the base is provided with two light beam inlet and outlet through holes, and a plane reflector with an angle of 45° with the central section is arranged above the two light beam inlet and outlet through holes, respectively, and a laser light source capable of emitting a light cone-shaped light beam with a very small divergence angle and a photoelectric detector are arranged below the two light beam inlet and outlet through holes, and the optical axes of the laser light source and the photoelectric detector are both perpendicular to the central section.

[0009] Furthermore, the laser light source, which forms a light cone-shaped light beam with a very small divergence angle using a parabolic concave reflector, is located below the base and outside the gas absorption cell; the laser light outlet is arranged at the focus of the parabolic concave reflector, and the laser beam is reflected by the parabolic concave reflector to form a light cone-shaped light beam with a very small divergence angle, and the light cone-shaped light beam enters the gas absorption cell through the light beam inlet and outlet through hole, and is reflected by the first 45° reflecting plane mirror, and the center line of the reflected light beam is parallel to the bottom of the gas absorption cell, and at the same time, the center line of the light beam and the center line of the three-dimensional annular concave reflection ring are parallel to each other. The cross sections overlap; after being reflected by the reflecting plane mirror, the light beam reaches the three-dimensional annular concave reflection ring and is reflected. Due to the effect of the concave mirror of the three-dimensional annular concave reflection ring, the incident light beam with a light cone shape with a very small divergence angle becomes a converging light cone and is focused at the center point of the light path between the two reflection points. Then, the light beam continues to propagate from the focusing point to the next reflection point in the form of a divergent light cone. After multiple reflections, the light cone is reflected by a second 45° reflecting plane mirror, passes through another light beam inlet and outlet through hole, and is finally focused on the photosensitive surface of the photodetector, forming a self-focusing reflection system in which the light source and the detector are mutually focused. The light beam enters the gas absorption pool from one of the light beam inlet and outlet holes, and is irradiated on the concave reflector on the inner wall of the three-dimensional annular concave reflective ring in a pre-designed direction; the center line of the light beam and the normal line at the reflection point of the three-dimensional annular concave reflective ring have a set incident angle, so that the light beam can be reflected multiple times on the concave reflective mirror surface of the three-dimensional annular concave reflective ring; when the incident light beam is reflected by the concave reflector of the three-dimensional annular concave reflective ring, under the action of the reflector of the three-dimensional annular concave reflective ring, this light beam in the shape of a light cone with a very small divergence angle is focused at the center of the light path between the two reflection points, and then after passing through the focusing point, the light beam continues to propagate to the next reflection point in the form of a divergent light cone, and continues to be reflected multiple times by the concave reflector of the three-dimensional annular concave reflective ring.

[0010] Taking the example of five reflections as a specific explanation, the light beam from the laser outlet to the first reflection point on the inner wall of the three-dimensional annular concave reflection ring is designed to be a light cone-shaped light beam (light cone 1) with a very small divergence angle. When the light cone 1 enters the gas absorption cell through a light beam inlet and outlet hole at the bottom of the gas absorption cell, it is then reflected by the first 45° plane reflector, and then reflected by the concave reflector of the three-dimensional annular concave reflection ring for the first time, it is focused at the center of the light path between the first and second reflection points in the gas absorption cell, and then irradiated on the concave mirror on the inner wall of the three-dimensional annular concave reflection ring in the shape of a light cone (light cone 2), and a second reflection is generated; after the second reflection of the light cone 2 by the concave mirror, it is between the second and third reflection points in the gas absorption cell. The light beam of light cone 3 is focused at the center of the optical path between the third and fourth reflection points in the gas absorption pool, and then irradiates the concave mirror on the inner wall of the three-dimensional annular concave reflection ring in the form of a light cone (light cone 3), and produces a third reflection; after the fourth reflection of the light beam of light cone 3 by the concave mirror, it is focused at the center of the optical path between the third and fourth reflection points in the gas absorption pool, and then irradiates the concave mirror on the inner wall of the three-dimensional annular concave reflection ring in the form of a light cone (light cone 4), and produces a fourth reflection; after the fifth reflection of the light beam of light cone 4 by the concave mirror on the inner wall of the three-dimensional annular concave reflection ring, it is reflected by the second 45° reflector to reflect the center line of the light beam into a beam perpendicular to the bottom of the gas absorption pool, which is refocused through another beam in and out through hole at the bottom of the absorption pool and focused on the photosensitive surface of the photodetector. Therefore, the conical light beam emitted from the laser is reflected by the spherical reflector on the inner wall of the circular ring, undergoes five reflections, and is also converged five times, and is focused on the photosensitive surface measured by the photodetector at the last convergence.

[0011] In order to make full use of the limited size of the gas absorption cell, this three-dimensional circular multi-point reflection gas chamber can also be designed into a multiple reflection structure of seven reflections, nine reflections, etc., provided that the two 45° mirrors of the laser beam, i.e., the entrance and exit mirrors, do not block other reflected light beams in the gas absorption cell.

[0012] Compared with the cylindrical reflective ring in Chinese patent CN108931504B, it has the following positive effects:

[0013] 1. Since the laser light outlet and the detector photosensitive surface are the convergence points or foci of each other's light cones, the light spot obtained by the detector is insensitive to changes in the direction of the light emitted by the laser.

[0014] 2. Since a parabolic concave reflector is used in the laser to form a light cone with a very small divergence angle, there is no lens in the entire detection optical path, thus effectively avoiding the interference noise caused by the reflection of the lens surface, thereby improving the measurement accuracy of the detection system.

[0015] 3. Due to the three-dimensional spherical reflection, the light energy in the light cone will be transferred to the photosensitive surface of the photodetector through focusing, and multiple reflections will not cause a significant reduction in the energy of the light beam.

[0016] 4. Since all spherical reflections are generated in the same reflection ring, that is, a three-dimensional annular concave reflection ring, the relative positions of each reflecting sphere are fixed, so the stability of the entire optical path is very good.

[0017] 5. Since the design is a ring-shaped self-focusing optical path, the adjustment of the optical path is very simple and easy during the production process.

[0018] Specifically, the basic optical structure of the laser light source capable of emitting a light cone-shaped light beam with a very small divergence angle includes a laser chip and a parabolic concave reflector. The light outlet of the laser chip is arranged at the focus of the parabolic concave reflector. The angle between the center line of the light cone emitted by the laser and the optical axis reflected by the parabolic concave reflector is 90°. The laser beam is reflected by the parabolic concave reflector to form a light cone-shaped light beam with a very small divergence angle.

[0019] Furthermore, the number of reflections of the light beam in the three-dimensional annular concave reflection ring is determined by the inner diameter of the three-dimensional annular concave reflection ring and the incident angle of the center line of the incident light cone of the light beam on the three-dimensional annular concave reflection ring; the number of reflections determines the total measurement optical path length of the light beam in the three-dimensional annular concave reflection ring, and the number of multi-point reflections includes five, seven, nine or more reflections.

[0020] Furthermore, the inner wall of the three-dimensional annular concave reflection ring is electroplated with a reflection coating film and a protective film.

[0021] Specifically, the cover plate is provided with a plurality of ventilation holes, and the gas to be measured diffuses from the ventilation holes into the gas absorption cell through the air inlet plug; the inner wall of the cover plate is coated with a black coating for reducing reflected light.

[0022] Specifically, the base is provided with a through hole, in which a temperature and pressure sensor for measuring the temperature and pressure in the gas absorption cell is installed.

[0023] Specifically, the three-dimensional annular concave reflection ring is made of metal, plastic or synthetic material, and is formed by machining or precision injection molding; the inner wall of the three-dimensional annular concave reflection ring is mirror-optically polished and coated with a reflective film to form an arc reflective mirror surface, or the inner wall of the three-dimensional annular concave reflection ring is pasted with reflective material to form an arc reflective mirror surface.

[0024] Furthermore, a cylinder is arranged at the center of the base, and according to the corresponding five-times, seven-times or nine-times reflected light paths, five, five or nine sector-shaped solid blocks are arranged at positions where no light beam passes, so as to reduce the total volume of the gas absorption cell.

[0025] Another technical solution of the present invention is to provide a self-focusing three-dimensional annular photoelectric gas sensor device, including the above-mentioned self-focusing three-dimensional annular photoelectric gas sensor probe, an upper part of the shell with an air inlet plug, a PCB for processing photoelectric signals, and a lower part of the shell with a wire through hole.

[0026] The present invention will be further described below in conjunction with the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the structure of the self-focusing three-dimensional annular photoelectric gas sensor probe.

[0028] Figure 2 Schematic diagram of a circular ring containing a central cross section cut from a hollow sphere.

[0029] Figure 3 A schematic diagram of a light beam that uses a parabolic concave reflector to form a light cone with a very small divergence angle.

[0030] Figure 4 (a) and (b) are schematic diagrams of the beam direction of a three-dimensional annular concave reflection ring with five reflections.

[0031] Figure 5 (a) and (b) are schematic diagrams of the beam direction of a three-dimensional annular concave reflection ring with seven reflections.

[0032] Figure 6 (a) and (b) are schematic diagrams of the beam direction of a three-dimensional annular concave reflection ring with nine reflections.

[0033] Figure 7 This is a schematic diagram of the structure of a self-focusing three-dimensional annular photoelectric gas sensor device.

[0034] Among them, 10-self-focusing three-dimensional annular photoelectric gas sensor probe; 120-three-dimensional annular concave reflection ring; 122-central section; 124-cutting surface; 130-base; 131-temperature and pressure sensor through hole; 140-plane reflector; 150-fan-shaped solid block; 160-solid cylinder; 20-upper part of the shell; 21-air inlet plug; 30-PCB; 40-lower part of the shell; 41-wire through hole; 50-light cone-shaped light beam with a very small divergence angle; 51-laser COC; 52-TEC; 53-parabolic concave reflector. DETAILED DESCRIPTION

[0035] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0036] It should be emphasized that the following detailed description is illustrative only, and the specific structure and features of the self-focusing three-dimensional annular photoelectric gas sensor probe and sensor device are described, and should not constitute any limitation on the present invention. The description here is only used to explain the design of the three-dimensional annular new type of the present invention, and is not used to limit the design of the present invention. At the same time, any of the technical features mentioned below (including implicit or disclosed), as well as those directly displayed or implicitly included in Figures 1 to 7 Any technical feature in the present invention may be combined or deleted between these technical features (or their equivalents) to form more other embodiments that may not be directly or indirectly mentioned in the present invention. Unless otherwise specified, all technical and scientific terms used in this document have the same meanings as those commonly understood by ordinary technicians in the technical field to which this application belongs.

[0037] See also Figures 1 to 7 , the self-focusing three-dimensional annular photoelectric gas sensor probe 10 and the sensor device are explained in combination with the working principle. The self-focusing three-dimensional annular photoelectric gas sensor device includes a self-focusing three-dimensional annular photoelectric gas sensor probe 10, an upper shell part 20 with an air inlet plug 21, a PCB 30 for processing photoelectric signals, and a lower shell part 40 with a wire through hole 41. The self-focusing three-dimensional annular photoelectric gas sensor probe 10 and the PCB 30 are arranged in the upper shell part 20 and the lower shell part 40 of the sensor device, thereby forming a sensor device that can perform gas detection, such as Figure 7 shown.

[0038] Among them, the self-focusing three-dimensional annular photoelectric gas sensor probe 10 is provided as follows Figure 2 The three-dimensional annular concave reflection ring 120 is shown as a concave reflection mirror. Figure 4-Figure 6 shown.

[0039] like Figure 2As shown, the three-dimensional annular concave reflection ring 120 is a concave ring including a central section 122 cut out of a hollow sphere with its central section 122 as the central symmetry plane reference, the central section 122 is parallel to the two cut surfaces 124, and the central section 122 is located at the center of the two cut surfaces 124, so the two cut surfaces 124 are the same size and symmetrical with respect to the central section 122. It should be pointed out that if the two cut surfaces are of different sizes or asymmetrical with respect to the central section, the incident light beam will deviate from the central section after multiple reflections, which will affect the consistency of the light path and cause difficulties in adjusting the light path during the production process.

[0040] The inner wall of the three-dimensional annular concave reflection ring 120 is electroplated with a reflection coating film and a protective film.

[0041] The upper part of the three-dimensional annular concave reflection ring 120 is provided with a cover plate, and the lower part is fixed on a cylindrical base 130. The cavity formed by the three-dimensional annular concave reflection ring 120, the cover plate and the base 130 is a gas absorption cell for accommodating the gas to be measured. The cover plate and the base 130 respectively overlap with the two cut surfaces 124, so that the central section 122 of the three-dimensional annular concave reflection ring 120 is parallel to the bottom surface of the base 130. The bottom surface of the base 130 is the bottom of the gas absorption cell.

[0042] The base 130 is provided with two light beam inlet and outlet holes and a temperature and pressure sensor hole 131. A plane reflector 140 with an angle of 45° to the base 130 is respectively arranged above the two light beam through holes inside the gas absorption cell and located on the base 130; a laser and a photodetector are respectively arranged below the base 130, and their optical axes are perpendicular to the base 130.

[0043] In the sensor probe, the laser light outlet is regarded as a focus and is set at the focus of the parabolic concave reflector 53, such as Figure 3As shown, the laser beam is reflected by the parabolic concave reflector 53 to form a light cone shaped light beam 50 with a very small divergence angle. The light beam from the laser light outlet to the first reflection point on the inner wall of the three-dimensional annular concave reflector 120 is designed to be a light cone shaped light beam 50 with a very small divergence angle. The light beam emitted from the laser light outlet passes through the light beam inlet and outlet through hole at the bottom of the absorption pool and enters the absorption pool, and then is reflected by the first 45° plane reflector 140. The center line of the reflected light beam is parallel to the bottom of the absorption pool. At the same time, the center line of the light beam coincides with the center section 122 of the circular ring, and is irradiated on the three-dimensional annular concave reflector 120 in a pre-designed direction. On the inner wall; the center line of the light beam and the normal line at the reflection point of the three-dimensional annular concave reflection ring 120 have a set incident angle, so that the light beam can be reflected multiple times on the concave mirror formed by the three-dimensional annular concave reflection ring 120; when the incident light beam is reflected by the three-dimensional annular concave reflection ring 120, due to the effect of the concave mirror of the annular arc reflection mirror surface, the incident light beam in the shape of a light cone with a very small divergence angle becomes a converging light cone and focuses on the center point of the light path between the two reflection points, and then the light beam continues to propagate from the focusing point to the next reflection point in the form of a divergent light cone, and is reflected multiple times by the three-dimensional annular concave reflection ring 120, such as Figures 4 to 6 As shown, until it is finally reflected by the second 45° plane reflector 140, the reflected light beam passes through another light beam in and out through hole at the bottom of the gas absorption cell and is focused onto the photosensitive surface of the photodetector, forming a self-focusing reflection system in which the light source and the detector are the foci of each other.

[0044] It should be pointed out that if the light beam emitted from the laser is not a divergent light beam with a small divergence angle before the first reflection, but a focused light beam, then under the reflection of the concave mirror on the annular arc reflector surface, it cannot converge between the two reflection points, and thus multiple reflections cannot be achieved.

[0045] The three-dimensional optical path design of the present invention not only greatly increases the stability of the optical path, but also simplifies the entire optical path adjustment process.

[0046] In order to reduce the total volume of the gas absorption cell, a fan-shaped solid block 150 can be arranged in the space where no light beam passes through the inner side of the three-dimensional annular concave reflection ring 120. For example, for a gas absorption cell that generates five reflections on the three-dimensional reflection ring, five fan-shaped solid blocks 150 are arranged at positions where no light beam passes through. Figure 4 (b) As shown; for the gas absorption cell that generates 7 reflections on the three-dimensional reflection ring, 7 fan-shaped solid blocks 150 are respectively set at the positions where no light beam passes, such as Figure 5(b) As shown; for the gas absorption cell that generates 9 reflections on the three-dimensional reflection ring, 9 fan-shaped solid blocks 150 are respectively set at the positions where no light beam passes, such as Figure 6 (b) as shown.

[0047] According to a further preferred technical solution, the laser light source may be a low-power vertical cavity surface emitting laser (VCSEL) or a DFB laser.

[0048] A further preferred technical solution is that the light beam is emitted from the laser light outlet, and after being reflected by the parabolic concave reflector 53, a light beam 50 with a very small divergence angle is formed, and after being reflected by the first 45° plane reflector 140, the light beam reaching the first reflection point of the three-dimensional annular concave reflector ring 120 forms a light cone, which is reflected multiple times, and then reflected by the second 45° plane reflector 140, passes through the light beam in and out of the through hole of the base 130, and finally focuses on the photosensitive surface of the photodetector, forming a self-focusing reflection system in which the light source and the detector are mutually focused. This not only greatly increases the stability of the optical path, but also simplifies the process of adjusting the entire optical path.

[0049] In a further preferred technical solution, the number of reflections of the light beam in the three-dimensional annular concave reflection ring 120 is determined by the inner diameter of the three-dimensional annular concave reflection ring 120 and the incident angle of the center line of the incident light cone of the light beam on the three-dimensional annular concave reflection ring 120. The number of reflections determines the total measurement optical path length of the light beam in the three-dimensional annular concave reflection ring 120, and the number of multi-point reflections includes five, seven, nine or more reflections.

[0050] According to a further preferred technical solution, a solid cylinder 160 is disposed at a position in the center of the three-dimensional annular concave reflection ring 120 where no light passes, so as to further reduce the total volume of the absorption pool.

[0051] According to a further preferred technical solution, the cover plate is provided with a plurality of ventilation holes, and the gas to be measured is filtered through powder metallurgy sintering and then diffused into the gas absorption pool through the ventilation holes.

[0052] According to a further preferred technical solution, the inner wall of the cover plate is coated with a black coating for reducing reflected light.

[0053] According to a further preferred technical solution, the base 130 of the gas absorption cell is provided with a through hole, in which a temperature and pressure sensor for measuring the temperature and pressure in the gas absorption cell is installed.

[0054] According to a further preferred technical solution, the three-dimensional annular concave reflection ring 120 is made of metal, plastic or synthetic material, and the three-dimensional annular concave reflection ring 120 is formed by machining or precision injection molding.

[0055] In a further preferred technical solution, the inner wall of the three-dimensional annular concave reflection ring 120 is optically polished and coated with a reflection film to form a three-dimensional arc reflection mirror surface, and a mirror protection layer is added. Or the inner wall of the three-dimensional annular concave reflection ring 120 is pasted with a reflective material to form an arc reflection mirror surface.

[0056] According to a further preferred technical solution, the laser light source is connected to its driving circuit, and the photodetector is connected to the signal processing circuit.

[0057] The self-focusing three-dimensional annular photoelectric gas sensor probe of the present invention adopts a three-dimensional annular concave reflection ring of a single optical element, which reduces the possibility of changes in the relative positions of various elements and improves the stability of the optical path system.

[0058] The present invention uses a parabolic concave reflector to collimate the divergent light beam of the laser into a light beam in the shape of a light cone with a very small divergence angle. Therefore, no lens is used in the entire detection light path, which effectively avoids the interference noise caused by the reflection of the lens surface, thereby improving the measurement accuracy of the detection system.

[0059] The present invention increases the total detection optical path in the gas absorption cell through multiple light beam reflections of the three-dimensional annular concave reflection ring, which is beneficial to improving the detection signal-to-noise ratio and measurement accuracy; the volume of the sensor probe is reduced by the three-dimensional annular concave reflection ring, thereby reducing the measurement response time.

[0060] The present invention adopts a laser light source with a light cone shape with a very small divergence angle, and utilizes the focusing characteristics of a three-dimensional annular concave mirror to converge the light beam after multiple reflections on the photoelectric detector light, thereby forming a self-focusing reflection system in which the light source and the detector are the focus of each other, thereby reducing the difficulty of adjusting the light path; the overall invention design reduces the complexity of the production process and improves the production yield, so as to facilitate large-scale production.

[0061] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A self-focusing three-dimensional annular photoelectric gas sensor probe, characterized in that: The invention comprises a three-dimensional annular concave reflection ring, wherein the three-dimensional annular concave reflection ring is obtained by cutting a concave circular ring including the central section of a hollow sphere with its central section as the central symmetry plane reference, wherein the central section is parallel to the two cut surfaces, and the central section is located at the center of the two cut surfaces; a cover plate is arranged on the upper part of the three-dimensional annular concave reflection ring, and the lower part of the three-dimensional annular concave reflection ring is arranged on a base, wherein the central section of the three-dimensional annular concave reflection ring is parallel to the bottom surface of the base; a cavity formed by the three-dimensional annular concave reflection ring, the cover plate and the base is a gas absorption cell for accommodating the gas to be measured; the base is provided with two light beam inlet and outlet through holes, and a plane reflector with an angle of 45° with the central section is arranged above the two light beam inlet and outlet through holes respectively, and a laser light source capable of emitting a light cone-shaped light beam with a very small divergence angle and a photoelectric detector are arranged below the two light beam inlet and outlet through holes respectively, and the optical axes of the laser light source and the photoelectric detector are perpendicular to the central section respectively.

2. The self-focusing three-dimensional annular photoelectric gas sensor probe according to claim 1, characterized in that: The laser light source, which forms a light cone-shaped light beam with a very small divergence angle by a parabolic concave reflector, is located below the base and outside the gas absorption cell; the laser light outlet is arranged at the focus of the parabolic concave reflector, and the laser beam is reflected by the parabolic concave reflector to form a light cone-shaped light beam with a very small divergence angle, and the light cone-shaped light beam enters the gas absorption cell through the light beam inlet and outlet through hole, and is reflected by the first 45° reflecting plane mirror, and the center line of the reflected light beam is parallel to the bottom of the gas absorption cell, and at the same time, the center line of the light beam and the center cross section of the three-dimensional annular concave reflection ring are parallel to each other. Overlap; after being reflected by the reflecting plane mirror, the light beam reaches the three-dimensional annular concave reflection ring and is reflected. Due to the effect of the concave mirror of the three-dimensional annular concave reflection ring, the incident light beam with a light cone shape with a very small divergence angle becomes a converging light cone and is focused at the center point of the light path between the two reflection points. Then, the light beam continues to propagate from the focusing point to the next reflection point in the form of a divergent light cone. After multiple reflections, the light cone is reflected by a second 45° reflecting plane mirror, passes through another light beam inlet and outlet through hole, and is finally focused on the photosensitive surface of the photodetector, forming a self-focusing reflection system in which the light source and the detector are the foci of each other.

3. The self-focusing three-dimensional annular photoelectric gas sensor probe according to claim 1, characterized in that: The basic optical structure of the laser light source capable of emitting a light cone-shaped light beam with a very small divergence angle includes a laser chip and a parabolic concave reflector. The light outlet of the laser chip is arranged at the focus of the parabolic concave reflector. The angle between the center line of the light cone emitted by the laser and the optical axis reflected by the parabolic concave reflector is 90°. The laser beam is reflected by the parabolic concave reflector to form a light cone-shaped light beam with a very small divergence angle.

4. The self-focusing three-dimensional annular photoelectric gas sensor probe as claimed in claim 2, characterized in that: The number of reflections of the light beam in the three-dimensional annular concave reflection ring is determined by the inner diameter of the three-dimensional annular concave reflection ring and the incident angle of the center line of the incident light cone of the light beam on the three-dimensional annular concave reflection ring; The number of reflections determines the total measured optical path length of the light beam within the three-dimensional annular concave reflection ring, and the number of multi-point reflections includes five, seven, nine or more reflections.

5. The self-focusing three-dimensional annular photoelectric gas sensor probe according to claim 1, characterized in that: The inner wall of the three-dimensional annular concave reflection ring is electroplated with a reflection coating film and a protective film.

6. The self-focusing three-dimensional annular photoelectric gas sensor probe according to claim 1, characterized in that: The cover plate is provided with a plurality of ventilation holes, and the gas to be measured diffuses from the ventilation holes into the gas absorption pool through the air inlet plug; the inner wall of the cover plate is coated with a black coating for reducing reflected light.

7. The self-focusing three-dimensional annular photoelectric gas sensor probe according to claim 1, characterized in that: The base is provided with a through hole, in which a temperature and pressure sensor for measuring the temperature and pressure in the gas absorption cell is installed.

8. The self-focusing three-dimensional annular photoelectric gas sensor probe according to claim 1, characterized in that: The three-dimensional annular concave reflective ring is made of metal, plastic or synthetic material, and the three-dimensional annular concave reflective ring is formed by machining or precision injection molding; The inner wall of the three-dimensional annular concave reflection ring is optically polished and plated with a reflection film to form an arc reflection mirror surface, or the inner wall of the three-dimensional annular concave reflection ring is pasted with a reflection material to form an arc reflection mirror surface.

9. The self-focusing three-dimensional annular photoelectric gas sensor probe according to claim 1, characterized in that: A cylinder is arranged at the center of the base, and five, five or nine sector-shaped solid blocks are arranged at positions where no light beam passes, respectively, according to the corresponding five-times, seven-times or nine-times reflected light paths, so as to reduce the total volume of the gas absorption cell.

10. A self-focusing three-dimensional annular photoelectric gas sensor device, characterized in that: It comprises the self-focusing three-dimensional annular photoelectric gas sensor probe as described in any one of claims 1 to 9, an upper shell portion with an air inlet plug, a PCB for processing photoelectric signals, and a lower shell portion with a wire through hole.

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