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

Abstract

A self-focusing three-dimensional annular photoelectric gas sensor probe (10) and a sensor device. The self-focusing three-dimensional annular photoelectric gas sensor probe comprises a three-dimensional annular concave reflecting ring (120), which is a concave circular ring taken from a hollow sphere with a central section (122) as a central symmetry plane reference and including the central section (122), wherein the reflecting ring (120) is fixed on a base (130), the base (130) is provided with two beam entry and exit through holes, and a planar reflecting mirror (140) at an angle of 45°to the central section (122) is arranged above each of the beam entry and exit through holes; and one laser (51) and one detector are respectively arranged below the two through holes, and the optical axes of the two beam entry and exit through holes are both perpendicular to the central section (122). By using the laser (51) as a light source that emits a light-cone-shaped beam (50) having a very small divergence angle, and utilizing the focusing characteristics of a three-dimensional annular concave mirror, the beam subjected to multiple reflections is converged on a photosensitive surface of a detector, so as to form a self-focusing reflection system in which the light source and the detector serve as focal points for each other. The difficulty of adjusting a light path is reduced; and the overall design reduces the complexity of the production process and improves the production yield, thereby facilitating large-scale production.

Description

A self-focusing three-dimensional ring-shaped photoelectric gas sensor probe and sensor device Technical Field

[0001] This invention relates to the field of laser spectroscopy gas sensor technology, and in particular to a self-focusing three-dimensional ring photoelectric gas sensor probe capable of focusing a laser beam multiple times. Background Technology

[0002] Tunable diode laser absorption spectroscopy (TDLAS) technology boasts advantages such as high sensitivity, high selectivity, and rapid detection. In practical applications, the sensor size needs to be as small as possible. Given this limitation on the absorption cell size, to increase the measurement optical path length, the measuring gas cell typically employs multiple mirrors or reflectors to reflect the light multiple times within the cell. Therefore, the main technical challenge for gas sensors based on the TDLAS detection principle is how to design a gas absorption cell with a long optical path within a limited sensor size, enabling long-term use in harsh real-world application environments.

[0003] To increase the optical path length of the absorption cell, various novel designs have been proposed. In Chinese patent CN110632008A, a spiral optical path is formed in a sensor head with a circular cross-section using five planar mirrors; in Chinese patent CN113406001A, two parallel mirrors are used to extend the optical path by causing it to undergo four reflections; and in Chinese patent CN108931504B, a ring-shaped multi-point reflective photoelectric gas sensor probe is disclosed, including a two-dimensional ring-shaped multi-point optical reflection ring, which is a hollow cylindrical structure. This design maximizes the use of the absorption cell space to increase the optical path length.

[0004] However, because the design uses a cylindrical structure, theoretically only a small portion of the light in the collimated laser beam can meet the conditions for multiple reflections and eventually reach the detector. This would greatly reduce the utilization rate of the light energy of the detection beam.

[0005] To overcome the shortcomings of cylindrical reflective structures, this invention proposes a self-focusing three-dimensional ring photoelectric gas sensor probe and sensor device. This solution can effectively utilize laser beam energy while maintaining a long optical path and increasing the stability of the entire optical path. Summary of the Invention

[0006] To address the technical problems existing in the prior Chinese patent CN108931504B, the self-focusing three-dimensional ring photoelectric gas sensor probe and sensor device of the present invention employs two 45° plane mirrors and a reflective element with a three-dimensional ring concave reflective ring structure. This overcomes the defects of multiple separate elements in the prior art, simplifies the optical path adjustment, and makes the detection optical path very stable, thus solving the problems in this technical field and making the gas sensor more compact and efficient.

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

[0008] A self-focusing three-dimensional ring-shaped photoelectric gas sensor probe includes a three-dimensional ring-shaped concave reflective ring. The three-dimensional ring-shaped concave reflective ring is formed by cutting a concave ring containing the central cross-section of a hollow sphere with the central cross-section as the reference plane of symmetry. The central cross-section is parallel to the two cut surfaces and is located at the center of the two cut surfaces. A cover plate is provided on the upper part of the three-dimensional ring-shaped concave reflective ring, and the lower part of the three-dimensional ring-shaped concave reflective ring is provided on a base. The central cross-section of the three-dimensional ring-shaped concave reflective ring is parallel to the bottom surface of the base. The cavity formed by the three-dimensional ring-shaped concave reflective ring, the cover plate, and the base is a gas absorption cell for containing the gas to be measured. The base is provided with two beam inlet and outlet holes. Above the two beam inlet and outlet holes, a plane reflector is provided at a 45° angle to the central cross-section. Below the two beam inlet and outlet holes, a laser source capable of emitting a cone-shaped beam with a very small divergence angle and a photodetector are provided, respectively. The optical axes of both are perpendicular to the central cross-section.

[0009] Furthermore, the laser source, which forms a cone-shaped 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 exit port is positioned at the focal point of the parabolic concave reflector. The laser beam, after being reflected by the parabolic concave reflector, forms a cone-shaped beam with a very small divergence angle. This cone-shaped beam enters the gas absorption cell through the beam inlet / outlet aperture, and after reflection by the first 45° reflecting plane mirror, the center line of the reflected beam is parallel to the bottom of the gas absorption cell. Simultaneously, the center line of the beam and the center of the three-dimensional annular concave reflecting ring are aligned. The cross sections coincide; after being reflected by the reflecting plane mirror, the light beam reaches the three-dimensional annular concave reflecting ring and is reflected. Due to the effect of the concave mirror of the three-dimensional annular concave reflecting ring, the incident light beam with a small divergence angle becomes a converging light cone and is focused at the center point of the optical path between the two reflection points. Then, the light beam continues to propagate from the focal point to the next reflection point in the form of a diverging light cone. After multiple reflections, the light cone is reflected again 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 cell through one of the beam inlet / outlet holes and shines on the concave mirror on the inner wall of the three-dimensional annular concave reflector ring in a pre-designed direction. The center line of the light beam and the normal at the reflection point of the three-dimensional annular concave reflector ring have a set incident angle, which allows the light beam to be reflected multiple times on the concave reflector surface of the three-dimensional annular concave reflector ring. When the incident light beam is reflected by the concave reflector of the three-dimensional annular concave reflector ring, under the action of the reflector of the three-dimensional annular concave reflector ring, the light beam with a small divergence angle is focused at the center of the optical path between the two reflection points. Then, after passing the focal point, the light beam continues to propagate to the next reflection point in the form of a diverging light cone and continues to be reflected multiple times by the concave reflector of the three-dimensional annular concave reflector ring.

[0010] Using a five-reflection example for specific illustration, the light beam from the laser's output port to the first reflection point on the inner wall of the three-dimensional annular concave reflector is designed as a cone-shaped beam (cone 1) with a very small divergence angle. When this cone 1 enters the gas absorption cell through a beam inlet / outlet aperture at the bottom, it is reflected by the first 45° plane mirror, then by the concave mirror of the three-dimensional annular concave reflector, and finally focused at the center of the optical path between the first and second reflection points in the gas absorption cell. It then forms a cone shape (cone 2) and strikes the concave mirror on the inner wall of the three-dimensional annular concave reflector, resulting in a second reflection. After the second reflection by the concave mirror, the beam of cone 2 is focused between the second and third reflection points in the gas absorption cell. The light beam is focused at the center of the optical path between the three-dimensional annular concave reflector rings, and then, in the form of a light cone (light cone 3), it illuminates the concave mirror on the inner wall of the three-dimensional annular concave reflector ring, producing a third reflection. After the fourth reflection by the concave mirror, the 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 cell, and then, in the form of a light cone (light cone 4), it illuminates the concave mirror on the inner wall of the three-dimensional annular concave reflector ring, producing a fourth reflection. After the fifth reflection by the concave mirror on the inner wall of the three-dimensional annular concave reflector ring, the beam of light cone 4 is reflected by a second 45° reflector, making the beam centerline perpendicular to the bottom of the gas absorption cell. This beam is then refocused through another beam inlet / outlet at the bottom of the absorption cell and focused on the photosensitive surface of the photodetector. Therefore, the conical beam emitted from the laser undergoes five reflections and converges five times after being reflected by the spherical reflector on the inner wall of the annulus, and finally focuses on the photosensitive surface of the photodetector during the final convergence.

[0011] To make full use of the limited size of the gas absorption cell, this three-dimensional annular multi-point reflection gas chamber can also be designed as a structure with multiple reflections such as seven or nine reflections, provided that the two 45° reflecting mirrors of the laser beam, namely the inlet and outlet reflecting mirrors, do not block other reflected 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's output port and the detector's photosensitive surface are the convergence point or focal point of each other's light cones, the light spot obtained by the detector is not sensitive to changes in the direction of the light emitted by the laser.

[0014] 2. Because a parabolic concave mirror is used in the laser to form a beam with a small divergence angle and a cone shape, there are no lenses in the entire detection optical path. Therefore, interference noise caused by reflection from the lens surface is effectively avoided, thereby improving the measurement accuracy of the detection system.

[0015] 3. Because it is a three-dimensional spherical reflection, the light energy within 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 beam energy.

[0016] 4. Since all spherical reflections are generated within the same reflective ring, i.e. a three-dimensional concave annular reflective ring, the relative positions of each reflecting spherical surface are fixed, thus ensuring excellent stability of the entire optical path.

[0017] 5. Because this 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 source capable of emitting a cone-shaped beam with a very small divergence angle includes a laser chip and a parabolic concave mirror. The laser chip's output port is positioned at the focal point of the parabolic concave mirror. The center line of the laser cone emitted by the laser makes a 90° angle with the optical axis reflected by the parabolic concave mirror. The laser beam is reflected by the parabolic concave mirror to form a cone-shaped beam with a very small divergence angle.

[0019] Furthermore, the number of reflections of the light beam in the three-dimensional annular concave reflective ring is determined by the inner diameter of the three-dimensional annular concave reflective ring and the incident angle of the incident light beam's centerline on the three-dimensional annular concave reflective ring; the number of reflections determines the total measured optical path length of the light beam within the three-dimensional annular concave reflective 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 reflective ring is electroplated with a reflective coating and a protective film.

[0021] Specifically, the cover plate has multiple vent holes, and the gas to be tested diffuses into the gas absorption pool through the vent holes via the air inlet plug; the inner wall of the cover plate is coated with a black coating to reduce 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 inside the gas absorption pool is installed.

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

[0024] Furthermore, a cylinder is set at the center of the base, and according to the corresponding fifth, seventh, or ninth reflection light paths, five, five, or nine fan-shaped solid blocks are respectively set at positions where no light beam passes, in order to reduce the total volume of the gas absorption pool.

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

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments. Attached Figure Description

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

[0028] Figure 2 is a schematic diagram of a circular ring containing the central section cut from a hollow sphere.

[0029] Figure 3 is a schematic diagram of a beam of light with a small divergence angle formed by using a parabolic concave mirror to form a light cone shape.

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

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

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

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

[0034] Among them, 10-self-focusing three-dimensional ring photoelectric gas sensor probe; 120-three-dimensional ring concave reflective ring; 122-central section; 124-cut 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 outer shell; 21-air inlet plug; 30-PCB; 40-lower part of the outer shell; 41-wire through hole; 50-light cone-shaped beam with a very small divergence angle; 51-laser COC; 52-TEC; 53-parabolic concave reflector. Detailed Implementation

[0035] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0036] It should be emphasized that the following detailed descriptions are illustrative, describing the specific structure and characteristics of the self-focusing three-dimensional ring photoelectric gas sensor probe and sensor device, and should not constitute any limitation on the present invention. The description herein is only used to explain the novel three-dimensional ring design of the present invention and is not intended to limit the design described herein. Furthermore, any of the technical features mentioned below (including implicit or explicit ones), as well as any technical feature directly shown or implied in Figures 1 to 7, can be arbitrarily combined or deleted among these technical features (or their equivalents) to form further embodiments that may not be directly or indirectly mentioned in the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0037] Please refer to Figures 1 to 7 for an explanation of the self-focusing three-dimensional ring photoelectric gas sensor probe 10 and the sensor device, based on their working principle. The self-focusing three-dimensional ring photoelectric gas sensor device includes a self-focusing three-dimensional ring photoelectric gas sensor probe 10, an upper housing portion 20 with an air inlet plug 21, a PCB 30 for processing photoelectric signals, and a lower housing portion 40 with a wire through-hole 41. The self-focusing three-dimensional ring photoelectric gas sensor probe 10 and the PCB 30 are housed within the upper housing portion 20 and the lower housing portion 40 of the sensor device, thus forming a sensor device capable of gas detection, as shown in Figure 7.

[0038] The self-focusing three-dimensional ring-shaped photoelectric gas sensor probe 10 is equipped with a three-dimensional ring-shaped concave reflective ring 120 with an inner wall that is a concave reflective mirror, as shown in Figure 2. Examples of three different optical path reflection paths in the sensor probe are shown in Figures 4-6.

[0039] As shown in Figure 2, the three-dimensional annular concave reflective ring 120 is a concave annulus segment cut from a hollow sphere with its central cross-section 122 as the central symmetry plane. This central cross-section 122 is parallel to two cut surfaces 124, and is located at the center of the two cut surfaces 124. Therefore, the two cut surfaces 124 are the same size and symmetrical with respect to the central cross-section 122. It should be noted that if the two cut surfaces are different sizes or asymmetrical with respect to the central cross-section, the incident light beam will deviate from the central cross-section after multiple reflections, affecting the consistency of the optical path and causing difficulties in adjusting the optical path during production.

[0040] Among them, the inner wall of the three-dimensional annular concave reflective ring 120 is electroplated with a reflective coating and a protective film.

[0041] A cover plate is provided on the upper part of the three-dimensional annular concave reflective ring 120, and the lower part is fixed on a columnar base 130. The cavity formed by the three-dimensional annular concave reflective ring 120, the cover plate, and the base 130 is a gas absorption cell for containing the gas to be measured. The cover plate and the base 130 coincide with two cross-sectional surfaces 124, such that the central cross-section 122 of the three-dimensional annular concave reflective 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 beam inlet and outlet through holes and a temperature and pressure sensor through hole 131. Inside the gas absorption pool and above the two beam inlet and outlet through holes on the base 130, a plane reflector 140 is respectively provided at a 45° angle to the base 130. A laser and a photodetector are respectively provided below the base 130, and their optical axes are both perpendicular to the base 130.

[0043] In the sensor probe, the laser output port is considered as a focal point and is set at the focal point of the parabolic concave reflector 53, as shown in Figure 3. The laser beam is reflected by the parabolic concave reflector 53 to form a beam 50 with a small divergence angle in the shape of a light cone. The beam from the laser output port to the first reflection point on the inner wall of the three-dimensional annular concave reflector ring 120 is designed as a beam 50 with a small divergence angle in the shape of a light cone. The beam emitted from the laser output port enters the absorption cell through the beam inlet and outlet through-hole at the bottom of the absorption cell, and then is reflected by the first 45° plane reflector 140. The center line of the reflected beam is parallel to the bottom of the absorption cell. At the same time, the center line of the beam coincides with the central section 122 of the annulus and illuminates the inner wall of the three-dimensional annular concave reflector ring 120 in the pre-designed direction. The center line of the beam and the reflection point of the three-dimensional annular concave reflector ring 120 are parallel to the center line of the beam. The normal at the injection point has a set incident angle, allowing the beam to be reflected multiple times on the concave mirror formed by the three-dimensional annular concave reflector ring 120. When the incident beam is reflected by the three-dimensional annular concave reflector ring 120, due to the effect of the concave mirror of the annular arc reflector, the incident beam with a small divergence angle becomes a converging beam and is focused at the center point of the optical path between the two reflection points. Then the beam continues to propagate from the focal point to the next reflection point in the form of a diverging beam and is reflected multiple times by the three-dimensional annular concave reflector ring 120, as shown in Figures 4 to 6, until it is finally reflected by the second 45° plane reflector ring 140, so that the reflected beam passes through another beam inlet and outlet through the bottom of the gas absorption cell and is 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.

[0044] It should be noted that if the beam emitted from the laser is not a divergent beam with a small divergence angle before the first reflection, but a focused beam, then under the reflection of the concave mirror of the annular arc-shaped reflecting mirror, it cannot converge between the two reflection points, and therefore multiple reflections cannot be achieved.

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

[0046] To reduce the overall volume of the gas absorption cell, fan-shaped solid blocks 150 can be placed in the space where no light beam passes inside the three-dimensional annular concave reflective ring 120. For example, for a gas absorption cell that produces 5 reflections on the three-dimensional reflective ring, 5 fan-shaped solid blocks 150 are placed at the positions where no light beam passes, as shown in Figure 4(b); for a gas absorption cell that produces 7 reflections on the three-dimensional reflective ring, 7 fan-shaped solid blocks 150 are placed at the positions where no light beam passes, as shown in Figure 5(b); for a gas absorption cell that produces 9 reflections on the three-dimensional reflective ring, 9 fan-shaped solid blocks 150 are placed at the positions where no light beam passes, as shown in Figure 6(b).

[0047] In a further preferred embodiment, the laser source can be a low-power vertical cavity surface-emitting laser (VCSEL) or a DFB laser.

[0048] A further preferred technical solution involves the light beam emitted from the laser output port. After reflection by the parabolic concave reflector 53, it forms a light cone 50 with a very small divergence angle. After further reflection by the first 45° plane reflector 140, the light beam reaches the first reflection point of the three-dimensional annular concave reflector ring 120, forming a light cone. This light cone undergoes multiple reflections, followed by reflection by the second 45° plane reflector 140. It then passes through the light beam inlet / outlet aperture of the base 130 and is finally focused onto the photosensitive surface of the photodetector, forming a self-focusing reflection system where the light source and detector are mutually focused. This not only greatly increases the stability of the optical path but also simplifies the entire optical path adjustment process.

[0049] In a further preferred embodiment, the number of reflections of the light beam within the three-dimensional annular concave reflecting ring 120 is determined by the inner diameter of the three-dimensional annular concave reflecting ring 120 and the incident angle of the incident light beam's centerline on the three-dimensional annular concave reflecting ring 120. The number of reflections determines the total measurement optical path length of the light beam within the three-dimensional annular concave reflecting ring 120, and the number of multi-point reflections includes five, seven, nine, or more reflections.

[0050] In a further preferred embodiment, a solid cylinder 160 is provided at the center of the three-dimensional annular concave reflective ring 120 where no light passes through, in order to further reduce the total volume of the absorption cell.

[0051] In a further preferred embodiment, the cover plate has multiple ventilation holes. After the gas to be tested is filtered by powder metallurgy sintering, it diffuses into the gas absorption pool through the ventilation holes.

[0052] In a further preferred embodiment, the inner wall of the cover plate is coated with a black coating to reduce reflected light.

[0053] In a further preferred embodiment, the base 130 of the gas absorption tank is provided with a through hole. A temperature and pressure sensor for measuring the temperature and pressure inside the gas absorption tank is installed in the through hole.

[0054] In a further preferred embodiment, the three-dimensional annular concave reflective ring 120 is made of metal, plastic, or synthetic material, and is formed by machining or precision injection molding.

[0055] A further preferred technical solution is that the inner wall of the three-dimensional annular concave reflective ring 120 is optically polished with a mirror and coated with a reflective film to form a three-dimensional arc-shaped reflective mirror surface, and a protective mirror layer is added. Alternatively, the inner wall of the three-dimensional annular concave reflective ring 120 is adhered with reflective material to form an arc-shaped reflective mirror surface.

[0056] In a further preferred embodiment, the laser source is connected to its driving circuit, and the photodetector is connected to the signal processing circuit.

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

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

[0059] This invention increases the total detection optical path within the gas absorption cell through multiple beam reflections via a three-dimensional annular concave reflective ring, which is beneficial for improving the detection signal-to-noise ratio and measurement accuracy. Furthermore, the three-dimensional annular concave reflective ring reduces the size of the sensor probe, thereby reducing the measurement response time.

[0060] This invention employs a laser light source with a cone-shaped beam having a very small divergence angle. By utilizing the focusing characteristics of a three-dimensional annular concave mirror, the beam, after multiple reflections, is focused onto the photodetector light, forming a self-focusing reflection system where the light source and detector are mutually focused. This reduces the difficulty of adjusting the optical path. The overall design of the invention reduces the complexity of the manufacturing process and improves the production yield, thus facilitating large-scale production.

[0061] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A self-focusing three-dimensional ring-shaped photoelectric gas sensor probe, characterized in that, The system includes a three-dimensional annular concave reflective ring, which is formed by cutting a concave ring containing the central cross-section of a hollow sphere with the central cross-section as the reference plane. The central cross-section is parallel to the two cut surfaces and is located at the center of the two cut surfaces. A cover plate is provided on the upper part of the three-dimensional annular concave reflective ring, and the lower part of the three-dimensional annular concave reflective ring is provided on a base. The central cross-section of the three-dimensional annular concave reflective ring is parallel to the bottom surface of the base. The cavity formed by the three-dimensional annular concave reflective ring, the cover plate, and the base is a gas absorption cell for containing the gas to be measured. The base is provided with two beam inlet and outlet holes. Above the two beam inlet and outlet holes, a plane mirror at a 45° angle to the central cross-section is provided. Below the two beam inlet and outlet holes, a laser source capable of emitting a cone-shaped beam with a very small divergence angle and a photodetector are provided, respectively. The optical axes of both are perpendicular to the central cross-section.

2. The self-focusing three-dimensional ring-shaped photoelectric gas sensor probe as described in claim 1, characterized in that, The laser source, which forms a cone-shaped 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 exit port is positioned at the focal point of the parabolic concave reflector. The laser beam, reflected by the reflector, forms a cone-shaped beam with a very small divergence angle. This cone-shaped beam enters the gas absorption cell through the beam inlet / outlet aperture and is reflected by the first 45° reflecting plane mirror. The centerline of the reflected beam is parallel to the bottom of the gas absorption cell. Simultaneously, the centerline of the beam and the central section of the three-dimensional annular concave reflecting ring are aligned. The beam coincides with the reflection of the plane mirror and reaches the three-dimensional annular concave reflection ring. Due to the effect of the concave mirror of the three-dimensional annular concave reflection ring, the incident beam with a small divergence angle becomes a converging beam and is focused at the center point of the optical path between the two reflection points. Then, the beam continues to propagate from the focal point to the next reflection point in the form of a diverging beam. After multiple reflections, the beam is reflected again by a second 45° plane mirror, passes through another beam inlet / outlet aperture, 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.

3. The self-focusing three-dimensional ring-shaped photoelectric gas sensor probe as described in claim 1, characterized in that, The basic optical structure of the laser source capable of emitting a cone-shaped beam with a very small divergence angle includes a laser chip and a parabolic concave mirror. The laser chip's output port is positioned at the focal point of the parabolic concave mirror. The center line of the laser cone emitted by the laser makes a 90° angle with the optical axis reflected by the parabolic concave mirror. The laser beam is reflected by the parabolic concave mirror to form a cone-shaped beam with a very small divergence angle.

4. The self-focusing three-dimensional ring-shaped photoelectric gas sensor probe as described in claim 2, characterized in that, The number of reflections of the light beam in the three-dimensional annular concave reflective ring is determined by the inner diameter of the three-dimensional annular concave reflective ring and the incident angle of the incident cone centerline of the light beam on the three-dimensional annular concave reflective ring. The number of reflections determines the total optical path length of the 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 ring-shaped photoelectric gas sensor probe as described in claim 1, characterized in that, The inner wall of the three-dimensional annular concave reflective ring is electroplated with a reflective coating and a protective film.

6. The self-focusing three-dimensional ring-shaped photoelectric gas sensor probe as described in claim 1, characterized in that, The cover plate has multiple vent holes, and the gas to be tested diffuses into the gas absorption pool through the vent holes via the air inlet plug; the inner wall of the cover plate is coated with a black coating to reduce reflected light.

7. The self-focusing three-dimensional ring-shaped photoelectric gas sensor probe as described in claim 1, characterized in that, The base has a through hole, through which a temperature and pressure sensor for measuring the temperature and pressure inside the gas absorption pool is installed.

8. The self-focusing three-dimensional ring-shaped photoelectric gas sensor probe as described in claim 1, characterized in that, The material used to manufacture the three-dimensional annular concave reflective ring is 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 reflective ring is optically polished with a mirror and coated with a reflective film to form an arc-shaped reflective mirror surface, or the inner wall of the three-dimensional annular concave reflective ring is made of reflective material to form an arc-shaped reflective mirror surface.

9. The self-focusing three-dimensional ring-shaped photoelectric gas sensor probe as described in claim 1, characterized in that, A cylinder is set at the center of the base, and five, five or nine fan-shaped solid blocks are respectively set at the positions where no beam passes, according to the corresponding fifth, seventh or ninth reflection light paths, in order to reduce the total volume of the gas absorption pool.

10. A self-focusing three-dimensional ring-shaped photoelectric gas sensor device, characterized in that, It includes the self-focusing three-dimensional ring photoelectric gas sensor probe as described in any one of claims 1-9, an upper part of the housing with an air inlet plug, a PCB for processing photoelectric signals, and a lower part of the housing with wire through holes.

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