Small optical detection gas cell and laser gas sensor

Abstract

The utility model discloses a small-sized optical detection gas chamber and laser gas sensor relates to gas detection technical field, small-sized optical detection gas chamber includes cavity, optical cell and at least one restriction insert, the middle of cavity concaves inward to form a recess, optical cell is provided in the cavity, and the restriction insert is provided with the restriction insert. Comprising a first reflecting mirror, a second reflecting mirror, a light input end and a light output end, the first reflecting mirror and the second reflecting mirror are arranged at the two ends of the cavity, and light beams entering from the light input end are reflected by the first reflecting mirror and the second reflecting mirror for multiple times and then are emitted out through the light output end; the limiting plug-in is arranged in the optical pool and is positioned between the first reflecting mirror and the second reflecting mirror; therefore, the gas to be measured can be measured in a long-optical-path and high-precision manner, and the flowable range of the gas to be measured is limited through the limiting plug-in, so that the light beam fully acts with the gas to be measured, and the response time is shortened; meanwhile, the concave part is arranged to reduce the volume of the cavity, the miniaturization design is realized, the flowing range of the to-be-detected gas is reduced, and the response time is further shortened.

Description

Technical Field

[0001] The utility model relates to the technical field of gas detection, in particular to a small optical detection gas chamber and a laser gas sensor. Background Art

[0002] Oxygen consumption measurement is of great significance for accurately evaluating human cardiopulmonary function. The basic requirements for sensors for measuring oxygen consumption in clinical practice are: first, they must be small in size and light in weight, so that the subject will not feel uncomfortable when measuring in the respiratory tract; second, they must be able to respond quickly, so that continuous analysis can be performed while the subject breathes one by one.

[0003] At present, oxygen sensors used for clinical respiratory monitoring on the market are generally designed based on the paramagnetic principle, electrochemical principle, solid electrolyte principle and TDALS laser principle.

[0004] Among them, paramagnetic oxygen sensors use the paramagnetic characteristics of oxygen to measure and analyze oxygen. The oxygen content can be determined by measuring the magnetic susceptibility of the mixed gas. For example, the device for measuring the concentration of paramagnetic gases disclosed in Draeger's patent US8596109B2 and the compact paramagnetic oxygen sensor disclosed in Servomex Group's patent US8847579B2 can meet the requirements of miniaturization and rapid response, but the paramagnetic characteristics will be affected by vibration, causing the sensor to drift, and in severe cases may cause permanent damage; the service life of the electrochemical oxygen sensor is short, and its detection accuracy will be reduced in an environment with high oxygen concentration; the solid electrolyte oxygen sensor needs to be heated to at least 800°C, cannot be installed in the patient's respiratory tract, and has safety hazards.

[0005] Compared with these technologies, tunable semiconductor laser absorption spectroscopy (TDLAS) is a technology that uses the wavelength tuning characteristics of semiconductor lasers and the selective absorption of lasers by the gas to be measured to detect gas concentration. It has the advantages of high sensitivity, real-time, dynamic, and simultaneous measurement of multiple components.

[0006] For example, a TDLAS laser oxygen sensor (US5448071A) proposed by the American Oxigraf company adopts a through-beam receiving method and designs the air chamber as a slender strip structure. The sensor is die-cast in one piece, and the laser, detector, air chamber, optical lens, etc. are placed in the same housing. However, since the light absorption wavelength of oxygen is 760nm, the light absorption is still relatively weak. In order to ensure accuracy, a longer optical path is required. Based on the through-beam structure, the overall structure is large in size, which limits its clinical application.

[0007] In order to further reduce the size of the sensor, the US patent US20220233097A1 of Princeton University discloses a mainstream exhaled oxygen sensor that uses a miniature Herriot cell to increase the optical path. Although it reduces the overall volume to a certain extent, it cannot meet the requirements of rapid response. Utility Model Content

[0008] The main purpose of the utility model is to provide a small optical detection chamber and a laser gas sensor which can realize high-precision detection, rapid response and miniaturization design.

[0009] In order to achieve the above-mentioned purpose, the utility model proposes a small optical detection gas chamber, which is used in a laser gas sensor and includes:

[0010] The cavity is used for the flow of the gas to be tested, and the middle of the cavity is sunken inward to form a concave portion;

[0011] an optical pool, arranged in the cavity, comprising a first reflector, a second reflector, a light input end and a light output end, wherein the first reflector and the second reflector are arranged at two ends of the cavity, and a light beam incident from the light input end is reflected multiple times by the first reflector and the second reflector and then emitted from the light output end; and

[0012] At least one limiting plug-in is disposed in the optical pool and located between the first reflector and the second reflector.

[0013] Optionally, the maximum width of the reflector is w1, the diameter of the spot formed by the light beam on the first reflector or the second reflector is d1, the diameter of the concave portion of the cavity is d, and d1 <d<w1。

[0014] Optionally, two limiting plug-ins are provided, and the two limiting plug-ins are symmetrically spaced apart along the concave portion of the cavity.

[0015] Optionally, each of the limiting plugs has a root and a head, the root is arranged at the end of the cavity and passes through a reflector, the head is close to the middle position of the cavity, and each of the limiting plugs is tapered from its root to its head.

[0016] Optionally, the diameter of the spot formed by the light beam on the first reflector or the second reflector is set to d1, the maximum width of the root of the limiting plug is set to w2, the maximum width of the head of the limiting plug is set to w3, the safety factor for limiting the safe distance between the root and the spot is set to a, and w3 <w2<(w1-2d1)×a。

[0017] Optionally, the limiting plug is provided with one, the limiting plug is arranged along the length direction of the cavity, one of the two ends of the limiting plug is arranged at one end of the cavity and passes through one of the first reflector and the second reflector, the other of the two ends of the limiting plug is arranged at the other end of the cavity and passes through the other of the first reflector and the second reflector, and the limiting plug is arranged to be gradually reduced from its two ends to the middle of the cavity;

[0018] The diameter of the spot formed by the light beam on the first reflector or the second reflector is set to d1', the maximum width of the end of the limiting plug is set to w2', the width of the middle of the limiting plug is set to w3', the safety factor for limiting the end of the limiting plug to have a safety distance from the spot is set to a', and w3' <w2'<(w1-2d1')×a'。

[0019] Optionally, the inner wall of the cavity is provided with a light absorbing layer; and / or,

[0020] The outer surface of the limiting plug-in is provided with a light absorbing layer.

[0021] The utility model also provides a laser gas sensor for detecting the concentration of a gas to be measured, the laser gas sensor comprising:

[0022] The shell is provided with an air inlet pipe and an air outlet pipe;

[0023] A small optical detection air chamber is disposed in the housing and is connected to the air inlet pipe and the air outlet pipe;

[0024] A laser, disposed in the housing, for emitting a light beam into the small optical detection chamber to a light input end of the small optical detection chamber;

[0025] a detector, disposed in the housing, for receiving a light beam emitted from a light output end of the small optical detection chamber and generating a detection signal; and,

[0026] A controller is electrically connected to the laser and the detector, and is used to control the laser to emit a light beam, and receive and process the detection signal transmitted from the detector to obtain the concentration of the gas to be measured; wherein the small optical detection gas chamber includes:

[0027] The cavity is used for the flow of the gas to be tested, and the middle of the cavity is sunken inward to form a concave portion;

[0028] an optical pool, arranged in the cavity, comprising a first reflector, a second reflector, a light input end and a light output end, wherein the first reflector and the second reflector are arranged at two ends of the cavity, and a light beam incident from the light input end is reflected multiple times by the first reflector and the second reflector and then emitted from the light output end; and

[0029] At least one limiting plug-in is disposed in the optical pool and located between the first reflector and the second reflector.

[0030] Optionally, the laser gas sensor also includes a first mounting seat and a second mounting seat provided on the shell, one of the first reflector and the second reflector and the laser are mounted on the first mounting seat, the other of the first reflector and the second reflector and the detector are mounted on the second mounting seat, and the limiting plug-in is mounted on the first mounting seat and / or the second mounting seat.

[0031] Optionally, the laser gas sensor further includes a heating component, the heating component includes a heater and a heat-insulating component, the heater is disposed in the shell and is electrically connected to the controller, and the heat-insulating component is wrapped around the outer circumference of the shell.

[0032] In the technical solution of the utility model, the optical cell of the small optical detection gas chamber is improved based on the structure of the traditional Herriott cell, and not only has the long optical path characteristics of the traditional Herriott cell to ensure high-precision measurement of the gas to be measured, but also by arranging at least one limiting plug-in in the cavity, that is, between the first reflector and the second reflector, the flowable range of the gas to be measured entering the cavity is limited, and the light beam and the gas to be measured can fully interact, thereby shortening the response time; at the same time, the middle of the cavity is recessed inward to form a recessed portion, thereby reducing the volume of the cavity, realizing a miniaturized design, and can reduce the flowable range of the gas to be measured in the cavity, further shortening the response time; further, the structural design of the cavity and the arrangement of the limiting plug-in can also block part of the stray light and reduce the optical path noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0034] Figure 1 A schematic structural diagram of an embodiment of a small optical detection air chamber provided by the utility model;

[0035] Figure 2 A schematic structural diagram of another embodiment of the small optical detection air chamber provided by the utility model;

[0036] Figure 3This is a schematic structural diagram of an embodiment of the laser gas sensor provided by the utility model.

[0037] Description of Figure Numbers:

[0038] Label name Label name 1000 Laser gas sensor 200 case 100 Small optical detection chamber 201 Intake pipe 1 Cavity 202 Exhaust pipe 11 concavity 300 Laser 2 First reflector 400 First Mount 3 Second reflector 500 Second Mount 4 Limit plugins 600 First driver circuit board 41 Root 700 Second driver circuit board 42 head

[0039] The realization of the purpose, functional features and advantages of the utility model will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0041] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back...), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0042] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the utility model, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the meaning of "and / or" appearing in the full text includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the utility model.

[0043] Oxygen consumption measurement is of great significance for accurately evaluating human cardiopulmonary function. The basic requirements for sensors for measuring oxygen consumption in clinical practice are: first, they must be small in size and light in weight, so that the subject will not feel uncomfortable when measuring in the respiratory tract; second, they must be able to respond quickly, so that continuous analysis can be performed while the subject breathes one by one.

[0044] Tunable semiconductor laser absorption spectroscopy (TDLAS) is a technology that uses the wavelength tuning characteristics of semiconductor lasers and the selective absorption of lasers by the gas to be measured to detect gas concentration. It has the advantages of high sensitivity, real-time, dynamic, and simultaneous measurement of multiple components. For example, a TDLAS laser oxygen sensor (US5448071A) proposed by Oxigraf, USA, adopts a counter-beam receiving method and designs the air chamber as a slender strip structure. The sensor is die-cast in one piece, and the laser, detector, air chamber, optical lens, etc. are placed in the same housing. However, since the light absorption wavelength of oxygen is 760nm, the light absorption is still relatively weak. In order to ensure accuracy, a longer optical path is required. Based on the counter-beam structure, the overall structure is large in volume, which limits its clinical application. In order to further reduce the size of the sensor, the patent US20220233097A1 of Princeton University in the United States discloses a mainstream exhaled oxygen sensor that uses a miniature Herriot cell to increase the optical path. Although the overall volume is reduced to a certain extent, it cannot meet the requirements of rapid response.

[0045] In view of this, the utility model provides a small optical detection gas chamber 100, which is used in a laser gas sensor 1000. Figure 1 and Figure 2 This is an embodiment of a small optical detection air chamber provided by the utility model.

[0046] See also Figure 1 and Figure 2 The small optical detection chamber 100 includes a cavity 1, an optical pool and at least one limiting plug-in 4. The cavity 1 is used for the flow of the gas to be tested, and the middle of the cavity 1 is recessed inward to form a recess 11; the optical pool is arranged in the cavity 1, and includes a first reflector 2, a second reflector 3, a light input end and a light output end. The first reflector 2 and the second reflector 3 are arranged at both ends of the cavity 1. The light beam incident from the light input end is reflected multiple times by the first reflector 2 and the second reflector 3 and then emitted through the light output end; the limiting plug-in 4 is arranged in the optical pool and is located between the first reflector 2 and the second reflector 3.

[0047] In the technical solution of the present utility model, the optical cell of the small optical detection gas chamber 100 is improved based on the structure of the traditional Herriott cell. It not only has the characteristic of long optical path of the traditional Herriott cell to ensure high-precision measurement of the gas to be measured, but also by arranging at least one limiting plug 4 in the cavity 1, that is, between the first mirror 2 and the second mirror 3, the flowable range of the gas to be measured introduced into the cavity 1 is limited, so that the light beam can fully interact with the gas to be measured, thereby shortening the response time. At the same time, a concave portion 11 is formed by the middle of the cavity 1 indenting inward, which can reduce the volume of the cavity 1 to achieve miniaturization design, and can also narrow the flowable range of the gas to be measured in the cavity 1 to further shorten the response time. Moreover, the structural design of the cavity 1 and the setting of the limiting plug 4 can also block part of the stray light and reduce the optical path noise.

[0048] In addition, the concave portion 11 is formed in the middle of the cavity 1, that is to say, the cross-sectional area of the middle of the cavity 1 is smaller than the cross-sectional area of the end of the cavity 1. Thus, the light spot formed on the mirror is concentrated as much as possible at a position close to the periphery of the mirror.

[0049] It should be noted that in the present utility model, the type of the gas to be measured is not limited. Specifically, in an embodiment of the present utility model, the gas to be measured is oxygen.

[0050] It should also be noted that in an embodiment of the present utility model, both the first mirror 2 and the second mirror 3 are concave mirrors, and the radius of curvature of the first mirror 2 is the same as that of the second mirror 3.

[0051] Further, please refer to Figure 1 , the cross-sections of the ends of the cavity 1 and the cross-section of the concave portion 11 are both circular. The maximum width of the mirror is w1, the diameter of the light spot formed by the light beam on the first mirror 2 or the second mirror 3 is set as d1, and the diameter of the concave portion 11 of the cavity 1 is set as d, and d1 < d < w1. In this way, when the light beam incident into the cavity 1 passes through the middle of the cavity 1, it can be avoided from being interfered by the concave portion 11.

[0052] Specifically, in the present utility model, the number of the limiting plugs 4 is not limited. It can be two. Please refer to Figure 1 , in an embodiment of the present utility model, two limiting plugs 4 are provided, and the two limiting plugs 4 are symmetrically and spaced apart along the concave portion 11 of the cavity 1.

[0053] Further, in the present utility model, the shape of the limiting plug 4 is not limited. Specifically, please refer to Figure 1, in an embodiment of the present utility model, each of the limiting plugs 4 has a root portion 41 and a head portion 42. The root portion 41 is disposed at the end of the cavity 1 and penetrates through a reflecting mirror. The head portion 42 is close to the middle position of the cavity 1, and each of the limiting plugs 4 is tapered from its root portion 41 to its head portion 42. More specifically, the limiting plug 4 is provided in a frustum shape.

[0054] Further, based on the embodiment of "the diameter of the light spot formed by the light emitted from the light input end on the first reflecting mirror 2 or the second reflecting mirror 3 is set as d1" described above, the maximum width of the root portion 41 of the limiting plug 4 is set as w2, the maximum width of the head portion 42 of the limiting plug 4 is set as w3, the safety factor for defining a safety distance between the root portion 41 and the light spot is set as a, and w3 < w2 < (w1 - d1) × a. With such a setting, both the flowing volume of the gas to be measured can be limited, and the interference of the limiting plug 4 with the reflection of the light beam can be avoided, realizing a fast response.

[0055] Of course, in the present utility model, the limiting plug 4 can also be one (as Figure 2 shown). The limiting plug 4 extends along the length direction of the cavity 1. One of the two ends of the limiting plug 4 is disposed at one end of the cavity 1 and penetrates through one of the first reflecting mirror 2 and the second reflecting mirror 3, and the other of the two ends of the limiting plug 4 is disposed at the other end of the cavity 1 and penetrates through the other of the first reflecting mirror 2 and the second reflecting mirror 3. The limiting plug 4 is tapered from its two ends towards the middle of the cavity 1.

[0056] Further, the diameter of the light spot formed by the light beam on the first reflecting mirror 2 or the second reflecting mirror 3 is set as d1', the maximum width of the end portion of the limiting plug 4 is set as w2', the width of the middle portion of the limiting plug 4 is set as w3', the safety factor for defining a safety distance between the end portion of the limiting plug 4 and the light spot is set as a', and w3' < w2' < (w1 - 2d1') × a'.

[0057] It should be noted that the design of the safety distance is to prevent the root portion 41 of the limiting plug 4 from being disposed adjacent to the periphery of the reflecting mirror, which may affect the reflection of the light beam on the reflecting mirror.

[0058] Specifically, a sensor of an embodiment of the small optical detection gas chamber 100 provided by the present utility model is used for a comparative test experiment with a sensor using a traditional Herriott cell. The gas to be measured (oxygen) is introduced into the absorption cell at a flow rate of 250 ml / min, and the original data of the sensor is recorded using a serial port tool. The response time of the sensor from air to the mileage point T90 is calculated. The experimental results are shown in the following table:

[0059]

[0060] It can be concluded that, under the same test conditions, compared with the sensor using the traditional Herriott cell, the response time of the laser gas sensor using the small optical detection chamber 100 provided by the present application can be shortened from 470.8ms to 329.2ms, and the response time is shortened by 30.1%. While achieving miniaturized design and high-precision measurement, it can also achieve fast response, greatly improving practicality.

[0061] Specifically, a light absorbing layer is provided on the inner wall of the cavity 1 . Thus, by providing the light absorbing layer, stray light can be eliminated and the signal-to-noise ratio of the laser gas sensor 1000 can be improved.

[0062] Specifically, a light absorbing layer is provided on the outer surface of the limiting plug 4 . Thus, by providing the light absorbing layer, stray light can be eliminated and the signal-to-noise ratio of the laser gas sensor 1000 can be improved.

[0063] It should be noted that, in the present invention, the above two technical features can be set at the same time, or one of them can be set selectively. Specifically, in one embodiment of the present invention, the above two technical features are set at the same time, that is, the inner wall of the cavity 1 and the outer surface of the limiting plug 4 are both provided with a light absorbing layer, which greatly improves the signal-to-noise ratio of the laser gas sensor 1000.

[0064] Furthermore, the material of the light absorbing layer includes a black body material.

[0065] The utility model also provides a laser gas sensor 1000, which is used to detect the concentration of the gas to be measured. Figure 3 This is an embodiment of the laser gas sensor 1000 provided by the utility model.

[0066] See also Figure 3 The laser gas sensor 1000 includes a shell 200, a small optical detection chamber 100, a laser 300, a detector and a controller. The shell 200 is inserted with an air inlet pipe 202 and an air outlet pipe 203. The small optical detection chamber 100 is arranged in the shell 200 and is connected with the air inlet pipe 202 and the air outlet pipe 203; the laser 300 is arranged in the shell 200, and is used to emit a light beam into the small optical detection chamber 100 to the light input end of the small optical detection chamber 100; the detector is arranged in the shell 200, and is used to receive the light beam emitted from the light output end of the small optical detection chamber 100 and generate a detection signal; the controller is electrically connected to the laser 300 and the detector, and is used to control the laser 300 to emit a light beam, and receive and process the detection signal transmitted from the detector to obtain the concentration of the gas to be measured.

[0067] In the technical solution of the present utility model, the laser gas sensor 1000 adopts the TDLAS technical principle, and compared with the paramagnetic sensor, it has obvious anti-vibration effect and improves the service life.

[0068] It should be noted that the small optical detection chamber 100 adopts the small optical detection chamber 100 as described above, that is, the laser gas sensor 1000 has all the technical features of all the embodiments of the above-mentioned small optical detection chamber 100, and also has all the technical effects brought by all the above-mentioned technical features, which will not be described one by one here.

[0069] It should also be noted that the air inlet pipe 202 is used to introduce the gas to be tested into the small optical detection air chamber 100, one end of which is connected to the air chamber, and the other end is connected to the small optical detection air chamber 100, and the air outlet pipe 203 is used to discharge the gas in the small optical detection air chamber 100 to the outside, one end of which is connected to the air chamber, and the other end is connected to the small optical detection air chamber 100.

[0070] For details, please refer to Figure 3 The laser gas sensor 1000 also includes a first mounting seat 400 and a second mounting seat 500 provided on the housing 200, one of the first reflector 2 and the second reflector 3 and the laser 300 are mounted on the first mounting seat 400, the other of the first reflector 2 and the second reflector 3 and the detector are mounted on the second mounting seat 500, and the limiting plug-in 4 is mounted on the first mounting seat 400 and / or the second mounting seat 500.

[0071] It should be noted that, in the present invention, the connection method between each reflector and its corresponding mounting seat is not limited, and it can be bonding, or clamping, etc.

[0072] More specifically, based on the above-mentioned embodiment of "two limiting plugs 4 are provided, and the two limiting plugs 4 are symmetrically spaced along the concave portion 11 of the cavity 1", please refer to Figure 3 One of the two limiting plug-ins 4 is installed on the first mounting seat 400, and the other of the two limiting plug-ins 4 is installed on the second mounting seat 500.

[0073] It should be noted that, in the present invention, the connection method between the limiting plug-in 4 and its corresponding mounting seat is not limited, and can be a threaded connection, a clamping connection, etc.

[0074] For further information, see Figure 3The laser gas sensor 1000 also includes a first driving circuit board 600 and a second driving circuit board 700. The first driving circuit board 600 is mounted on the first mounting seat 400 and is electrically connected to the laser 300 and the controller. The second driving circuit board 700 is mounted on the second mounting seat 500 and is electrically connected to the detector and the controller.

[0075] It should be noted that, in the present invention, the connection method between each driving circuit board and its corresponding mounting seat is not limited, and can be a threaded connection, a clamping connection, etc.

[0076] Specifically, the laser gas sensor 1000 also includes a heating component, which includes a heater and a thermal insulation component. The heater is arranged on the shell 200 and is electrically connected to the controller. The thermal insulation component is wrapped around the outer periphery of the shell 200. In this way, heating is performed by the heater, and the temperature of the first reflector 2, the second reflector 3 and the inner wall of the air chamber 201 is quickly increased by the thermal insulation component to prevent condensation of the reflector and the inner wall of the air chamber 201, thereby ensuring the normal operation of the laser gas sensor 1000 and ensuring monitoring stability and accuracy.

[0077] Furthermore, the thermal insulation component includes thermal insulation cotton.

[0078] The above description is only a preferred embodiment of the utility model, and does not limit the patent scope of the utility model. All equivalent structural changes made by using the contents of the utility model specification and drawings under the utility model concept, or directly / indirectly used in other related technical fields are included in the patent protection scope of the utility model.

Claims

1. A small optical detection gas chamber for use in a laser gas sensor, characterized in that: include: The cavity is used for the flow of the gas to be tested, and the middle of the cavity is sunken inward to form a concave portion; An optical pool is disposed in the cavity, comprising a first reflector, a second reflector, a light input end and a light output end, wherein the first reflector and the second reflector are disposed at two ends of the cavity, and a light beam incident from the light input end is reflected multiple times by the first reflector and the second reflector and then emitted from the light output end; as well as, At least one limiting plug-in is disposed in the optical pool and located between the first reflector and the second reflector.

2. The small optical detection gas chamber according to claim 1, characterized in that: The maximum width of the reflector is w1, the diameter of the spot formed by the light beam on the first reflector or the second reflector is d1, the diameter of the concave portion of the cavity is d, and d1 <d<w1。 3. The small optical detection gas chamber according to claim 1, characterized in that: There are two limiting plug-ins, and the two limiting plug-ins are symmetrically spaced along the concave portion of the cavity.

4. The small optical detection air chamber according to claim 3, characterized in that: Each limiting plug-in has a root and a head, the root is arranged at the end of the cavity and passes through a reflector, the head is close to the middle position of the cavity, and each limiting plug-in is gradually arranged from its root to its head.

5. The small optical detection air chamber according to claim 4, characterized in that: The maximum width of the reflector is w1, the diameter of the spot formed by the light beam on the first reflector or the second reflector is d1, the maximum width of the root of the limiting plug is w2, the maximum width of the head of the limiting plug is w3, the safety factor for limiting the safe distance between the root and the spot is a, and w3 <w2<(w1-2d1)×a。 6. The small optical detection gas chamber according to claim 1, characterized in that: The limiting plug is provided with one, and the limiting plug is arranged along the length direction of the cavity, one of the two ends of the limiting plug is arranged at one end of the cavity and passes through one of the first reflector and the second reflector, and the other of the two ends of the limiting plug is arranged at the other end of the cavity and passes through the other of the first reflector and the second reflector, and the limiting plug is arranged to be gradually reduced from the two ends thereof to the middle of the cavity; The maximum width of the reflector is w1, the diameter of the spot formed by the light beam on the first reflector or the second reflector is d1', the maximum width of the end of the limiting plug is w2', the width of the middle of the limiting plug is w3', the safety factor for limiting the end of the limiting plug to have a safety distance from the spot is a', and w3' <w2'<(w1-2d1')×a'。 7. The small optical detection gas chamber according to claim 1, characterized in that: The inner wall of the cavity is provided with a light absorbing layer; and / or, The outer surface of the limiting plug-in is provided with a light absorbing layer.

8. A laser gas sensor for detecting the concentration of a gas to be measured, characterized in that: The laser gas sensor comprises: The shell is provided with an air inlet pipe and an air outlet pipe; The small optical detection air chamber according to any one of claims 1 to 7 is arranged in the housing and is connected to the air inlet pipe and the air outlet pipe; A laser, disposed in the housing, for emitting a light beam into the small optical detection chamber to a light input end of the small optical detection chamber; a detector, disposed in the housing, for receiving a light beam emitted from a light output end of the small optical detection chamber and generating a detection signal; and, The controller is electrically connected to the laser and the detector, and is used to control the laser to emit a light beam, and receive and process the detection signal transmitted from the detector to obtain the concentration of the gas to be measured.

9. The laser gas sensor according to claim 8, characterized in that: The laser gas sensor also includes a first mounting seat and a second mounting seat provided on the shell, one of the first reflector and the second reflector and the laser are mounted on the first mounting seat, the other of the first reflector and the second reflector and the detector are mounted on the second mounting seat, and the limiting plug-in is mounted on the first mounting seat and / or the second mounting seat.

10. The laser gas sensor according to claim 8, characterized in that: The laser gas sensor further comprises a heating component, which comprises a heater and a heat-insulating component. The heater is arranged in the shell and is electrically connected to the controller. The heat-insulating component is wrapped around the outer circumference of the shell.

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