Gas concentration detection method and low-power infrared gas sensor implementing the method

Abstract

The present invention relates to a gas concentration detection method, which collects the signal intensity of infrared light emitted by the same low-power infrared light source reaching two infrared detectors, and inverts and calculates the concentration of the gas to be detected by the ratio of the signal intensity of the two infrared detectors; the present invention also relates to a low-power infrared gas sensor, whose gas chamber is provided with a gas detection optical path to be detected, and the gas detection optical path to be detected includes a low-power infrared light source, a spectroscopic structure and two infrared detectors, and the emission light of the low-power infrared light source is respectively emitted to two infrared detectors with the same filter band after passing through the spectroscopic structure; the difference in the optical path length from the low-power infrared light source to the two infrared detectors is defined as the length of the equivalent optical path of the gas detection optical path to be detected. The present invention ensures that the low-power sensor is not affected by factors such as the external environment temperature and the aging of the light source during operation, and realizes the stability and accuracy of the low-power infrared gas sensor in detecting gas concentration.

Description

Technical Field

[0001] The present invention relates to the technical field of gas concentration detection, in particular to a gas concentration detection method and a low-power infrared gas sensor for implementing the method. Background Art

[0002] Infrared gas sensors have the advantages of fast response speed, high measurement accuracy, strong anti-interference ability, normal use in oxygen-free environment, and long service life. They have important market application prospects in the field of gas sensors. The working principle of infrared gas sensors is to use the inherent vibration and rotation frequency of gas molecules to absorb infrared light signals of specific wavelengths, and the relationship between light absorption intensity and gas molecule concentration satisfies the Lambert-Beer law. Therefore, by detecting the change in the absorption intensity of light of a specific wavelength after the interaction between infrared light and gas molecules, the concentration of a specific gas can be detected.

[0003] The common problem of infrared gas sensors is installation. For example, cables need to be laid in advance at the installation site, and in some cases, road construction needs to be destroyed. There is even no power supply in extremely harsh environments. Therefore, the industry hopes that infrared gas sensors can be installed and used anytime and anywhere without any external cables. However, due to the high power consumption of traditional infrared gas sensors, they cannot be powered by batteries, so low-power infrared gas sensors came into being.

[0004] Although low-power infrared gas sensors can solve a series of installation problems by being powered by batteries, the reason why low-power infrared gas sensors have low power consumption is that they are equipped with low-power infrared light sources (LED light sources). Low-power LED light sources are particularly sensitive to temperature. The higher the temperature, the lower the luminous efficiency and the lower the luminous intensity. Especially in the temperature range of -40℃ to +70℃ for industrial products, under the influence of temperature changes, the maximum luminous intensity of the LED light source can reach more than 7 times the minimum value. It can be seen that the luminous intensity of the LED light source changes significantly with temperature. Figure 7 .

[0005] The low-power infrared gas sensor detects gas concentration based on the measured light intensity, and generally speaking, the change in detection light intensity caused by gas absorption is within the range of 0.5-1 times. By comparison, the change in sensor signal value caused by temperature change is much greater than the change in sensor signal value caused by gas absorption. If no corresponding compensation is performed, the gas concentration measurement error is extremely large and the low-power sensor cannot work properly.

[0006] At present, there are some light intensity compensation methods, such as China Patent Publication No. CN108444935A and China Patent Publication No. CN112925363A, which both compensate light intensity by pulse width modulation of the light source, ensuring the stability of the light intensity of the low-power infrared light source at any temperature. However, the method of using pulse width modulation to compensate light intensity has the following problems:

[0007] 1. The light intensity compensation operation is complicated. It requires collecting a large amount of data on the variation of light source intensity with ambient temperature and the variation of light source intensity with light source pulse width. Then, the two sets of data are integrated to obtain the curve relationship between light source pulse width and ambient temperature for light intensity compensation.

[0008] 2. It is impossible to compensate for the aging of the light source. As the light emission time increases, the brightness of the light source will gradually decrease. The pulse width modulation method to compensate for the light intensity cannot compensate for the aging of the light source.

[0009] 3. Different sensors have different light sources. Due to the individual differences in the temperature characteristics of the light sources, the compensation amount of each light source is different. Each sensor needs to be compensated individually, which is not conducive to the mass production of sensors.

[0010] The above problems need to be solved urgently. Summary of the invention

[0011] In order to overcome the deficiencies of the prior art, the present invention provides a gas concentration detection method and a low-power infrared gas sensor for implementing the method.

[0012] The technical solution of the present invention is as follows:

[0013] A high-precision and high-stability gas concentration detection method is provided. The gas to be tested is introduced, and the signal intensity of infrared light emitted by the same low-power infrared light source reaching two infrared detectors with the same filter band is collected. The concentration of the gas to be tested is calculated by inverting the ratio of the signal intensities of the two infrared detectors.

[0014] As a preferred technical solution of the present invention, the following steps are specifically included:

[0015] Step 1: introducing a gas to be tested with a known concentration gradient into the low-power infrared gas sensor;

[0016] Step 2, obtaining a fitting calculation formula for concentration and normalized detection signal intensity;

[0017] Record the normalized detection signal intensity measured by the low-power infrared gas sensor at different concentrations; obtain the calculation formula by nonlinear curve fitting and write it into the chip;

[0018] Step 3: The low-power infrared gas sensor detects the normalized detection signal intensity of the gas to be tested of unknown concentration;

[0019] Step 4: Calculate the concentration of the gas to be measured according to the calculation formula.

[0020] The present invention also provides a low-power infrared gas sensor for realizing the high-precision and high-stability gas concentration detection method described in the above scheme; the low-power infrared gas sensor has an air chamber for passing gas; the air chamber is provided with a gas detection optical path to be measured, and the gas detection optical path to be measured includes a first low-power infrared light source, a first spectroscopic structure, a first infrared detector and a second infrared detector, the emission light of the first low-power infrared light source is divided into two beams of light with the same central wavelength by the first spectroscopic structure, and respectively emitted to the first infrared detector and the second infrared detector with the same filter band; the distance from the first infrared detector to the first spectroscopic structure is different from the distance from the second infrared detector to the first spectroscopic structure, so that the optical path length from the first low-power infrared light source to the first infrared detector is not equal to the optical path length from the first low-power infrared light source to the second infrared detector, and the difference is defined as the length of the equivalent optical path of the gas detection optical path to be measured.

[0021] As a preferred technical solution of the present invention, the gas detection optical path to be tested also includes a first off-axis parabolic reflection surface, an outer ring reflection surface and a second off-axis parabolic reflection surface, the first off-axis parabolic reflection surface is used to collimate the emission light of the first low-power infrared light source and reflect it onto the outer ring reflection surface, the outer ring reflection surface is used to reflect the light four times to form a rectangular optical path; the outer ring reflection surface reflects the light once, twice or three times and then emits it toward the first spectroscopic structure, and the light passing through the first spectroscopic structure is emitted toward the next reflection point of the outer ring reflection surface, and the light reflected by the first spectroscopic structure is emitted toward the first infrared detector; the outer ring reflection surface reflects the light four times and then emits it toward the second off-axis parabolic reflection surface, and the light is reflected by the second off-axis parabolic reflection surface and converges to the second infrared detector.

[0022] Furthermore, the air chamber has a first mounting surface and a second mounting surface that are opposite and parallel to each other, the outer ring reflection surface is located between the first mounting surface and the second mounting surface, and the surface where the rectangular optical path of the outer ring reflection surface is located is parallel to the two mounting surfaces; the first low-power infrared light source, the first infrared detector and the second infrared detector are arranged on the first mounting surface, and the first splitting structure, the first off-axis parabolic reflection surface and the second off-axis parabolic reflection surface are located on the second mounting surface; the optical path from the first low-power infrared light source to the first off-axis parabolic reflection surface, the optical path from the first splitting structure to the first infrared detector, and the optical path from the second off-axis parabolic reflection surface to the second infrared detector are all perpendicular to the surface where the rectangular optical path is located.

[0023] As a preferred technical solution of the present invention, the gas chamber is provided with an interference gas detection optical path, which includes a second low-power infrared light source, a second spectroscopic structure, a third infrared detector and a fourth infrared detector. The emission light of the second low-power infrared light source is divided into two beams of light with the same central wavelength by the second spectroscopic structure, and is respectively emitted to the third infrared detector and the fourth infrared detector with the same filter band; the distance from the third infrared detector to the second spectroscopic structure is different from the distance from the fourth infrared detector to the second spectroscopic structure, so that the optical path length from the second low-power infrared light source to the third infrared detector is not equal to the optical path length from the second low-power infrared light source to the fourth infrared detector, and the difference is defined as the length of the equivalent optical path of the interference gas detection optical path.

[0024] Furthermore, the interference gas detection optical path also includes a third off-axis parabolic reflection surface, an inner ring reflection surface and a fourth off-axis parabolic reflection surface. The third off-axis parabolic reflection surface is used to collimate the emission light of the second low-power infrared light source and reflect it to the second spectroscopic structure. The second spectroscopic structure reflects part of the light to the third infrared detector, and the light passing through the second spectroscopic structure is emitted to the inner ring reflection surface. The inner ring reflection surface reflects the light to the fourth off-axis parabolic reflection surface. The light is reflected by the fourth off-axis parabolic reflection surface and converges to the fourth infrared detector.

[0025] As a preferred technical solution of the present invention, the first light-splitting structure and the second light-splitting structure both have a metal reflective plate, and the metal reflective plate is provided with a plurality of light-transmitting holes. The ratio of the area of ​​all the light-transmitting holes to the area of ​​the metal reflective plate is the light transmittance of the metal reflective plate, and the ratio of the area of ​​the metal reflective plate after removing all the light-transmitting holes to the area of ​​the metal reflective plate is the reflectivity of the metal reflective plate; the number of light-transmitting holes of the metal reflective plate is fixed or adjustable.

[0026] Furthermore, a toggle plate is provided in the middle layer of the metal reflective plate, and the surfaces of the metal reflective plate and the toggle plate are coated with a reflective film. The number of light-transmitting holes blocked by the toggle plate can be adjusted by adjusting the relative position of the toggle plate and the metal reflective plate.

[0027] Furthermore, a plate movable groove is provided at a position of the top plate of the air chamber corresponding to the light splitting structure, and the shifting plate can slide in the corresponding plate movable groove.

[0028] As a preferred technical solution of the present invention, the air chamber has a first mounting surface and a second mounting surface that are opposite and parallel to each other, and the inner ring reflection surface is located between the first mounting surface and the second mounting surface; the second low-power infrared light source, the third infrared detector and the fourth infrared detector are arranged on the first mounting surface, and the second spectroscopic structure, the third off-axis parabolic reflection surface and the fourth off-axis parabolic reflection surface are located on the second mounting surface; the optical path from the second low-power infrared light source to the third off-axis parabolic reflection surface, the optical path from the second spectroscopic structure to the third infrared detector, and the optical path from the fourth off-axis parabolic reflection surface to the fourth infrared detector are all perpendicular to the surface where the rectangular optical path is located.

[0029] Furthermore, the distance from the straight line where the optical path from the first off-axis parabolic reflector to the outer ring reflector is located to the center point of the outer ring reflector is equal to the square root of two of the radius of the outer ring reflector, so that the rectangular optical path is a square optical path.

[0030] As a preferred technical solution of the present invention, the air chamber is composed of a bottom plate, a hollow plate and a top plate, the upper surface of the bottom plate constitutes the first mounting surface of the air chamber, and the lower surface of the top plate constitutes the second mounting surface of the air chamber; the upper surface of the hollow plate is provided with an outer plate and an inner plate in a concentric circle structure, the inner side wall of the outer plate is plated with a reflective surface to form an outer ring reflective surface, and the inner side wall of the inner plate is plated with a reflective surface to form an inner ring reflective surface; the hollow plate is provided with a plurality of hollow openings, and the hollow openings are used to pass the emission light of the low-power infrared light source on the bottom plate, the receiving light of the infrared detector, or the reflected light through the spectroscopic structure on the top plate.

[0031] Furthermore, the top plate is provided with a plurality of vent holes, and the vent holes are used to pass gas into the to-be-detected gas detection optical path and the interfering gas detection optical path.

[0032] Furthermore, the top plate is provided with a limiting boss or a limiting groove, and the peripheral plate on the hollow plate is provided with a matching limiting groove or limiting boss.

[0033] As a preferred technical solution of the present invention, it also includes a low-power circuit board arranged at the bottom of the air chamber, and the pins of the low-power infrared light source and infrared detector in the air chamber pass through the bottom of the air chamber and are welded to the low-power circuit board.

[0034] As a preferred technical solution of the present invention, it also includes a shell, which includes an outer protective cover and a bottom shell. The top of the outer protective cover is provided with an air inlet, and a plurality of sensor pins pass through the bottom shell.

[0035] The present invention according to the above scheme has the following beneficial effects:

[0036] The present invention simultaneously collects the signal strength of the infrared light emitted by the same low-power infrared light source of the low-power infrared gas sensor reaching two infrared detectors, and inversely calculates the concentration of the gas to be measured by the ratio of the detection signal strengths of the two infrared detectors, thereby ensuring that the low-power sensor is not affected by factors such as the external environment temperature and the aging of the light source during operation, and realizing the stability and accuracy of the low-power infrared gas sensor in detecting the gas concentration;

[0037] Through the implementation method of high-stability low-power infrared gas sensors, individual differences between temperature characteristics of different light sources of different sensors can be eliminated, and each sensor does not need to be compensated separately, which is conducive to the mass production of low-power infrared gas sensors.

[0038] Furthermore, the optical path structure of the low-power infrared gas sensor can be divided into an internal and external optical path structure. The external optical path is the gas detection optical path for measuring the concentration of the gas to be measured; the internal optical path is the interference gas detection optical path, which is used to measure the concentration of specific interference gases. Through the data processing algorithm, the low-power infrared gas sensor has the gas concentration detection function that is resistant to specific interference gases; and, whether it is the concentration detection of the gas to be measured or the concentration detection of the interference gas, it can be achieved that the concentration detection result is not affected by factors such as the external ambient temperature and the aging of the light source, thereby ensuring the stability and accuracy of the detected gas concentration. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a flow chart of the method of the present invention;

[0040] Figure 2 It is a structural exploded diagram of the present invention;

[0041] Figure 3 It is a structural schematic diagram of the hollow plate of the present invention;

[0042] Figure 4 It is a schematic structural diagram of the top plate of the present invention;

[0043] Figure 5 It is a schematic diagram of the optical path of the present invention;

[0044] Figure 6 The detection light intensity ratio of the present invention varies with temperature;

[0045] Figure 7 This is a graph showing the change in light intensity versus temperature for existing low-power infrared gas sensors.

[0046] In the figure,

[0047] 1. Hollow plate; 11. Outer ring reflective surface; 12. Inner ring reflective surface; 13. Hollow opening; 14. Limiting groove;

[0048] 20. Bottom plate; 2. First low-power infrared light source; 3. First infrared detector; 4. Second infrared detector; 5. Second low-power infrared light source; 6. Third infrared detector; 7. Fourth infrared detector;

[0049] 8. top plate; 81. first off-axis parabolic reflector; 82. second off-axis parabolic reflector; 83. third off-axis parabolic reflector; 84. fourth off-axis parabolic reflector; 85. first light splitting structure; 86. second light splitting structure; 87. vent hole; 88. position limiting boss;

[0050] 9. Low power circuit board; 10. External protective cover; 101. Air inlet. DETAILED DESCRIPTION

[0051] In order to better understand the purpose, technical scheme and technical effect of the present invention, the present invention is further explained in conjunction with the accompanying drawings and embodiments. It should be noted that similar numbers and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. At the same time, it is stated that the embodiments described below are only used to explain the present invention and are not used to limit the present invention.

[0052] It should be noted that when an element is referred to as being "fixed on" or "disposed on" another element, it may be directly on the other element or there may also be a central element, and when an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time.

[0053] The indicated orientation or position relationship is based on the orientation or position relationship shown in the drawings, or the orientation or position relationship in which the product of the application is usually placed when used, or the orientation or position relationship commonly understood by technical personnel in this field, or the orientation or position relationship in which the product of the application is usually placed when used. It is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0054] The terms "first", "second", "third" and "fourth" are used only for descriptive purposes and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features. "Several" means two or more, unless otherwise clearly and specifically defined.

[0055] like Figures 1 to 6As shown, a high-precision and high-stability gas concentration detection method is used. The gas to be tested is introduced, and the signal intensity of the infrared light emitted by the same low-power infrared light source reaching two infrared detectors with the same filter band is collected. The concentration of the gas to be tested is calculated by inverting the ratio of the signal intensities of the two infrared detectors. The filter band of the internal filter of the infrared detector determines its detection band, so the detection bands of the two infrared detectors are the same and are both within the absorption band of the gas to be tested. After the gas to be tested is introduced, the molecules of the gas to be tested absorb the emitted infrared light, and the two identical infrared detectors can detect the change in light intensity. When the ambient temperature changes, the light intensity change law of the two infrared detectors with the same filter band is consistent, so the ratio of the signal intensities of the two infrared detectors is not affected by temperature. Therefore, by inverting the ratio of the signal intensities of the two infrared detectors to calculate the concentration of the gas to be tested, the influence of temperature changes on the calculation of gas concentration can be eliminated.

[0056] The following example illustrates the principle of this method:

[0057] Let the optical path length from the low-power infrared light source to the infrared detector A be , the optical path length from the low-power infrared light source to the infrared detector B is ;

[0058] When the ambient temperature is When there is no gas to be detected, the light intensity detected by infrared detector A is , the light intensity detected by infrared detector B is ; When there is a gas to be tested, the light intensity detected by infrared detector A is , the light intensity detected by infrared detector B is , according to Beer-Lambert law:

[0059] (1),

[0060] (2);

[0061] When the ambient temperature is When there is no gas to be detected, the light intensity detected by infrared detector A is , the light intensity detected by infrared detector B is ; When there is a gas to be tested, the light intensity detected by infrared detector A is , the light intensity detected by infrared detector B is , according to Lambert-Beer law:

[0062] (3),

[0063] (4);

[0064] In the formula, α(υ) is the absorption coefficient of the gas to be measured, C is the concentration of the gas to be measured, and e is a constant;

[0065] Dividing formula (2) by formula (1) yields: (5);

[0066] Formula (4) is divided by formula (3), and since the ambient temperature is The light source brightness when the ambient temperature is k times of the time, that is = , = , so we can get:

[0067] (6);

[0068] In formula (6), due to is the value measured without the gas to be tested, is a constant.

[0069] It can be seen from equations (5) and (6) that under different ambient temperatures, even if the low-power infrared light source has different luminous brightness, for the same concentration of the gas to be tested, , that is, the normalized detection signal intensity remains constant and does not change with the brightness of the light source, and is not affected by temperature factors.

[0070] like Figure 6 As shown, the intensity of the light signal received by the infrared detector A is divided by the intensity of the light signal of the infrared detector B and multiplied by 10000 to obtain the normalized detection signal intensity. It can be seen that the normalized detection signal intensity is not affected by the change of the external ambient temperature. When the external ambient temperature changes from -40 degrees to 70 degrees, the normalized detection signal intensity remains basically constant.

[0071] Similarly, for the low-power infrared gas sensor, the brightness of the light source becomes smaller due to the aging of the light source, and the individual differences in the temperature characteristics of the light source between different sensors cause the brightness of the light source to change with temperature differently. Since the measured normalized detection signal intensity remains constant, the gas concentration obtained by inversion calculation is not affected by factors such as the external ambient temperature and the aging of the light source, thereby ensuring the stability and accuracy of the detected gas concentration. It can also eliminate the individual differences between the temperature characteristics of different light sources of different sensors, and there is no need to compensate for each sensor separately, which is conducive to the mass production of low-power infrared gas sensors.

[0072] In a specific embodiment, a high-precision and high-stability gas concentration detection method specifically includes the following steps:

[0073] Step 1: introducing a gas to be tested with a known concentration gradient into the low-power infrared gas sensor;

[0074] For different concentrations of the gas to be tested, the formula It can be seen that the low-power infrared gas sensor can obtain different normalized detection signal intensities.

[0075] Step 2, obtaining a fitting calculation formula for concentration and normalized detection signal intensity;

[0076] Record the normalized detection signal intensity corresponding to each gas concentration at different concentrations; use nonlinear curve fitting to obtain an exponential function The calculation formula is written into the chip of the low-power infrared gas sensor;

[0077] Step 3, detecting the normalized detection signal intensity of the gas to be tested with unknown concentration;

[0078] The low-power infrared gas sensor is placed in an environment with an unknown concentration of the gas to be tested, and a normalized detection signal intensity can be measured.

[0079] Step 4: derive the concentration of the gas to be measured according to the calculation formula;

[0080] The chip of the low-power infrared gas sensor automatically calculates the concentration value corresponding to the normalized detection signal intensity measured in step 3, which is the concentration of the unknown concentration of the gas to be measured. Embodiment 1

[0081] like Figures 2 to 6 As shown, a low-power infrared gas sensor is used to implement the high-precision and high-stability gas concentration detection method of the above scheme. The low-power infrared gas sensor has an air chamber for passing gas, and the air chamber is provided with a gas detection optical path to be detected, and the gas detection optical path to be detected includes a first low-power infrared light source 2, a first spectroscopic structure 85, a first infrared detector 3, and a second infrared detector 4. The emission light of the first low-power infrared light source 2 is divided into two beams of light with the same central wavelength by the first spectroscopic structure 85, and is emitted to the first infrared detector 3 and the second infrared detector 4 respectively, and the first infrared detector 3 and the second infrared detector 4 have the same filter band, so that the detection bands of the first infrared detector 3 and the second infrared detector 4 are both within the absorption band of the gas to be detected. The distance from the first infrared detector 3 to the first spectroscopic structure 85 is different from the distance from the second infrared detector 4 to the first spectroscopic structure 85, so that the optical path length from the first low-power infrared light source 2 to the first infrared detector 3 is not equal to the optical path length from the first low-power infrared light source 2 to the second infrared detector 4, and the difference between the two optical path lengths is defined as the length of the equivalent optical path of the gas detection optical path to be detected.

[0082] When the low-power infrared gas sensor of this embodiment is used and the gas is introduced, the ratio of the detection light intensity signal of the first infrared detector 3 and the second infrared detector 4 is , which is the normalized detection signal intensity obtained by measuring the gas to be tested in the gas detection optical path.

[0083] like Figure 5 As shown, in this embodiment, the gas detection optical path to be measured also includes a first off-axis parabolic reflective surface 81, an outer ring reflective surface 11 and a second off-axis parabolic reflective surface 82. The infrared light emitted by the first low-power infrared light source 2 is first directed to the first off-axis parabolic reflective surface 81, and the first off-axis parabolic reflective surface 81 collimates the infrared light, so that the divergent infrared light becomes collimated light or nearly collimated light, forming parallel reflected light. The first off-axis parabolic reflective surface 81 reflects the light to the outer ring reflective surface 11. Since the outer ring reflective surface 11 forms a closed ring internal reflection, the light entering the space of the outer ring reflective surface 11 will be reflected multiple times, so as to achieve a longer optical path in a narrow space or an effective space. After the light is reflected four times by the outer ring reflective surface 11, the second off-axis parabolic reflective surface 82 is used to guide the light out of the space of the outer ring reflective surface 11, so that the outer ring reflective surface 11 reflects the light four times to form a rectangular optical path.

[0084] The first light splitting structure 85 can be arranged behind the first reflection point of the outer ring reflection surface 11, or behind the second reflection point of the outer ring reflection surface 11, or behind the third reflection point of the outer ring reflection surface 11, and the first infrared detector 3 is correspondingly arranged directly below the first light splitting structure 85 to ensure receiving the reflected light from the first light splitting structure 85. Changing the setting position of the first light splitting structure 85 changes the optical path length L1 from the first low-power infrared light source 2 to the first infrared detector 3.

[0085] If the first spectroscopic structure 85 is arranged after the first reflection point of the outer ring reflection surface 11, the optical path length L1 from the first low-power infrared light source 2 to the first infrared detector 3 can be determined by the light propagation path, and its optical path is: first low-power infrared light source 2-first off-axis parabolic reflection surface 81-first reflection point of the outer ring reflection surface 11-first spectroscopic structure 85-first infrared detector 3.

[0086] If the first spectroscopic structure 85 is arranged after the second reflection point of the outer ring reflection surface 11, the optical path from the first low-power infrared light source 2 to the first infrared detector 3 is: the first low-power infrared light source 2-the first off-axis parabolic reflection surface 81-the first reflection point of the outer ring reflection surface 11-the second reflection point of the outer ring reflection surface 11-the first spectroscopic structure 85-the first infrared detector 3.

[0087] If the first spectroscopic structure 85 is arranged after the third reflection point of the outer ring reflection surface 11, the optical path from the first low-power infrared light source 2 to the first infrared detector 3 is: the first low-power infrared light source 2-the first off-axis parabolic reflection surface 81-the first reflection point of the outer ring reflection surface 11-the second reflection point of the outer ring reflection surface 11-the third reflection point of the outer ring reflection surface 11-the first spectroscopic structure 85-the first infrared detector 3.

[0088] The first light splitting structure 85 has a light transmission function in addition to the reflection function. Part of the light passing through the first light splitting structure 85 is emitted to the next reflection point of the outer ring reflection surface 11. Therefore, no matter where the first light splitting structure 85 is set in the rectangular optical path, the outer ring reflection surface 11 reflects the light four times and then emits it to the second off-axis parabolic reflection surface 82. After being reflected by the second off-axis parabolic reflection surface 82, it converges to the second infrared detector 4. Therefore, the light propagation path from the first low-power infrared light source 2 to the second infrared detector 4 remains unchanged, and the optical path length L2 is a fixed value. Its optical path: first low-power infrared light source 2-first off-axis parabolic reflection surface 81-the first reflection point of the outer ring reflection surface 11-the second reflection point of the outer ring reflection surface 11-the third reflection point of the outer ring reflection surface 11-the fourth reflection point of the outer ring reflection surface 11-the second off-axis parabolic reflection surface 82-the second infrared detector 4.

[0089] It can be seen that different setting positions of the first spectroscopic structure 85 can adjust the distance difference from the two infrared detectors to the first low-power infrared light source 2, that is, (L2-L1), thereby changing the equivalent optical path of the gas detection optical path to be measured. Since the longer the equivalent optical path is, the higher the detection accuracy of the sensor is, and the shorter the equivalent optical path is, the larger the range of the sensor is, when producing low-power infrared gas sensors, the position of the first spectroscopic structure 85 can be adjusted according to needs to select higher detection accuracy or a larger range.

[0090] The first light-splitting structure 85 has a metal reflector plate, the surface of which is coated with a reflective film and provided with a plurality of light-transmitting holes. When light is directed toward the non-light-transmitting holes of the metal reflector plate, it will be reflected, and when light is directed toward the light-transmitting holes, it will pass through the first light-splitting structure 85. It can be seen that: the ratio of the area of ​​all light-transmitting holes to the area of ​​the metal reflector plate is the transmittance of the metal reflector plate, that is, the transmittance of the first light-splitting structure 85; the ratio of the area of ​​the metal reflector plate after removing all light-transmitting holes to the area of ​​the metal reflector plate is the reflectivity of the metal reflector plate, that is, the reflectivity of the first light-splitting structure 85.

[0091] In a preferred embodiment, the number of light-transmitting holes of the metal reflector is adjustable. Specifically, a toggle plate is provided in the middle layer of the metal reflector, and the surfaces of the metal reflector and the toggle plate are coated with a reflective film. By adjusting the relative position of the toggle plate and the metal reflector, the number of light-transmitting holes blocked by the toggle plate can be changed, thereby achieving an adjustable number of light-transmitting holes of the metal reflector. The number of light-transmitting holes of the metal reflector can also be fixed when the low-power infrared gas sensor leaves the factory.

[0092] like Figure 2 and Figure 3 As shown, in this embodiment, the low-power infrared gas sensor includes a shell and an air chamber. The shell serves as a sensor housing to protect the internal air chamber and the electrical components therein. The air chamber is composed of a bottom plate 20, a hollow plate 1 and a top plate 8. The hollow plate 1 is located between the bottom plate 20 and the top plate 8. The top plate 8 is provided with a plurality of vents 87, through which gas can enter the air chamber and thus enter the detection optical path of the gas to be measured.

[0093] The upper surface of the bottom plate 20 constitutes the first mounting surface of the air chamber, and the lower surface of the top plate 8 constitutes the second mounting surface of the air chamber, and the first mounting surface and the second mounting surface are opposite and parallel. The first low-power infrared light source 2, the first infrared detector 3 and the second infrared detector 4 are arranged on the first mounting surface, and the first light splitting structure 85, the first off-axis parabolic reflection surface 81 and the second off-axis parabolic reflection surface 82 are located on the second mounting surface. Specifically, the first light splitting structure 85, the first off-axis parabolic reflection surface 81 and the second off-axis parabolic reflection surface 82 are directly machined onto the second mounting surface.

[0094] An outer plate is provided on the outer periphery of the upper surface of the hollow plate 1, and a reflective surface is plated on the inner side wall of the outer plate to form an outer ring reflective surface 11, so the outer ring reflective surface 11 is located between the first mounting surface and the second mounting surface, and the surface where the rectangular optical path of the outer ring reflective surface 11 is located is parallel to the two mounting surfaces. The hollow plate 1 is provided with a plurality of hollow openings 13, which correspond to the first low-power infrared light source 2, the first infrared detector 3, and the second infrared detector 4, respectively, so that the emission light of the first low-power infrared light source 2 enters the space of the outer ring reflective surface 11 through the corresponding hollow openings, and the reflected light through the first light splitting structure 85 enters the first infrared detector 3 through the corresponding hollow openings, and the reflected light through the second off-axis parabolic reflective surface 82 enters the second infrared detector 4 through the corresponding hollow openings. It can be seen that the first low-power infrared light source 2 is arranged correspondingly to the first off-axis parabolic reflector 81, the first splitting structure 85 is arranged correspondingly to the first infrared detector 3, and the second off-axis parabolic reflector 82 is arranged correspondingly to the second infrared detector 4; the optical path of the first low-power infrared light source 2 to the first off-axis parabolic reflector 81, the optical path from the first splitting structure 85 to the first infrared detector 3, and the optical path from the second off-axis parabolic reflector 82 to the second infrared detector 4 are all perpendicular to the plane where the rectangular optical path is located.

[0095] The top plate 8 is provided with a limiting boss 88, and the peripheral plate on the hollow plate 1 is provided with a matching limiting groove 14. Through the matching connection of the limiting boss 88 and the limiting groove 14, the hollow plate 1 and the top plate 8 can be quickly positioned and installed, and the hollow plate 1 and the bottom plate 20 can be quickly positioned and installed through the hollow opening 13, so the low-power infrared gas sensor can be quickly positioned and installed. In other optional embodiments, the top plate is provided with a limiting groove, and the peripheral plate on the hollow plate 1 is provided with a matching limiting boss.

[0096] Embodiment 2

[0097] like Figures 2 to 5 As shown, a low-power infrared gas sensor is provided with a gas detection optical path to be detected inside the gas chamber of the sensor, which is the same as the first embodiment, but the difference is that: an interference gas detection optical path is also provided inside the gas chamber, and the interference gas detection optical path includes a second low-power infrared light source 5, a second splitting structure 86, a third infrared detector 6 and a fourth infrared detector 7. The infrared light emitted by the second low-power infrared light source 5 is divided into two beams of light with the same central wavelength by the second splitting structure 86, and is respectively emitted to the third infrared detector 6 and the fourth infrared detector 7 with the same filter band. The distance from the third infrared detector 6 to the second splitting structure 86 is different from the distance from the fourth infrared detector 7 to the second splitting structure 86, so that the optical path length from the second low-power infrared light source 5 to the third infrared detector 6 is not equal to the optical path length from the second low-power infrared light source 5 to the fourth infrared detector 7, and the difference is defined as the length of the equivalent optical path of the interference gas detection optical path.

[0098] The working principle of the interfering gas detection optical path is the same as that of the gas detection optical path to be detected, except that the interfering gas detection optical path is used to detect the normalized detection signal intensity of the interfering gas to inversely calculate the concentration of the interfering gas.

[0099] like Figures 4 to 5As shown, in this embodiment, the interference gas detection optical path also includes a third off-axis parabolic reflection surface 83, an inner ring reflection surface 12 and a fourth off-axis parabolic reflection surface 84. The infrared light emitted by the second low-power infrared light source 5 first reaches the third off-axis parabolic reflection surface 83, and after being collimated by the third off-axis parabolic reflection surface 83, it becomes parallel reflected light and is emitted to the second light splitting structure 86. The second light splitting structure 86 uses its reflection effect to reflect part of the light to the third infrared detector 6, and the remaining part of the light is emitted to the inner ring reflection surface 12 through the second light splitting structure 86. The light is reflected only once on the inner ring reflection surface 12, and after reflection, it is emitted to the fourth off-axis parabolic reflection surface 84. The light is reflected by the fourth off-axis parabolic reflection surface 84 and converges to the fourth infrared detector 7. The inner ring reflection surface 12 is located inside the ring of the outer ring reflection surface 11, and its size should be small to avoid affecting the detection optical path of the gas to be measured. The second low-power infrared light source 5 , the third infrared detector 6 , the fourth infrared detector 7 , the second light splitting structure 86 , the third off-axis parabolic reflecting surface 83 and the fourth off-axis parabolic reflecting surface 84 are all located within the projected circular area of ​​the inner ring reflecting surface 12 .

[0100] The second splitting structure 86 is arranged on the optical path between the reflection point of the inner ring reflection surface 12 and the third off-axis parabolic reflection surface 83, ensuring that the optical path length L3 from the second low-power infrared light source 5 to the third infrared detector 6 and the optical path length L4 from the second low-power infrared light source 5 to the fourth infrared detector 7 are not equal, so the equivalent optical path of the interference gas detection optical path is (L4-L3).

[0101] The second light-splitting structure 86 has a metal reflective plate, the surface of the metal reflective plate is coated with a reflective film, and the metal reflective plate is provided with a plurality of light-transmitting holes. When light is directed to the non-light-transmitting holes of the metal reflective plate, it will be reflected, and when it is directed to the light-transmitting holes, it will pass through the second light-splitting structure 86. Like the first light-splitting structure 85, the transmittance and reflectance of the second light-splitting structure 86 depend on the number of light-transmitting holes on its metal reflective plate. In a preferred embodiment, the number of light-transmitting holes of the metal reflective plate is adjustable or fixed. Similarly, a plate movable groove is provided at a position of the top plate 8 corresponding to the second light-splitting structure 86, and the toggle plate of the metal reflective plate of the second light-splitting structure 86 can slide in the corresponding plate movable groove, so that the number of light-transmitting holes of the metal reflective plate of the second light-splitting structure 86 can be adjusted, thereby changing the reflectance and transmittance of the second light-splitting structure 86.

[0102] Compared with the first embodiment, the top plate 8 is provided with a greater number of vent holes 87 , and the additional vent holes 87 are used to correspond to the interfering gas detection optical path so that the gas enters the interfering gas detection optical path.

[0103] The second low-power infrared light source 5, the third infrared detector 6 and the fourth infrared detector 7 are arranged on the first mounting surface (i.e., the upper surface of the bottom plate 20), and the second light splitting structure 86, the third off-axis parabolic reflection surface 83 and the fourth off-axis parabolic reflection surface 84 are located on the second mounting surface (i.e., the lower surface of the top plate 8). Specifically, the second light splitting structure 86, the third off-axis parabolic reflection surface 83 and the fourth off-axis parabolic reflection surface 84 are directly machined onto the second mounting surface by machining.

[0104] like Figure 3 As shown, compared with the first embodiment, the upper surface of the hollow plate 1 is provided with an outer plate and an inner plate in a concentric circle structure. The structural features and functions of the outer plate are the same as those of the first embodiment, and are not described in detail here. The inner side wall of the inner plate is plated with a reflective surface to form an inner ring reflective surface 12, and the surface where the light path reflected by the inner ring reflective surface 12 is located is parallel to the first mounting surface and the second mounting surface.

[0105] Compared with the first embodiment, the hollow plate 1 is provided with a larger number of hollow openings 13, and the additional hollow openings correspond to the second low-power infrared light source 5, the third infrared detector 6 and the fourth infrared detector 7, respectively, so that the emitted light of the second low-power infrared light source 5 enters the space of the inner ring reflection surface 12 through the corresponding hollow openings, and the reflected light through the second light splitting structure 86 enters the third infrared detector 6 through the corresponding hollow openings, and the reflected light through the fourth off-axis parabolic reflection surface 84 enters the fourth infrared detector 7 through the corresponding hollow openings. It can be seen that the second low-power infrared light source 5 is arranged correspondingly to the third off-axis parabolic reflection surface 83, the second light splitting structure 86 is arranged correspondingly to the third infrared detector 6, and the fourth off-axis parabolic reflection surface 84 is arranged correspondingly to the fourth infrared detector 7. The optical path from the second low-power infrared light source 5 to the third off-axis parabolic reflection surface 83, the optical path from the second light splitting structure 86 to the third infrared detector 6, and the optical path from the fourth off-axis parabolic reflection surface 84 to the fourth infrared detector 7 are all perpendicular to the surface where the reflected light path of the inner ring reflection surface 12 is located, and are also perpendicular to the surface where the rectangular light path is located.

[0106] like Figure 5 As shown, in a preferred embodiment, the distance from the straight line where the optical path from the first off-axis parabolic reflective surface 81 to the outer ring reflective surface 11 is located to the center point of the outer ring reflective surface 11 is equal to the root of two of the radius of the outer ring reflective surface 11, so that the rectangular optical path of the outer ring reflective surface 11 is a square optical path. It can be known from geometry that when the rectangle inside the circle is a square, the rectangle has the largest area, so the internal space of the square optical path is the largest, and there is ample space to set the inner enclosure to avoid the inner enclosure blocking the light of the peripheral gas detection optical path to be detected.

[0107] The low-power infrared gas sensor of this embodiment is suitable for application scenarios where interfering gases exist in the gas detection environment. The detection band of the infrared detector in the detection optical path of the gas to be measured is within the absorption band of the gas to be measured, and the detection band of the infrared detector in the interfering gas detection optical path is within the absorption band of the interfering gas.

[0108] The test results of the gas detection optical path to be tested and the interference gas detection optical path have the following situations:

[0109] Case 1--

[0110] The detection optical path of the gas to be measured only responds to the gas to be measured, that is, the light center wavelength of the first low-power infrared light source and the detection bands of the first and second infrared detectors are both within the absorption band of the gas to be measured, but not within the absorption band of the interfering gas. The detection optical path of the interfering gas only responds to the interfering gas, that is, the light center wavelength of the second low-power infrared light source and the detection bands of the third and fourth infrared detectors are both within the absorption band of the interfering gas, but not within the absorption band of the gas to be measured.

[0111] In this case, the interfering gas will not affect the concentration result of the gas to be measured.

[0112] Case 2--

[0113] The optical path for detecting the gas to be measured responds to both the gas to be measured and the interfering gas, that is, the light center wavelength of the first low-power infrared light source and the detection bands of the first and second infrared detectors are both within the absorption band of the gas to be measured and the absorption band of the interfering gas. The optical path for detecting the interfering gas responds only to the interfering gas, that is, the light center wavelength of the second low-power infrared light source and the detection bands of the third and fourth infrared detectors are both within the absorption band of the interfering gas and not within the absorption band of the gas to be measured.

[0114] In this case, in the optical path of the gas to be tested, the relationship between the concentration of the gas to be tested and the absorbance is f1, and the relationship between the concentration of the interfering gas and the absorbance is f2; in the optical path of the interfering gas detection, the relationship between the concentration of the interfering gas and the absorbance is f3; then, f1, f2, and f3 can be obtained through theoretical calculations or experimental data. Assuming that the gas concentration of the gas A to be tested is C1, the gas concentration of the interfering gas B is C2, the absorbance of the optical path of the gas to be tested is D1, and the absorbance of the optical path of the interfering gas detection is D2, D1 and D2 can be calculated by the ratio of the currently detected light intensity to the zero-point detection light intensity. Therefore, the following relationship can be obtained:

[0115] f1(C1)+f2(C2)=D1 (7)

[0116] f3(C2)=D2 (8);

[0117] In formulas (7) and (8), f1, f2, f3, D1, and D2 are known. The values ​​of the concentration of the gas to be measured C1 and the concentration of the interfering gas C2 can be calculated by mathematical calculation or the least square method. For ease of understanding, an example of a linear relationship is given. If the absorption rate of the gas to be measured and the interfering gas is low, and the optical path lengths of the detection optical path of the gas to be measured and the detection optical path of the interfering gas are short, the relationship between the concentration and the absorption rate of the gas to be measured and the interfering gas can be regarded as a linear relationship, then:

[0118] k1×C1+ k2×C2=D1 (71),

[0119] k3×C2=D2 (81);

[0120] In formulas (71) and (81), k1, k2, k3, D1, and D2 are all known, and the values ​​of the measured gas concentration C1 and the interfering gas concentration C2 can be easily calculated by mathematical calculation.

[0121] Case 3--

[0122] The detection optical path of the gas to be measured responds to both the gas to be measured and the interfering gas, that is, the light center wavelength of the first low-power infrared light source and the detection bands of the first and second infrared detectors are both within the absorption band of the gas to be measured and the absorption band of the interfering gas. The detection optical path of the interfering gas responds to both the gas to be measured and the interfering gas, that is, the light center wavelength of the second low-power infrared light source and the detection bands of the third and fourth infrared detectors are both within the absorption band of the gas to be measured and the absorption band of the interfering gas.

[0123] In this case, in the optical path of the gas to be tested, the relationship between the concentration of the gas to be tested and the absorbance is f1, and the relationship between the concentration of the interfering gas and the absorbance is f2; in the optical path of the interfering gas detection, the relationship between the concentration of the gas to be tested and the absorbance is f3, and the relationship between the concentration of the interfering gas and the absorbance is f4; then, f1, f2, f3, and f4 can be obtained through theoretical calculations or experimental data. Assuming that the gas concentration of the gas A to be tested is C1, the gas concentration of the interfering gas B is C2, the absorbance of the optical path of the gas to be tested is D1, and the absorbance of the optical path of the interfering gas detection is D2, D1 and D2 can be calculated by the ratio of the current detected light intensity to the zero-point detection light intensity. Therefore, the following relationship can be obtained:

[0124] f1(C1)+f2(C2)=D1 (9),

[0125] f3(C1)+f4(C2)=D2 (10);

[0126] In formulas (9) and (10), f1, f2, f3, f4, D1, and D2 are known. The values ​​of the concentration of the gas to be measured C1 and the concentration of the interfering gas C2 can be calculated by mathematical calculation or the least square method. Similarly, taking an example of a linear relationship, we have:

[0127] k1×C1+ k2×C2=D1 (91),

[0128] k3×C1+ k4×C2=D2 (101);

[0129] In formulas (91) and (101), k1, k2, k3, k4, D1, and D2 are all known, and the values ​​of the measured gas concentration C1 and the interfering gas concentration C2 can be easily calculated by mathematical calculation.

[0130] In summary, in Case 2 and Case 3, if the interfering gas affects the concentration calculation of the gas to be measured, the actual concentration of the gas to be measured and the concentration of the interfering gas can be calculated separately by adding an interfering gas detection optical path, thereby eliminating the influence of the interfering gas on the calculation result of the concentration of the gas to be measured.

[0131] In the present invention, the first off-axis parabolic reflective surface 81 is used to collimate and reflect the first low-power infrared light source 2, and the third off-axis parabolic reflective surface 83 is used to collimate and reflect the second low-power infrared light source 5. In order to ensure that the off-axis parabolic reflective surface can efficiently reflect the light emitted by the corresponding low-power infrared light source, the vertical position of the center of the light-emitting surface of the low-power infrared light source is directly above the focus of the off-axis parabolic reflective surface. The distance between the center of the light-emitting surface and the focus of the off-axis parabolic reflective surface depends on the size and divergence angle of the light-emitting surface. The reverse extension line of the light emitted at the edge of the light-emitting surface with the maximum divergence angle coincides with the focus of the off-axis parabolic reflective surface.

[0132] like Figure 2 As shown, the low-power infrared gas sensor adopts a low-power circuit board 9, which is located at the bottom of the air chamber, specifically, below the bottom plate 20 of the air chamber; and the pins of the first low-power infrared light source, the second low-power infrared light source and the four infrared detectors in the air chamber pass through the bottom plate 20 at the bottom of the air chamber and are welded to the low-power circuit board 9.

[0133] The housing includes an outer protective cover 10 and a bottom shell. The top of the outer protective cover 10 is provided with an air inlet 101 to allow the gas from the external environment to enter the sensor and then enter the air chamber through the vent 87. The bottom shell is provided with a number of sensor pins for connecting and fixing the low-power infrared gas sensor.

[0134] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0135] The above embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for realizing high-precision and high-stability gas concentration detection using a low-power infrared gas sensor, characterized in that: The low-power infrared gas sensor has an air chamber for passing gas, the air chamber is provided with a gas detection optical path to be detected, the gas detection optical path to be detected includes a first low-power infrared light source, a first spectroscopic structure, a first infrared detector and a second infrared detector, the emission light of the first low-power infrared light source is divided into two beams of light with the same central wavelength by the first spectroscopic structure, and respectively emitted to the first infrared detector and the second infrared detector with the same filter band; The distance from the first infrared detector to the first spectroscopic structure is different from the distance from the second infrared detector to the first spectroscopic structure, so that the optical path length from the first low-power infrared light source to the first infrared detector is different from the optical path length from the first low-power infrared light source to the second infrared detector, and the difference is defined as the length of the equivalent optical path of the gas detection optical path to be detected; The gas detection optical path to be tested also includes a first off-axis parabolic reflection surface, an outer ring reflection surface and a second off-axis parabolic reflection surface, wherein the first off-axis parabolic reflection surface is used to collimate the emitted light of the first low-power infrared light source and reflect it onto the outer ring reflection surface, and the outer ring reflection surface is used to reflect the light four times to form a rectangular optical path; The outer ring reflection surface reflects the light once, twice or three times and then emits it to the first light splitting structure, and the light passing through the first light splitting structure is emitted to the next reflection point of the outer ring reflection surface, and the light reflected by the first light splitting structure is emitted to the first infrared detector; The outer ring reflective surface reflects the light four times and then emits it to the second off-axis parabolic reflective surface, and then is reflected by the second off-axis parabolic reflective surface and converged to the second infrared detector; The air chamber has a first mounting surface and a second mounting surface facing and parallel to each other, the outer ring reflection surface is located between the first mounting surface and the second mounting surface, and the surface where the rectangular optical path of the outer ring reflection surface is located is parallel to the two mounting surfaces; The first low-power infrared light source, the first infrared detector and the second infrared detector are arranged on the first mounting surface, and the first light splitting structure, the first off-axis parabolic reflective surface and the second off-axis parabolic reflective surface are located on the second mounting surface; The optical path from the first low-power infrared light source to the first off-axis parabolic reflector, the optical path from the first light splitting structure to the first infrared detector, and the optical path from the second off-axis parabolic reflector to the second infrared detector are all perpendicular to the plane where the rectangular optical path is located; The gas chamber is provided with an interference gas detection optical path, which includes a second low-power infrared light source, a second spectroscopic structure, a third infrared detector and a fourth infrared detector. The emission light of the second low-power infrared light source is divided into two beams of light with the same central wavelength by the second spectroscopic structure, and respectively emitted to the third infrared detector and the fourth infrared detector with the same filter band; The distance from the third infrared detector to the second spectroscopic structure is different from the distance from the fourth infrared detector to the second spectroscopic structure, so that the optical path length from the second low-power infrared light source to the third infrared detector is not equal to the optical path length from the second low-power infrared light source to the fourth infrared detector, and the difference is defined as the length of the equivalent optical path of the interfering gas detection optical path; The interference gas detection optical path also includes a third off-axis parabolic reflection surface, an inner ring reflection surface and a fourth off-axis parabolic reflection surface, wherein the third off-axis parabolic reflection surface is used to collimate the emitted light of the second low-power infrared light source and reflect it to the second light splitting structure, the second light splitting structure reflects part of the light to the third infrared detector, and the light passing through the second light splitting structure is emitted to the inner ring reflection surface, the inner ring reflection surface reflects the light to the fourth off-axis parabolic reflection surface, and the light is reflected by the fourth off-axis parabolic reflection surface and converges to the fourth infrared detector; The inner ring reflection surface is located between the first mounting surface and the second mounting surface; the second low-power infrared light source, the third infrared detector and the fourth infrared detector are arranged on the first mounting surface, and the second light splitting structure, the third off-axis parabolic reflection surface and the fourth off-axis parabolic reflection surface are located on the second mounting surface; The optical path from the second low-power infrared light source to the third off-axis parabolic reflector, the optical path from the second light splitting structure to the third infrared detector, and the optical path from the fourth off-axis parabolic reflector to the fourth infrared detector are all perpendicular to the plane where the rectangular optical path is located; The air chamber is composed of a bottom plate, a hollow plate and a top plate, the upper surface of the bottom plate constitutes the first mounting surface of the air chamber, and the lower surface of the top plate constitutes the second mounting surface of the air chamber; the upper surface of the hollow plate is provided with an outer plate and an inner plate in a concentric circle structure, the inner side wall of the outer plate is plated with a reflective surface to form an outer ring reflective surface, and the inner side wall of the inner plate is plated with a reflective surface to form an inner ring reflective surface; the hollow plate is provided with a plurality of hollow openings, and the hollow openings are used to transmit the emission light of the low-power infrared light source on the bottom plate, the receiving light of the infrared detector, and the reflected light of the spectroscopic structure on the top plate; the inner ring reflective surface is located inside the ring of the outer ring reflective surface, and the second low-power infrared light source, the third infrared detector, the fourth infrared detector, the second spectroscopic structure, the third off-axis parabolic reflective surface and the fourth off-axis parabolic reflective surface are all located in the projected circular area of ​​the inner ring reflective surface; The method comprises: The gas to be tested is introduced, the signal intensity of the infrared light emitted by the same low-power infrared light source reaching two infrared detectors with the same filter band is collected, and the concentration of the gas to be tested is calculated by inverting the ratio of the signal intensity of the two infrared detectors; specifically, the following steps are included: Step 1: introducing a gas to be tested with a known concentration gradient into the low-power infrared gas sensor; Step 2, obtaining a fitting calculation formula of concentration and normalized detection signal intensity, wherein the normalized detection signal intensity is a ratio of signal intensities of two infrared detectors having the same filter band; Record the normalized detection signal intensity measured by the low-power infrared gas sensor at different concentrations; obtain the calculation formula by nonlinear curve fitting and write it into the chip; Step 3: The low-power infrared gas sensor detects the normalized detection signal intensity of the gas to be tested of unknown concentration; Step 4: derive the concentration of the gas to be measured according to the calculation formula; The working principle of the interfering gas detection optical path is the same as that of the gas detection optical path to be detected. The interfering gas detection optical path is used to detect the normalized detection signal intensity of the interfering gas to inversely calculate the concentration of the interfering gas.

2. The method for realizing high-precision and high-stability gas concentration detection using a low-power infrared gas sensor according to claim 1 is characterized in that: The first light-splitting structure and the second light-splitting structure both have a metal reflective plate, and the metal reflective plate is provided with a plurality of light-transmitting holes. The ratio of the area of ​​all the light-transmitting holes to the area of ​​the metal reflective plate is the light transmittance of the metal reflective plate, and the ratio of the area of ​​the metal reflective plate after removing all the light-transmitting holes to the area of ​​the metal reflective plate is the reflectivity of the metal reflective plate; the number of light-transmitting holes of the metal reflective plate is fixed or adjustable.

3. The method for realizing high-precision and high-stability gas concentration detection using a low-power infrared gas sensor according to claim 1, characterized in that: The rectangular light path is a square light path.

4. A low-power infrared gas sensor having a gas chamber for introducing gas, characterized in that: The low-power infrared gas sensor is used to implement the method for realizing high-precision and high-stability gas concentration detection as described in any one of claims 1 to 3; The gas chamber is provided with a gas detection optical path to be detected, and the gas detection optical path to be detected includes a first low-power infrared light source, a first spectroscopic structure, a first infrared detector and a second infrared detector. The emission light of the first low-power infrared light source is divided into two beams of light with the same central wavelength by the first spectroscopic structure, and respectively emitted to the first infrared detector and the second infrared detector with the same filter band; The distance from the first infrared detector to the first spectroscopic structure is different from the distance from the second infrared detector to the first spectroscopic structure, so that the optical path length from the first low-power infrared light source to the first infrared detector is different from the optical path length from the first low-power infrared light source to the second infrared detector, and the difference is defined as the length of the equivalent optical path of the gas detection optical path to be detected; The gas detection optical path to be tested also includes a first off-axis parabolic reflection surface, an outer ring reflection surface and a second off-axis parabolic reflection surface, wherein the first off-axis parabolic reflection surface is used to collimate the emitted light of the first low-power infrared light source and reflect it onto the outer ring reflection surface, and the outer ring reflection surface is used to reflect the light four times to form a rectangular optical path; The outer ring reflection surface reflects the light once, twice or three times and then emits it to the first light splitting structure, and the light passing through the first light splitting structure is emitted to the next reflection point of the outer ring reflection surface, and the light reflected by the first light splitting structure is emitted to the first infrared detector; The outer ring reflective surface reflects the light four times and then emits it to the second off-axis parabolic reflective surface, and then is reflected by the second off-axis parabolic reflective surface and converged to the second infrared detector; The air chamber has a first mounting surface and a second mounting surface facing and parallel to each other, the outer ring reflection surface is located between the first mounting surface and the second mounting surface, and the surface where the rectangular optical path of the outer ring reflection surface is located is parallel to the two mounting surfaces; The first low-power infrared light source, the first infrared detector and the second infrared detector are arranged on the first mounting surface, and the first light splitting structure, the first off-axis parabolic reflective surface and the second off-axis parabolic reflective surface are located on the second mounting surface; The optical path from the first low-power infrared light source to the first off-axis parabolic reflector, the optical path from the first light splitting structure to the first infrared detector, and the optical path from the second off-axis parabolic reflector to the second infrared detector are all perpendicular to the plane where the rectangular optical path is located; The gas chamber is provided with an interference gas detection optical path, which includes a second low-power infrared light source, a second spectroscopic structure, a third infrared detector and a fourth infrared detector. The emission light of the second low-power infrared light source is divided into two beams of light with the same central wavelength by the second spectroscopic structure, and respectively emitted to the third infrared detector and the fourth infrared detector with the same filter band; The distance from the third infrared detector to the second spectroscopic structure is different from the distance from the fourth infrared detector to the second spectroscopic structure, so that the optical path length from the second low-power infrared light source to the third infrared detector is not equal to the optical path length from the second low-power infrared light source to the fourth infrared detector, and the difference is defined as the length of the equivalent optical path of the interfering gas detection optical path; The interference gas detection optical path also includes a third off-axis parabolic reflection surface, an inner ring reflection surface and a fourth off-axis parabolic reflection surface, wherein the third off-axis parabolic reflection surface is used to collimate the emitted light of the second low-power infrared light source and reflect it to the second light splitting structure, the second light splitting structure reflects part of the light to the third infrared detector, and the light passing through the second light splitting structure is emitted to the inner ring reflection surface, the inner ring reflection surface reflects the light to the fourth off-axis parabolic reflection surface, and the light is reflected by the fourth off-axis parabolic reflection surface and converges to the fourth infrared detector; The inner ring reflection surface is located between the first mounting surface and the second mounting surface; the second low-power infrared light source, the third infrared detector and the fourth infrared detector are arranged on the first mounting surface, and the second light splitting structure, the third off-axis parabolic reflection surface and the fourth off-axis parabolic reflection surface are located on the second mounting surface; The optical path from the second low-power infrared light source to the third off-axis parabolic reflector, the optical path from the second light splitting structure to the third infrared detector, and the optical path from the fourth off-axis parabolic reflector to the fourth infrared detector are all perpendicular to the plane where the rectangular optical path is located; The air chamber is composed of a bottom plate, a hollow plate and a top plate, the upper surface of the bottom plate constitutes the first mounting surface of the air chamber, and the lower surface of the top plate constitutes the second mounting surface of the air chamber; the upper surface of the hollow plate is provided with an outer plate and an inner plate in a concentric circle structure, the inner side wall of the outer plate is plated with a reflective surface to form an outer ring reflective surface, and the inner side wall of the inner plate is plated with a reflective surface to form an inner ring reflective surface; the hollow plate is provided with a plurality of hollow openings, and the hollow openings are used to pass the emission light of the low-power infrared light source on the bottom plate, the receiving light of the infrared detector, or the reflected light of the spectroscopic structure on the top plate; the inner ring reflective surface is located inside the ring of the outer ring reflective surface, and the second low-power infrared light source, the third infrared detector, the fourth infrared detector, the second spectroscopic structure, the third off-axis parabolic reflective surface and the fourth off-axis parabolic reflective surface are all located in the projected circular area of ​​the inner ring reflective surface.

5. The low power consumption infrared gas sensor according to claim 4, characterized in that: The first light-splitting structure and the second light-splitting structure both have a metal reflective plate, and the metal reflective plate is provided with a plurality of light-transmitting holes. The ratio of the area of ​​all the light-transmitting holes to the area of ​​the metal reflective plate is the light transmittance of the metal reflective plate, and the ratio of the area of ​​the metal reflective plate after removing all the light-transmitting holes to the area of ​​the metal reflective plate is the reflectivity of the metal reflective plate; the number of light-transmitting holes of the metal reflective plate is fixed or adjustable.

6. The low power consumption infrared gas sensor according to claim 4, characterized in that: The rectangular light path is a square light path.

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