A multi-path cell compatible and integrated detection multi-optical-path gas detection system

Abstract

The present application relates to the technical field of spectral detection, and specifically provides a multi-path gas detection system compatible with multiple cells and integral detection, comprising a light source, a gas absorption cell and a detection unit, wherein the light source is used for providing corresponding waveband light for multiple gas detection, the gas absorption cell is a region for measuring sample gas, and the cavity mirror of the gas absorption cell is designed to at least include an integral zone and a multiple cell annular reflection zone, wherein the optical axes of at least two cavity mirrors have an included angle, and multiple light path transmissions are realized; and the detection unit is used for detecting detection light of different light paths to realize different gas detection. The present application combines multiple cell and off-axis integral cavity technologies to design a special-shaped mirror which can realize multi-path detection and replace a conventional cavity mirror, overcomes the problem that different light paths cannot be compatible in a single gas chamber structure, and can realize multi-component, self-defined range trace gas absorption detection through a single gas chamber.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of spectral detection, and particularly relates to a multi-optical-path gas detection system compatible with a multi-pass cell and integral detection. BACKGROUND

[0002] At present, the technical route for improving the sensitivity of a gas detection system in detecting trace gases is mainly to increase the action path of light and gas (i.e. the absorption optical path). The relatively mature technologies are the integral cavity output spectrum technology and the multi-pass cell technology. The multi-pass cell uses a specially designed mirror array (usually a combination of spherical mirrors or plane mirrors) to make the incident laser light reflect multiple times in a limited space, thereby significantly increasing the action path of light and gas (i.e. the absorption optical path), and greatly improving the sensitivity of trace gas detection. The limitation is the uniqueness of the optical path, i.e. the light spots cannot overlap. Due to factors such as the number of reflections, energy loss, light spot diffusion, mirror diameter, etc., the effective optical path of the multi-pass cell is usually in the range of several meters to tens of meters, and it is impossible to achieve an ultra-long optical path of hundreds of meters or kilometers. Such an optical path can cover the detection of some gases under certain concentration conditions, but when it comes to gases with higher precision and weaker absorption peaks, it cannot meet the detection conditions. At the same time, the existing multi-pass cell structure generally only has a unique optical path, which also limits its practical application in the multi-range field.

[0003] Compared with the multi-pass cell, the integral cavity enhanced output spectrum technology is to construct a resonant cavity structure and let the light beam repeatedly go back and forth between the two cavity mirrors (in which the coaxial cavity enhances the complete overlap of the light beam, and the off-axis cavity enhances the non-overlapping light spots as much as possible). Regardless of which cavity enhancement technology is used, the mirror transmissive light is used as the detection signal, and the light beam repeatedly reflects between the two cavity mirrors to achieve the effect of increasing the optical path of the optical cell structure. This cell structure can achieve an extremely long effective absorption optical path in a limited mirror space, and the weak energy signal transmitted by the laser beam when it reaches the mirror is the final detection signal.

[0004] At the present stage, regardless of which cell structure is used, there is usually only a unique absorption optical path, and it is impossible to cover several meters, tens of meters, hundreds of meters or kilometers of optical path at the same time.

[0005] In summary, at the present stage, it has been recognized that the method of multi-gas detection and meeting the self-defined detection range accuracy is a difficult problem that needs to be solved, and the demand for multi-range, multi-band, multi-component and small sample size detection is becoming increasingly urgent. SUMMARY

[0006] Therefore, the application aims to provide a multi-path gas detection system compatible with multiple cells and integral detection, which overcomes the problem that different optical paths cannot be compatible in a single gas chamber structure by combining a multiple cell and an integral cavity structure to design a special-shaped mirror as a cavity mirror.

[0007] To achieve the above-mentioned purpose, the technical scheme of the application is as follows:

[0008] The application provides a multi-path gas detection system compatible with multiple cells and integral detection, comprising a light source, a gas absorption cell and a detection unit, wherein the gas absorption cell comprises a gas chamber, a first cavity mirror and a second cavity mirror arranged in the gas chamber, and a half-transmission half-reflection mirror.

[0009] The first cavity mirror and the second cavity mirror each comprise at least an integral zone, a first annular reflection zone and a second annular reflection zone arranged outside the integral zone.

[0010] The optical axes of the first annular reflection zone of the first cavity mirror and the first annular reflection zone of the second cavity mirror form an angle; and the optical axes of the second annular reflection zone of the first cavity mirror and the second annular reflection zone of the second cavity mirror coincide.

[0011] The second annular reflection zone of the first cavity mirror is provided with a first incident hole, and the second annular reflection zone of the second cavity mirror is provided with a first emission hole; the first annular reflection zone of the second cavity mirror is provided with a second incident hole and a second emission hole.

[0012] The light source is configured to provide first detection light transmitted into the integral zone of the first cavity mirror and reciprocally reflected between the integral zones of the first cavity mirror and the second cavity mirror, and to provide second detection light emitted from the first incident hole and reciprocally reflected between the second annular reflection zones of the first cavity mirror and the second cavity mirror.

[0013] During the integral reflection between the integral zones, part of the first detection light is emitted from the integral zone of the second cavity mirror to the detection unit each time.

[0014] The second detection light is emitted from the first emission hole to the half-transmission half-reflection mirror, the half-transmission half-reflection mirror is configured to split the second detection light into third detection light and fourth detection light, the third detection light is transmitted from the half-transmission half-reflection mirror to the detection unit, and the fourth detection light is reflected from the half-transmission half-reflection mirror to the second incident hole and reciprocally reflected between the first annular reflection zones of the first cavity mirror and the second cavity mirror and emitted from the second emission hole to the detection unit.

[0015] Preferably, the outer wall of the gas chamber is provided with an air inlet and an air outlet, the air inlet is provided with a mass flow controller, the mass flow controller is used to configure the gas flow parameter of the gas entering the gas chamber through the air inlet; the air outlet is provided with a pressure closed-loop measurement and control component and an adjustable air pump, the pressure closed-loop measurement and control component is used to measure the air pressure in the gas chamber, and the adjustable air pump is used to control the air outlet rate according to the measured air pressure in the gas chamber.

[0016] Preferably, the integration area of the first cavity mirror and the integration area of the second cavity mirror are both plano-concave lens structures, the opposite surfaces of the integration area of the first cavity mirror and the integration area of the second cavity mirror are concave, and the opposite surfaces are flat, and the concave surfaces of the integration area of the first cavity mirror and the integration area of the second cavity mirror are both provided with a reflection-increasing film.

[0017] Preferably, the first probe light is coherent light or incoherent light.

[0018] Preferably, the curvature radius of the first type of annular reflection area is smaller than the curvature radius of the second type of annular reflection area and the integration area, and the curvature radius of the second type of annular reflection area and the integration area is the same or different.

[0019] Preferably, the spot falling point of the second probe light in the second type of annular reflection area presents a single circular multi-cell spot falling point; and the spot falling point of the fourth probe light in the first type of annular reflection area presents a non-coincident multi-circular multi-cell spot falling point.

[0020] Preferably, the processor is further used to collect the probe light signals of multiple light paths obtained by the detection unit, and realize self-defined detection of different gases according to the probe light signals of different light paths, wherein the probe light signals of multiple light paths include: a first probe light collection signal of a first light path, a third probe light collection signal of a second light path, and a fourth probe light collection signal of a third light path.

[0021] Preferably, a special-shaped light beam adjusting assembly is arranged between the second cavity mirror and the detection unit, and the special-shaped light beam adjusting assembly is used to adjust the inclination angles of different probe lights incident to different detection target surfaces in the detection unit.

[0022] Preferably, the inclination angles of different probe lights incident to different detection target surfaces are adjusted by the special-shaped light beam adjusting assembly, so that the different detection target surfaces in the detection unit can be arranged in different planes, or the spot spacing of different probe lights incident to the same plane is increased.

[0023] Preferably, the special-shaped light beam adjusting assembly is a special-shaped lens, the special-shaped lens includes a plurality of lens areas corresponding to different probe lights, and different lens areas of the special-shaped lens have different thicknesses and inclination angles of probe light exit surfaces.

[0024] The special-shaped lens is arranged between the second cavity mirror and the detection unit as an independent optical element, or is integrated on the surface of the second cavity mirror facing away from the first cavity mirror.

[0025] Compared with the prior art, the application can achieve the following beneficial effects:

[0026] The gas chamber cavity mirror in the gas detection system is innovatively designed, the cavity mirror is designed as a special-shaped mirror by combining a multi-pass cell and an integrating cavity structure, the central region of the cavity mirror is designed as a plano-concave lens with a concave surface coated with a high-reflection film, the detection light is injected through the plane side of the plano-concave lens, part of the detection light is collected by the cavity mirror during reflection between the two cavity mirrors, and the integral detection is realized by using the integral cavity output spectrum technology, the optical path of the integral detection is generally hundreds of meters to several kilometers, and the multi-pass cell structure cannot realize the long optical path advantage.

[0027] Since the special-shaped optical gas chamber can simultaneously realize the detection of multiple gases through a single absorption cell, multiple detectors for detecting different gases need to be arranged on the detection plane, but the space of the traditional detection plane is limited, and it is difficult to arrange multiple detectors in the same plane, especially for large-volume detection, therefore, the special-shaped beam adjusting assembly is additionally arranged outside the gas absorption cell exit cavity mirror, different wavelength beams (different gas detection) are separated in space and converged on different detectors, the disadvantage that the traditional detection method cannot simultaneously detect multiple separated wavelength beams is solved, and the simultaneous detection of multiple detectors avoids the time consumption of time division multiplexing and the introduction of extra spectral noise of frequency division multiplexing.

[0028] Since the light beam transmission optical path of the multi-pass cell is limited, the present application further designs a half-transmission half-reflection mirror and a mirror structure to split the probe light emitted by the gas chamber, wherein one beam is used for short optical path gas detection, and the other beam is reflected by the mirror to enter the gas chamber again to increase the optical path. Since the light spot of the traditional multi-pass cell structure cannot overlap and the number of reflections is limited, in order to increase the optical path of the light beam entering the gas chamber twice as much as possible, the present application designs the mirror surface of at least one annular reflection area to be in a tilted state based on the non-axial optical fiber transmission theory, that is, the front and rear cavity mirrors in this area are not parallel and have a certain angle, and the optical axes of this area do not coincide, so that a small angle exists in each reflection during the reflection of the light beam in the annular reflection area. In this way, the light beam can realize non-coincident multi-turn transmission, which can increase the optical path as much as possible while avoiding light spot overlap. Therefore, the light spot landing point of the annular reflection area with an optical axis angle presents a dense light spot multi-pass cell structure, that is, multiple small circular ring light spots are distributed in the annular area, and the light spot landing point presents a non-overlapping multi-circular multi-pass cell light spot landing point, rather than a traditional single-circular multi-pass cell light spot landing point.

[0029] The present application designs a multi-optical path gas detection system compatible with multi-pass cell and integral detection, which can flexibly select or synchronously acquire in multiple effective optical paths such as meter level (short), ten to one hundred meters level (medium), and kilometer level (long) according to detection requirements through the unique special-shaped cavity mirror partition design and secondary incidence light path, thereby fundamentally solving the pain points of single optical path of the traditional gas detection system and the inability to adapt to multi-component concentration detection, and simultaneously realizing multiple different optical path detection in a single gas absorption cell, satisfying multi-gas, multi-spectrum, and self-selected range / precision gas detection, greatly reducing equipment cost, and improving detection efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0030] The accompanying drawings, which form a part of the present application, are used to provide further understanding of the present application, and serve as an aid in explaining the principles of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application, and do not constitute an improper limitation on the present application. In the drawings:

[0031] Figure 1 is a schematic diagram of a multi-optical path gas detection system compatible with multi-pass cell and integral detection according to an embodiment of the present application;

[0032] Figure 2 is a structure and spatial position schematic diagram of a special-shaped cavity mirror according to an embodiment of the present application;

[0033] Figure 3 is a reflection partition and light spot landing point schematic diagram of a cavity mirror according to an embodiment of the present application;

[0034] Figure 4 is a structure schematic diagram of a special-shaped light beam adjusting assembly according to an embodiment of the present application.

[0035] In the drawings, reference signs include:

[0036] The light source 1, the first collimator 201, the second collimator 202, the gas chamber 301, the gas inlet 3011, the gas outlet 3012, the mass flow controller 3013, the pressure closed-loop measurement and control component 3014, the tunable gas pump 3015;

[0037] The first cavity mirror 302, the first incident hole 3021;

[0038] The second cavity mirror 303, the first exit hole 3031, the second incident hole 3032, the second exit hole 3033;

[0039] The half-mirror 4, the mirror 5, the detection unit 6, the first detector 601, the second detector 602, the third detector 603, the data acquisition unit 701, the FPGA 702, the communication interface 703, the light source driving circuit 704, the special-shaped light beam adjusting assembly 8. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and do not constitute a limitation on the present application. Similar elements in different embodiments use associated similar element reference numbers. In the following embodiments, many details are described in order to make the present application better understood. However, those skilled in the art can easily recognize that some features can be omitted in different cases, or can be replaced by other elements, materials, methods. In some cases, some operations related to the present application are not shown or described in the specification in order to avoid the core part of the present application being overwhelmed by too much description, and it is not necessary for those skilled in the art to describe these related operations in detail according to the description in the specification and the general technical knowledge in the art.

[0041] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other to form various embodiments without conflict. Meanwhile, each step or action in the method description can also be sequentially adjusted or adjusted in a manner that is obvious to those skilled in the art. Therefore, the order in the specification and the drawings is only for the purpose of clearly describing a certain embodiment, and does not mean that it is the necessary order, unless otherwise stated that a certain order must be followed.

[0042] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application. In addition, the terms "first", "second" and the like are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined with "first", "second" and the like can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise stated, the meaning of "a plurality of" is two or more.

[0043] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0044] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0045] Please refer to Figure 1 , Figure 2 and Figure 3 In one embodiment of the present application, a multi-path gas detection system compatible with multi-cell and integral detection is provided, comprising:

[0046] The light source 1, the gas absorption cell, the semi-transmissive and semi-reflective mirror 4 and the detection unit 6, wherein the gas absorption cell comprises a gas chamber 301, and a first cavity mirror 302 and a second cavity mirror 303 arranged in the gas chamber 301;

[0047] The first cavity mirror 302 and the second cavity mirror 303 each comprise at least an integration zone (a region with a radius R1), and a first annular reflective zone (an annular region between R1 and R2) and a second annular reflective zone (an annular region between R2 and R3) arranged outside the integration zone;

[0048] The optical axes of the first annular reflective region of the first cavity mirror 302 and the first annular reflective region of the second cavity mirror 303 have an included angle; and the optical axes of the second annular reflective region of the first cavity mirror 302 and the second annular reflective region of the second cavity mirror 303 coincide;

[0049] The second annular reflective region of the first cavity mirror 302 is provided with a first entrance hole 3021, and the second annular reflective region of the second cavity mirror 303 is provided with a first exit hole 3031; the first annular reflective region of the second cavity mirror 303 is provided with a second entrance hole 3032 and a second exit hole 3033;

[0050] The light source 1 is configured to provide first probe light transmitted into the integration region of the first cavity mirror 302 and reciprocally reflected between the integration regions of the first cavity mirror 302 and the second cavity mirror 303; and provide second probe light emitted from the first entrance hole 3021 and reciprocally reflected between the second annular reflective region of the first cavity mirror 302 and the second cavity mirror 303;

[0051] During the integration reflection between the integration regions, part of the first probe light is emitted from the integration region of the second cavity mirror 303 to the detection unit 6 each time;

[0052] The second probe light is emitted from the first exit hole 3031 to the half-transmission half-reflection mirror 4, which is configured to split the second probe light into third probe light and fourth probe light, the third probe light is transmitted from the half-transmission half-reflection mirror 4 to the detection unit 6, and the fourth probe light is reflected from the half-transmission half-reflection mirror 4 to the second entrance hole 3032 and reciprocally reflected between the first annular reflective region of the first cavity mirror 302 and the second cavity mirror 303, and emitted from the second exit hole 3033 to the detection unit 6.

[0053] As an optional embodiment, the light source 1 includes a plurality of lasers of different wavelengths, and a group of DFB lasers can be specifically selected, which correspond to the absorption peak center wavelengths of different sample gases to be measured. When measuring a certain sample gas, the light source 1 provides probe light of the corresponding wavelength. In addition, a light source driving circuit 704 is provided for driving and controlling the light source 1.

[0054] As an optional embodiment, the front end of the gas absorption cell is further provided with a collimator group, which includes a plurality of collimators corresponding to different light beams, and different wavelengths of probe light emitted by the light source enter different collimators. The collimators are used to collimate and shape the probe light, and in addition, the transmission angle of the probe light beam can be changed by adjusting the angle of each collimator.

[0055] It should be understood that the present application is not limited to dividing the first mirror 302 and the second mirror 303 into the three regions of the above-mentioned integral zone (the region with a radius of R1), the first type of annular reflection zone (the annular region between R1 and R2), and the second type of annular reflection zone (the annular region between R2 and R3), and the number of regions and the size of each region depend on the actual gas detection requirements, such as the detection wavelength, the size and shape of the light spot, and the like determined according to the type of detected gas. In the embodiment of the present application, the first mirror 302 and the second mirror 303 of the gas absorption cell are specifically divided into a circular integral zone based on the integral cavity output spectrum technology, and a plurality of annular reflection zones based on the multi-pass cell technology outside the integral zone, wherein at least one annular reflection zone of the first mirror 302 and the second mirror 303 has an included angle between the optical axes, and this type of annular reflection zone is referred to as the first type of annular reflection zone, and the other annular reflection zones with coinciding optical axes are referred to as the second type of annular reflection zone.

[0056] As an optional embodiment, the gas chamber 301 is a closed cavity filled with the gas sample to be detected, which provides a space for the gas detection to interact with the detection light. The gas inlet 3011 and the gas outlet 3012 are respectively arranged on the outer wall of the gas chamber 301, wherein the mass flow controller 3013 is arranged at the position of the gas inlet 3011, and the mass flow controller 3013 is used to configure the gas flow parameter of the gas entering the gas chamber 301 through the gas inlet 3011. The pressure closed-loop measurement and control component 3014 and the tunable air pump 3015 are arranged at the position of the gas outlet 3012, the pressure closed-loop measurement and control component 3014 is used to measure the internal gas pressure of the gas chamber 301, and the tunable air pump 3015 is controlled through a closed loop to realize the gas pressure balance of the gas chamber 301. The gas pressure in the gas chamber 301 can ensure that the detection light and the gas to be detected are in an optimal reaction condition.

[0057] The first mirror 302 and the second mirror 303 are respectively arranged at two ends of the gas chamber 301, and are commonly referred to as a front mirror and a rear mirror. In the embodiment of the present application, the mirror structure is specially designed, and a multi-partition special-shaped mirror is designed to replace the traditional mirror by combining the multi-pass cell and the off-axis integrating cavity enhancement technology. Specifically, since the traditional absorption cell usually adopts a multi-pass cell structure, the optical path is single, and it is impossible to simultaneously meet the needs of several meters, tens of meters, dozens of meters and other optical paths, therefore, in the embodiment of the present application, the first mirror 302 and the second mirror 303 are both divided into an integrating zone based on the off-axis integrating cavity enhancement technology and a plurality of annular reflection zones based on the multi-pass cell technology, and at least one pair of annular reflection zones of the first mirror 302 and the second mirror 303 have an included angle between the optical axes. Specifically, in the embodiment of the present application, the first mirror 302 and the second mirror 303 are designed to be divided into three regions, which are respectively: an integrating zone (a region with a radius of R1), a first type of annular reflection zone (an annular region between R1 and R2), and a second type of annular reflection zone (an annular region between R2 and R3), to correspond to the detection needs of different optical paths. In the order from the center of the circle to the edge of the mirror, the integrating zone (the region with a radius of R1) of the first mirror 302 and the second mirror 303 is processed into a coaxial plano-concave lens structure, and the concave surface faces the inside of the gas chamber 301, that is, the opposite surfaces of the integrating zone of the first mirror 302 and the integrating zone of the second mirror 303 are concave, and the opposite surfaces are flat. And the concave surface is coated with a dielectric film. In the embodiment of the present application, the specific material of the dielectric film is Ta2O5 and SiO2, which are stacked to form the dielectric film. According to the material ratio and the number of stacked layers, the center reflection wavelength position and the maximum reflectivity of the film layer are determined to meet the detection needs of different gases. Specifically, taking the strong absorption peak of carbon monoxide as an example, the center wavelength position is 2332nm, when the reflectivity of the dielectric film is designed to be 99.95%, the number of stacked layers is 27, and the film layer thickness is 9.3 microns. At this time, the radius R1 of the integrating zone is determined according to the designed collimated light radius in the coherent light off-axis beam expansion type detection mode in the present application, that is, it is determined according to the diameter of the probe light beam entering the integrating zone, and the radius R1 of the integrating zone generally has a margin. For example, assuming that the first probe light provided by the light source 1 is transmitted by the integrating zone of the first mirror 302 and reciprocally reflected between the integrating zones of the first mirror 302 and the second mirror 303. After being expanded by the collimator, the first probe light is 9 microns in diameter, so the radius R1 of the integrating zone needs to have a margin of 12 microns. And the curvature radius of the integrating zone is generally designed to be , close to the plane mirror. The integral zone of the first cavity mirror 302 and the integral zone of the second cavity mirror 303 constitute an off-axis integral cavity structure, and the first probe light reciprocally reflects between the integral zone of the first cavity mirror 302 and the integral zone of the second cavity mirror 303. In each reflection cycle, when the first probe light is reflected to the second cavity mirror 303, a part of the first probe light will be emitted from the integral zone of the second cavity mirror 303. The higher the reflectivity of the integral zone, the longer the effective optical path during the reflection process, which can reach hundreds of meters to kilometers. Therefore, the ppm-level and higher-precision carbon monoxide gas concentration can be detected according to the integral spectrum detection result of the part of the emitted light.

[0058] In the traditional multi-cell structure design, coherent light is relied on to form stable interference, and incoherent light cannot realize detection because of random phase. Therefore, the traditional detection needs to use coherent light. In the present application, the integral zones of the first cavity mirror 302 and the second cavity mirror 303 form an integral cavity structure, which relies on high-reflective film to realize long optical path oscillation reflection, and does not rely on coherence. Therefore, the first probe light can also use incoherent light. The intensity of the first probe light transmitted from the emission surface has been significantly weakened due to the cumulative gas absorption of multiple reflections. The spectrum can be measured by a spectrum detection device, and compared with the incident spectrum. According to the Lambert-Beer law, the gas concentration can be inversely calculated according to the absorbance. The integral zones of the first cavity mirror 302 and the second cavity mirror 303 can realize long optical path transmission, and the optical path can reach hundreds of meters to kilometers. Therefore, the integral zone can be used as a detection area for detecting ppm-level and higher-precision carbon monoxide gas concentration.

[0059] The outer side of the integral zone is a type of annular reflection zone (the annular area between R1 and R2). Through processing technology, the area is processed into a type of annular reflection zone of the first cavity mirror 302 and a type of annular reflection zone of the second cavity mirror 303, and the optical axes of the two types of annular reflection zones have an included angle, that is, the type of annular reflection zone of the first cavity mirror 302 and the type of annular reflection zone of the second cavity mirror 303 are in a relative inclined state, and are not parallel to each other, and have a certain inclination angle. Figure 2 In the figure, the type of annular reflection zone of the first cavity mirror 302 is processed into an inclined state. In fact, the type of annular reflection zone of the first cavity mirror 302 can be processed into an inclined state, or the type of annular reflection zone of the second cavity mirror 303 can be processed into an inclined state, or both the type of annular reflection zone of the first cavity mirror 302 and the type of annular reflection zone of the second cavity mirror 303 can be processed into an inclined state, that is, the maximum tangent plane of the type of annular reflection zone of the first cavity mirror 302 and the optical axis of the integral zone of the first cavity mirror 302 are in a non-perpendicular state, and / or the maximum tangent plane of the type of annular reflection zone of the second cavity mirror 303 and the optical axis of the integral zone of the second cavity mirror 303 are in a non-perpendicular state. The center of the type of annular reflection zone of the first cavity mirror 302 and the center of the type of annular reflection zone of the second cavity mirror 303 have a certain spacing k in the vertical direction. In addition, the radius of curvature of the type of annular reflection zone The curvature radius of the integral zone is obviously smaller than that of the first annular reflection zone The curvature radius of the second annular reflection zone is obviously larger than that of the first annular reflection zone The curvature radius of the second annular reflection zone is obviously larger than that of the first annular reflection zone The design purpose is to realize a kind of annular reflection zone with a reflection state of spot dense multi-pass cell design structure, that is, a plurality of small circular ring type spots are distributed in a kind of annular reflection zone. The coating on the first annular reflection zone can be coated with metal materials such as gold and silver to realize wide spectral range reflection, and the reflectivity is generally designed to be more than 95%.

[0060] The outer side of the first annular reflection zone is the second annular reflection zone (the annular region between R2 and R3), which is processed by a processing process to coincide with the optical axis of the second annular reflection zone of the first cavity mirror 302 and the second cavity mirror 303, that is, the second annular reflection zone of the first cavity mirror 302 and the second cavity mirror 303 are parallel to each other. In addition, the curvature radius of the second annular reflection zone is a large curvature radius, which can also be designed as The design purpose is to make the spot landing point of the second annular reflection zone present as a traditional single circular multi-pass cell circular spot landing point, forming a short light path multi-pass cell structure. The coating of this region is coated with metal materials such as gold and silver to realize wide spectral range reflection, and the reflectivity is generally designed to be more than 95%. It should be noted that the curvature radii of the integral zone (R1 region) and the second annular reflection zone (annular region between R2 and R3) can be designed to be the same , or different, but both are obviously larger than the curvature radius of the first annular reflection zone (annular region between R1 and R2).

[0061] The above three regions are used to provide three different light path designs, in which the integral zone constitutes an off-axis integral cavity structure, and the effective light path of this region can reach hundreds of meters to kilometers; the first annular reflection zone constitutes a long light path small dense multi-pass cell structure, and the effective light path of this region is smaller than that of the integral zone; the second annular reflection zone constitutes a short light path traditional multi-pass cell structure, and the effective light path is obviously smaller than that of the first annular reflection zone.

[0062] In the embodiment of the present application, the first cavity mirror 302 and the second cavity mirror 303 are divided and processed into three reflection zones, respectively corresponding to three different light paths. The light source 1 of the embodiment of the present application is used to provide two beams of probe light, that is, the first probe light and the second probe light. Correspondingly, the collimator group is designed to include the first collimator 201 and the second collimator 202, which are respectively used to process the first probe light and the second probe light.

[0063] For the integral zone, the mirror body is a lens structure, so the first probe light can be directly transmitted into the outer surface of the integral zone and reciprocally reflected between the integral zones of the first cavity mirror 302 and the second cavity mirror 303, realizing long optical path transmission, corresponding to the first gas detection.

[0064] Since the mirror bodies of the first type of annular reflection zone and the second type of annular reflection zone are non-lens structures, the embodiment of the present application first opens a first incident hole 3021 on the first cavity mirror 302, so as to facilitate the second probe light to be incident from the first incident hole 3021 and reciprocally reflected between the second type of annular reflection zones of the first cavity mirror 302 and the second cavity mirror 303. In addition, the first cavity mirror 303 is provided with a first exit hole 3031, a second incident hole 3032 and a second exit hole 3033, wherein the first exit hole 3031 is used to facilitate the second probe light to exit, and the spot landing points of the second type of annular reflection zone present single circular multi-cell spot landing points.

[0065] After the second probe light exits from the first exit hole 3031, a half-transmission half-reflection mirror 4 is further arranged on the light path between the second cavity mirror 303 and the detection unit 6, and the second probe light is irradiated on the half-transmission half-reflection mirror 4 and is split into two beams by the half-transmission half-reflection mirror 4, i.e. third probe light and fourth probe light. Among them, the third probe light is transmitted to the detection unit 6 by the half-transmission half-reflection mirror 4, and the effective absorption optical path of the third probe light between the second type of annular reflection zones of the first cavity mirror 302 and the second cavity mirror 303 is set as L1, which is used to realize short optical path transmission, corresponding to the second gas detection.

[0066] Because the light spots of the multi-pass cell structure cannot be overlapped, the number of reflections is limited, and the common optical path is in the order of meters to tens of meters. To improve the optical path and achieve an optical path of tens of meters to hundreds of meters, the application designs a semi-transparent half mirror 4 to realize the second incidence of the probe light, so that the fourth probe light is emitted from the first exit hole 3031 into the gas chamber 301, and then the semi-transparent half mirror 4 re-emits the fourth probe light from the second incidence hole 3032 into the gas chamber, and the fourth probe light is reflected back and forth between the first cavity mirror 302 and the second cavity mirror 303 in the first type of annular reflection area and the second type of annular reflection area. Because the first cavity mirror 302 and the second cavity mirror 303 are not parallel to each other, there is a certain angle, so the fourth probe light will have a small deflection angle every time it is reflected in the first type of annular reflection area. Therefore, the fourth probe light can realize non-coincident multi-circle transmission, and small and dense multi-circle light spots are formed on the first type of annular reflection area, that is, non-coincident multi-circle multi-pass cell light spot landing points. The reflection path of the semi-transparent half mirror 4 is longer than the ordinary circular light path of the second type of annular reflection area, and finally the fourth probe light exits the gas chamber 301 through the second exit hole 3033. Assuming that the effective optical path of the fourth probe light in the first type of annular reflection area is L2, the effective optical path of the fourth probe light is L1+L2, which is generally in the order of tens of meters to hundreds of meters. After the fourth probe light is emitted, it is received by the detector group 6 and converted into an electrical signal to realize medium and long optical path transmission, and corresponds to the third gas detection.

[0067] As an optional embodiment, a mirror 5 is also provided, and the fourth probe light is reflected by the semi-transparent half mirror 4 to the mirror 5. The angle of the fourth probe light is adjusted by the mirror 5, and the incidence angle of the fourth probe light can be flexibly changed under the action of the semi-transparent half mirror 4 and the mirror 5, so that the fourth probe light is transmitted between the second incidence hole 3032 and the first cavity mirror 302 and the second cavity mirror 303.

[0068] As an optional embodiment, the reflectivity and transmissivity of the semi-transparent half mirror are not limited to 1:1, but can be replaced by other ratios to adjust the signal-to-noise ratio of the final received signal.

[0069] The reason for forming the small and dense multi-circle light spots in the first type of annular reflection area is explained as follows: In the embodiment of the application, the optical axes of the first type of annular reflection area of the first cavity mirror 302 and the first type of annular reflection area of the second cavity mirror 303 have an included angle, and they are not relatively parallel. Therefore, the fourth probe light will have a certain angle of deflection every time it is reflected due to the inclination of the first cavity mirror 302 and / or the second cavity mirror 303. Therefore, it will not continue the traditional single-circle multi-pass cell light spot landing point of the second type of annular reflection area, but will appear the non-coincident multi-circle multi-pass cell light spot landing point as shown in FIG. 6B, and the landing points of the fourth probe light will form multi-circle trajectories. Figure 3 Figure 3 ​The small and dense multi-pass cell effect is not that a complete small-diameter circular spot is formed by the fourth probe light once, but that each time a spot is formed by the fourth probe light, and a small-diameter circular spot is gradually formed by multiple reflections. Figure 3

[0070] The present application can realize flexible selection of an effective optical path in a range of meters to kilometers by a single optical integrating cavity, and can realize gas detection in multiple spectrums and multiple ranges with self-selected accuracy, and can solve the problem that the optical path is single in a traditional gas absorption cell with a multi-pass cell structure, and the multi-pass cell only has a unique spot structure, and even if the optical path is increased, the problem of the multi-pass cell optical structure and the integrating cavity optical structure cannot be realized simultaneously in the same gas absorption cell.

[0071] As an optional embodiment, the detection unit 6 includes a first detector 601, a second detector 602, and a third detector 603, which are respectively used to detect a plurality of optical path detection light signals obtained by the detection unit, and realize self-defined detection of different gases according to the detection light signals of different optical paths, wherein the plurality of optical path detection light signals include a first detection light collection signal of a first optical path, a third detection light collection signal of a second optical path, and a fourth detection light collection signal of a third optical path. The light signal collection process of the detection unit 6 is as follows: the detection unit 6 collects the detection light signal after the gas absorption.

[0072] As an optional embodiment, the multi-optical-path gas detection system compatible with the multi-pass cell and the integrating detection further includes a processor, and the processor specifically includes a data acquisition unit 701 and an FPGA 702, and a communication interface 703, wherein the data acquisition unit 701 is used to acquire the light signal recorded by the detection unit 6 and convert it into an electrical signal to realize acquisition of gas detection data. The gas detection data is transmitted to the FPGA 702, the gas detection data is processed by the FPGA 702, and the gas detection data is transmitted to the outside in the form of a scanning signal through the communication interface 703. In addition, in the embodiment of the present application, the FPGA 702 realizes multi-line parallel control, and the FPGA 702 can also control the mass flow controller 3013, the pressure closed-loop measurement and control component 3014, and the tunable gas pump 3015 to realize real-time measurement and control of the gas pressure of the gas chamber 301. On the other hand, the FPGA 702 can also control the light source driving circuit 704 to control different lasers in the light source 1 to provide different wavelength detection light by sending a modulation signal.

[0073] As an optional embodiment, the first detector 601, the second detector 602, and the third detector 603 are arranged in the same plane.​

[0074] As an optional embodiment, since the second cavity mirror 303 has a second exit hole 3033 on the annular reflection region of the second cavity mirror 303 and a first exit hole 3031 on the second annular reflection region of the second cavity mirror 303, the integration region is the transmitted signal. The three sets of signals to be measured are at different distances from the center of the second cavity mirror 303 in space. That is, if the first detector 601, the second detector 602 and the third detector 603 are arranged in the same plane, the detectors need to be arranged in a longitudinal space on one plane. However, when the detector volume is large or the number of detectors to be designed is large, such as when there is a cooled mercury cadmium telluride detector in the detection unit 6, it is difficult to arrange multiple wavelength detectors simultaneously on the same plane. Therefore, the present invention adds a feature such as between the second cavity mirror 303 and the detection unit 6. Figure 4 The irregular beam adjustment component 8 shown adjusts the tilt angles of the first, third, and fourth probe beams incident on the different detection target surfaces of the first detector 601, second detector 602, and third detector 603 in the detection unit 6. Specifically, the irregular beam adjustment component 8 is an irregularly shaped lens, which includes multiple annular lens areas corresponding to different probe beams. Different lens areas of the irregularly shaped lens have different thicknesses and probe beam exit surface tilt angles. The lens thickness of each annular lens area increases or decreases from its inner diameter to its outer diameter. The design is tailored to different optical paths and exit points in different regions, achieving focusing or changing the direction of the optical path. The adjusted probe beams are focused or transmitted to the first detector 601, second detector 602, and third detector 603 for reception. In this design, the first detector 601, second detector 602, and third detector 603 can be distributed horizontally, solving the pressure of a compact planar layout of the detectors. It should be noted that the distribution of the first detector 601, the second detector 602, and the third detector 603 is related to the focusing degree or the direction of probe light transmission. The first detector 601, the second detector 602, and the third detector 603 can not only be arranged strictly horizontally, but they may also have distances in both the horizontal and vertical directions. That is, the target surfaces of the first detector 601, the second detector 602, and the third detector 603 can be arranged on different planes.

[0075] Furthermore, the target surfaces of the first detector 601, the second detector 602, and the third detector 603 are arranged on the same plane. The irregular beam adjustment component 8 can also be used to increase the spacing between the light spots of different detection beams incident on the same plane, which facilitates the arrangement of detectors.

[0076] As an optional embodiment, for the special-shaped light beam adjusting assembly 8, by adjusting the optical parameters such as the inclination angle, thickness, and spatial position of the detector of each lens area, the inclination angle of the probe light incident on the detector surface can be changed. When the inclination angle and the width of each lens area are completely symmetrical around the center, the incident angle of the probe light incident on the detector surface is fixed and completely axially symmetrical around the center, and the phase difference caused by the incident angle of the probe signal received by the detector does not exist. The lens area can also be designed to be non-axially symmetrical, and the inclination angle and the width of different positions of the lens area are appropriately adjusted, so that the angle of the probe light presents an asymmetric angle difference. At this time, the deviation of the 360-degree incident angle cannot be completely offset, and there is an angle deviation of the incident light, that is, a phase difference of the received electrical signal. Through this method, the phase modulation of the electrical signal after photoelectric conversion can be realized.

[0077] As an optional embodiment, the special-shaped light beam adjusting assembly 8 can be processed as an independent optical element and arranged between the first cavity mirror 303 and the detection unit 6.

[0078] As an optional embodiment, the special-shaped light beam adjusting assembly 8 can be directly integrated on the back of the first cavity mirror 303, that is, the surface facing away from the first cavity mirror 302. The special-shaped light beam adjusting assembly 8 is formed by processing on the back of the first cavity mirror 303.

[0079] In summary, the above is only a preferred embodiment of the present specification and is not used to limit the protection scope of the present specification. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present specification shall be included in the protection scope of the present specification.

[0080] The system, device, module or unit illustrated in one or more embodiments above can be specifically implemented by a computer chip or entity, or by a product with certain functions. A typical implementation device is a computer. Specifically, the computer may, for example, be a personal computer, a laptop computer, a cellular phone, a camera phone, a smart phone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or a combination of any of these devices.

[0081] It should also be noted that the terms "comprising", "containing", or any other variant thereof are intended to cover non-exclusive inclusion, such that processes, methods, articles or devices including a series of elements not only include those elements, but also include other elements not explicitly listed, or other elements inherent to such processes, methods, articles or devices. Without more limitations, the element defined by the statement "comprising a" does not exclude the presence of additional identical elements in the process, method, article or device including the element.

[0082] Each of the various embodiments in the specification are described in a progressive manner, and the same or similar parts among the various embodiments can be referred to each other. Each of the various embodiments focuses on the differences from other embodiments. In particular, the system embodiments are described in a relatively simple manner because they are substantially similar to the method embodiments, and the relevant parts can be referred to the description of the method embodiments.

Claims

1. A multi-path gas detection system compatible with multi-pass cell and integral detection, comprising: A light source, a gas absorption cell, and a detection unit, wherein the gas absorption cell includes a gas chamber, and a first cavity mirror and a second cavity mirror disposed within the gas chamber, characterized in that it further includes a semi-transparent and semi-reflective mirror; Both the first cavity mirror and the second cavity mirror include at least: an integrating region, and a first-class annular reflection region and a second-class annular reflection region disposed outside the integrating region; The optical axes of the first type of annular reflection region of the first cavity mirror and the second type of annular reflection region of the second cavity mirror are at an angle; the optical axes of the second type of annular reflection region of the first cavity mirror and the second type of annular reflection region of the second cavity mirror coincide. The first cavity mirror has a first entrance aperture on its type II annular reflection area, and the second cavity mirror has a first exit aperture on its type II annular reflection area; the second cavity mirror has a second entrance aperture and a second exit aperture on its type I annular reflection area. The light source is used to provide a first probe light that is transmitted through the integrating region of the first cavity mirror and reciprocated between the integrating regions of the first cavity mirror and the second cavity mirror; and to provide a second probe light that is incident through the first entrance aperture and reciprocated between the two types of annular reflection regions of the first cavity mirror and the second cavity mirror. During the integration and reflection process between the integration regions, a portion of the first probe light is emitted from the integration region of the second cavity mirror to the detection unit each time. The second detection light is emitted from the first exit hole to the semi-transparent mirror, which splits the second detection light into a third detection light and a fourth detection light. The third detection light is transmitted through the semi-transparent mirror to the detection unit. The fourth detection light is reflected by the semi-transparent mirror to the second entrance hole and is reflected back and forth between a type of annular reflection area of ​​the first cavity mirror and the second cavity mirror, and is emitted from the second exit hole to the detection unit.

2. The multi-path gas detection system compatible with multi-pass cells and integral detection according to claim 1, characterized in that, The outer wall of the air chamber is provided with an air inlet and an air outlet. A mass flow controller is installed at the air inlet, which is used to configure the gas flow rate parameters entering the air chamber through the air inlet. A pressure closed-loop measurement and control component and an adjustable air pump are installed at the air outlet. The pressure closed-loop measurement and control component is used to measure the air pressure inside the air chamber, and the adjustable air pump is used to control the air outlet rate according to the measured air pressure inside the air chamber.

3. The multi-path gas detection system compatible with multi-pass cells and integral detection according to claim 1, characterized in that, Both the integrating regions of the first and second cavitation mirrors are plano-concave lens structures. The opposite surfaces of the integrating regions of the first and second cavitation mirrors are concave, while the opposite surfaces are planar. Furthermore, anti-reflection coatings are provided on the concave surfaces of the integrating regions of both the first and second cavitation mirrors.

4. The multi-path gas detection system compatible with multi-pass cell and integral detection according to claim 1, characterized in that, The first probe light is either coherent or incoherent.

5. The multi-path gas detection system compatible with multi-pass cell and integral detection according to claim 1, characterized in that, The radius of curvature of the first type of annular reflection region is smaller than that of the second type of annular reflection region and the integral region. The radii of curvature of the second type of annular reflection region and the integral region may be the same or different.

6. The multi-path gas detection system compatible with multi-pass cell and integral detection according to claim 4, characterized in that, The second probe light spot in the type II annular reflection region appears as a single circular multi-pass cell spot; the fourth probe light spot in the type I annular reflection region appears as a non-overlapping multi-circular multi-pass cell spot.

7. The multi-path gas detection system compatible with multi-pass cell and integral detection according to claim 1, characterized in that, Also includes: The processor is used to collect detection light signals of multiple optical paths obtained by the detection unit, and to realize customized detection of different gases according to the detection light signals of different optical paths. The detection light signals of multiple optical paths include: a first detection light acquisition signal of a first optical path, a third detection light acquisition signal of a second optical path, and a fourth detection light acquisition signal of a third optical path.

8. The multi-path gas detection system compatible with multi-pass cell and integral detection according to claim 1, characterized in that, An irregular beam adjustment component is provided between the second cavity mirror and the detection unit. The irregular beam adjustment component is used to adjust the tilt angle of different detection beams incident on different detection target surfaces in the detection unit.

9. The multi-path gas detection system compatible with multi-pass cell and integral detection according to claim 8, characterized in that, The tilt angle of different probe beams incident on different probe target surfaces is adjusted by the irregular beam adjustment component, so that different probe target surfaces in the detection unit can be arranged on different planes, or the spacing between the light spots of different probe beams incident on the same plane can be increased.

10. The multi-path gas detection system compatible with multi-pass cells and integral detection according to claim 8, characterized in that, The irregular beam adjustment component is an irregular lens, which includes multiple lens areas corresponding to different probe beams. The different lens areas of the irregular lens have different thicknesses and probe beam exit surface tilt angles. The irregularly shaped lens is disposed as an independent optical element between the second cavity mirror and the detection unit; or the irregularly shaped lens is integrated and processed on the surface of the second cavity mirror facing away from the first cavity mirror.

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