CN218003225U - Gas sensor air chamber structure and Housing of gas sensor air chamber - Google Patents
Gas sensor air chamber structure and Housing of gas sensor air chamber Download PDFInfo
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- CN218003225U CN218003225U CN202221336234.XU CN202221336234U CN218003225U CN 218003225 U CN218003225 U CN 218003225U CN 202221336234 U CN202221336234 U CN 202221336234U CN 218003225 U CN218003225 U CN 218003225U
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Abstract
The utility model discloses a gas sensor air chamber structure and a Housing of a gas sensor air chamber, which comprises a concave reflector, a first plane reflector, a second plane reflector and a third plane reflector; the first plane reflector and the second plane reflector are both plane reflectors, and the normal line of the mirror surface of each plane reflector and the incident light beam form an angle of 45 degrees and are arranged opposite to the concave reflector; the normal line of the mirror surface of the first plane reflecting mirror is orthogonal to the normal line of the mirror surface of the second plane reflecting mirror, and the first plane reflecting mirror is arranged above the second plane reflecting mirror; the third plane mirror is a plane mirror of which the mirror surface is arranged opposite to the concave mirror in an orthogonal mode with the incident light beam; the third plane reflector is positioned between the first plane reflector and the second plane reflector and is closer to the concave reflector than the first plane reflector/the second plane reflector; the utility model discloses can improve the detectivity of the optical formula low concentration gas detector of tunable semiconductor laser absorption spectrum of near-infrared by a wide margin.
Description
Technical Field
The utility model belongs to the technical field of gas sensing, concretely relates to compact high-efficient multipass gas absorption light path's gas sensor air chamber structure and a Housing of gas sensor air chamber.
Background
Methane is a flammable and explosive gas, has an explosion lower limit of 5.0 vol% and an explosion upper limit of 15.0 vol% in the atmosphere, is a main component of coal mine gas, methane, natural gas and various liquid fuels, and has very important significance for the safe operation of industry and mines by timely and accurately detecting the concentration of methane gas and finding a generation source and a leakage source. Although the Tunable Diode Laser Absorption Spectroscopy (TDLAS) harmonic detection technology is widely applied in the field of gas detection, especially low-concentration gas detection, the sensitivity of the technology in practical use still needs to be improved. The sensitivity and the precision of the laser gas sensor depend on the signal-to-noise ratio, and under the condition of certain electrical noise, the most direct method for improving the sensitivity of the tunable semiconductor laser absorption spectrum harmonic gas detector is to lengthen the length of a gas chamber so as to increase the effective acting distance of light and gas and enhance the effective absorption of the gas to be detected so as to improve the detection sensitivity. In addition, a so-called folded cavity technique is also commonly used in the design of gas cells for tunable semiconductor laser absorption spectrum harmonic gas detectors, and the key point of the technique is to make the laser beam repeatedly pass through the gas cells according to a certain path to increase the effective acting distance of light and gas, and enhance the effective absorption of the gas to be detected, so as to improve the detection sensitivity. The basic optical path of a conventional folded cavity gas cell employing this technique is shown in figure 1.
In fig. 1, 13 and 14 are two mirrors, 11 is the beam emitted by the tunable semiconductor laser, and 12 is the beam emitted from the folded gas cell to the photodetector. Both the long gas chamber and the traditional folding gas chamber occupy a large space, and when the volume of the tunable semiconductor laser absorption spectrum harmonic gas detector is limited in specific application, the two methods for improving the sensitivity fail. The laser gas sensor used in the urban inspection well and the urban comprehensive pipe gallery has very high requirements on miniaturization, and the allowable actual gas chamber linearity is generally limited to the range of 30mm x 20mm x 20mm. The effective working distance of light and gas that can be achieved in the conventional manner is also in the range of 30mm to 70mm, so it is not possible to improve the accuracy of the laser gas sensor to an accuracy of less than 0.05% vol methane detectable in high and low temperature environments. In addition, in the conventional folding gas cell as shown in fig. 1, the light beam emitted from the laser only has a finite collimation distance during the process of multiple folding propagation in the gas cell, so that the emergent light of the gas cell cannot be sufficiently received by the photodetector, and the signal-to-noise ratio of the laser gas sensor is affected.
SUMMERY OF THE UTILITY MODEL
Utility model purpose: when the volume of for solving at tunable semiconductor laser absorption spectrum harmonic gas detector has the restriction, the problem that detectivity reduces to and the problem that the emergent light that causes the air chamber can not be fully accepted by the photo detector for solving the light beam divergence that only has limited collimation distance that launches from the laser instrument, the utility model provides a gas sensor air chamber structure and the houseing of a gas sensor air chamber of compact high-efficient multipass gas absorption light path.
The technical scheme is as follows: a compact and efficient gas sensor gas chamber structure with a multi-pass gas absorption light path comprises a concave reflector, a first plane reflector, a second plane reflector and a third plane reflector;
the first plane reflector is a plane reflector, and the normal line of the first plane reflector and the incident beam form an angle of 45 degrees and are arranged opposite to the concave reflector;
the second plane reflector is a plane reflector, and the normal line of the second plane reflector and the incident beam form an angle of 45 degrees and are arranged opposite to the concave reflector; the normal line of the first plane reflector is orthogonal to the normal line of the second plane reflector, and the first plane reflector is arranged above the second plane reflector;
the third plane mirror is a plane mirror of which the mirror surface is arranged opposite to the concave mirror in an orthogonal mode with the incident light beam;
the third plane reflector is positioned between the first plane reflector and the second plane reflector, and the third plane reflector is closer to the concave reflector than the first plane reflector/the second plane reflector;
the incident beam is incident on the third plane mirror through the light beam reflected by the concave mirror, the light beam reflected by the third plane mirror is incident on the concave mirror again, the light beam reflected by the concave mirror is incident on the first plane mirror, the light beam reflected by the first plane mirror is incident on the second plane mirror, the light beam reflected by the second plane mirror is incident on the concave mirror, the light beam reflected by the concave mirror is incident on the third plane mirror, the light beam reflected by the third plane mirror is reflected back to the concave mirror again, and finally the light beam reflected by the concave mirror is the emergent light beam of the air chamber.
Further, the concave reflecting mirror is a spherical concave mirror.
Further, the concave reflecting mirror is a cylindrical concave mirror.
The utility model also discloses a Housing of the gas sensor gas chamber, which comprises a light beam emitter, a gas chamber and a light detector;
the gas chamber is the gas sensor gas chamber structure of the compact high-efficiency multi-pass gas absorption light path disclosed above;
the light beam emitter is arranged on one side opposite to the concave reflector and used for emitting collimated light beams to the air chamber to serve as incident light beams of the air chamber;
the light detector is arranged on one side opposite to the concave reflecting mirror and used for receiving the emergent light beam of the air chamber.
Further, the light beam emitter is a tunable semiconductor laser.
Furthermore, the light detector comprises a window and a PD chip, and the normal of the PD chip and the normal of the window form a certain angle with the emergent light beam of the air chamber.
Further, the angle is in the range of 3-15 degrees.
Further, the light beam emitter is arranged at a position corresponding to one edge of the gas chamber, and the light detector is arranged at a position corresponding to the other edge of the gas chamber.
Has the beneficial effects that: compared with the prior art, the utility model, have following advantage:
(1) The air chamber structure provided by the utility model realizes that the effective acting distance of light and gas in the air chamber reaches the light path which is several times of the length of the air chamber by the reflection of the light beam back and forth for many times in the extremely limited small space so as to improve the detection sensitivity of the tunable semiconductor laser absorption spectrum harmonic gas detector; the effective action distance of light and gas is increased in the process of repeatedly reflecting the light beam back and forth, so that the light detector can fully and effectively receive the light beam emitted from the gas chamber; the air chamber structure provided by the utility model can be applied to the optical type low-concentration methane gas accurate detection technology neighborhood based on the near-infrared tunable semiconductor laser absorption spectrum;
(2) The utility model discloses a concave surface speculum, the light beam that only has limited collimation distance of compensatable laser output produces when light path long distance propagates diverges, thereby has improved photo detector light collection efficiency and has improved the SNR of gas detection ware, improves the effect of the detectivity of the optical type low concentration gas detection ware of near-infrared tunable semiconductor laser absorption spectrum by a wide margin.
Drawings
FIG. 1 is a basic optical path diagram of a conventional folded chamber gas cell;
fig. 2 is a typical light path diagram of the air chamber according to the present invention;
FIG. 3 is a configuration diagram of the window of the photodetector and the normal of the PD chip forming an angle α with the axis of the exit beam from the air chamber;
fig. 4 is a 3D partial cross-sectional view of the inventive Housing overall structure of the gas cell together with the semiconductor laser and photodetector mounting mounts;
FIG. 5 is a front view of the general structure of the Housing of the gas cell together with the semiconductor laser and photodetector mounting block;
fig. 6 is a 3D profile view of the Housing overall structure of the gas cell together with the semiconductor laser and optical receiver mount.
Detailed Description
The technical solution of the present invention will be further explained with reference to the accompanying drawings and embodiments.
The utility model discloses an optical type low concentration gas detector's air chamber for based on near-infrared tunable semiconductor laser absorption spectrum, applicable in all kinds of gases, like the optical type low concentration gas detector air chamber of the tunable semiconductor laser absorption spectrum of methane, ethane, propane, carbon monoxide and so on gas. As shown in fig. 2, the basic structure is composed of a concave mirror 21, a first plane mirror 23 disposed at 45 degrees, a second plane mirror 24 disposed at 45 degrees, and a third plane mirror 22 whose mirror surface is orthogonal to the incident light of the gas cell. Wherein, the normal line of the mirror surface of the first plane reflector 23 and the normal line of the mirror surface of the second plane reflector 24 are both at 45 degrees with the laser beam with finite collimation distance emitted from the tunable semiconductor laser. The normal of the first plane mirror 23 is orthogonal to the normal of the second plane mirror 24, and the first plane mirror 23 is disposed above the second plane mirror 24. For convenience, the tunable semiconductor laser will be referred to as a laser for short. Both the laser and the photodetector are placed on the side of the gas cell opposite the concave mirror 21 so that the opposite concave mirror 21 can achieve the necessary maximum aperture in the limited space of the gas cell. The laser beam is emitted from the gas chamber and the other side of the gas chamber, so as to utilize the limited space of the gas chamber to the maximum.
The first plane mirror 23, the second plane mirror 24 and the third plane mirror 22 are all arranged opposite to the concave mirror 21, the arrangement position of the third plane mirror 22 is between the first plane mirror 23 and the second plane mirror 24 when viewed from the longitudinal direction, and the arrangement position of the third plane mirror 22 is slightly deviated to one side of the concave mirror 21 direction than the first plane mirror 23 and the second plane mirror 24 on the same side when viewed from the transverse direction so as to avoid physical interference when the three plane mirrors are installed.
As shown in fig. 2, a light beam 25 emitted from the laser with only a limited collimation distance is incident on the concave mirror 21, the curvature radius of the concave mirror can be determined according to the actual geometric configuration of the concave mirror 21, the first planar mirror 23, the second planar mirror 24 and the third planar mirror 22, so that a light beam 27 reflected by the concave mirror 21 is incident on the third planar mirror 22 after being reflected, a light beam 28 reflected by the third planar mirror 22 is incident on the concave mirror 21 again, a light beam 29 reflected by the concave mirror 21 is incident on the first planar mirror 23 placed at 45 °, a light beam 30 reflected by the first planar mirror 23 is incident on another second planar mirror 24 placed at 45 °, a light beam 31 reflected by the concave mirror 21 is incident on the concave mirror 21 again, a light beam 32 reflected by the concave mirror 21 is incident on the third planar mirror 22 and is reflected back to the concave mirror 21, and finally an exit light beam is emitted from the concave mirror 21 as an exit light detector 26 of the concave mirror 21. During which the beam undergoes a total of 8 reflections, 4 of which are reflected via the concave mirror 21. The effective distance of action of the light and gas that can be achieved in the gas cell can be up to 8 times the length of the gas cell itself, since 8 reflections are experienced.
A concave mirror 21 with a large aperture at one end of the chamber acts as all the reflection of the beam at this end and compensates for the divergence of the incident beam over long distance propagation with only a limited collimation distance by using the converging action of the concave mirror 21.
The concave reflecting mirror 21 used in the present invention may be a cylindrical concave mirror or a spherical concave mirror. When the concave mirror 21 is a cylindrical concave mirror, the beams 25 to 33 are on one plane. When the concave mirror 21 is a spherical concave mirror, the beams 25 and 26 are in the same plane, and the beams 29, 30 and 31 are in another plane parallel thereto. Beams 27 and 28, and beams 32 and 33 travel between these two planes. The beam 25 emerging from the laser, although collimated, has only a certain collimation distance and the beam emerging from the laser will diverge over a long propagation distance, which is disadvantageous for the photo detector to receive the beam emerging from the gas cell sufficiently and efficiently. Therefore, the utility model discloses an air chamber structure has adopted concave surface mirror 21, because concave surface mirror 21 has certain light beam convergence effect to light beam has been reflected 4 times by concave surface mirror in the light path, and the reflection all can lead to certain light beam and assemble with the divergence of compensating beam, so enable the last light beam 26 that exits and still can keep being collimated. However, the cylindrical concave mirror can only compensate the divergence direction perpendicular to the cylindrical line surface, and the spherical concave mirror can completely compensate the divergence. Therefore, the effect of using a spherical concave mirror is better in beam divergence compensation.
In the present invention, the window of the photodetector and the normal of the PD chip form an angle α with respect to its incident light beam, i.e. the outgoing light beam of the air chamber, to suppress the noise caused by etalon effect, and this angle value can be determined by the effect of actually suppressing the reflection of the window and the PD chip, generally between 3 ° and 15 °. The window of the light detector may be a planar light window or a converging lens. The reflected light from the window of the photodetector and the surface of the PD chip in the configuration shown in fig. 3 is not reflected back to the semiconductor laser, which causes etalon effect noise.
The limited space of the air chamber light path structure of the utility model can be cylindrical or rectangular column.
Example (b):
fig. 4 and 5 show an embodiment of the invention. In the embodiment, the limited space of the gas chamber, the laser and the light receiver is a cylindrical space with the outer diameter of 2.3cm and the length of 4.85 cm. The gas chamber in the laser gas sensor, the semiconductor laser and the light detector can obtain a typical allowable space in the application fields of urban inspection wells, pipe corridors and the like. The length of the air chamber can be about 3cm-4 cm. Even if the traditional folded light path is adopted, the maximum length of the light path in the air chamber is about 7 cm. But the optical path in the gas cell, i.e. the effective working distance of the light and the gas, can be increased to 25cm in this embodiment.
Figure 4 is a 3D partial cross-sectional view of the general structure of the gas cell of this embodiment together with a laser and photodetector mount Housing. The concave mirror in the structure of the embodiment is a spherical concave mirror. The whole structure is like a cylindrical surface 41 with a base and a part of which is hollowed out. The base portion is divided into two parts inside the cylindrical surface, and one of the two parts is formed with two circular holes TO be a mounting hole 42 for the TO-type semiconductor laser and a mounting hole 43 for the photodetector. The other part is cut with two symmetrical 45-degree inclined planes 44 for attaching two 45-degree plane mirrors.
The mounting holes (42 and 43) open on the same plane, which is perpendicular to the axis of the cylindrical surface. The other end of the cylindrical surface opposite to the base is provided with a spherical concave mirror. A plane reflector 46 is attached to the plane of the mounting hole for the semiconductor laser and the photodetector opposite the spherical concave mirror, and only half of the plane reflector 46 is attached to the plane, and the other half of the plane reflector extends to the other half of the mount.
In order to correspond to fig. 2, fig. 5 is an elevation view of the overall structure of the gas cell together with the laser and light receiver mounting, the gas cell optical path shown in this figure being identical to that of fig. 2.
Fig. 6 is a 3D profile view of the overall structure of the gas cell along with the semiconductor laser and photodetector mounting. The overall appearance of the structure shown in the figures omits all planar and concave mirrors. From this figure it can be seen that the overall structure of the gas cell together with the semiconductor laser and photodetector mounting is a very compact structure, only about half a finger in size, but in which a 25cm long gas absorption path is achieved.
Claims (8)
1. A gas sensor gas cell structure characterized in that: the device comprises a concave reflector, a first plane reflector, a second plane reflector and a third plane reflector;
the first plane reflector is a plane reflector, and the normal line of the first plane reflector and the incident beam form an angle of 45 degrees and are arranged opposite to the concave reflector;
the second plane reflector is a plane reflector, and the normal line of the second plane reflector and the incident beam form an angle of 45 degrees and are arranged opposite to the concave reflector; the normal line of the first plane reflector is orthogonal to the normal line of the second plane reflector, and the first plane reflector is arranged above the second plane reflector;
the third plane reflector is a plane reflector, and the mirror surface of the third plane reflector is orthogonal to the incident light beam and is arranged opposite to the concave reflector;
the third plane reflector is positioned between the first plane reflector and the second plane reflector, and the third plane reflector is closer to the concave reflector than the first plane reflector/the second plane reflector;
the incident beam is incident on the third plane mirror through the light beam reflected by the concave mirror, the light beam reflected by the third plane mirror is incident on the concave mirror again, the light beam reflected by the concave mirror is incident on the first plane mirror, the light beam reflected by the first plane mirror is incident on the second plane mirror, the light beam reflected by the second plane mirror is incident on the concave mirror, the light beam reflected by the concave mirror is incident on the third plane mirror, the light beam reflected by the third plane mirror is reflected back to the concave mirror again, and finally the light beam reflected by the concave mirror is the emergent light beam of the air chamber.
2. A gas sensor plenum structure according to claim 1, wherein: the concave reflecting mirror is a spherical concave mirror.
3. A gas sensor plenum structure as claimed in claim 1, wherein: the concave reflecting mirror is a cylindrical concave mirror.
4. The utility model provides a Housing of gas sensor gas chamber which characterized in that: the device comprises a semiconductor laser as a light beam emitter, a gas chamber and a light detector;
the gas cell is a gas sensor gas cell structure according to any one of claims 1 to 3;
the semiconductor laser serving as the light beam emitter is arranged on one side opposite to the concave reflecting mirror and used for emitting collimated light beams to the air chamber to serve as incident light beams of the air chamber;
the light detector is arranged on one side opposite to the concave reflecting mirror and used for receiving the emergent light beam of the air chamber.
5. A Housing of a gas sensor cell according to claim 4, characterized in that: the semiconductor laser is a tunable semiconductor laser.
6. The Housing of a gas sensor cell of claim 4, wherein: the light detector comprises a window and a PD chip, and the normal of the PD chip and the normal of the window form a certain angle with the emergent light beam of the air chamber.
7. A Housing of a gas sensor cell according to claim 6, characterized in that: the angle is in the range of 3-15 degrees.
8. A Housing of a gas sensor cell according to claim 4, characterized in that: the arrangement position of the light beam emitter corresponds to one edge of the air chamber, and the arrangement position of the light detector corresponds to the other edge of the air chamber.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202221336234.XU CN218003225U (en) | 2022-05-31 | 2022-05-31 | Gas sensor air chamber structure and Housing of gas sensor air chamber |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202221336234.XU CN218003225U (en) | 2022-05-31 | 2022-05-31 | Gas sensor air chamber structure and Housing of gas sensor air chamber |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN218003225U true CN218003225U (en) | 2022-12-09 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202221336234.XU Active CN218003225U (en) | 2022-05-31 | 2022-05-31 | Gas sensor air chamber structure and Housing of gas sensor air chamber |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN218003225U (en) |
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2022
- 2022-05-31 CN CN202221336234.XU patent/CN218003225U/en active Active
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