Multi-element small-size long-optical-path gas absorption cell based on strip-shaped concave reflecting mirror

Abstract

The utility model relates to the technical field of gas detection, in particular to a multi-element small-volume long-optical-path gas absorption cell based on a strip-shaped concave reflector, which comprises a gas chamber and an optical path structure, and the gas chamber comprises a cavity upper cover and a cavity lower cover; the light path structure comprises a first right-angle reflecting mirror, a first strip-shaped concave reflecting mirror, a second strip-shaped concave reflecting mirror, a second right-angle reflecting mirror, a third right-angle reflecting mirror, a third strip-shaped concave reflecting mirror, a fourth strip-shaped concave reflecting mirror and a fourth right-angle reflecting mirror. The strip-shaped concave reflecting mirror can be obtained by cutting the circular concave reflecting mirror with the same focal length, through the matching of the strip-shaped concave reflecting mirror and the right-angle reflecting mirror, the optical path can be increased on the premise of not increasing the volume of the gas chamber, meanwhile, quick response and high-precision detection are realized, and the strip-shaped concave reflecting mirror can be widely applied to the detection of gas concentration.

Description

Technical Field

[0001] The utility model relates to the technical field of gas detection, in particular to a multi-element small-volume long-optical-path gas absorption cell based on a strip-shaped concave reflector. Background Art

[0002] Tunable diode laser absorption spectroscopy (TDLAS) has developed rapidly in recent years. Due to its high detection accuracy, strong selectivity and fast response, TDLAS technology has been increasingly used in gas measurement. By using the narrow line width, low power consumption and tunable characteristics of diode lasers, the characteristic absorption spectrum of the laser after multiple reflections in the cavity is obtained by wavelength scanning, and then the absorption line shape of the gas is fitted to invert the concentration of the gas to be measured.

[0003] The development of gas absorption cells is based on the application in TDLAS technology. According to the Lambert-Beer law, the absorption of light intensity by gas is affected by the optical path of the chamber and the gas concentration. When the optical path of the chamber remains unchanged, the concentration of the measured gas can be obtained by analyzing the change of the outgoing light intensity after gas absorption. There are many types of gas absorption cells. At present, the more mature types include White cell, Herriott cell, matrix cell, etc. However, whether it is White cell or Herriott cell, since most of them use circular concave reflectors, the volume of the absorption cell is large when a long optical path is obtained, which makes the gas update rate extremely low, which seriously affects the response time of the entire device, especially in some applications for trace gases, it is extremely passive. There are also some gas sensors based on the NDIR principle, which can make the volume of the gas absorption part very small, but they are often limited by the optical path, and their detection accuracy is low, which cannot meet the requirements of field applications. Summary of the invention

[0004] In view of this, the utility model provides a multi-element small-volume long-optical-path gas absorption cell based on a strip concave reflector to solve the problem that under the limitation of the effective absorption optical path length, the absorption cell volume is large due to the size of the reflector, thereby affecting the gas detection response speed of the entire device.

[0005] Therefore, the technical solution adopted by the utility model is: a multi-element small-volume long-optical-path gas absorption cell based on a strip-shaped concave reflector, comprising an air chamber and an optical path structure.

[0006] The optical path structure includes a first right-angle reflector, a first strip concave reflector, a second strip concave reflector, a second right-angle reflector, a third right-angle reflector, a third strip concave reflector, a fourth strip concave reflector, and a fourth right-angle reflector;

[0007] The first right-angle reflector is a right-angle reflector whose mirror normal is 45 degrees to the incident laser and is arranged diagonally opposite to the second strip concave mirror;

[0008] The first strip-shaped concave reflector and the second strip-shaped concave reflector have the same focal length and size, are relatively parallel and are placed, and the centers of the two mirror surfaces are on the same straight line;

[0009] The second right-angle reflector is opposite to the third right-angle reflector, and the third right-angle reflector is a right-angle reflector arranged diagonally opposite to the third strip concave mirror;

[0010] The third strip concave reflector and the fourth strip concave reflector have the same focal length and size, are relatively parallel and placed, and the centers of the two mirror surfaces are in the same straight line and are perpendicular to the first strip concave reflector and the second strip concave reflector;

[0011] The fourth right-angle reflector is a right-angle reflector whose mirror normal is 45 degrees to the outgoing laser and is arranged diagonally opposite to the fourth strip concave mirror.

[0012] The light beam is vertically incident, reflected by the first right-angle reflector to the second strip concave reflector, and then reflected by the second strip concave reflector to the first strip concave reflector, after multiple reflections between the first strip concave reflector and the second strip concave reflector, reflected to the second right-angle reflector, and then reflected by the second right-angle reflector to the third right-angle reflector, and then reflected by the third right-angle reflector to the third strip concave reflector, and then reflected by the third strip concave reflector to the fourth strip concave reflector, after multiple reflections between the third strip concave reflector and the fourth strip concave reflector, reflected to the fourth right-angle reflector, and finally the light beam reflected by the fourth right-angle reflector is the output light beam of the absorption cell.

[0013] Furthermore, the incident and emitting directions of the laser are perpendicular to the absorption cell.

[0014] Furthermore, the distance between the first strip-shaped concave reflecting mirror and the second strip-shaped concave reflecting mirror is approximately twice their focal lengths, and changing the distance can change the optical path of the absorption cell.

[0015] The air chamber comprises a cavity upper cover and a cavity lower cover.

[0016] The upper cover of the cavity is provided with a laser entrance hole, a laser exit hole, a gas inlet and a gas outlet;

[0017] The lower cover of the cavity is provided with an O-ring groove to ensure the sealing performance of the cabin.

[0018] Furthermore, the laser entrance hole and the laser exit hole of the cavity cover can be used in conjunction with an optical window.

[0019] Furthermore, the laser entrance hole and the laser exit hole of the upper cover of the cavity can be used in conjunction with optical fibers;

[0020] Furthermore, the laser incident hole of the cavity upper cover corresponds to the position of the first right-angle reflector of the absorption pool optical path structure, and the laser exit hole corresponds to the position of the fourth right-angle reflector of the absorption pool optical path structure.

[0021] Compared with the prior art, the beneficial effect of the utility model is that through the cooperation of multiple strip concave reflectors and right-angle reflectors, the volume of the gas chamber can be greatly reduced while ensuring a longer absorption light path, thereby improving the gas detection response speed. Finally, the device can achieve fast response and high-precision detection at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The utility model provides a schematic diagram of the optical path structure of a multi-element small-volume long-optical-path gas absorption cell based on a strip concave reflector.

[0023] Figure 2 A schematic diagram of a cavity cover of a multi-element, small-volume, long-optical-path gas absorption cell based on a strip-shaped concave reflector provided in an embodiment of the utility model.

[0024] Figure 3 A schematic diagram of the optical path structure and the cavity bottom cover of a multi-element small-volume long-optical-path gas absorption cell based on a strip concave reflector provided in an embodiment of the utility model.

[0025] Figure 4 A 3D appearance diagram of a multi-element, small-volume, long-optical-path gas absorption cell based on a strip concave reflector provided in an embodiment of the utility model.

[0026] Figure 5 A schematic diagram of cutting a strip concave reflector in a multi-element small-volume long-optical-path gas absorption cell based on a strip concave reflector provided in an embodiment of the utility model.

[0027] Description of reference numerals:

[0028] 11. The first right-angle reflector; 12. The first strip concave reflector; 13. The second strip concave reflector; 14. The second right-angle reflector; 15. The third right-angle reflector; 16. The third strip concave reflector; 17. The fourth strip concave reflector; 18. The fourth right-angle reflector; 21. The laser incident hole; 22. The laser exit hole; 23. The gas inlet hole; 24. The gas outlet hole; 31. The optical path structure of the absorption cell; 32. The O-ring hole; 33. The cavity fixing hole; 34. The absorption cell fixing hole. Implementation

[0029] The technical solution of the utility model is now described in further detail in conjunction with the accompanying drawings and embodiments.

[0030] The utility model provides a gas absorption cell which can be used for a gas sensor based on the TDLAS technology and can be used in various gas concentration detection devices, such as methane, carbon dioxide and the like. Figure 1 The figure shows a schematic diagram of the optical path structure of a multi-element small-volume long-optical-path gas absorption cell based on a strip concave reflector. The basic structure thereof is composed of a first right-angle reflector 11 whose mirror normal is 45 degrees to the incident light, a first strip concave reflector 12, a second strip concave reflector 13 placed opposite to the first strip concave reflector 12, a second right-angle reflector 14, a third right-angle reflector 15, a third strip concave reflector 16, a fourth strip concave reflector 17 placed opposite to the third strip concave reflector 16, and a fourth right-angle reflector 18. The first right-angle reflector 11 is arranged opposite to the second strip concave reflector 13, and has a certain angle with the normal direction of the second strip concave reflector 13. By changing the angle, the light is reflected to the vicinity of the center position of the second strip concave reflector 13, and the incident light to the position of the second strip concave reflector 13 will affect the optical path; the first strip concave reflector 12 and the second strip concave reflector 13 have the same focal length and size, and are relatively parallel, and the centers of the two mirror surfaces are in the same straight line, and the distance is about twice the focal length. The distance can be changed, but the optical path will also change.

[0031] The second right-angle reflector 14 and the third right-angle reflector 15 have mirror surfaces opposite to each other, and the third right-angle reflector 15 is a right-angle reflector arranged diagonally opposite to the third strip concave reflector 16; by moving the positions of the second right-angle reflector 14 and the third right-angle reflector 15, the reflected light is made to reach the center position of the third strip concave reflector 16, and the position where the reflected light is incident on the third strip concave reflector 16 will affect the length of the optical path; the third strip concave reflector 16 and the fourth strip concave reflector 17 have the same focal length and size, and are relatively parallelly placed, and the centers of the two mirror surfaces are in the same straight line, and are perpendicular to the first strip concave reflector 12 and the second strip concave reflector 13; the fourth right-angle reflector 18 is a right-angle reflector arranged diagonally opposite to the fourth strip concave reflector 17, and its mirror normal is 45 degrees to the emitted laser.

[0032] The light beam is vertically incident, reflected by the first right-angle reflector 11 to the second strip concave reflector 13, and then reflected by the second strip concave reflector 13 to the first strip concave reflector 12, reflected multiple times between the first strip concave reflector 12 and the second strip concave reflector 13, reflected to the second right-angle reflector 14, and then reflected by the second right-angle reflector 14 to the third right-angle reflector 15, and then reflected by the third right-angle reflector 15 to the third strip concave reflector 16, and then reflected by the third strip concave reflector 16 to the fourth strip concave reflector 17, and reflected multiple times between the third strip concave reflector 16 and the fourth strip concave reflector 17, and then reflected to the fourth right-angle reflector 18, and finally the light beam reflected by the fourth right-angle reflector 18 is the output light beam of the absorption cell. Finally, the light is reflected 28 times between the first concave reflector 12 and the second concave reflector 13, and 36 times between the third concave reflector 16 and the fourth concave reflector 17. The effective optical path can reach more than 50 times the length of the air chamber itself. Compared with a circular concave reflector of the same size and focal length, the volume can be reduced by more than 30 times.

[0033] The confined space of the optical path structure of the gas absorption cell of the utility model can be cylindrical or rectangular.

[0034] Embodiment:

[0035] Figure 2 , Figure 3 , Figure 4 An embodiment of the utility model is shown in FIG. 5 . In this embodiment, the confined space where the optical path structure of the absorption cell is located is a rectangular space with a length of 60 mm, a width of 45 mm, and a height of 5 mm. By filling the useless space in the space, the volume of the absorption cell can be compressed to about 5 mL, which is very suitable for the detection environment of trace gases. Using a traditional circular concave reflector, the minimum volume of the absorption cell is 24 mL, which will seriously affect the response speed of the equipment. And the final effective absorption light path length is also greater than 1.5 m, which can meet the requirements of detection accuracy.

[0036] Figure 2 A schematic diagram of a cavity cover of a multi-element small-volume long-optical-path gas absorption cell based on a strip concave reflector provided in an embodiment of the utility model. The laser enters the gas absorption cell through the laser entrance hole 21, and exits through the laser exit hole 22 after multiple reflections in the absorption optical path structure. The gas to be measured enters the gas absorption cell through the gas inlet hole 23 and is discharged from the gas absorption cell through the gas outlet hole 24.

[0037] Figure 3A schematic diagram of the optical path structure and cavity lower cover of a multi-element small-volume long-optical-path gas absorption cell based on a strip concave reflector provided in an embodiment of the utility model. The laser enters the absorption cell optical path structure 31 inside the gas absorption cell through the laser incident hole 21, and is emitted through the laser exit hole 22 after multiple reflections in the absorption optical path structure 31. The gas to be measured enters the gas absorption cell through the gas inlet hole 23, and after the absorption cell optical path structure 31 absorbs the laser, it is discharged from the gas absorption cell through the gas outlet hole 24. The gas absorption cell is sealed by placing an O-ring with a suitable wire diameter and inner diameter in the O-ring hole 32, and connecting it to the cavity upper cover through the cavity fixing hole 33. And the gas absorption cell can be connected and fixed with other equipment through the absorption cell fixing hole 34 reserved at the edge.

[0038] Figure 4 A 3D outline diagram of a multi-element small-volume long optical path gas absorption cell based on a strip concave reflector provided in an embodiment of the utility model. The figure shows the overall appearance of the absorption cell, omitting the internal absorption cell optical path structure. It can be seen from the figure that the overall volume of the gas absorption cell is very small, but a 2.5m long gas absorption optical path is realized in it.

[0039] Figure 5 A schematic diagram of the cutting of a strip concave reflector in a multi-element small-volume long-optical-path gas absorption cell based on a strip concave reflector provided in an embodiment of the utility model. As shown in the figure, based on a circular concave reflector with a diameter of 25 mm and a focal length of 25 mm, two semicircles are symmetrically cut off 2.5 mm from the center of the mirror, and then the remaining part is a strip concave reflector with a width of 5 mm. One side of the long side of this strip concave reflector is further cut off by 1 mm, and the remaining part is the strip concave reflector used in this embodiment. The reason why 1 mm is cut off on one side of the long side is that the laser can be incident into the gas chamber at a small angle, so that it is easier to form multiple reflections.

Claims

1. A multi-element small-volume long-optical-path gas absorption cell based on a strip concave reflector, comprising an optical path structure and a gas chamber, wherein the optical path structure comprises a first right-angle reflector, a first strip concave reflector, a second strip concave reflector, a second right-angle reflector, a third right-angle reflector, a third strip concave reflector, a fourth strip concave reflector, and a fourth right-angle reflector; The air chamber comprises a cavity upper cover and a cavity lower cover; the cavity upper cover is provided with a laser entrance hole, a laser exit hole, a gas inlet and a gas outlet, and the cavity lower cover is provided with an O-ring groove to ensure the sealing of the chamber.

2. A multi-element small-volume long-optical-path gas absorption cell based on a strip-shaped concave reflector according to claim 1, characterized in that: The first right-angle reflector is a right-angle reflector whose mirror normal is 45 degrees to the incident laser and is arranged diagonally opposite to the second strip concave mirror; The first strip-shaped concave reflector and the second strip-shaped concave reflector have the same focal length and size, are relatively parallel and are placed, and the centers of the two mirror surfaces are on the same straight line; The second right-angle reflector is opposite to the third right-angle reflector, and the third right-angle reflector is a right-angle reflector arranged diagonally opposite to the third strip concave mirror; The third strip concave reflector and the fourth strip concave reflector have the same focal length and size, and are relatively parallel and arranged, with the centers of the two mirror surfaces being in the same straight line and perpendicular to the first strip concave reflector and the second strip concave reflector; The fourth right-angle reflector is a right-angle reflector that is arranged diagonally opposite to the fourth strip concave mirror at a 45° angle between its mirror surface normal and the outgoing laser. The light beam is vertically incident, reflected by the first right-angle reflector to the second strip concave reflector, and then reflected by the second strip concave reflector to the first strip concave reflector, after multiple reflections between the first strip concave reflector and the second strip concave reflector, reflected to the second right-angle reflector, and then reflected by the second right-angle reflector to the third right-angle reflector, and then reflected by the third right-angle reflector to the third strip concave reflector, and then reflected by the third strip concave reflector to the fourth strip concave reflector, after multiple reflections between the third strip concave reflector and the fourth strip concave reflector, reflected to the fourth right-angle reflector, and finally the light beam reflected by the fourth right-angle reflector is the output light beam of the absorption cell.

3. A multi-element small-volume long-optical-path gas absorption cell based on a strip-shaped concave reflector according to claim 2, characterized in that: The laser incident and outgoing directions are perpendicular to the absorption cell.

4. A multi-element small-volume long-optical-path gas absorption cell based on a strip concave reflector according to claim 2, characterized in that: The distance between the first strip concave reflecting mirror and the second strip concave reflecting mirror is twice their focal lengths, and changing the distance can change the optical path of the absorption cell.

5. The multi-element small-volume long-optical-path gas absorption cell based on a strip-shaped concave reflector according to claim 1, characterized in that: The strip concave reflecting mirror can be obtained by cutting a circular concave reflecting mirror with the same focal length. A circular concave reflecting mirror is symmetrically cut off to the same size, and the remaining part can be used as the strip concave reflecting mirror.

6. The multi-element small-volume long-optical-path gas absorption cell based on a strip-shaped concave reflector according to claim 1, characterized in that: The laser inlet hole and the laser outlet hole of the cavity upper cover can be used in conjunction with the optical window.

7. The multi-element small-volume long-optical-path gas absorption cell based on a strip concave reflector according to claim 1, characterized in that: The laser inlet hole and the laser outlet hole of the cavity upper cover can be used in conjunction with optical fibers.

8. The multi-element small-volume long-optical-path gas absorption cell based on a strip-shaped concave reflector according to claim 1, characterized in that: The laser incident hole of the cavity upper cover corresponds to the position of the first right-angle reflector of the absorption pool optical path structure, and the laser exit hole corresponds to the position of the fourth right-angle reflector of the absorption pool optical path structure.

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