Self-calibration method and system applied to TDLAS (Tunable Diode Laser Absorption Spectroscopy) equipment

Abstract

The invention discloses a TDLAS laser measurement equipment self-calibration method based on a light source scanning technology, and aims to improve the measurement stability of equipment in a complex industrial environment. The TDLAS (modulated laser absorption spectroscopy) technology is widely applied to gas detection due to high sensitivity and selectivity. However, the equipment is easily influenced by position deviation and vibration in the installation process, so that the measurement precision is reduced. Therefore, the invention designs a self-calibration system which comprises a laser transmitting module, a plurality of groups of adjustable self-calibration light transmitters and a target receiver, and all the components are fixed on a module base. The angle of the self-calibration light emitter is quickly scanned through the control system, so that the receiver is accurately positioned. The self-calibration process is divided into a preliminary step and a fine step, and a surface light source and a point light source are used for conducting large-range scanning and small-range scanning respectively, so that the purpose of efficient and accurate correction is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of TDLAS measurement, and in particular relates to a self-calibration method of TDLAS laser measurement equipment based on light source scanning technology. Background Art

[0002] TDLAS (modulated laser absorption spectroscopy) technology has been widely used in the field of gas detection due to its high sensitivity and selectivity. The absorption spectroscopy technology layout includes a laser transmitting module and a signal receiving module. The measurement process is that the laser transmitting module emits a laser, and after being absorbed by the target medium in the area to be measured, the laser beam reaches the signal receiver to obtain an absorption signal. With the complexity of the scene in the industrial site, for the in-situ layout of a large space, the performance of the TDLAS equipment is highly dependent on the accuracy of its installation position. If the installation position deviates, the contact efficiency between the laser beam and the gas to be measured may decrease, thereby affecting the measurement accuracy.

[0003] In actual applications, TDLAS equipment often faces vibration problems, which may come from nearby mechanical equipment, vibration during the operation of the equipment itself, or deformation of the mounting base and its connecting parts, resulting in slight changes in the position of its optical components, thereby affecting the laser emission angle and receiving ability. The originally stable measurement system may produce errors due to position changes, and the position changes caused during operation are difficult to correct in time.

[0004] For equipment layout in a closed environment, the position changes of the equipment caused by environmental factors make manual correction more difficult. Summary of the invention

[0005] The present invention provides a self-calibration method for TDLAS equipment, which can realize automatic position correction of the transmitting module and the receiving module of the laser equipment and ensure the stability of the measurement system, and is characterized by:

[0006] The self-calibration system is composed of a laser emitting module with a universal joint, multiple groups of universally adjustable self-calibration light emitters on the module base, and a corresponding target receiver located in the laser receiving module. The laser emitter, laser signal receiver and target receiver are all fixed on the module base, that is, they form a whole with the base. The control system controls the angle of each self-calibration light emitter to quickly scan the target receiver position, thereby realizing the search for the receiver position. There are four self-calibration light emitters, one of which is a surface light source and the other three are point light sources. The self-calibration process includes using the surface light source as the first step of the self-calibration laser to perform the first step of scanning the receiving module, and preliminarily adjusting the angle of the laser emitting module according to the signal reception of the target receiver to obtain the target position of the laser receiving module, and controlling the universal joint of the laser emitting module for preliminary adjustment. The search range is greatly reduced compared to the workload of directly using a point light source to scan a large area. Furthermore, a point light source is used to perform a small-range scan to preliminarily obtain the precise position. In order to prevent the laser emitting module from having a three-dimensional rotation angle, a second three-beam laser is used for further scanning and calibration. The three sets of self-calibration light emitters and the corresponding target receivers located in the laser receiving module are composed of three sets of self-calibration points to achieve base parallelism, that is, to achieve calibration of the laser emitter and signal receiver in fixed relative position.

[0007] Compared with the prior art, the present invention has the following advantages:

[0008] 1. The use of the TDLAS self-calibration system can reduce the difficulty of installation, reduce the requirements for equipment layout accuracy, optimize the TDLAS laser measurement equipment layout process, and is suitable for rapid installation and commissioning at industrial sites.

[0009] 2. The system can detect and automatically handle the problem that the installation location of the TDLAS equipment is affected by environmental changes during use, reducing the debugging work during operation and improving the equipment operation efficiency. It can achieve good engineering application development prospects in closed spaces. For in-situ online monitoring TDLAS measurement equipment installed in closed industrial environments, the self-calibration system makes it possible to debug the equipment without stopping the equipment for repair, greatly reducing the maintenance and debugging workload in this environment and reducing the cost of use.

[0010] 3. The TDLAS self-calibration system of the present invention has a flexible and compact structure and is easy to retrofit and improve on the basis of the original TDLAS equipment. It has excellent economy, adaptability and market potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Attached Figure 1 This is a front view of a laser emission module according to an embodiment of the present invention;

[0012] Attached Figure 2 is a front view of a laser receiving module according to an embodiment of the present invention;

[0013] Attached Figure 3 is a side view of a laser emission module according to an embodiment of the present invention;

[0014] Attached Figure 4 is a stereoscopic diagram of a laser emission module according to an embodiment of the present invention;

[0015] Attached Figure 5 is a three-dimensional diagram of a laser receiving module according to an embodiment of the present invention;

[0016] Attached Figure 6 It is an overall stereogram of an embodiment of the present invention;

[0017] Attached Figure 7 is a flow chart of a method according to an embodiment of the present invention;

[0018] In the figure: 1, light transmitter 2, universal adjustment bracket 3, mounting slot 4, laser transmitter 5, surface light source transmitter 6, laser transmitter module base 7, universal yoke 8, cross shaft 9, laser signal receiver 10, target receiver 11, surface light source target receiver 12, laser receiver module base 13, laser transmitter module 14, laser receiver module DETAILED DESCRIPTION

[0019] exist Figure 1-4 In the embodiment shown: the laser emitter 4 is fixed on the laser emission module base 6, and the two form a whole, and the laser emission direction is the normal direction of the base plane pointing to the laser signal receiver 9. The laser signal receiver 9, the target receiver 10 and the surface light source target receiver 11 are fixedly arranged on the front of the laser receiving module base 12, facing the laser emission module 13. There are four self-calibration light emitters fixed on the laser emission module mounting base 6, one of which is a surface light source light emitter 5, which is a square light spot surface light source. When it falls on the plane where the laser receiving module 14 is located, the length of the side of the light spot is the same as the length of the side of the laser receiving module 14, and the other three are point light source light emitters 1.

[0020] The self-calibration process includes: performing the first step of scanning the laser receiving module 14 through the universal adjustment bracket 2 on the surface light source light emitter 5, scanning the possible position area of ​​the surface light source target receiver 11 line by line, finding the spatial position of the laser signal receiver 9 through the signal reception of the surface light source target receiver 11, and preliminarily adjusting the laser emitting module 13 through the universal joint structure universal joint fork 7 and the cross shaft 8 controlled by the motor for fixing the laser emitting module base 6 to obtain the target position area of ​​the laser receiving module 14, that is, the laser signal receiver 9. After the adjustment, the deflection angle of the laser emitting module 13 relative to the laser receiving module 14 is reduced to complete the first step of calibration, and the search range is greatly reduced compared with the workload of directly using a point light source to scan a large area. During the first step of adjustment, the positions of all light emitters 1 are kept parallel to the light emitting direction of the laser emitting module 13. The size of the target position area is set to a square area relative to the plane where the surface light source irradiates the laser receiving module 14, and the center position of the square area is kept unchanged. The enlarged square area with a side length three times the original side length is the target position area, the purpose is to prevent the surface light source target receiver 11 from being located at the edge of the square area irradiated by the surface light source. In the second step, a light transmitter 1 is used to scan the target position area obtained in the first step line by line through a universal adjustment bracket 2, and the target receiver 10 located at the corresponding position on the base receives the signal. The direction of the light transmitter 1 is kept unchanged, and the laser emission module composed of the universal yoke 7 and the cross shaft 8 is adjusted to the direction of the light transmitter 1 by the universal joint adjustment laser emission module 13, thereby preliminarily obtaining the precise position. In the third step, after the precise position is preliminarily obtained, in order to prevent the laser emission module from having a three-dimensional rotation angle, the second and third light transmitters 1 are further scanned by performing the same scanning process as the first light transmitter 1, and finally the three groups of light transmitters 1 are matched with the target receivers 10 corresponding to their positions, and precise calibration is achieved.

[0021] The wavelength of the light emitted by the surface light source emitter 5 is different from the wavelength of the light emitted by the light emitter 1 , and both wavelengths avoid the wavelength of the light emitted by the laser emitter 4 .

[0022] The above only describes some exemplary embodiments of the present invention by way of illustration. For those skilled in the art, the described embodiments may be modified in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention. Various changes made without departing from the concept of the present application still fall within the scope of protection of the present invention.

Claims

1. A self-calibration method and system for TDLAS equipment, characterized in that: The laser signal receiver (9), the target receiver (10) and the surface light source target receiver (11) are fixedly arranged on the front side of the laser receiving module base (12) and face the laser emitting module (13); there are four self-calibration light emitters fixed on the laser emitting module mounting base (6), one of which is a surface light source emitter (5), which is a square light spot surface light source. When it falls on the plane where the laser receiving module (14) is located, the side length of the light spot is the same as the side length of the laser receiving module (14); the other three are point light source emitters (1); the self-calibration process includes the universal adjustment bracket (2) performing the first step of scanning the laser receiving module (14) with the surface light source emitter (5), scanning the possible position area of ​​the surface light source target receiver (11) line by line, and scanning the surface light source target receiver (11) line by line. The signal receiving condition of the light source target receiver (11) is used to find the spatial position of the laser signal receiver (9); the second step is to use a light transmitter (1) to scan the target position area obtained in the first step line by line through a universal adjustment bracket (2), and scan until the target receiver (10) located at the corresponding position on the base receives the signal, keep the direction of the light transmitter (1) unchanged, adjust the universal joint laser emission module (13) to the direction of the light transmitter (1), and preliminarily obtain the precise position; the third step is to use the second and third light transmitters (1) to perform the same scanning process as the first light transmitter (1) to further scan the target position area, so as to achieve matching of the three groups of light transmitters (1) and the target receivers (10) corresponding to their positions, and achieve precise calibration.

2. According to the self-calibration method and system for TDLAS equipment described in claim 1, the target position area obtained by the first step of calibration is characterized in that the size is set to a square area relative to the plane where the surface light source irradiates the laser receiving module (14), the center position of the square area is kept unchanged, and the enlarged square area with a side length three times the original side length is the target position area.

3. According to the self-calibration method and system for TDLAS equipment described in claim 1, in order to prevent the laser emission module from having a three-dimensional rotation angle, the third scanning process further scans the target position area through the second and third light emitters (1).

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