WO2020073968A1

WO2020073968A1 - Laser gas detection apparatus and correction method therefor

Info

Publication number: WO2020073968A1
Application number: PCT/CN2019/110440
Authority: WO
Inventors: 陶俊; 向少卿
Original assignee: 上海禾赛光电科技有限公司
Priority date: 2018-10-12
Filing date: 2019-10-10
Publication date: 2020-04-16
Also published as: CN108982413A

Abstract

A laser gas detection apparatus. Multiple lasers (100) are used for synchronously scanning. The lasers (100) are used for forming a laser light source group having a high transmit power; meanwhile, a light splitting device is used for splitting a light beam emitted by each laser (100) into a reference light (304) and a detection light (302). The position of an absorbing peak in the reference light (304) passing through a gas absorbing pool (104) is detected and the wavelength scanning of each laser (100) is regulated independently according to detection information so as to adjust the relative position of the absorbing peak in the finally received laser signal, which solves the signal quality deterioration problem.

Description

Laser gas detection device and correction method

Technical field

The invention relates to the field of gas analysis and detection. More specifically, the invention relates to a laser gas detection device.

Background technique

Tunable diode laser absorption spectroscopy (TDLAS) is an optical and spectroscopic measurement method that uses laser light in absorption spectroscopy. TDLAS utilizes the narrow linewidth and fast tuning characteristics of semiconductor lasers, and can detect gas quickly by detecting an isolated vibrational absorption line that absorbs molecules.

The application of TDLAS technology to measure the gas concentration is very extensive, including atmospheric detection, automobile exhaust gas measurement, hazardous gas leak detection, gas concentration measurement in the flue and so on. In some specific application scenarios (such as gas leak detection from the bottom of the building to high-rise residential buildings or the use of drones to measure the gas concentration of ground targets), it is often necessary to use a laser gas detection device with a long detection distance.

In order to increase the detection distance, some laser gas detection devices use multiple lasers to increase the transmission power. However, in the process of implementing the present invention, the inventor found that simply increasing the number of lasers can effectively increase Transmit power, but at the same time brings the following problem: With the increase of use time, the overall quality of the laser signal obtained by the detection device is seriously degraded.

Summary of the invention

In view of the above-mentioned problems in the prior art, the present invention provides a laser gas detection device that can perform individual wavelength scanning correction on a plurality of lasers after aging, so that the absorption peaks formed after each laser beam is collected can be well Superimposed to reduce or prevent the overall quality of the laser signal from deteriorating.

In the process of creating the present invention, the inventors found that the deterioration of the overall quality of the laser signal is mainly due to the change in the scanning range of the wavelength scan due to aging. The change of the wavelength scanning range will cause the shift of the absorption peak position in different laser spectra. The drifted absorption peak will cause the peak splitting phenomenon of the laser signal superposition result, which will affect the analysis of the light intensity signal and ultimately cause the signal quality. Deterioration.

In order to solve the above problems, the laser gas detection device provided by the technical solution of the present invention includes: a plurality of lasers; a control part, which is electrically connected to the plurality of lasers, can control the plurality of lasers to perform synchronized wavelength scanning, and the target absorption peak of the gas to be measured The center wavelength is preset to occupy the first relative position in the scan waveform of the wavelength scan; one or more beam splitting components, the output optical paths of multiple lasers all pass through the beam splitting component to split the laser beam emitted by each laser into probe light and Reference light; one or more gas absorption cells, each light path of the reference light passes through the gas absorption cell, and the gas absorption cell is filled with the gas to be measured; one or more detectors are arranged after each reference light passes through the gas absorption cell The optical path of the control section is electrically connected to the detector, which can determine the second relative position occupied by the target absorption peak of the gas to be measured in the light intensity signal waveform collected by the detector; the control section also includes a position correction module, a position correction module Electrically connected to multiple lasers, capable of deviating from the first relative position according to the second relative position, independently A plurality of lasers or wavelength scan can be adjusted.

Combined use of multiple lasers can produce a laser light source with high emission power. In order to eliminate the signal quality problems caused by the combined use of multiple lasers, the technical solution provided by the present invention adopts a position correction module to deviate from the absorption peak of different lasers due to aging Correction is performed to enable the final main detector to receive the absorption peak signal at the same or substantially the same time, to prevent peak splitting of the laser signal generated by the final superposition, to effectively improve the overall quality of the laser signal, and to prevent some lasers from aging. Serious deterioration of signal quality.

In a preferred technical solution of the present invention, the laser gas detection device includes a current driving device, which is electrically connected to a plurality of lasers and a control unit, and can perform current scanning according to a control signal output by the control unit to drive a plurality of lasers to perform Wavelength scanning. The current adjustment method realizes the adjustment of the wavelength scan by changing the injection current of the laser, and has extremely high adjustment response speed and low device cost.

Further, in a preferred technical solution of the present invention, the position correction module includes a current correction unit, which is electrically connected to the current driving device, and can adjust the current scanning range of the current driving device to adjust the wavelength scanning of the laser. The current correction unit is used for position correction, which has extremely high response rate and accuracy. In addition, a current correction unit is used to correct the current scanning range, and the device conversion difficulty and cost are low.

Furthermore, in the preferred technical solution of the present invention, the scanning waveform of the current scanning is a triangular wave or a sawtooth wave, and the current correction unit superimposes the amplitude offset on the basis of the scanning waveform to determine the Correspondence, adjust the scanning range of the wavelength scan accordingly. In some embodiments, the corresponding adjustment of the scan range of the wavelength scan refers to translation of the scan range of the wavelength scan. The triangular or sawtooth waveform is used for current scanning, which can linearly adjust the wavelength scanning range, which is convenient for the calculation of the adjustment amount.

Optionally, the control unit further includes a current offset calculation unit that can obtain a constant-amplitude offset according to the offset of the second relative position from the first relative position.

In the preferred technical solution of the present invention, the temperature of the laser is adjustable, and the position correction module includes a temperature correction unit, which can input a temperature control current to the laser to scan the wavelength of the laser according to the correspondence between the laser wavelength and the temperature Make adjustments. Using the temperature adjustment method, the scanning range of the wavelength can be adjusted in a larger range, so that the laser gas detection device can cope with the situation where the absorption peak deviates more seriously.

Further, in a preferred technical solution of the present invention, the laser includes a temperature sensor, the temperature correction unit is electrically connected to the temperature sensor, and can deviate from the temperature of the laser obtained by the temperature sensor and the deviation amount of the second relative position from the first relative position The laser outputs temperature control current. Using a laser with a temperature sensor for temperature adjustment can more accurately match the relationship between the wavelength, temperature and current, and adjust the wavelength scan of the laser.

In a preferred technical solution of the present invention, the laser gas detection device further includes a laser component bracket, and the laser component bracket has a plurality of bracket units arranged in parallel, and the bracket unit is installed and fixed with the spectroscopic component, the gas absorption cell, and the detector, one or more The two detectors are electrically connected to the same circuit board, and the circuit board is mounted on the outer shell of the laser gas detection device. Through the above installation methods, the heat dissipation performance of the circuit board is effectively improved.

Further, in a preferred technical solution of the present invention, the laser component bracket has multiple laser mounting ports, and the multiple lasers are detachably connected to the laser component bracket through the laser mounting port. It is convenient to replace in time when some lasers fail. At the same time, the number of lasers can be easily adjusted to meet the requirements of the number of lasers in different usage scenarios and improve the universality of laser gas detection devices.

In a preferred technical solution of the present invention, the laser gas detection device includes: a plurality of lasers; a control section, electrically connected to the plurality of lasers, capable of controlling the plurality of lasers to perform synchronized wavelength scanning, and the center wavelength of the target absorption peak of the gas to be measured The first relative position is preset in the scan waveform of the wavelength scan; the current driving device is electrically connected to the multiple lasers and the control part, and can perform current scanning according to the control signal output by the control part to drive the multiple lasers to perform Wavelength scanning; one or more beam splitting components, the exiting optical paths of multiple lasers pass through the beam splitting components to split the laser beam emitted from each laser into probe light and reference light; one or more gas absorption cells, each reference The light path of the light passes through the gas absorption cell, and the gas absorption cell is filled with the gas to be measured; one or more detectors are arranged on the light path after each reference light passes through the gas absorption cell; the control part is electrically connected to the detector and can Determine the second phase occupied by the target absorption peak of the gas to be measured in the light intensity signal waveform collected by the detector The control section further includes: a position correction module, which is electrically connected to the plurality of lasers and can independently deviate from one or more lasers according to the deviation amount of the second relative position from the first relative position The wavelength scanning is adjusted; the position correction module includes a current correction unit and a temperature correction unit. The current correction unit is electrically connected to the current drive device and can adjust the current scan range of the current drive device. The temperature correction unit can input a temperature control current to the laser to The wavelength scanning of the laser is adjusted; the position correction module is preset with an adjustment threshold. If the second relative position deviates from the first relative position by less than the adjustment threshold, the position correction module uses a current correction unit to perform position correction; if the second relative position deviates The deviation amount of the first relative position is greater than the adjustment threshold, and the position correction module uses the temperature correction unit or the temperature correction unit and the current correction unit to perform position correction.

In this preferred technical solution, the position correction module of the laser gas detection device uses a temperature correction unit and a current correction unit to correct the wavelength scanning range of the laser. When the deviation of the absorption peak is small, the correction speed is faster and more accurate. The current correction unit performs correction, and when the deviation amount of the absorption peak is large, the temperature correction unit is turned on to correct the wavelength scanning state of the laser within a large adjustment range. In the above manner, the laser gas detection device can be adjusted and corrected according to different aging conditions, and at the same time meet the requirements of adjustment speed, adjustment accuracy and adjustment range.

The invention also provides a correction method of a laser gas detection device for a laser gas detection device installed with multiple lasers. The correction method includes the following steps:

Multiple lasers perform synchronous wavelength scanning, wherein the center wavelength of the target absorption peak of the gas to be measured occupies the first relative position by default in the scanning waveform of the wavelength scanning;

Split the laser beams emitted by multiple lasers into probe light and reference light;

Pass multiple reference lights through the gas absorption cell filled with the gas to be measured;

Detect the intensity signal of each reference light after passing through the gas absorption cell;

Determine the second relative position occupied by the target absorption peak of the gas to be measured in the reference light intensity signal waveform;

According to the deviation amount of the second relative position from the first relative position, the wavelength scanning of one or more lasers is independently adjusted.

BRIEF DESCRIPTION

1 is a schematic diagram of the photoelectric structure of a laser assembly of a laser gas detection device in an embodiment of the present invention;

2 is a waveform diagram of the driving current signal in the embodiment of FIG. 1;

3 is a waveform diagram of a wavelength scanning signal in the embodiment of FIG. 1;

4 is a schematic diagram of the laser signal waveform of the aged laser received by the detector in the embodiment of FIG. 1;

5 is a schematic structural diagram of a feedback control loop of a laser gas detection device in another embodiment of the present invention;

6 is a schematic diagram of the installation structure of the laser assembly in the embodiment of FIG. 1;

7 is a schematic structural diagram of a laser gas detection device used to implement laser position correction in an embodiment of the present invention;

FIG. 8 is a flowchart of the operation method of the position correction structure in the embodiment of FIG. 7.

Reference mark:

100-laser, 102-spectral component, 104-gas absorption cell, 106-detector, 108-circuit board, 200-control section, 202-position correction module, 206-analog-to-digital conversion module, 2020-deviation calculation unit, 2022-current offset calculation unit, 2024-temperature control current calculation unit, 2026-current correction unit, 2028-temperature correction unit, 300-laser, 302-detection light, 304-reference light, 400-current drive device, 500 -Laser assembly holder, 502-stand unit, 504-laser mounting port, 506-collimating lens.

detailed description

As described in the background art, due to the limited power of the laser, in order to increase the detection distance of the laser gas detection device, technicians can achieve this by using multiple lasers to work simultaneously. However, simply increasing the number of lasers also brings certain problems, that is, as the instrument ages, the overall quality of the laser signal deteriorates significantly.

In the process of realizing the present invention, the inventor found that the technical problem was mainly due to the change of the scanning range of the wavelength scan brought about by aging, which caused the drift of the absorption peak position, and the absorption peak after the drift Peak splitting will occur in the signal superposition result of each laser, and this superposition result will affect the analysis of the light intensity signal, causing the overall quality of the laser signal to deteriorate.

Specifically, when the laser gas detection device is shipped, each laser is configured to perform strictly synchronized wavelength scanning. In some embodiments, the plurality of lasers are current-tuning lasers of the same model, and by controlling the driving current of each laser to scan synchronously, the plurality of lasers are synchronized to perform wavelength scanning with the same scanning range. The synchronized wavelength scanning process can be strictly executed when the instrument is shipped from the factory, but with the increase of use time, each current tuned laser will show different degrees of aging, and the aging phenomenon will change the wavelength-current correlation function of the current tuned laser . With the generation of aging phenomenon, although the lasers are loaded with synchronized scanning current, the obtained wavelength scanning range is not completely synchronized, and the wavelength-current correlation function of some lasers changes greatly, resulting in a specific absorption within the same scanning period. The wavelengths occupy different positions in the wavelength scan. At this time, the laser signal collected by the photodetector will divide multiple absorption peaks in the same period. This form of laser signal has poor quality and will seriously affect the subsequent gas concentration analysis.

For example, in one embodiment, an absorption line with a center wavelength of 1653.72 nm is selected, the corresponding temperature value is 22.9 ° C, and the current value is 70 mA; the laser scans the range of 20-120 mA, where the wavelength value corresponding to 20 mA is 1653.478 nm, The current value corresponding to 120mA is 1654.076nm. At the time of shipment, the center wavelength of the absorption line (corresponding to the current value of 70mA) will occupy the center position in the wavelength scanning curve, that is, the 1 / 2T position; and when the laser is aging, 20 -120mA current value scanning range will correspond to different wavelength scanning range, and then the current value corresponding to the center wavelength of 1653.72nm will also change, such as 50mA, at this time, the absorption peak is located at 1 / 4T position, if another laser If the absorption peak remains in place, the photodetector of the final instrument will detect the gas absorption signal at the sampling points at different times in the same cycle, that is, the collected laser signal will exhibit multiple absorptions occupying different positions in a cycle Peak, which seriously affects the subsequent calculation and analysis of gas concentration.

Through the above analysis, the inventors found that the deterioration of the laser signal quality results from the shift of the absorption peak positions caused by the aging of some lasers. In order to solve the above problems, the present invention provides a laser gas detection device, including: a plurality of lasers; a control section, electrically connected to the plurality of lasers, capable of controlling the plurality of lasers to perform synchronous wavelength scanning, and the target absorption peak of the gas to be measured The center wavelength presupposes to occupy the first relative position in the scanning waveform of the wavelength scan; the splitting component, the splitting components are provided on the output optical paths of multiple lasers to split the laser beam emitted from each laser into probe light and reference light; Gas absorption cell, each light path of reference light is equipped with gas absorption cell, and the gas absorption cell is filled with gas to be measured; detector, each light path of reference light passing through the gas absorption cell is provided with detector; control part It is electrically connected to the detector, which can determine the second relative position occupied by the target absorption peak of the gas to be measured in the light intensity signal waveform collected by the detector; the control part also includes a position correction module, which is electrically connected to multiple lasers , In response to the second relative position deviating from the first relative position, the position correction module can independently respond to the corresponding excitation The wavelength scan of the optical device is adjusted.

Using multiple lasers to scan synchronously, multiple lasers can be used to form a laser light source group with higher emission power. At the same time, a beam splitting device is used to split the beam emitted by each laser into reference light and detection light. The position of the absorption peak in the reference light after the absorption cell is detected, and the wavelength scan of each laser is independently adjusted according to the detection information, and then the relative position of the absorption peak in the finally received laser signal is adjusted to solve The problem of signal quality degradation.

Hereinafter, preferred embodiments of the present invention will be roughly described with reference to the drawings. In addition, the embodiments of the present invention are not limited to the following embodiments, and various embodiments within the scope of the technical idea of the present invention can be adopted.

Example one

This embodiment provides a laser gas detection device. As shown in FIG. 1, the laser gas detection device includes a plurality of lasers 100, and each laser 100 is provided with an independent control loop for adjusting the wavelength scanning state of the laser .

Specifically, the control circuit of each laser 100 is provided with a beam splitter 102, which can split the laser beam 300 emitted by the laser 100 into the detection light 302 and the reference light 304. Among them, the surface of the spectroscopic component 102 is coated with an antireflection film to further increase the light intensity of the detection light 302. In this embodiment, the antireflection coating on the surface of the beam splitting member 101 can make the detection light 302 and the reference light 304 have an intensity ratio of 99: 1 or more. The sample of the state of the probe light 302 is analyzed, and the wavelength scanning state of the probe light 302 is monitored.

A gas absorption cell 104 is provided on the path after the reference light 304 is separated, and the gas absorption cell 104 is filled with the gas to be measured. After the reference light 304 passes through the gas absorption cell 104, light of a specific wavelength is selectively absorbed by the gas and carried The reference light 304 with gas absorption information is received by the detector 106. The detector 106 converts the received light intensity signal of the reference light 304 into an electrical signal and transmits it to the control unit 200. The control unit 200 can perform analog-to-digital conversion on the electrical signal reflecting the light intensity information of the reference light 304 and generate a drive according to the analysis result The signal is used to control the wavelength scanning state of the laser 100. The above structure constitutes a control loop for beam splitting, detection, feedback, and control of the laser 100.

In this embodiment, the target gas to be measured by the laser gas detection device is methane gas. After passing through the methane gas, the reference light 304 will have characteristic absorption around 1653.72 nm, and there is no interference absorption peak near the center wavelength, so The absorption peak with the center wavelength of 1653.72 nm is selected as the target absorption peak of the gas to be measured in this embodiment. The laser gas detection device can combine easily accessible lasers into a laser light source group with higher emission power through multiple laser simultaneous scanning methods to deal with natural gas leakage inspection in some specific environments, such as from the bottom of the building to the high-rise of the residential building Carry out natural gas leak detection or use a drone to perform natural gas pipeline leak inspection on ground targets, etc. Of course, those skilled in the art can also design the laser gas detection device for different gas to be tested according to actual needs, and the optional gas to be tested includes ammonia, carbon monoxide, hydrogen and other gases. In addition, for the same gas to be measured, the technician can also select different absorption peaks of the gas to be measured as target absorption peaks, and only need to adjust parameters such as the type of laser, the center wavelength of the laser wavelength scan, and the scanning range.

The following further describes the control method of the laser 100 wavelength scanning by the control loop provided by this embodiment with reference to FIGS. 2 to 4. The laser 100 used in the laser gas detection device in this embodiment is a current tuning laser, and the control unit 200 can independently control the current modulation signal applied to each laser 100.

In this embodiment, the current modulation signal uses a sawtooth wave signal for low frequency scanning. Referring to FIG. 2, the minimum value of the drive current obtained by the factory-set low-frequency scan signal is 20 mA, and the maximum value is 120 mA. The laser 100 is driven to perform linear or substantially linear wavelength scanning. The corresponding waveform of the wavelength scanning is shown in FIG. 3 As shown. The center wavelength of the target absorption peak of the gas to be measured is 1653.72 nm, and the operating current value of the laser 100 corresponding to this wavelength is 70 mA. That is, the center wavelength of the target absorption peak is preset to occupy the first relative position in the scan waveform of the wavelength scan as a position of 1/2 cycle. In this embodiment, the first relative position refers to the ratio of the center wavelength of the target absorption peak in the wavelength-time curve of the wavelength scan to the period duration T within a scan period.

With the occurrence of the aging phenomenon, although each laser 100 is still loaded with the same synchronous scanning current signal, due to the different aging degree of each laser 100, its wavelength-current correlation function will change to varying degrees, resulting in a final wavelength scanning curve A certain degree of deviation occurs. The detector 106 converts the received light signal whose light intensity changes with time into an electrical signal, and then converts it into a digital signal by the control unit 200, and the resulting light intensity (normalized) -sampling point curve is shown in FIG. 4 Show. Due to aging, although the laser 100 is still driven by a current of 20-120 mA, the scanning range of the wavelength scanning signal it actually emits drifts to 1653.582-1654.207 nm. Accordingly, the target absorption peak with a center wavelength of 1653.72 nm will also drift from the original 1/2 period position to the second relative position of 1/4 period. In this embodiment, the second relative position refers to the ratio n / N of the sampling points n of the target absorption peak in the sampled digital signal to the total number N of sampling points in a cycle.

It should be noted that the “relative position” in the first relative position and the second relative position means that the specific absorption wavelength or the target absorption peak is in the target signal related to the wavelength (such as the current signal and the wavelength signal in this embodiment) The corresponding target parameters (such as t, n) account for the proportion of the total number of target parameters (such as T, N) in a cycle. In other embodiments of the present invention, the target signal and the target parameter can be selected according to actual conditions, and the above changes do not exceed the protection scope of the present invention without departing from the gist of the present invention.

In order to realize the correction of the second relative position of the target absorption peak, the laser gas detection device in this embodiment further includes a position correction module 202, which can correct the second relative position of the target absorption peak. Specifically, the parameter adjusted by the position correction module 202 is the scanning range of the driving current of the laser 100. By independently adjusting the scanning range of the driving current of each aging deviation laser 100, the wavelength scanning range of the laser light emitted by each laser 100 is shifted back to the original 1654.378-1654.076 nm.

In this embodiment, the scanning range of the driving current of the laser 100 is adjusted by superimposing an equal amplitude offset on the basis of the original driving current signal, that is, increasing or decreasing an equal amount of current on the basis of the original driving current signal. For example, for the laser 100 whose scanning range deviates to 1653.582-1654.207 nm, the position correction module 202 can uniformly reduce the corresponding scanning current at each time, for example, adjust the current scanning range from the original 20-120 mA to 17-117mA, so that the scanning range of the wavelength returns to 1653.478-1654.076nm. Correspondingly, since the adjusted wavelength scanning range of each laser 100 is the same, and the linear scanning signal with a sawtooth waveform is used, the final detector of the laser gas detection device will collect the absorption peak signal at the same or substantially the same time Therefore, the absorption peak signals of the lasers 100 can be superimposed well, avoiding that the absorption peaks in the final laser signal fall at different relative positions, thereby increasing the difficulty of analyzing the laser signal and reducing the signal quality.

It should be noted that although in this embodiment, each laser 100 is driven by a linear triangular wave or sawtooth wave signal, the technician can select other types of waveforms for wavelength scanning according to the actual situation, such as sine waves or combined waveforms, etc. As long as the waveform can scan a specific wavelength range and facilitate later calculation and analysis.

In this embodiment, the laser 100 is a current-tuned laser. Specifically, the current-tuned laser may be a sampling grating distributed Bragg reflection laser, an auxiliary grating directional coupling back-sampling reflection laser, a distributed feedback laser, or other suitable current-tunable laser.

In other embodiments of the present invention, the laser 100 may also be other types of tunable lasers, such as tunable lasers using temperature control technology or mechanical control technology. Accordingly, the adjustment method of the wavelength scanning range of the laser 100 can also be adjusted according to actual conditions, such as the type of the laser 100, the adjustable wavelength range, and other factors, such as temperature adjustment, current adjustment, mechanical adjustment, or a combination of adjustment methods. In addition, in other embodiments of the present invention, the spectroscopic component 102, the gas absorption cell 104, the detector 106 and other components can also be configured as one or more according to actual needs, and are shared by different lasers 100 without departing from the present invention Under the premise of the gist, the change of the number of such components should be understood as not exceeding the protection scope of the present invention.

In this embodiment, the control unit 200 integrates a current source for driving the laser 100. In other embodiments of the present invention, a separate current driving device 400 may also be used to drive each laser. Referring to FIG. 5, the control unit 200 includes a position correction module 202 that is electrically connected to the detector 106 corresponding to each laser 100 and can modulate the current signal according to the light intensity signal collected by the detector 106. The specific modulation method The first embodiment has been described in detail, and can be used until now, and will not be repeated here. The current drive device 400 is connected to the control unit 200, and the signal modulated by the position correction module 202 is transmitted to the current drive device 400. The modulated signal includes the drive signal of each laser 100, and the current drive device 400 is independently based on the drive signal Each laser 100 is driven.

In addition, in other embodiments of the present invention, the current driving device 400 may also be configured as one or more and shared by different lasers 100. A plurality of lasers 100 are connected to different interfaces of the current driving device 400, and the current driving device 400 can independently adjust the driving current of each laser 100 according to the received driving signal of the control section 200.

In the above manner, this embodiment provides a laser gas detection device that uses a plurality of lasers 100 in combination to generate a laser light source with high emission power, and uses a position correction module 202 to absorb absorption peaks generated by different lasers 100 due to aging The deviation is corrected to make the relative position of the absorption peak of each laser return to the preset state, so that each absorption peak can be superimposed on the finally collected light intensity-sampling point signal, improve the signal quality, and reduce the analysis difficulty .

This embodiment also provides a mechanical installation structure of the laser array formed by the laser 100 and the associated feedback control component in the laser gas detection device. As shown in FIG. 6, the laser gas detection device has a laser assembly bracket 500 for mounting a laser array and a feedback control component. The laser assembly bracket 500 includes a plurality of bracket units 502 arranged in parallel, and each bracket unit 502 is mounted with a spectroscopic component 102. A gas absorption cell 104 and a detector 106 that monitors the intensity of the reference light 304. In addition, the laser assembly holder 500 also has a screw hole that matches the thread of the laser 100, that is, the laser mounting port 504, which can be used for laser 100 detachable connection. The design of the support unit 502 and the detachable laser makes the device design and production process more flexible, the cost of the mold is lower, and the replacement and maintenance of the laser are also more convenient. The laser mounting ports 504 are arranged in parallel, so that each laser 100 mounted on the mounting port 504 keeps the exit optical path parallel, and a collimating lens 506 is further installed on the exit optical path of each laser 100 to further improve the parallelism of the exiting light. The lasers emitted from each channel can be combined or emitted individually, and can be flexibly configured according to the actual situation.

In this embodiment, each bracket unit 502 is also installed with a separate circuit board 108 electrically connected to the detector 106 for driving the detector 106 and converting the analog signal obtained by the detector 106 according to the light intensity signal into a digital signal And send the digital signal to the control part 200 of the instrument. In another embodiment of the present invention, multiple detectors 106 may also be electrically connected to the same circuit board 108, which may be installed at the outer casing (not shown in the figure) of the laser gas detection device to achieve Better heat dissipation effect.

Example 2

This embodiment provides a laser gas detection device that uses a combination of current and temperature to adjust the wavelength scanning range. The mechanical structure and the circuit structure other than the position correction module can follow the related structure of the laser gas detection device in Embodiment 1. I won't repeat them here.

The structure of the position correction module 202 of the laser gas detection device in this embodiment is described below with reference to the drawings, and how it is used in conjunction with two adjustment parameters of current and temperature to perform wavelength correction. Referring to FIGS. 7 and 8, the laser 100 used in the laser gas detection device in this embodiment is a current tunable laser, and a semiconductor refrigerator (ThermoElectric Cooler, TEC) is integrated in the laser 100. The temperature control current input by the semiconductor refrigerator can adjust the temperature of the laser 100.

Among them, the sensitivity of the laser 100 to adjust the wavelength scan by temperature is 0.09nm / ℃, which can achieve a wider range of wavelength adjustment, but the response speed is relatively slow and not accurate; and the sensitivity of adjusting the wavelength scan by changing the current is 0.01nm / mA, although the response speed is fast and accurate, but the adjustable wavelength range is narrow. In this embodiment, a temperature correction unit 2028 is used to control the temperature control current input to the laser 100 to coarsely adjust the wavelength of the laser 100; and a current correction unit 2026 is used to control the current intensity of the laser 100 to control the laser 100 Fine-tune the wavelength.

Specifically, the position correction module 202 includes a deviation amount calculation unit 2020, a current offset amount calculation unit 2022, a temperature control current calculation unit 2024, a current correction unit 2026, and a temperature correction unit 2028. The analog signal generated by the detector 106 is A / D converted by the analog-to-digital conversion module 206 of the control unit 200 and then sent to the deviation amount calculation unit 2020 of the position correction module 202. The deviation amount calculation unit 2020 calculates the deviation amount Δ of the second relative position from the first relative position, and selectively adjusts the wavelength scanning range using current or temperature according to the magnitude relationship between the deviation amount Δ and a preset adjustment threshold δ.

When the deviation Δ is less than or equal to the preset adjustment threshold δ, the position correction module 202 will use the current offset method to fine-tune the wavelength scan range. The deviation amount calculation unit 2020 sends the deviation amount signal to the current offset amount calculation unit 2022, and the current offset amount calculation unit 2022 can calculate the constant amplitude offset amount of the current for wavelength sweep adjustment according to the deviation amount Δ, and the The constant amplitude offset is sent to the current correction unit 2026, and the current correction unit 2026 is connected to the current driving device 400, which can superimpose the constant amplitude offset on the original current drive signal to adjust the wavelength scanning range.

When the deviation Δ is greater than the preset adjustment threshold δ, the position correction module 202 will use the method of changing the temperature of the laser 100 for coarse adjustment. When temperature adjustment is used, the deviation amount calculation unit 2020 sends the deviation amount result to the temperature control current calculation unit 2024, which can calculate the final temperature control input to the laser 100 based on the deviation amount Δ and the actual temperature of the laser 100 Current, and send the calculation result to the temperature correction unit 2028, and the temperature correction unit 2028 performs output adjustment of the temperature-controlled current.

It should be noted that, when the deviation Δ calculated by the deviation calculation unit 2020 is greater than the preset adjustment threshold δ, that is, temperature adjustment is required for coarse adjustment, after the coarse adjustment process is completed, the temperature correction unit 2028 sends the laser 100 After the step of inputting the temperature control current, the analog signal of the detector 106 can be re-acquired and subjected to analog-to-digital conversion, and then the Δ-δ size determination step and adjustment step until the deviation Δ is less than or equal to the adjustment threshold δ, then use The current correction unit 2026 fine-tunes the wavelength.

In this embodiment, the calibration process of the wavelength scan is configured to start up and shut down after the calibration is completed to save power. Of course, the technician can also configure the operating frequency of the calibration process according to the actual working conditions of the laser 100.

So far, the technical solutions of the present invention have been described with reference to the accompanying drawings, but it is easily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or replacements to the related technical features, and the technical solutions after these changes or replacements will fall within the protection scope of the present invention.

Claims

A laser gas detection device, characterized in that it includes:

Multiple lasers;

The control part is electrically connected to the plurality of lasers and can control the plurality of lasers to perform synchronous wavelength scanning. The center wavelength of the target absorption peak of the gas to be measured is preset to occupy the first relative position in the scanning waveform of the wavelength scanning ;

One or more beam splitting components, the output optical paths of a plurality of the lasers all pass through the beam splitting components, so as to split the laser beam emitted by each laser into detection light and reference light;

One or more gas absorption cells, each light path of the reference light passes through the gas absorption cell, and the gas absorption cell is filled with the gas to be measured;

One or more detectors, which are arranged on the optical paths after the reference light passes through the gas absorption cell;

The control part is electrically connected to the detector, and can determine the second relative position occupied by the target absorption peak of the gas to be measured in the light intensity signal waveform collected by the detector;

The control unit further includes a position correction module, which is electrically connected to the plurality of lasers, and can independently adjust one or more of the deviations from the first relative position according to the second relative position. The wavelength sweep of the laser is adjusted.
The laser gas detection device according to claim 1, wherein the laser gas detection device includes a current drive device, and the current drive device is electrically connected to the plurality of lasers and the control unit, and is capable of The control signal output by the control unit performs current scanning to drive the plurality of lasers to perform wavelength scanning.
The laser gas detection device according to claim 2, wherein the position correction module includes a current correction unit electrically connected to the current drive device and capable of adjusting the current scan of the current drive device Range to adjust the wavelength sweep of the laser.
The laser gas detection device according to claim 3, characterized in that the scanning waveform of the current scanning is a triangular wave or a sawtooth wave, and the current correction unit superimposes an equal amplitude offset on the basis of the scanning waveform to Adjust the scanning range of the wavelength scan accordingly.
The laser gas detection device according to claim 4, wherein the position correction module includes a current offset calculation unit that can obtain the obtained value according to the deviation of the second relative position from the first relative position Describe the offset of equal amplitude.
The laser gas detection device according to any one of claims 1 to 5, wherein the temperature of the laser is adjustable, and the position correction module includes a temperature correction unit, the temperature correction unit is capable of A temperature control current is input to adjust the wavelength scan of the laser.
The laser gas detection device according to claim 6, wherein the laser includes a temperature sensor, the temperature correction unit is electrically connected to the temperature sensor, and the temperature of the laser and the temperature can be obtained from the temperature sensor according to the temperature sensor. The deviation amount of the second relative position from the first relative position outputs a temperature control current to the laser.
The laser gas detection device according to any one of claims 1 to 5, characterized in that the laser gas detection device further comprises a laser component support, the laser component support has a plurality of support units arranged in parallel, the The bracket unit is installed and fixed with the spectroscopic component, the gas absorption cell, and the detector, one or more of the detectors are electrically connected to the same circuit board, and the circuit board is mounted on the housing of the laser gas detection device body.
A correction method for a laser gas detection device, the laser gas detection device includes a plurality of lasers, characterized in that the correction method includes the following steps:

Multiple lasers perform synchronous wavelength scanning, wherein the center wavelength of the target absorption peak of the gas to be measured occupies the first relative position by default in the scanning waveform of the wavelength scanning;

Split the laser beams emitted by multiple lasers into probe light and reference light;

Pass multiple reference lights through the gas absorption cell filled with the gas to be measured;

Detect the intensity signal of each reference light after passing through the gas absorption cell;

Determine the second relative position occupied by the target absorption peak of the gas to be measured in the reference light intensity signal waveform;

According to the deviation amount of the second relative position from the first relative position, the wavelength scanning of one or more lasers is independently adjusted.
A laser gas detection device, characterized in that it includes:

Multiple lasers;

The control part is electrically connected to the plurality of lasers and can control the plurality of lasers to perform synchronous wavelength scanning. The center wavelength of the target absorption peak of the gas to be measured is preset to occupy the first relative position in the scanning waveform of the wavelength scanning ;

A current driving device, the current driving device is electrically connected to the plurality of lasers and the control unit, and can perform current scanning according to the control signal output by the control unit to drive the plurality of lasers to perform wavelength scanning;

One or more beam splitting components, the output optical paths of a plurality of the lasers all pass through the beam splitting components, so as to split the laser beam emitted by each laser into detection light and reference light;

One or more gas absorption cells, each light path of the reference light passes through the gas absorption cell, and the gas absorption cell is filled with the gas to be measured;

One or more detectors, which are arranged on the optical paths after the reference light passes through the gas absorption cell;

The control unit is electrically connected to the detector, and can determine the second relative position occupied by the target absorption peak of the gas to be measured in the light intensity signal waveform collected by the detector; the control unit further includes:

A position correction module, which is electrically connected to the plurality of lasers, and can independently adjust the wavelength scan of one or more lasers according to the deviation amount of the second relative position from the first relative position The position correction module includes a current correction unit and a temperature correction unit, the current correction unit is electrically connected to the current drive device, can adjust the current scanning range of the current drive device, the temperature correction unit can A temperature control current is input to the laser to adjust the wavelength scan of the laser; the position correction module is preset with an adjustment threshold, if the deviation of the second relative position from the first relative position is less than the adjustment threshold , The position correction module adopts a current correction unit for position correction; if the deviation amount of the second relative position from the first relative position is greater than the adjustment threshold, the position correction module uses the temperature correction unit or at the same time Position correction is performed using the temperature correction unit and the current correction unit.