Optical assembly for laser wavelength self-calibration and laser methane gas detection system

Abstract

The utility model provides an optical assembly for laser wavelength self-calibration and a laser methane gas detection system. The optical assembly for laser wavelength self-calibration comprises a receiving lens, a reference gas chamber and a photoelectric detector which are arranged in sequence, the receiving lens is arranged at the tail part of an optical fiber collimator of the laser detection system and is used for receiving detection laser leaked from the tail part of the optical fiber collimator; standard concentration target gas is sealed in the reference gas chamber; and the photoelectric detector is used for converting the received optical signal absorbed by the target gas in the reference gas chamber into an electric signal for laser wavelength self-calibration of the laser detection system. The laser methane gas detection system comprises a laser methane gas detection system body and an optical assembly used for laser wavelength self-calibration. The laser wavelength calibration device performs laser wavelength calibration by collecting the detection laser leaked from the tail part of the optical fiber collimator, does not lose the main path detection laser, and is simple in structure, low in cost and high in practicability.

Description

Technical Field

[0001] The utility model relates to the technical field of semiconductor laser gas detection, in particular to an optical component for laser wavelength self-calibration and a laser methane gas detection system. Background Art

[0002] Tunable Diode Laser Absorption Spectroscopy (TDLAS) is an advanced method for gas detection and analysis. It calculates the concentration of a gas by measuring the gas's absorption of laser light of a specific wavelength. This method has been widely used in industrial process control, environmental monitoring, safety testing, and other fields. When using TDLAS technology for gas detection, the gas will absorb light energy only when the central wavelength of the laser output is stabilized at the gas absorption peak. The second harmonic is extracted from the absorbed light signal, and the concentration information of the gas to be measured is calculated. However, changes in time and temperature will affect the central wavelength of the semiconductor laser output. Therefore, the wavelength of the semiconductor laser output needs to be calibrated in real time. When it deviates from the gas absorption peak, the temperature of the laser TEC is adjusted to stabilize the laser's central wavelength at the gas absorption peak.

[0003] In existing technologies, the laser beam output by a semiconductor laser is typically passed through a spectrometer system, which separates a small portion of the laser light to lock the laser's central wavelength. The spectrometer system includes a fiber optic splitter or a spectrometer. These methods, on the one hand, increase the number of optical components, resulting in a relatively complex structure and increased cost. On the other hand, the increased number of optical components increases optical noise, affecting the accuracy of the detection system. Another approach uses a target gas in the main measurement optical path to calibrate the laser wavelength. However, the main measurement optical path cannot guarantee the presence of measurement gas in real time, making wavelength calibration impossible in real time; calibration is only possible when the target gas is present. Furthermore, in laser telemetry systems, for example, the signal in the main measurement optical path is unstable, making it impossible to accurately determine changes in the laser wavelength and perform accurate dynamic adjustments.

[0004] In order to solve the above problems, people have been seeking a better technical solution. Summary of the Invention

[0005] In the TDLAS detection system, the semiconductor laser is generally connected to the fiber collimator to emit light. After the emitted light passes through the target gas, it is received by the photodetector, and the received light signal is analyzed to obtain the gas concentration information. The fiber collimator is made of a self-focusing lens and a pigtail with precise positioning. Due to process problems during the coupling process between the pigtail and the self-focusing lens, a small amount of laser light generally leaks from the tail. In order to solve the problems existing in the prior art, the utility model provides an optical component for laser wavelength self-calibration and a laser methane gas detection system. The laser wavelength is calibrated by collecting the laser light leaked from the tail of the fiber collimator without wasting the main detection laser. The utility model has a simple structure, low cost and strong practicality.

[0006] The technical solution adopted in this utility model is:

[0007] In a first aspect, the utility model provides an optical component for laser wavelength self-calibration, comprising: a receiving lens, a reference gas chamber, and a photodetector arranged in sequence;

[0008] The receiving lens is arranged at the tail of the optical fiber collimator of the laser detection system, and is used to receive the detection laser leaked from the tail of the optical fiber collimator;

[0009] The reference gas chamber is sealed with a target gas of standard concentration;

[0010] The photoelectric detector is used to convert the received light signal absorbed by the target gas in the reference gas chamber into an electrical signal for self-calibration of the laser wavelength of the laser detection system.

[0011] Based on the above, the receiving lens is a focusing lens.

[0012] Based on the above, the surface of the focusing lens is coated with an antireflection film near the absorption peak of the target gas.

[0013] In a second aspect, the present invention provides a laser methane gas detection system, comprising the laser methane gas detection system itself, and also comprising the optical component for laser wavelength self-calibration;

[0014] The detection laser light emitted by the semiconductor laser of the laser methane gas detection system and leaking out at the tail of the optical fiber collimator is collected by the receiving lens, passes through the reference gas chamber, and is received by the photoelectric detector and converted into an electrical signal;

[0015] The electrical signal is transmitted to the signal control and processing module of the laser methane gas detection system for analysis and processing, and drives the laser driving module of the laser methane gas detection system to self-calibrate the wavelength of the semiconductor laser.

[0016] The present invention has substantial features and advancements over the prior art. Specifically:

[0017] 1. The optical component for laser wavelength self-calibration of the present invention has various application forms and can be applied to various laser gas detection systems that require laser wavelength self-calibration.

[0018] 2. The laser methane gas detection system of the present invention has a simple optical structure and does not consume the main detection laser, making the main detection laser stronger and the detection sensitivity higher.

[0019] 3. The laser methane gas detection system of the present invention saves optical path splitting components, has low cost and strong practicality.

[0020] 4. The laser methane gas detection system of the present invention reduces the optical noise between optical devices in the main detection laser link, making the detection signal more stable and improving the detection accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the structure of the optical component used for laser wavelength self-calibration in Example 1.

[0022] Figure 2 Schematic diagram of the structure of the laser methane gas remote sensing device in Example 2.

[0023] Figure 3 Schematic diagram of the structure of the laser gas detector in Example 3.

[0024] Figure 4 Schematic diagram of the structure of the long optical path laser gas detection system in Example 4.

[0025] In the figure: receiving lens 1; reference gas chamber 2; photodetector 3; fiber collimator 4; photodetector 5; receiving lens 6; multi-reflection cavity 7. DETAILED DESCRIPTION

[0026] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present application and the features therein can be combined with each other without conflict.

[0027] Example 1

[0028] like Figure 1 As shown, this embodiment provides an optical component for laser wavelength self-calibration, comprising: a receiving lens 1, a reference gas chamber 2, and a photodetector 3 arranged in sequence;

[0029] The receiving lens 1 is arranged at the tail of the optical fiber collimator 4 of the laser detection system to receive the detection laser leaked from the tail of the optical fiber collimator 4;

[0030] The reference gas chamber 2 is sealed with a target gas of standard concentration;

[0031] The photoelectric detector 3 is used to convert the received light signal absorbed by the target gas in the reference gas chamber 2 into an electrical signal for self-calibration of the laser wavelength of the laser detection system.

[0032] In some exemplary embodiments, the receiving lens is a focusing lens such as a plano-convex lens or an aspheric lens.

[0033] Preferably, in order to improve the transmittance of the receiving lens 1 to the laser and reduce the interference of reflected light, the surface of the focusing lens is coated with an anti-reflection film near the absorption peak of the target gas.

[0034] Example 2

[0035] This embodiment provides a specific laser methane gas detection system - a laser methane gas remote sensing device.

[0036] The laser methane gas remote sensing device includes a semiconductor laser, an aiming laser, a laser driving module, a signal control and processing module, a fiber collimator 4, a photodetector 5 and a receiving lens 6, and also includes the optical component for laser wavelength self-calibration described in Example 1.

[0037] like Figure 2 As shown, a DFB semiconductor laser with a central wavelength of 1653.7nm is selected as the light source, and InGaAs detectors are selected for both photodetector 3 and photodetector 5. Receiving lens 1 and receiving lens 6 are plano-convex lenses or aspheric lenses coated with anti-reflection films near the wavelength of 1653.7nm. The filter is a narrow-band interference filter near the wavelength of 1653.7nm, and the aiming laser is a 520nm green laser. The aiming laser emitted by the aiming laser is emitted in parallel with the detection laser emitted by the semiconductor laser, and the detection laser is emitted through the fiber collimator 4. After passing through the target gas, the detection laser is reflected by the background reflector. The photodetector 5 receives the return light signal absorbed by the target gas, and after photoelectric conversion, it is transmitted to the signal control and processing module. After analyzing and processing the signal, the concentration information of the target gas in the target area can be calculated.

[0038] The detection laser leaked from the tail of the optical fiber collimator 4 is collected by the receiving lens 1, passes through the reference gas chamber 2 sealed with a standard concentration of target gas, is received by the photodetector 3, and is transmitted to the signal control and processing module. The signal control and processing module analyzes the signal and then drives the laser driving module to self-calibrate the wavelength of the semiconductor laser according to the analysis results.

[0039] It should be noted that there are many methods in the prior art for analyzing the signal and then achieving self-calibration of the laser wavelength. For example, Chinese invention patent application publication number CN112782119A provides a laser gas detection method and system that can monitor wavelength, which will not be described in detail here.

[0040] Example 3

[0041] This embodiment provides a specific laser methane gas detection system - a laser gas detector.

[0042] The laser gas detector includes a semiconductor laser, a laser driving module, a signal control and processing module, a fiber collimator 4, a photodetector 5 and a receiving lens 6, and also includes the optical component for laser wavelength self-calibration described in Example 1.

[0043] like Figure 3 As shown, a semiconductor laser with a central wavelength near the absorption peak of the target gas is used as the light source. Photodetectors 3 and 5 are both designed to respond to the laser's absorption peak. Receiving lenses 1 and 6 are plano-convex or aspheric lenses coated with an antireflection coating near the absorption peak of the target gas. After passing through the target gas, the detection laser is collected by receiving lens 6 and focused on photodetector 5. After photoelectric conversion, the laser is transmitted to the signal control and processing module, which analyzes and processes the signal to calculate the target gas concentration.

[0044] The detection laser leaked from the tail of the optical fiber collimator 4 is collected by the receiving lens 1, passes through the reference gas chamber 2 sealed with a standard concentration of target gas, is received by the photodetector 3, and is transmitted to the signal control and processing module. The signal control and processing module analyzes the signal and then drives the laser driving module to self-calibrate the wavelength of the semiconductor laser according to the analysis results.

[0045] It should be noted that there are many methods in the prior art for analyzing the signal and then achieving self-calibration of the laser wavelength. For example, Chinese invention patent application publication number CN112782119A provides a laser gas detection method and system that can monitor wavelength, which will not be described in detail here.

[0046] Example 4

[0047] This embodiment provides a specific laser methane gas detection system—a long optical path laser gas detection system.

[0048] The long optical path laser gas detection system includes a semiconductor laser, a laser driving module, a signal control and processing module, a fiber collimator 4, a photodetector 5 and a multi-reflection cavity 7, and also includes the optical component for laser wavelength self-calibration described in Example 1.

[0049] like Figure 4 As shown, the detection laser emitted by the semiconductor laser is emitted into the multi-reflection cavity through the fiber collimator. After being reflected in the multi-reflection cavity, it is received by the photoelectric detector 5. After photoelectric conversion, it is transmitted to the signal control and processing module. After analyzing and processing the signal, the concentration information of the target gas is calculated.

[0050] The detection laser leaked from the tail of the optical fiber collimator 4 is collected by the receiving lens 1, passes through the reference gas chamber 2 sealed with a standard concentration of target gas, is received by the photodetector 3, and is transmitted to the signal control and processing module. The signal control and processing module analyzes the signal and then drives the laser driving module to self-calibrate the wavelength of the semiconductor laser according to the analysis results.

[0051] It should be noted that there are many methods in the prior art for analyzing the signal and then achieving self-calibration of the laser wavelength. For example, Chinese invention patent application publication number CN112782119A provides a laser gas detection method and system that can monitor wavelength, which will not be described in detail here.

[0052] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. An optical component for laser wavelength self-calibration, characterized in that: include: A receiving lens, a reference gas chamber and a photodetector are arranged in sequence; The receiving lens is arranged at the tail of the optical fiber collimator of the laser detection system, and is used to receive the detection laser leaked from the tail of the optical fiber collimator; The reference gas chamber is sealed with a target gas of standard concentration; The photoelectric detector is used to convert the received light signal absorbed by the target gas in the reference gas chamber into an electrical signal for self-calibration of the laser wavelength of the laser detection system.

2. The optical component for laser wavelength self-calibration according to claim 1, characterized in that: The receiving lens is a condenser lens.

3. The optical component for laser wavelength self-calibration according to claim 2, characterized in that: The surface of the condensing lens is coated with an antireflection film near the absorption peak of the target gas.

4. A laser methane gas detection system, including the laser methane gas detection system itself, characterized in that: Also includes the optical component for laser wavelength self-calibration according to any one of claims 1 to 3; The detection laser light emitted by the semiconductor laser of the laser methane gas detection system and leaking out at the tail of the optical fiber collimator is collected by the receiving lens, passes through the reference gas chamber, and is received by the photoelectric detector and converted into an electrical signal; The electrical signal is transmitted to the signal control and processing module of the laser methane gas detection system for analysis and processing, and drives the laser driving module of the laser methane gas detection system to self-calibrate the wavelength of the semiconductor laser.

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