Array type methane detection method and device based on TDLAS (Tunable Diode Laser Absorption Spectroscopy)

Abstract

The invention relates to an array type methane detection method and device based on TDLAS, and belongs to the technical field of laser methane detection. The method comprises the following steps: adopting a plurality of lasers, and screening the lasers; arranging the screened lasers on a substrate to form a laser array, and sealing the laser array; sequentially driving each laser light source, and for each laser, carrying out linear scanning in a process of increasing a light-emitting initial threshold current to a full-scale current to obtain laser array absorption spectral line data; and carrying out harmonic demodulation on the light intensity data corresponding to each laser light source, and taking the data corresponding to the laser light source with the maximum absorption degree as the current detection data. The problem that a single laser needs temperature control to keep methane absorption peaks within a scanning range is solved, a plurality of light sources are adopted to form a light source array, the overall light emitting wavelength range within the working temperature is increased, heating and refrigerating devices are omitted, and power consumption is reduced.

Description

Technical Field

[0001] This invention belongs to the field of laser methane detection technology, and relates to an array-based methane detection method and device based on TDLAS. Background Technology

[0002] Tunable semiconductor laser absorption spectroscopy (TDLAS) technology, as a highly sensitive and selective gas detection method, has been widely used in environmental monitoring, industrial safety, energy and chemical industries. Its basic principle is to modulate the injection current of a semiconductor laser so that the wavelength of the output laser sweeps across specific absorption lines of the gas to be measured, and the gas concentration is deduced by detecting changes in the transmitted light intensity. This method has significant advantages such as fast response speed, non-contact measurement, and the ability to detect trace gases, making it particularly suitable for leak monitoring and concentration early warning of flammable and explosive hazardous gases such as methane. In existing technologies, methane detection systems based on TDLAS typically use a single laser as the light source. To ensure the accuracy and stability of detection, research has generally focused on solving a series of technical challenges in single-source operation mode. For example, how to stabilize the center wavelength of the laser near the characteristic absorption peak of methane through precise current and temperature control to prevent signal distortion caused by wavelength drift; how to effectively suppress optical and electrical noise under limited optical path conditions through signal processing techniques such as wavelength modulation and harmonic detection, thereby improving the system's signal-to-noise ratio and detection limit; and how to optimize optical path design to achieve open path or long optical path absorption, enhancing the detection capability for low-concentration or long-distance leaks. These studies have greatly promoted the advancement of single-source TDLAS technology in terms of detection resolution, measurement accuracy, and system stability.

[0003] However, the aforementioned single-laser-based technology also faces inherent limitations and engineering challenges, the most prominent being its dependence on laser operating temperature. Semiconductor lasers are extremely sensitive to temperature changes; temperature fluctuations cause significant wavelength drift. To ensure the laser scanning range consistently covers and precisely locks onto methane's absorption spectrum, traditional solutions integrate high-precision thermoelectric coolers (TECs) and associated temperature control circuits. However, this temperature control system significantly increases the overall power consumption of the equipment, making it unsuitable for deployment in remote areas, underground, or along pipelines where stable power supply is unavailable or requires long-term battery power. It also increases hardware complexity and manufacturing costs. Furthermore, the presence of the temperature control module itself increases the system's size and weight, and may introduce additional thermal noise and potential points of failure, affecting the equipment's reliability and lifespan.

[0004] In summary, existing technologies have not thoroughly explored detection methods for multi-source and temperature-controlled scenarios. Therefore, the challenge lies in constructing a TDLAS methane detection system capable of stable operation over a wide ambient temperature range without relying on or significantly simplifying active temperature control. Specifically, this requires addressing the issues of insufficient wavelength coverage and unstable detection signals caused by laser temperature drift after eliminating heating and cooling devices. This necessitates innovation in the working mechanism of the light source itself and the system architecture design, exploring new paths beyond single-source modes to achieve a truly low-power, highly robust methane detection solution. This is crucial for promoting the practical application and large-scale deployment of TDLAS technology in a wider range of fields. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide an array-based methane detection method and device based on TDLAS, which uses time-division scanning of the light source array to select the light source signal with the highest absorption degree from the scan data for methane concentration calculation, thus avoiding the complex process of requiring constant temperature control of the light source to stabilize the center wavelength.

[0006] To achieve the above objectives, the present invention provides an array-based methane detection method based on TDLAS, comprising: Multiple lasers are used, and the lasers are selected. The selected lasers are arranged on a substrate to form a laser array, and the laser array is then sealed. All laser sources are driven sequentially. For each laser, a linear scan is performed as the emission threshold current increases to the full-scale current to obtain the absorption spectrum data of the laser array. Harmonic demodulation is performed on the light intensity data corresponding to each laser source, and the data corresponding to the laser source with the highest absorption is used as the current detection data.

[0007] Furthermore, the number of multiple lasers acquired is an even number.

[0008] Furthermore, the laser selection process includes: among the acquired lasers, half of the lasers exhibit a positive shift in the center wavelength of their output laser as the temperature increases; and the other half exhibit a positive shift in the center wavelength of their output laser as the temperature decreases.

[0009] Furthermore, the sealed laser array includes a laser array sealed with a spherical lampshade.

[0010] Furthermore, a 10% Vol nitrogen standard gas is encapsulated inside the lampshade.

[0011] Furthermore, during the process of ambient temperature change, the data corresponding to the laser source with the highest absorption degree is selected as the current detection data for each scan.

[0012] On the other hand, the present invention provides an array-type methane detection device based on TDLAS, which includes a laser array, a drive control circuit, an optical gas chamber, a photodetector, a signal processing unit, and a sealed lamp cover; The drive control circuit is used to independently drive each laser in the laser array; the optical signal output from the laser array enters the optical gas chamber for gas absorption; the photodetector is used to collect the optical signal after gas absorption and input it into the signal processing unit for processing; the sealing lamp cover is used to seal the laser array; The signal processing unit performs harmonic demodulation on the light intensity data corresponding to each laser and uses the data corresponding to the laser with the highest absorption as the current detection data.

[0013] Furthermore, a 10% Vol nitrogen standard gas is encapsulated within the sealed lampshade.

[0014] The beneficial effects of this invention are as follows: (1) The present invention eliminates the high-precision thermoelectric cooler and the matching temperature control circuit, simplifies the hardware architecture of methane detection, reduces power consumption, and makes the equipment more suitable for long-term operation in the field and mobile scenarios without stable power supply or battery power supply. At the same time, it reduces potential failure points introduced by the temperature control module and improves the reliability and service life of the system.

[0015] (2) By selectively screening and combining lasers, the center wavelength drift characteristics of different lasers in the laser array are made complementary. When the ambient temperature changes, the output wavelength of some lasers can always effectively cover the characteristic absorption spectrum of methane. By dynamically selecting the light source data with the strongest absorption signal, an intelligent compensation mechanism for temperature drift is essentially formed, thus ensuring the stability and accuracy of the detection signal without the need for active temperature control.

[0016] (3) The simplified structure results in a smaller size, lighter weight, and lower manufacturing cost, while the system starts up faster without waiting for temperature control to stabilize. This low-power, highly environmentally adaptable design provides a practical technical solution for the large-scale, networked deployment of methane leak monitoring in complex sites such as petrochemical plants, underground coal mines, and gas pipelines, expanding the application boundaries of TDLAS technology.

[0017] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0018] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the array-based methane detection method based on TDLAS provided in an embodiment of the present invention. Detailed Implementation

[0019] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0020] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0021] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0022] This invention provides a TDLAS laser-based methane detection method, solving the problem of requiring temperature control to maintain the methane absorption peak within the scanning range for a single laser. The main difference lies in using a multi-light source array to increase the overall emission wavelength range within the operating temperature range, thereby eliminating the need for heating and cooling devices and reducing power consumption.

[0023] Specifically, the method is as follows: A laser array composed of n*n lasers is encapsulated in the same lamp cover, with a background gas of 10% Vol sealed.

[0024] 1. Laser selection: Half of the lasers should have a positive shift in the center wavelength of their output laser as the temperature rises, while the other half should have a positive shift in the center wavelength of their output laser as the temperature falls.

[0025] 2. Arrange the selected laser light sources on the substrate to form an n*n array, wherein each laser light source can be driven individually; 3. A spherical lampshade is used to seal the laser array, and 10% Vol of nitrogen standard gas is encapsulated inside the lampshade as background gas.

[0026] 4. As the single laser source increases from the emission initiation threshold current to the full-scale current, a linear scan is performed to obtain the absorption spectrum at the current temperature.

[0027] 5. Drive all laser sources sequentially, and perform a linear scan as the emission threshold current increases to the full-scale current to obtain the absorption spectrum data of the laser array.

[0028] 6. Perform harmonic demodulation on the light intensity data corresponding to all laser sources, and use the data corresponding to the laser source with the highest absorption as the current detection data.

[0029] 7. As the ambient temperature changes, the center wavelength of each laser source shifts. However, during each scan, the data corresponding to the laser source with the highest absorption is selected as the current detection data, and methane concentration is converted.

[0030] Another embodiment of the present invention provides an array-type methane detection device based on TDLAS, the device comprising: A laser array, consisting of n×n lasers arranged in a matrix on a substrate; The drive control circuit is used to independently drive each laser and control its current linear scanning. An optical gas cell, with the gas being measured inside and light-transmitting windows at both ends; A photodetector receives the laser signal after it passes through the gas chamber and converts it into an electrical signal; The signal processing unit performs harmonic demodulation, data selection, and concentration calculation on the electrical signal. The spherical sealed lamp cover encapsulates the laser array and is filled with nitrogen gas at a volume concentration of 10% as a background gas.

[0031] This invention enables laser methane detection without temperature control, reducing power consumption while maintaining detection accuracy.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An array-based methane detection method based on TDLAS, characterized in that, The method includes: Multiple lasers are used, and the lasers are selected. The selected lasers are arranged on a substrate to form a laser array, and the laser array is then sealed. Each laser source is driven sequentially. For each laser, a linear scan is performed as the emission threshold current increases to the full-scale current to obtain the absorption spectrum data of the laser array. Harmonic demodulation is performed on the light intensity data corresponding to each laser source, and the data corresponding to the laser source with the highest absorption is used as the current detection data.

2. The method according to claim 1, characterized in that, The number of lasers acquired is an even number.

3. The method according to claim 2, characterized in that, The screening of lasers includes: Of the multiple lasers obtained, half of the lasers showed a positive shift in the center wavelength of their output laser as the temperature increased, while the other half showed a positive shift in the center wavelength of their output laser as the temperature decreased.

4. The method according to claim 1, characterized in that, The sealed laser array includes a laser array sealed with a spherical lampshade.

5. The method according to claim 4, characterized in that, The lampshade is encapsulated with 10% Vol of nitrogen standard gas.

6. The method according to claim 1, characterized in that, During the process of ambient temperature change, the data corresponding to the laser source with the highest absorption degree is selected as the current detection data for each scan.

7. An array-type methane detection device based on TDLAS, characterized in that, The device includes a laser array, a drive control circuit, an optical gas chamber, a photodetector, a signal processing unit, and a sealed lamp cover; The drive control circuit is used to independently drive each laser in the laser array; the optical signal output from the laser array enters the optical gas chamber for gas absorption; the photodetector is used to collect the optical signal after gas absorption and input it into the signal processing unit for processing; the sealing lamp cover is used to seal the laser array; The signal processing unit performs harmonic demodulation on the light intensity data corresponding to each laser and uses the data corresponding to the laser with the highest absorption as the current detection data.

8. The apparatus according to claim 7, characterized in that, The sealed lamp cover contains 10% Vol of nitrogen standard gas.

Images