Laser remote sensing type fire smoke and methane composite detection device

Abstract

The present application belongs to the technical field of gas detection, and discloses a laser remote sensing type fire smoke and methane composite detection device, which comprises: a stepped scanning signal generator for generating a stepped periodic scanning signal, the signal comprising a first channel signal and a second channel signal; a modulation signal generator for generating a sinusoidal signal; a first laser device for outputting a first laser signal according to the coupling signal of the first channel signal and the sinusoidal signal; a second laser device for outputting a second laser signal according to the coupling signal of the second channel signal and the sinusoidal signal; a photoelectric detection device for emitting the first laser signal and the second laser signal after beam combination to a target space, and converting the received laser feedback signal into an electric signal; and a signal processing device for acquiring smoke extinction information, smoke extinction signal ratio information and methane concentration information according to the electric signal and the sinusoidal signal, and performing alarm when the acquired information meets a preset alarm condition.

Description

Technical Field

[0001] This invention relates to the field of gas detection technology, and in particular to a laser remote sensing device for detecting the combined effects of fire smoke and methane. Background Technology

[0002] With the widespread use of natural gas, the dual safety risks of natural gas leaks, explosions, and fires are becoming increasingly prominent. However, most detectors currently on the market are single-function devices, namely combustible gas detectors or fire smoke detectors. There is a lack of composite devices that can simultaneously detect methane leaks and fire smoke, resulting in the need to install two different types of detectors at the same site, which increases costs and construction difficulty.

[0003] For long-distance methane detection, related laser telemetry technologies utilize tunable semiconductor laser absorption spectroscopy and wavelength modulation harmonic detection techniques to achieve long-distance unilateral remote sensing. However, because methane has narrow-band absorption, it generates second harmonic signals, while fire smoke has broadband absorption and does not generate harmonic responses. Therefore, this type of technology cannot detect smoke. For large-scale fire smoke detection, related linear beam smoke detection technologies trigger an alarm by measuring the attenuation of the beam after passing through the smoke. However, these technologies use broadband light sources, lack wavelength tuning capabilities, cannot detect methane, and typically require precise alignment of the transmitter and receiver, making installation complex. Summary of the Invention

[0004] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, one objective of this invention is to propose a laser remote sensing fire smoke and methane composite detection device, which achieves long-distance, single-sided installation of fire smoke and methane composite detection. It can accurately distinguish between real smoke and interfering factors such as water vapor and dust, significantly reducing the false alarm rate and significantly improving detection accuracy and environmental adaptability.

[0005] To achieve the above objectives, a first aspect of the present invention provides a laser telemetry-based fire smoke and methane composite detection device, wherein the laser telemetry-based fire smoke and methane composite detection device comprises: a stepped scanning signal generator for generating a stepped periodic scanning signal, the stepped periodic scanning signal including a first channel signal and a second channel signal; a modulation signal generator for generating a sinusoidal signal; a first laser device for outputting a first laser signal based on the coupling signal of the first channel signal and the sinusoidal signal; a second laser device for outputting a second laser signal based on the coupling signal of the second channel signal and the sinusoidal signal, wherein the wavelength of the second laser signal is less than the wavelength of the first laser signal; a photoelectric detection device for transmitting the combined first laser signal and the second laser signal to a target space, and converting the received laser feedback signal from the target space into an electrical signal; and a signal processing device for acquiring smoke extinction information, smoke extinction signal ratio information, and methane concentration information respectively based on the electrical signal and the sinusoidal signal, and triggering an alarm when the smoke extinction information, the smoke extinction signal ratio information, and the methane concentration information meet preset alarm conditions.

[0006] According to an embodiment of the present invention, a laser remote sensing fire smoke and methane composite detection device generates a first channel signal and a second channel signal through a stepped scanning signal generator. These signals, combined with a sinusoidal signal from a modulation signal generator, drive the first and second laser devices to output laser signals of different wavelengths. The signals are then combined and transmitted by a photoelectric detection device, and a feedback signal is received. Finally, a signal processing device simultaneously acquires smoke extinction information, smoke extinction signal ratio information, and methane concentration information, and performs analysis based on preset alarm conditions. This achieves long-distance, single-sided fire smoke and methane composite detection, accurately distinguishing between real smoke and interfering factors such as water vapor and dust, significantly reducing false alarm rates, and substantially improving detection accuracy and environmental adaptability.

[0007] In addition, the laser remote sensing fire smoke and methane composite detection device according to the above embodiments of the present invention may further include the following additional technical features: According to one embodiment of the present invention, the first channel signal includes a first stage voltage signal, a second stage voltage signal, and a third stage voltage signal, and the second channel signal includes a fourth stage voltage signal, wherein the first stage voltage signal is used to keep the laser wavelength constant outside the methane absorption line, the second stage signal is used to make the laser wavelength scan cover the methane absorption line, the third stage signal is used to keep the laser wavelength constant outside the methane absorption line, and the fourth stage voltage signal is used to generate the smoke extinction signal ratio information.

[0008] According to an embodiment of the present invention, the signal processing device includes: a phase-sensitive demodulator connected to the modulation signal generator and the photoelectric detection device, respectively, for demodulating the electrical signal using the sinusoidal signal to obtain the second harmonic signal absorbed by methane; a signal acquisition unit connected to the photoelectric detection device and the phase-sensitive demodulator, respectively, for acquiring the electrical signal and the second harmonic signal; and a signal processor connected to the signal acquisition unit, for acquiring the smoke extinction information and the smoke extinction signal ratio information based on the electrical signal and a preset signal intensity, acquiring the methane concentration information based on the second harmonic signal, and triggering an alarm when the smoke extinction information, the smoke extinction signal ratio information, and the methane concentration information meet preset alarm conditions.

[0009] According to one embodiment of the present invention, the signal processor is further configured to obtain the smoke extinction signal ratio information by means of the following formula: B = [((X0+X3) / 2) / X4]; Wherein, B is the smoke extinction signal ratio information, X0 is the extinction information corresponding to the first stage voltage signal, X3 is the extinction information corresponding to the third stage voltage signal, and X4 is the extinction information corresponding to the fourth stage voltage signal.

[0010] According to an embodiment of the present invention, the signal processor is further configured to: determine that the preset alarm condition is met when the extinction information corresponding to the first stage voltage signal and / or the extinction information corresponding to the third stage voltage signal is greater than the corresponding preset threshold, and it is determined that the extinction is caused by smoke based on the smoke extinction signal ratio information, and / or when it is determined that the methane concentration is greater than the preset methane concentration based on the methane concentration information.

[0011] According to one embodiment of the present invention, the signal processor is further configured to: determine that the extinction is caused by smoke when the smoke extinction signal ratio information is within a preset ratio range.

[0012] According to one embodiment of the present invention, the signal processor is further configured to: normalize the amplitude of the second harmonic signal using the amplitude of an electrical signal corresponding to the first stage voltage signal or the third stage voltage signal.

[0013] According to one embodiment of the present invention, the photoelectric detection device includes: an optical transceiver tube, on which a collimator, a lens, and a photodetector are disposed; an optical fiber combiner for combining the first laser signal and the second laser signal into a composite laser beam; the collimator is connected to the optical fiber combiner for collimating and transmitting the composite laser beam to the target space; the lens is used to receive the laser feedback signal reflected back by a reflector in the target space and converge it to the photodetector; the photodetector is used to convert the laser feedback signal into an electrical signal.

[0014] According to one embodiment of the present invention, the wavelength of the first laser signal is 1653 nm, and the wavelength of the second laser signal is 780 nm.

[0015] According to one embodiment of the present invention, the laser telemetry fire smoke and methane composite detection device further includes: an audible and visual alarm, connected to the signal processing device, for performing audible and visual alarms for abnormal concentration.

[0016] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0017] Figure 1 This is a block diagram of a laser remote sensing fire smoke and methane composite detection device according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the waveform of the stepped periodic scanning signal according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the waveform of the coupled signal according to an embodiment of the present invention; Figure 4 This is a block diagram of a laser remote sensing fire smoke and methane composite detection device according to a specific embodiment of the present invention.

[0018] Figure label: A laser remote sensing fire smoke and methane composite detection device 100, a stepped scanning signal generator 10, a modulation signal generator 20, a first laser device 30, a second laser device 40, a photoelectric detection device 50, a signal processing device 60, a phase-sensitive demodulator 61, a signal acquisition device 62, a signal processor 63, an optical transceiver tube 51, an optical fiber combiner 52, a collimator 53, a photoelectric detector 54, a lens 55, a first signal coupler 31, a first laser driver 32, a first laser 33, a second signal coupler 41, a second laser driver 42, a second laser 43, and an audible and visual alarm 70. Detailed Implementation

[0019] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0020] The following describes an embodiment of the laser telemetry fire smoke and methane composite detection device of the present invention with reference to the accompanying drawings.

[0021] Figure 1 This is a block diagram of a laser remote sensing fire smoke and methane composite detection device according to an embodiment of the present invention.

[0022] Specifically, in some embodiments of the present invention, such as Figure 1 As shown, the laser remote sensing fire smoke and methane composite detection device 100 includes a stepped scanning signal generator 10, a modulation signal generator 20, a first laser device 30, a second laser device 40, a photoelectric detection device 50, and a signal processing device 60.

[0023] The system includes a stepped scanning signal generator 10 for generating a stepped periodic scanning signal, which includes a first channel signal and a second channel signal; a modulation signal generator 20 for generating a sinusoidal signal; a first laser device 30 for outputting a first laser signal based on the coupling signal between the first channel signal and the sinusoidal signal; a second laser device 40 for outputting a second laser signal based on the coupling signal between the second channel signal and the sinusoidal signal, wherein the wavelength of the second laser signal is shorter than the wavelength of the first laser signal; a photoelectric detection device 50 for transmitting the combined first and second laser signals to the target space and converting the received laser feedback signal from the target space into an electrical signal; and a signal processing device 60 for acquiring smoke extinction information, smoke extinction signal ratio information, and methane concentration information based on the electrical signal and the sinusoidal signal, and for triggering an alarm when the smoke extinction information, smoke extinction signal ratio information, and methane concentration information meet preset alarm conditions.

[0024] Specifically, in this embodiment, the stepped scanning signal generator 10 outputs two time-synchronized periodic scanning signals: the first channel signal is used to control the wavelength scanning of the first laser device 30, and the second channel signal is used to control the output of the second laser device 40. The modulation signal generator 20 generates a sinusoidal signal, which, after coupling with the first channel signal, jointly drives the first laser device 30, enabling the first laser signal to simultaneously possess wavelength scanning and wavelength modulation characteristics, thereby supporting harmonic detection of methane absorption; the second channel signal, after coupling with the sinusoidal signal, drives the second laser device 40, making the second laser signal a modulated light with a fixed wavelength, used to obtain an independent smoke extinction reference signal. The first laser signal output by the first laser device 30 (e.g., wavelength 1653nm) and the second laser signal output by the second laser device 40 (e.g., wavelength 780nm) are combined into a coaxial composite laser beam by the fiber combiner inside the photodetector 50, and then emitted into the target space by the collimator. The composite laser beam, after illuminating distant reflectors such as walls and the ground, undergoes diffuse reflection. Part of the reflected light (i.e., the laser feedback signal) returns along its original path, is collected by the lens in the photoelectric detection device 50, and converges onto the photoelectric detector, converting it into an electrical signal. The signal processing device 60 receives this electrical signal and simultaneously obtains a sinusoidal signal from the modulation signal generator 20 as a demodulation reference. The signal processing device 60 first extracts the light intensity information for each time period (T1–T4) from the electrical signal, calculates the smoke extinction information (X0, X3, X4) and the extinction signal ratio information B, and obtains the second harmonic signal of methane absorption through phase-sensitive demodulation, thereby retrieving the methane concentration. Finally, the signal processing device 60 outputs an alarm signal according to preset multi-condition logic.

[0025] Furthermore, in some embodiments of the present invention, the first channel signal includes a first stage voltage signal, a second stage voltage signal, and a third stage voltage signal, and the second channel signal includes a fourth stage voltage signal. The first stage voltage signal is used to keep the laser wavelength constant outside the methane absorption line, the second stage signal is used to make the laser wavelength scan cover the methane absorption line, the third stage signal is used to keep the laser wavelength constant outside the methane absorption line, and the fourth stage voltage signal is used to generate smoke extinction signal ratio information.

[0026] Specifically, in this embodiment, timing control of the two laser sources is achieved by setting four time-period voltage signals with different functions. In the first stage (T1) and the third stage (T3), the wavelength of the first laser device is locked outside the methane absorption line. At this time, the laser is not absorbed by methane, but only affected by the extinction of aerosols such as smoke and dust, thus it can be used to obtain smoke extinction information. In the second stage (T2), the laser wavelength scan covers the methane absorption line. At this time, the signal contains the absorption characteristics of methane, and the methane concentration can be extracted using modulation and demodulation techniques. In the fourth stage (T4), a fixed short-wavelength laser (e.g., 780nm) is output from the second laser device. This wavelength is sensitive to smoke but not to methane, and is used to generate smoke extinction signal ratio information. The signals of the four stages work alternately, providing basic data for subsequent ratio calculation and smoke identification.

[0027] It should be noted that, as Figure 2 As shown, the stepped-scan signal generator produces a stepped-periodic scanning signal including a first channel signal (H1) and a second channel signal (H2). The first channel signal (H1) controls the first laser device (tunable laser), and within one cycle, it sequentially includes voltage signals for the first time period T1, the second time period T2, and the third time period T3. In stage T1, the output voltage is V1, keeping the laser wavelength constant outside the methane absorption line; in stage T2, the voltage gradually scans from V1 to V2, covering the methane absorption line; in stage T3, the voltage stabilizes at V2, keeping the laser wavelength constant outside the methane absorption line. The second channel signal (H2) controls the second laser device (fixed-wavelength laser), which outputs a constant voltage V3, corresponding to the fourth time period T4. Stage T4 is independent of the T1-T3 time sequence and is used to acquire short-wavelength reference extinction information. Furthermore, Figure 2 The time sequence arrangement of T1, T2, T3, and T4 is for illustrative purposes only. In actual operation, each time period can be output in a cyclical manner according to the set order.

[0028] like Figure 3 As shown, the sinusoidal signal generated by the modulation signal generator is coupled with the first channel signal (H1) via a signal coupler to obtain an amplitude-modulated sinusoidal wave whose amplitude varies with the step wave. This coupled signal is input to the laser driver, causing the laser wavelength output by the first laser device to be superimposed with high-frequency modulation on the step scan, thus meeting the requirements of wavelength modulation spectroscopy technology and facilitating the subsequent extraction of the second harmonic signal absorbed by methane through phase-sensitive demodulation. The second channel signal (H2) can also be coupled with the sinusoidal signal, but since the second laser device outputs a fixed wavelength, the coupled signal is only used to improve the anti-interference capability of smoke detection and does not change the wavelength tuning characteristics.

[0029] Furthermore, in some embodiments of the present invention, such as Figure 4As shown, the signal processing device 60 includes: a phase-sensitive demodulator 61, connected to the modulation signal generator 20 and the photoelectric detection device 50 respectively, for demodulating the electrical signal using a sinusoidal signal to obtain the second harmonic signal absorbed by methane; a signal acquisition device 62, connected to the photoelectric detection device 50 and the phase-sensitive demodulator 61 respectively, for acquiring the electrical signal and the second harmonic signal; and a signal processor 63, connected to the signal acquisition device 62, for acquiring smoke extinction information and smoke extinction signal ratio information based on the electrical signal and a preset signal intensity, acquiring methane concentration information based on the second harmonic signal, and triggering an alarm when the smoke extinction information, smoke extinction signal ratio information, and methane concentration information meet preset alarm conditions.

[0030] Specifically, in this embodiment, the signal processing device 60 employs phase-sensitive demodulation technology, using the sinusoidal signal output by the modulation signal generator 20 as a reference signal to perform phase-locked amplification on the electrical signal output by the photodetector 54, thereby extracting the second harmonic component corresponding to methane absorption. This effectively suppresses low-frequency noise and background light interference, improving the signal-to-noise ratio. The signal acquisition device 62 simultaneously acquires the original electrical signal and the demodulated second harmonic signal; the former is used to calculate the light intensity attenuation (i.e., extinction information) at different time periods, and the latter is used to invert the methane concentration. The signal processor 63 integrates data processing and logical judgment functions, enabling real-time calculation of smoke extinction information, ratio information, and methane concentration, and comprehensive alarm judgment based on preset multi-condition thresholds, achieving intelligent detection.

[0031] Furthermore, in some embodiments of the present invention, such as Figure 4 As shown, the signal processor 63 is also used to obtain the smoke extinction signal ratio information through the following formula: B = [((X0+X3) / 2) / X4]; Wherein, B is the smoke extinction signal ratio information, X0 is the extinction information corresponding to the first stage voltage signal, X3 is the extinction information corresponding to the third stage voltage signal, and X4 is the extinction information corresponding to the fourth stage voltage signal.

[0032] Specifically, in this embodiment, the smoke extinction information is defined as the ratio of the current signal intensity I1 to the initial signal intensity I10 when there is no smoke (e.g., X0 = I1 / I10). X0 and X3 represent the extinction information of the first laser device 30 in stages T1 and T3 (both wavelengths are outside the methane absorption line), respectively. The average of the two can eliminate errors caused by laser wavelength drift or short-term fluctuations. X4 represents the extinction information of the second laser device 40 in stage T4. Since the extinction characteristics of smoke, water vapor, and dust differ significantly in different wavelength bands (for example, the extinction ratio of smoke in short-wavelength (780nm) and near-infrared (1653nm) is usually close to 1, while the extinction of water vapor is significantly stronger in the short-wavelength band), the ratio information B can be calculated to effectively distinguish between real smoke and interference factors.

[0033] Furthermore, in some embodiments of the present invention, such as Figure 4 As shown, the signal processor 63 is further configured to: determine that a preset alarm condition is met when the extinction information corresponding to the first stage voltage signal and / or the extinction information corresponding to the third stage voltage signal are greater than the corresponding preset threshold, and the extinction is determined to be caused by smoke based on the smoke extinction signal ratio information, and / or when the methane concentration is determined to be greater than the preset methane concentration based on the methane concentration information.

[0034] Specifically, in this embodiment, the alarm condition determination adopts a "multi-channel, multi-condition" logic. For smoke alarms, two sub-conditions must be met simultaneously: first, the extinction information in stages T1 and / or T3 exceeds a preset threshold (indicating significant light intensity attenuation in the detection area); second, based on the ratio information B, it is determined that the attenuation is indeed caused by smoke rather than water vapor or dust. Only when both conditions are met simultaneously is the smoke alarm triggered, thereby significantly reducing false alarms. For methane alarms, the determination is independent: when the methane concentration derived from the second harmonic exceeds a preset safety threshold, the methane alarm is directly triggered. In addition, the device can also support a simultaneous alarm mode, that is, smoke and methane alarms can be output independently without interference. Furthermore, in some embodiments of the present invention, such as Figure 4 As shown, the signal processor 63 is also used to: determine that the extinction is caused by smoke when the smoke extinction signal ratio information is within a preset ratio range.

[0035] Specifically, in this embodiment, the signal processor 63 compares the real-time calculated ratio information B with a preset range: if the value of B falls within the smoke characteristic range, it is determined to be real smoke; otherwise, it is determined to be an interference factor, and the smoke alarm is not triggered. The preset ratio range is an empirical range obtained based on extensive experimental calibration and is not specifically limited here. In addition, the preset range can be adaptively calibrated or manually set according to the usage environment (such as kitchen, construction site, warehouse), further improving flexibility.

[0036] Furthermore, in some embodiments of the present invention, such as Figure 4 As shown, the signal processor 63 is also used to: normalize the amplitude of the second harmonic signal using the amplitude of the electrical signal corresponding to the first stage voltage signal or the third stage voltage signal.

[0037] Specifically, in this embodiment, since smoke extinction leads to a decrease in the overall intensity of the returned light signal, directly using the absolute amplitude of the second harmonic to invert methane concentration would result in a negative bias (i.e., the measured concentration value would be too low). To eliminate this effect, the signal processor 63 extracts the electrical signal amplitude from stage T1 or T3 (when the laser wavelength is outside the methane absorption line, and signal attenuation is only caused by non-methane factors such as smoke) as a reference light intensity. The amplitude of the second harmonic signal is divided by this reference light intensity (or multiplied by a normalization coefficient) to obtain a normalized harmonic signal independent of the light intensity. This normalized signal has a linear relationship with the methane concentration, ensuring that methane concentration measurement remains accurate and reliable even in dense smoke environments.

[0038] Furthermore, in some embodiments of the present invention, such as Figure 4 As shown, the photoelectric detection device 50 includes: an optical transceiver tube 51, on which a collimator 53, a lens 55, and a photodetector 54 are disposed; an optical fiber combiner 52 for combining a first laser signal and a second laser signal into a composite laser beam; the collimator 53 is connected to the optical fiber combiner 52 for collimating and transmitting the composite laser beam to the target space; the lens 55 for receiving the laser feedback signal reflected back from the reflector in the target space and focusing it onto the photodetector 54; and the photodetector 54 for converting the laser feedback signal into an electrical signal.

[0039] Specifically, in this embodiment, the optical transceiver tube 51 integrates transmission and reception functions, enabling unilateral telemetry. The lasers output from the first laser device 30 and the second laser device 40 are fed into the fiber optic combiner 52 via optical fiber, combining into a coaxial composite laser beam. This beam is then expanded and collimated by the collimator 53 before being directed towards the target space. The collimated beam has a small divergence angle, enabling detection at distances of hundreds of meters or even further. When the laser illuminates a distant reflector (such as a wall, ground, pipe, or other natural surface), diffuse reflection occurs. Part of the reflected light (i.e., the laser feedback signal) returns along the original path and is collected by the large-aperture lens 55 in the transceiver tube, converging onto the photosensitive surface of the photodetector 54. The photodetector 54 then converts the laser feedback signal into an electrical signal. The first laser device 30 includes a first signal coupler 31, a first laser driver 32, and a first laser 33. The input terminal of the first signal coupler 31 is connected to the first channel output terminal of the stepped scanning signal generator 10 and the output terminal of the modulation signal generator 20, respectively, for coupling the first channel signal (stepped scanning signal) with a sinusoidal modulation signal to generate a composite drive signal with wavelength scanning and wavelength modulation characteristics. The first laser driver 32 is connected to the output terminal of the first signal coupler 31, for providing a stable constant current drive current according to the composite drive signal, and controlling the operating temperature and output power of the laser. The second laser device 40 includes a second signal coupler 41, a second laser driver 42, and a second laser 43. The input terminal of the second signal coupler 41 is connected to the second channel output terminal of the stepped scanning signal generator 10 and the output terminal of the modulation signal generator 20, respectively, for coupling the second channel signal (constant voltage signal) with a sinusoidal modulation signal to output a drive signal with a fixed amplitude and superimposed modulation. The second laser driver 42 is connected to the output of the second signal coupler 41 and is used to drive the second laser 43 to work stably.

[0040] Furthermore, in some embodiments of the present invention, the wavelength of the first laser signal is 1653 nm, and the wavelength of the second laser signal is 780 nm.

[0041] Furthermore, in some embodiments of the present invention, such as Figure 4 As shown, the laser remote sensing fire smoke and methane composite detection device 100 also includes: an audible and visual alarm 70, which is connected to the signal processing device 60 and is used to provide audible and visual alarms for abnormal concentrations.

[0042] Specifically, in this embodiment, the audible and visual alarm 70 includes a buzzer and a high-brightness LED indicator. When the signal processor 63 determines that the smoke alarm conditions are met or the methane concentration exceeds the limit, it immediately outputs an alarm trigger signal, and the audible and visual alarm 70 then emits a loud buzzer and flashing red light to remind on-site personnel to take timely emergency measures. The alarm mode can be configured to distinguish between smoke alarms and methane alarms (e.g., buzzers of different frequencies or indicator lights of different colors), making it easy for on-site personnel to quickly identify the type of hazard.

[0043] In summary, the laser remote sensing fire smoke and methane composite detection device according to the embodiments of the present invention generates a first channel signal and a second channel signal through a stepped scanning signal generator. Combined with a sinusoidal signal from a modulation signal generator, these signals drive the first and second laser devices to output laser signals of different wavelengths. The signals are then combined and transmitted by a photoelectric detection device, and a feedback signal is received. Finally, a signal processing device simultaneously acquires smoke extinction information, smoke extinction signal ratio information, and methane concentration information, and performs analysis based on preset alarm conditions. This achieves long-distance, single-sided fire smoke and methane composite detection, accurately distinguishing between real smoke and interfering factors such as water vapor and dust, significantly reducing the false alarm rate, and significantly improving detection accuracy and environmental adaptability.

[0044] It should be noted that the logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0045] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0046] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0047] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to 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, they should not be construed as limitations on this invention.

[0048] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0049] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0050] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "beneath" of the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0051] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A laser remote sensing fire smoke and methane composite detection device, characterized in that, The laser remote sensing fire smoke and methane composite detection device includes: A stepped scanning signal generator is used to generate a stepped periodic scanning signal, wherein the stepped periodic scanning signal includes a first channel signal and a second channel signal. A modulation signal generator is used to generate sinusoidal signals; A first laser device is configured to output a first laser signal based on a coupling signal between the first channel signal and the sinusoidal signal; A second laser device is configured to output a second laser signal based on the coupling signal of the second channel signal and the sinusoidal signal, wherein the wavelength of the second laser signal is less than the wavelength of the first laser signal; A photoelectric detection device is used to transmit the combined first laser signal and the second laser signal to the target space, and to convert the received laser feedback signal from the target space into an electrical signal; The signal processing device is used to acquire smoke extinction information, smoke extinction signal ratio information, and methane concentration information respectively based on the electrical signal and the sinusoidal signal, and to issue an alarm when the smoke extinction information, the smoke extinction signal ratio information, and the methane concentration information meet preset alarm conditions.

2. The laser remote sensing fire smoke and methane composite detection device according to claim 1, characterized in that, The first channel signal includes a first-stage voltage signal, a second-stage voltage signal, and a third-stage voltage signal. The second channel signal includes a fourth-stage voltage signal. The first-stage voltage signal is used to keep the laser wavelength constant outside the methane absorption line. The second-stage signal is used to make the laser wavelength scan cover the methane absorption line. The third-stage signal is used to keep the laser wavelength constant outside the methane absorption line. The fourth-stage voltage signal is used to generate the smoke extinction signal ratio information.

3. The laser remote sensing fire smoke and methane composite detection device according to claim 2, characterized in that, The signal processing device includes: A phase-sensitive demodulator is connected to the modulation signal generator and the photoelectric detection device, respectively, and is used to demodulate the electrical signal using the sinusoidal signal to obtain the second harmonic signal absorbed by methane; A signal acquisition unit is connected to the photoelectric detection device and the phase-sensitive demodulator respectively, and is used to acquire the electrical signal and the second harmonic signal; A signal processor, connected to the signal acquisition unit, is used to acquire the smoke extinction information and the smoke extinction signal ratio information based on the electrical signal and a preset signal strength, and to acquire the methane concentration information based on the second harmonic signal. Furthermore, it is used to trigger an alarm when the smoke extinction information, the smoke extinction signal ratio information, and the methane concentration information meet preset alarm conditions.

4. The laser remote sensing fire smoke and methane composite detection device according to claim 3, characterized in that, The signal processor is also used to obtain the smoke extinction signal ratio information using the following formula: B = [((X0+X3) / 2) / X4]; Wherein, B is the smoke extinction signal ratio information, X0 is the extinction information corresponding to the first stage voltage signal, X3 is the extinction information corresponding to the third stage voltage signal, and X4 is the extinction information corresponding to the fourth stage voltage signal.

5. The laser remote sensing fire smoke and methane composite detection device according to claim 3, characterized in that, The signal processor is also used for: When the extinction information corresponding to the first stage voltage signal and / or the extinction information corresponding to the third stage voltage signal are greater than the corresponding preset threshold, and it is determined that the extinction is caused by smoke based on the smoke extinction signal ratio information, and / or when it is determined that the methane concentration is greater than the preset methane concentration based on the methane concentration information, the preset alarm condition is determined to be met.

6. The laser remote sensing fire smoke and methane composite detection device according to claim 5, characterized in that, The signal processor is also used for: When the ratio of the smoke extinction signal is within a preset ratio range, it is determined that the extinction is caused by smoke.

7. The laser remote sensing fire smoke and methane composite detection device according to claim 3, characterized in that, The signal processor is also used for: The amplitude of the second harmonic signal is normalized using the amplitude of the electrical signal corresponding to the first stage voltage signal or the third stage voltage signal.

8. The laser remote sensing fire smoke and methane composite detection device according to claim 1, characterized in that, The photoelectric detection device includes: An optical transceiver tube, wherein a collimator, a lens and a photodetector are provided on the optical transceiver tube; An optical fiber combiner is used to combine the first laser signal and the second laser signal into a composite laser beam. The collimator is connected to the fiber optic combiner and is used to collimate and transmit the composite laser beam to the target space. The lens is used to receive the laser feedback signal reflected back from the reflector in the target space and converge it to the photodetector; The photodetector is used to convert the laser feedback signal into an electrical signal.

9. The laser remote sensing fire smoke and methane composite detection device according to claim 1, characterized in that, The wavelength of the first laser signal is 1653nm, and the wavelength of the second laser signal is 780nm.

10. The laser remote sensing fire smoke and methane composite detection device according to claim 1, characterized in that, The laser remote sensing fire smoke and methane composite detection device also includes: An audible and visual alarm, connected to the signal processing device, is used to provide audible and visual alarms for abnormal concentrations.

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