CN105445206A - Gas detection system - Google Patents

Abstract

The invention provides a gas detection system. The system includes ground system and flight system. The ground system includes a laser emitting device and a spectral data processing device; the flight system includes a flying device and an optical path conversion device arranged on the flying device; the laser emitting device is used to emit laser light; the optical path conversion device is used to receive the laser emitted by the laser emitting device The received laser light is diverted to the detected area; the optical path conversion device is also used to receive the reflected laser light from the detected area, and redirect the received reflected laser light to the spectral data processing device; the spectral data processing device is used to receive the reflected laser light , and determine the gas composition and/or content of the detected area according to the reflected laser light. In the present invention, the heavier laser emitting device and the spectral data processing device are arranged on the ground, and only the lighter optical path conversion device is carried into the air through the flying device, thereby reducing the overall weight of the flying module and increasing the battery life.

Description

Gas detection system

technical field

The invention relates to the technical field of detection, in particular to a gas detection system.

Background technique

With the development of the economy, the application of gas in industry and civil use is becoming more and more extensive. As a kind of energy, the leakage of gas pipelines will not only cause economic losses, but also may cause personal injury. Therefore, gas detection is used as a preventive measure appears to be particularly important. At present, the commonly used detection method is through gas detectors, but due to the low detection efficiency and slow speed of gas detectors, it is difficult to meet the needs of practical applications, especially for some special applications, such as overhead pipelines in the chemical industry, Pipelines placed in the air, such as gas pipelines in high-rise buildings, are even more difficult to detect.

Contents of the invention

In view of this, the present invention proposes a gas detection system aimed at solving the problem in the prior art that it is difficult to detect the leakage of pipelines placed in the air.

In one aspect, the present invention provides a gas detection system, which includes: a ground system and a flight system; wherein, the ground system includes a laser emitting device and a spectral data processing device; the flight system includes a flight device and is arranged on the The optical path conversion device of the flying device; the laser emitting device is used to emit laser; the spectral data processing device is also connected with the laser emitting device, and is used to receive the emitted laser parameters emitted by the laser emitting device; The optical path conversion device is used to receive the laser light emitted by the laser emitting device and redirect the received laser light to the detected area; the optical path conversion device is also used to receive the laser light reflected back from the detected area, and convert the received reflected laser light The returned laser light is diverted to the spectral data processing device; the spectral data processing device is used to receive the reflected laser light, and determine according to the parameters of the reflected laser light and the emitted laser light parameters received from the laser emitting device The gas composition and/or content of the area being tested.

Further, in the above gas detection system, the spectral data processing device includes: a laser receiving device, a spectrum conversion device and a processing device; wherein the laser receiving device is used to receive the reflected laser light diverted by the optical path conversion device, And the received reflected laser light is transmitted to the spectrum conversion device; the spectrum conversion device is used to receive the reflected laser light and convert the reflected laser light into a spectrum; the processing device is related to the spectrum conversion device connected to receive the spectrum, and compare the received spectrum with a pre-stored spectrum database to determine the composition and/or content of the gas to be detected.

Further, in the above gas detection system, the optical path conversion device includes: a first optical device, configured to receive the laser light emitted by the laser emitting device, and redirect the received laser light to the detected area; a second optical device, It is used for receiving the laser light reflected back from the detected area, and diverting the received reflected laser light to the spectral data processing device.

Further, in the above gas detection system, the laser light emitted by the laser emitting device is transmitted to the optical path conversion device through air or optical fiber.

Furthermore, in the above gas detection system, the laser light received by the optical path conversion device and reflected back by the detected area is transmitted to the spectral data processing device through air or optical fiber.

Further, the above-mentioned gas detection system further includes: a vehicle on the ground, the laser emitting device and the spectral data processing device are arranged on the vehicle on the ground.

Further, the above-mentioned gas detection system further includes: a first positioning system, configured to determine that the flying device is placed within a preset range above the ground system, so that the optical path conversion device receives the light emitted by the laser emitting device. laser.

Further, in the above-mentioned gas detection system, the first positioning system includes: a laser, arranged on the ground system, for emitting laser light to the flying device; a photosensitive plate, arranged at the bottom of the flying device, for receiving the laser light emitted by the light-emitting device, and returning the photosensitive signal; the receiving device is arranged on the ground system, and is used to receive the returned photosensitive signal and determine whether the flying device is in the position according to the returned photosensitive signal. within a preset range above the ground system described above.

Further, in the above gas detection system, the first positioning system includes: a first GPS system, a second GPS system and a control device; wherein, the first GPS system is set on the ground system for locating the position of the ground system The second GPS system is set in the flight system for locating the position of the flight system; the control device is connected with the first GPS system and the second GPS system for receiving the ground system and the The location of the flight system, and controlling the flight system to place the flight system within a predetermined range above the ground system.

Further, the above gas detection system further includes: a second positioning system, arranged on the flying device, for ensuring that the distance between the flying device and the detected area is within a preset distance range.

Further, in the above gas detection system, the second positioning system is also used to send an abnormal detection alarm signal when the reflection distance is less than a preset distance; the reflection distance is the distance between the optical path conversion device and the laser reflection in the detected area The distance in distance between points.

The gas detection system provided by the present invention detects the gas in the detected area through the laser emitted by the laser emitting device, and the gas detection system is divided into two parts: the ground system and the flight system. The laser emitting device in the ground system emits laser light, and the flight system In the flying device, the optical path conversion device is carried into the air, and the laser beam is irradiated into the detected area in the air through the optical path conversion device. It can be seen that compared with the prior art, the present invention can more conveniently detect In order to know the leakage situation of the aerial pipeline in time; in addition, because the present invention arranges the heavier laser emission device and the spectral data processing device on the ground, only the lighter weight The optical path conversion device is carried into the air by the flight device, and the core heavy equipment is transferred to the ground by this method, thereby reducing the overall weight of the flight module and increasing the endurance, and can complete the gas detection of a large area at one time.

Description of drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiment. The drawings are only for the purpose of illustrating a preferred embodiment and are not to be considered as limiting the invention. Also throughout the drawings, the same reference numerals are used to designate the same components. In the attached picture:

Fig. 1 is a structural block diagram of a gas detection system provided by an embodiment of the present invention;

Fig. 2 is a structural block diagram of the spectral data processing device in the gas detection system provided by the embodiment of the present invention;

Fig. 3 is a structural block diagram of the optical path conversion device in the gas detection system provided by the embodiment of the present invention;

Fig. 4 is another structural block diagram of the gas detection system provided by the embodiment of the present invention;

Fig. 5 is a schematic view of the working state of the gas detection system provided by the embodiment of the present invention.

detailed description

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided for more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that, in the case of no conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and examples.

Referring to FIG. 1 , FIG. 1 is a structural block diagram of a gas detection system provided by an embodiment of the present invention. As shown in the figure, the detection system includes: a ground system 1 and a flight system 2 . Wherein, the ground system 1 is set on the ground, and the flight system 2 can fly in the air. In this embodiment, the detection is completed through the cooperation of the ground system 1 and the flight system 2 .

The ground system 1 may include a laser emitting device 11 and a spectral data processing device 12 . Wherein, the laser emitting device is used to emit laser light, and in specific implementation, the laser emitting device 11 may be a laser. The laser emitting device 11 can emit laser light with different wavelengths. The specific emitted wavelength can be selected according to the detected gas. For example, when the detected gas is methane, the laser working wavelength is 1653.7nm, because methane gas can absorb laser light of this wavelength. The spectral data processing device 12 is also connected to the laser emitting device 11 for receiving parameters of the emitted laser light emitted by the laser emitting device 11 .

The flying system 2 may include a flying device 21 and an optical path conversion device 22 . The flying device 21 may be an aircraft, such as a helicopter, a drone, and the like. The optical path conversion device 22 is installed on the flying device 21. The function of the optical path conversion device 22 is to receive the laser light emitted by the laser emitting device 11, and change the propagation direction of the received laser light so that the laser light hits the detected area. At the same time, the optical path conversion device 22 is also used to receive the laser light reflected back from the detected area, and change the propagation direction of the laser light reflected back from the detected area, so that the reflected laser light propagates to the ground system 1 . During specific implementation, the laser light emitted by the laser emitting device 11 can be transmitted to the optical path conversion device 22 through air or optical fiber, and the laser light received by the optical path conversion device 22 and reflected back by the detected area can also be transmitted to the spectral data processing device 12 through air or optical fiber. It should be noted that, during specific implementation, the optical path conversion device 22 can be composed of optical devices such as concave mirrors, lenses, and prisms. As long as the optical conversion device 22 can achieve the purpose of turning, there are various specific implementation methods, and this embodiment does not address it. Make any restrictions.

The spectral data processing device 12 in the ground system 1 is used to receive the laser light reflected back from the detected area diverted by the optical path conversion device 22, and determine the detected laser light according to the parameters of the reflected laser light and the parameters of the emitted laser light received from the laser emitting device 11. The gas composition and/or content of the zone. Specifically, the spectral data processing device 12 can obtain the composition and content of each gas according to the wavelength and intensity loss of the received reflected laser light. Specifically, the composition of the detected gas can be determined by analyzing the wavelength information of the laser spectrum, and the reflected laser intensity loss and other information can be used to obtain the content of each component in the detected gas. The analysis method can be selected as the three-level identification well known to those skilled in the art. method, overall analysis method, etc. It should be noted that the spectral data processing device 12 and specific analysis methods are well known to those skilled in the art, so details are not repeated here.

The working principle of this embodiment is: for a specific gas, laser light with a specific wavelength can be absorbed, and the embodiment of the present invention uses this characteristic of the gas to detect the gas. For example, methane can absorb laser light with a wavelength of 1653.7nm. When detecting methane, adjust the laser emitting device 11 so that the laser emitting device 11 emits laser light with a wavelength of 1653.7nm. If there is methane gas in the detection area, the methane gas will absorb all or part of the laser light of this wavelength, and the laser light reflected by the methane gas will no longer have the laser light of this wavelength or the laser light of this wavelength will be weakened; if there is no laser light of this wavelength in the detected area If there is methane gas, the laser light of this wavelength will not be absorbed, and the laser light of this wavelength will not be weakened in the reflected laser light. It can be seen that according to this characteristic, the gas composition in the detected area can be determined by analyzing the spectrum of the laser light reflected back from the detected area. In addition, when the laser absorbs gas, it will also cause loss of laser intensity, and different gases have different abilities to cause loss of laser light, so the gas content can be determined by analyzing the loss of laser intensity.

The working process of this embodiment is: start the flying device 21, the flying device 21 carries the optical path replacement device 22 and rises to the vicinity of the detected area, then the flying device 21 adjusts the position, and then adjusts the position of the optical path conversion device 22, so that the optical path conversion device 22 can receive the laser light emitted by the laser emitting device 11. At the same time, the spectral data processing device 12 can also receive the reflected laser light after the optical path conversion device 22 turns. After the position of the flying device 21 is adjusted, the detection starts. At this time, The laser light emitted by the laser emitting device 11 propagates in the air or the fiber medium, and the optical path conversion device 22 receives the laser light and changes the direction of the laser light, so that the laser light is directed to the detected area, and the laser light is reflected by the gas to be detected and then reflected back to the detected area. The laser light is redirected through the optical path conversion device 22, and the redirected laser propagates in the air or optical fiber medium, and is transmitted to the spectral data processing device 12. The spectral data processing device 12 analyzes the spectrum of the laser light to obtain the composition of the gas to be detected and/or content.

The gas detection system provided in this embodiment detects the gas in the detected area through the laser emitted by the laser emitting device, and the gas detection system is divided into two parts: the ground system 1 and the flight system 2. The laser emitting device in the ground system 1 11 emits laser light, and the flying device 21 in the flight system 2 carries the optical path conversion device 22 into the air, and the laser light is irradiated into the detected area in the air through the optical path conversion device 22. In comparison, this embodiment can more conveniently detect the gas leakage of the aerial pipeline, so as to know the leakage of the aerial pipeline in time. Because the present embodiment arranges the heavier laser emission device 11 and the spectral data processing device 12 on the ground, but only carries the lighter optical path conversion device 22 into the air through the flying device 21, the core is heavier by this method. The equipment is transferred to the ground, thereby reducing the weight carried by the flying device 12, increasing the endurance of the flying device 12, and can complete the gas detection in a larger area at one time. In addition, when there is a problem with the flying device 12, only the optical conversion device 22 needs to be replaced, which effectively reduces the cost of high-altitude gas detection.

Referring to FIG. 2 , in the above embodiments, the spectral data processing device 12 may include a laser receiving device 121 , a spectral conversion device 122 and a processing device 123 . Among them, the laser receiving device 121 is used to receive the reflected laser light turned by the optical path conversion device 22, and transmit the received reflected laser light to the spectrum conversion device 122; the spectrum conversion device 122 is used to receive the reflected laser light and reflect The returned laser light is converted into a spectrum; the processing device 123 is connected with the spectrum conversion device 122 for receiving the spectrum and comparing it with a pre-stored spectrum database to determine the composition and/or content of the detected gas. During specific implementation, the laser receiving device 111 may be a combination of optical instruments such as lenses and total reflection mirrors, and the specific structure of the laser receiving device 111 is not limited in this embodiment. The spectrum conversion device 112 may be a spectrum detector, and the processing device 113 may be a processor such as a single-chip microcomputer DSP.

Referring to Fig. 3 and Fig. 4, the preferred structure of the optical path conversion device is shown in the figures. As shown in the figure, the optical path conversion device 22 may include: a first optical device 221 and a second optical device 222 . Wherein, the first optical device 221 is used for receiving the laser light emitted by the laser emitting device 11, and redirecting the received laser light so that the laser light is radiated to the detected area. Specifically, the first optical device 221 may be a set of prisms, and the laser light emitted by the laser conversion device 11 may be horizontally incident on the detected area after being redirected by each prism. The second optical device 222 is used for receiving the laser light reflected back from the detected area, and diverting the received reflected laser light to the spectral data processing device 12 . Specifically, the second optical device 222 can be an optical device such as a concave mirror, a prism, etc. The laser light emitted back from the detected area can first be condensed by a concave mirror, and then the prism can redirect the condensed laser light so that the reflected laser light The light is irradiated into the spectral data processing device 12 on the ground.

It should be noted that, during specific implementation, the first optical device 221 and the second optical device 222 may be implemented in various ways, which are not limited in this embodiment.

The above embodiments may also include: ground vehicles. Wherein, the laser emitting device 11 and the spectral data processing device 12 are both arranged on the ground vehicle. Specifically, the ground vehicle may be a motor vehicle, etc., and the laser emitting device 11 and the spectral data processing device 12 are arranged on the ground vehicle. It can be seen that the movement of the vehicle on the ground can drive the ground system 1 to move to any position on the ground, which facilitates the adjustment of the position of the ground system 1 and greatly improves the detection efficiency.

Referring to Fig. 4 and Fig. 5, in order to make the laser emitting device 11 and the spectral data processing device 12 better correspond to the optical path conversion device 22, a first positioning system can also be added in each of the above-mentioned embodiments. Wherein, the first positioning system is used to determine that the flying device 21 is placed within a preset range above the ground system 1 , so that the optical path conversion device 22 can receive the laser light emitted by the laser emitting device 11 .

In one embodiment of the present invention, the first positioning system may include: a laser, a photosensitive plate, and a receiving device. Wherein, the laser device is arranged on the vehicle in the ground system 1, and is used to emit laser light to the bottom of the flying device 21; the photosensitive plate can be arranged on the bottom of the flying device 21, and is used to receive the laser light emitted by the laser device and return the sensing photoelectric signal; the receiving device It is connected with the photosensitive plate, and is used for receiving the returned photosensitive signal and determining whether the flying device 21 is within the preset range according to the returned photosensitive signal. When the receiving device can receive the photoelectric signal, it is determined that the flying device 21 is within the preset range, and when the receiving device cannot receive the photoelectric signal, it is confirmed that the flying device 21 is outside the preset range. The ground system 1 emits a vertical positioning laser at a certain frequency to correct the vertical position of the ground system 1 and the flying device 21. During specific implementation, a laser rapid positioning system can be used, for example, more than 100 positioning signals per second.

In another embodiment of the present invention, the first positioning system may include a first GPS system, a second GPS system and a control device. Wherein, the first GPS system is arranged on the ground system 1, and is used for positioning the position of the ground system 1; the second GPS system is arranged on the flight system 2, and is used for positioning the position of the flight system; the control device is connected with the first GPS system and the second GPS The systems are connected for receiving the positions of the ground system 1 and the flight system 2 , and controlling the flight system 1 so that the flight system 2 is placed within a preset range above the ground system 1 . During specific implementation, the control device can be connected with the control system in the flight device 21. When the flight device 21 exceeds the preset range, the control device sends a position adjustment signal to the flight device 21, and the flight device 21 adjusts the position according to the position adjustment signal. within the preset range. The control device can be a single chip microcomputer, DSP, etc.

It should be noted that during specific implementation, the preset range may be determined according to actual conditions, which is not limited in this embodiment.

It can be seen that this embodiment uses the first positioning system to locate the flying device 21. On the one hand, it can ensure that the optical path conversion device 22 receives the laser light emitted by the laser emitting device 11, and on the other hand, it can ensure that the spectral data processing device 12 receives Laser light reflected back from the inspected area.

In order to achieve a better detection effect, the above embodiment can be further improved by adding a second positioning system. Wherein, the second positioning system is arranged on the flying device 21 to ensure that the distance between the flying device 21 and the detected area is within a preset distance. Specifically, the second positioning system may include a laser and a receiving device. The laser emits laser light to the detected device, and the detected area reflects the laser light emitted by the laser device, and the receiving device receives the reflected laser light from the detected area, and determines the distance between the flying device 21 and the detected area according to the received reflected laser light .

In this embodiment, the second positioning system can ensure that the distance between the flying device 21 and the detected area is within a preset distance, thereby better ensuring the detection effect.

In the above embodiment, the second positioning system is also used to send out an abnormal detection alarm signal when the reflection distance is less than the preset distance; the reflection distance is the distance between the optical path conversion device 22 and the laser reflection point in the detected area. For example, for the detection of gas pipelines in a residential building, assuming that the distance between the flying device 21 and the residential building is 10 meters, and the depth of the residential building is 4 meters, the reflection distance should be between 10 meters and 14 meters. . If the reflection distance is 10 meters, it is considered that the laser light may be blocked by the curtain at the window of the residential building, it is judged that the detection is wrong, and an abnormal alarm signal is sent.

Take the detection of whether there is methane gas in a residential building as an example below to describe the embodiment of the present invention in more detail:

A diode laser is used for the laser emitting device, a drone is used for the flying device, and a prism is used for both the first optical device and the second optical device. The prisms in the first optical device and the second optical device are all installed at the lower end of the drone. When installing, a certain angle must be ensured. This angle is mainly to ensure that the laser beam passes through the first optical device and second optical device. Total reflection, so that the laser light is irradiated on the detected area along the horizontal direction and the spectral data processing device is irradiated along the vertical direction, the total reflection angle can be determined according to the formula, wherein, c is the critical angle, n is the refractive index, so that the laser light Critical angle incident prism, the prism can be made of glass, the critical angle of glass is: 32-42°. When installing, make the light-transmitting side of the prism vertical to the ground at an angle of 45°, and install and fix the prism to ensure that the angle remains unchanged during the drone’s battery life. Detection area. In addition, the laser emitting device 11 and the spectral data processing device 12 must be assembled in the ground system.

Since the absorption wavelength of methane gas is 1653.7nm, during detection, the laser emission wavelength of the laser emitting device 11 is first adjusted around 1653.7nm, and then the flight position of the drone is adjusted so that the laser emitted by the laser in the first positioning system can Shooting on the photosensitive plate at the lower end of the drone, the laser emitted by the laser can be received by the first optical device at this time, the drone stops at this position, and the laser emitted by the transmitter propagates into the first optical device in the air Then the prism changes the direction of the laser, so that the laser is horizontally directed to the detected area, the laser is reflected by the gas to be measured, and the reflected and absorbed laser is condensed by the prism in the second optical device. The laser is transmitted to the spectral data processing device in the air, and the spectral data processing device performs spectral analysis on the reflected laser light to obtain the composition and content of the measured gas.

In summary, because the embodiment of the invention arranges the heavier laser emitting device and the spectral data processing device on the ground, but only carries the lighter optical path conversion device into the air through the flying device, this will greatly reduce the weight of the flying device. burden, increase the mileage of the flight device, and can complete the gas detection of a large area at one time.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and equivalent technologies thereof, the present invention also intends to include these modifications and variations.

Claims (10)

1. A gas detection system, characterized in that it comprises: a ground system (1) and a flight system (2); wherein, The ground system (1) includes a laser emitting device (11) and a spectral data processing device (12); the flight system (2) includes a flight device (21) and an optical path conversion device arranged on the flight device (21) (twenty two); The laser emitting device (11) is used to emit laser light; the spectral data processing device (12) is also connected to the laser emitting device (11), and is used to receive the emitted laser light emitted by the laser emitting device (11) parameter; The optical path conversion device (22) is used to receive the laser light emitted by the laser emitting device (11) and redirect the received laser light to the detected area; The optical path conversion device (22) is also used to receive the laser light reflected back from the detected area, and divert the received reflected laser light to the spectral data processing device (12); The spectral data processing device (12) is used to receive the reflected laser light, and determine the gas composition of the detected area according to the parameters of the reflected laser light and the parameters of the emitted laser light received from the laser emitting device (11) and/or content. 2. The gas detection system according to claim 1, characterized in that the spectral data processing device (12) comprises: a laser receiving device (121), a spectral conversion device (122) and a processing device (123); wherein, The laser receiving device (121) is used to receive the reflected laser light diverted by the optical path conversion device (22), and transmit the received reflected laser light to the spectrum conversion device (122); The spectrum conversion device is used to receive the reflected laser light and convert the reflected laser light into a spectrum; The processing device (123) is connected with the spectrum conversion device, and is used for receiving the spectrum, and comparing the received spectrum with a pre-stored spectrum database, so as to determine the composition and/or content of the detected gas. 3. The gas detection system according to claim 1, characterized in that the optical path conversion device (22) comprises: The first optical device (221), configured to receive the laser light emitted by the laser emitting device (11), and redirect the received laser light to the detected area; The second optical device (222) is configured to receive the laser light reflected back from the detected area, and divert the reflected laser light to a spectral data processing device. 4. The gas detection system according to claim 1, characterized in that, The laser light emitted by the laser emitting device (11) is transmitted to the optical path conversion device (22) through air or optical fiber; and/or The laser light received by the optical path conversion device (22) and reflected back by the detected area is transmitted to the spectral data processing device (12) through air or optical fiber. 5. The gas detection system according to claim 1, further comprising: The ground vehicle, the laser emitting device (11) and the spectral data processing device (12) are both arranged on the ground vehicle. 6. The gas detection system according to any one of claims 1 to 5, further comprising: A first positioning system, configured to determine that the flying device (21) is placed within a preset range above the ground system (1), so that the optical path conversion device (22) receives the laser emitting device (11) emitted laser light. 7. The gas detection system according to claim 6, wherein the first positioning system comprises: a laser, arranged on the ground system, for emitting laser light to the flying device; A photosensitive plate, arranged at the bottom of the flying device (21), is used to receive the laser light emitted by the laser and return a photosensitive signal; The receiving device is arranged on the ground system (1), and is used for receiving the returned photosensitive signal and determining whether the flying device (21) is above the ground system (1) according to the returned photosensitive signal. within the set range. 8. The gas detection system according to claim 6, wherein the first positioning system comprises: a first GPS system, a second GPS system and a control device; wherein, The first GPS system is set on the ground system (1), and is used for locating the position of the ground system (1); The second GPS system is set in the flight system (2), and is used for locating the position of the flight system (2); A control device, connected to the first GPS system and the second GPS system, for receiving the positions of the ground system (1) and the flight system (2), and controlling the flight system (2) so that the flight system (2) is placed within a preset range above the ground system (1). 9. The gas detection system according to any one of claims 1 to 5, further comprising: The second positioning system is arranged on the flying device (21), and is used to ensure that the distance between the flying device (21) and the detected area is within a preset distance range. 10. The gas detection system according to claim 9, characterized in that, The second positioning system is also used to send out a detection abnormality alarm signal when the reflection distance is less than a preset distance; the reflection distance is the distance between the optical path conversion device (22) and the laser reflection point in the detected area.