A method for calibrating a gas leak detection and rapid tracing device

Abstract

The application discloses a kind of gas leakage detection and fast traceability device's calibration method, belong to the angle between the optical axis of visible light imaging module and spectral detection module in gas leakage detection and traceability device, it includes gas leakage detection and fast traceability device, when the angle between two optical axes in device is calibrated, the calibration method is by first calibrating inner parameter, outer parameter matrix, then the coordinates of laser spot under the coordinate system of visible light imaging module are constrained, finally the spot centroid is calculated and the optical axis of tunable semiconductor laser absorption spectrometry module is adjusted, and after the centroid meets the limit, just complete adjustment, calibration;Using the calibration method can reduce the spatial misalignment of gas tunable semiconductor laser absorption spectrometry module concentration data and visible light imaging module center point radiation value.

Description

Technical Field

[0001] This invention belongs to the field of gas detection technology, and relates to the detection and tracing of gas leaks, and particularly to a calibration method for a gas leak detection and rapid tracing device. Background Technology

[0002] Gas leak detection technology has wide and important applications in fields such as air pollution control, petrochemicals, and industrial process monitoring. For example, in industries such as petrochemicals, there are a large number of complex methane gas storage or transportation devices, and effectively monitoring leaks in these devices is an important prerequisite for ensuring safe production.

[0003] For gas leaks, contact leak detection equipment is currently widely used. The sensors in this equipment need to come into contact with the target gas to detect a leak. However, some leak points may be leaking, while most potential leak points are not yet leaking. Therefore, operators must personally inspect each potential leak point, which is inefficient and poses a health and safety hazard to the inspectors. Furthermore, traditional gas leak detection technologies can only measure concentration at a single point. While infrared imaging technology for methane leak detection, developed specifically for this purpose, uses an infrared focal plane array detector to image the leaking gas, offering advantages such as wide-area monitoring and rapid source tracing, it cannot quantitatively measure the leak concentration, thus failing to provide accurate situational assessment for subsequent accident evaluation and remedial measures.

[0004] Patent application number 202010443190X discloses an infrared imaging and concentration detection device and method for methane gas leaks. The device includes an infrared thermal imager and a laser methane detection module. The infrared thermal imager performs infrared imaging on the area to be monitored to detect methane gas leaks. The laser methane detection module aligns itself with the leak point detected by the infrared imaging and measures the methane concentration. The laser methane detection module is embedded in the infrared thermal imager, and the laser beam emission direction of the laser methane detection module is adjusted to be consistent with the optical axis of the infrared thermal imager. The two communicate with each other to achieve data exchange. The infrared thermal imager can detect large-area windows to determine if there is a natural gas leak within the window. The laser methane detection module performs long-distance, non-contact measurement of the methane leak point and obtains accurate methane gas concentration information. By combining infrared thermal imaging technology and laser methane detection technology for methane gas leak detection, it simultaneously achieves non-contact, large-area rapid search for methane leak points and quantitative detection of methane gas concentration, realizing a more efficient and accurate comprehensive detection than existing single detection devices.

[0005] While the aforementioned patent application for an infrared imaging and concentration detection device and method achieves quantitative detection of methane leak points and methane gas concentration, it suffers from several drawbacks. First, like traditional gas leak detection technologies, it can only measure concentration at a single point, failing to capture the stepwise concentration field. Second, traditional gas leak tracing methods mostly utilize infrared sensors for gas imaging, but these sensors are expensive, hindering widespread application. Third, existing visible light images only provide on-site evidence collection and lack rapid tracing capabilities. Therefore, to reduce costs and promote widespread application, it is crucial to utilize visible light imaging for gas leak tracing and achieve rapid tracing. It is necessary to provide a visible light imaging-based gas leak detection and rapid tracing device and method, along with a method for calibrating the optical axis angle within this tracing device. Summary of the Invention

[0006] The purpose of this invention is to provide a calibration method for a gas leak detection and rapid source tracing device, used to calibrate the angle between the optical axis of the visible light imaging module and the optical axis of the gas tunable semiconductor laser absorption spectroscopy detection module. Perform calibration.

[0007] To achieve the above objectives, the present invention specifically adopts the following technical solution:

[0008] A calibration method for a gas leak detection and rapid tracing device includes a gas leak detection and rapid tracing device and a broadband camera. The gas leak detection and rapid tracing device includes a visible light imaging module, a gas tunable semiconductor laser absorption spectroscopy detection module, a signal synchronous acquisition module, and a data processing unit.

[0009] The visible light imaging module is used to image the leaked gas scene, providing the background and basic coordinate system for leak location;

[0010] The gas tunable semiconductor laser absorption spectroscopy detection module is used to collect the gas leakage concentration at the leakage point in the scene.

[0011] The signal synchronization acquisition module is used to synchronize the data acquisition of the visible light imaging module and the gas tunable semiconductor laser absorption spectroscopy detection module.

[0012] The data processing unit is used to perform gas leakage modeling, concentration field fitting, and projection.

[0013] There is an angle between the optical axis of the visible light imaging module and the optical axis of the gas tunable semiconductor laser absorption spectroscopy detection module. and included angle Satisfying Relationship:

[0014] ;

[0015] ;

[0016] in, The upper limit of the angle, This refers to the distance between the optical center of the visible light imaging module and the optical center of the gas tunable semiconductor laser absorption spectroscopy detection module. This refers to the nominal working distance.

[0017] The broadband camera's spectral range covers the spectral range of the gas tunable semiconductor laser absorption spectroscopy detection module, and the included angle... The calibration steps are as follows:

[0018] Step S1-1: Fix the broadband camera and visible light imaging module;

[0019] Step S1-2: Use a target to calibrate the intrinsic parameters of the broadband camera to the visible light imaging module. and extrinsic parameter matrix ;

[0020] Steps 1-3: Place a white board with good laser reflection for the gas tunable semiconductor laser absorption spectroscopy detection module, and calculate the white board plane in the coordinate system of the visible light imaging module based on the four mark positions marked on the four corners of the white board.

[0021] Steps 1-4: When the whiteboard plane is perpendicular to the optical axis of the visible light imaging module, the coordinates of the laser spot of the gas tunable semiconductor laser absorption spectroscopy detection module in the coordinate system of the visible light imaging module must satisfy the following constraints:

[0022] Steps 1-5: Based on the constraints obtained in Step 1-4, and combined with the intrinsic parameters obtained in Step 1-2... and extrinsic parameter matrix Calculate the range of coordinates of the constrained range projected onto the image plane of the broadband camera:

[0023] Steps 1-6: Use a broadband camera to image the laser spot of the gas tunable semiconductor laser absorption spectroscopy detection module;

[0024] Steps 1-7: Calculate the centroid of the laser spot and adjust the optical axis of the gas tunable semiconductor laser absorption spectroscopy detection module. When the centroid of the laser spot meets the limitations of steps 1-5, the calibration and adjustment are completed.

[0025] Furthermore, in steps 1-3, at a distance of 2 from the broadband camera... A white board with good laser reflection for the gas tunable semiconductor laser absorption spectroscopy detection module is placed at a position. Four marker positions are marked on the four corners of the white board. The plane of the white board in the coordinate system of the visible light imaging module is calculated based on the four marker positions.

[0026] Furthermore, in steps 1-4, by At a distance of 2 Below, when the whiteboard plane is perpendicular to the optical axis of the visible light imaging module, the coordinates of the laser spot of the gas tunable semiconductor laser absorption spectroscopy detection module in the coordinate system of the visible light imaging module are ( The following constraints must be met:

[0027] ;

[0028] .

[0029] Furthermore, in steps 1-5, based on the constraints obtained in step 1-4, and combined with the intrinsic parameters obtained in step 1-2... and extrinsic parameter matrix The coordinate range of the constraint range projected onto the image plane of the broadband camera is calculated using the following formula:

[0030] ;

[0031] .

[0032] Furthermore, in steps 1-7, the formula for calculating the centroid of the laser spot is as follows:

[0033] ;

[0034] ;

[0035] in, This represents the value located at coordinates (i, j) in image I. Indicates the image height. Indicates the image width.

[0036] Furthermore, in the gas leak detection and rapid tracing device, the frame rate of the visible light imaging module... Sampling frequency of the gas tunable semiconductor laser absorption spectroscopy detection module The following conditions must be met:

[0037] ;

[0038] ;

[0039] ;

[0040] ;

[0041] in, This is the lower limit of the sampling frame rate for visible light images. This is the lower limit of the TDLAS data sampling rate. The angular velocity of the gas leak detection and rapid tracing device; This is an empirical value, set to 1.

[0042] Furthermore, in the gas leak detection and rapid tracing device, when installing the visible light imaging module and the gas tunable semiconductor laser absorption spectroscopy detection module, the distance between the optical center of the visible light imaging module and the optical center of the gas tunable semiconductor laser absorption spectroscopy detection module is... The following conditions must be met:

[0043] ;

[0044] in, The width of the laser beam waist, Rayleigh distance for laser; This is an empirical value, set to 10.

[0045] Furthermore, in the gas leak detection and rapid tracing device, during synchronous data acquisition, the deviation between the time the visible light imaging module acquires the image and the time the gas tunable semiconductor laser absorption spectroscopy detection module acquires the concentration is controlled within a certain range. Inside, and that Represented as:

[0046] ;

[0047] in, The angular velocity of the gas leak detection and rapid tracing device; This is an empirical value, set to 1.

[0048] The beneficial effects of this invention are as follows:

[0049] In this invention, the gas leakage concentration field model established in the source tracing device is subject to spatial physical constraints and fluid dynamic physical constraints, and its spatial distribution has certain regularities. Through scene understanding and fluid dynamic models, mathematical models such as the Gaussian feathering model can be used to simplify the spatial distribution of gas concentration. By combining the concentration values ​​of multiple spatial locations collected by the tunable semiconductor laser absorption spectroscopy detection module, the spatial distribution of gas concentration is fitted. This spatial distribution is projected onto the visible light image coordinate system, enabling rapid location of the gas leakage source with high accuracy. This achieves the rapid source tracing capability of gas leakage that cannot be achieved using visible light wireless methods in traditional methods. By using a lower-cost visible light imaging module to replace the more expensive infrared sensor, the cost of gas leakage and source tracing is effectively reduced, which is conducive to the widespread application of this gas leakage and source tracing technology. In addition, an angle is also provided. The calibration method first calibrates the intrinsic and extrinsic parameter matrices, then constrains the coordinates of the laser spot in the visible light imaging module coordinate system, and finally calculates the centroid of the spot and adjusts the optical axis of the tunable semiconductor laser absorption spectroscopy detection module. The calibration is completed only after the centroid meets the constraints. This calibration method can reduce the spatial misalignment between TDLAS concentration data and the radiation value at the center point of the visible light imaging module. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the structure of the present invention;

[0051] The dashed boxes represent optional functional modules;

[0052] Figure 2 This is a schematic diagram of the area defined by the light spot in the whiteboard in this invention. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0054] Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0055] Example 1

[0056] This embodiment provides a gas leak detection and rapid source tracing device that tightly integrates visible light imaging and a gas tunable semiconductor laser absorption spectroscopy (TDLAS) module. It designs a TDLAS leak concentration acquisition trajectory and combines spatial perception of visible light images with the hydrodynamic constraints of gas leaks to achieve large-scale leak concentration field estimation and rapid source tracing. Figure 1 As shown, it includes a visible light imaging module, a gas tunable semiconductor laser absorption spectroscopy detection module, a signal synchronous acquisition module, and a data processing unit.

[0057] Among them, the visible light imaging module is used to image the leaked gas scene and provide the background and basic coordinate system for leak location.

[0058] The gas tunable semiconductor laser absorption spectroscopy detection module is used to collect the gas leakage concentration at the leak point in the scene.

[0059] The signal synchronization acquisition module is used to synchronize the data acquisition of the visible light imaging module and the gas tunable semiconductor laser absorption spectroscopy detection module.

[0060] The data processing unit is used to perform gas leakage modeling, concentration field fitting, and projection.

[0061] In addition, a display screen, battery, and motion actuator can be selected as needed. The display screen is used to show the detection and tracing process and results, the battery provides power to the entire device, and the motion actuator controls the imaging and TDLAS detection direction, including horizontal and vertical rotation. The aforementioned display screen, battery, and motion actuator can be directly derived from existing technologies, requiring no innovative effort.

[0062] There is an angle between the optical axis of the visible light imaging module and the optical axis of the gas tunable semiconductor laser absorption spectroscopy detection module. and included angle Satisfying Relationship:

[0063] ;

[0064] angle The solution can be obtained using the following formula:

[0065] ;

[0066] in, This is the upper limit of the included angle. This refers to the distance between the optical center of the visible light imaging module and the optical center of the gas tunable semiconductor laser absorption spectroscopy detection module. This is the nominal working distance. When L=10m and B=0.05m, the included angle is... .

[0067] The included angle It can be calibrated and fixed using standardization methods, eliminating the need for secondary calibration during use. Furthermore, this included angle... The calibration can be performed using existing angle calibration methods or innovative calibration methods (the innovative calibration methods will be described and claimed in another patent filed with this application). In this embodiment, the existing calibration method will suffice.

[0068] Frame rate of visible light imaging module Sampling frequency of the gas tunable semiconductor laser absorption spectroscopy detection module The following conditions must be met:

[0069] ;

[0070] ;

[0071] Should and All are within the nominal working distance and the angular velocity of the device Relevant, specifically:

[0072] ;

[0073] ;

[0074] in, This is the lower limit of the sampling frame rate for visible light images. This is the lower limit of the TDLAS data sampling rate. The angular velocity of the gas leak detection and rapid tracing device; This is an empirical value, taken as 1. For example, when L = 10m and B = 0.05m, When = 10° / s, = =35.

[0075] When installing the visible light imaging module and the gas tunable semiconductor laser absorption spectroscopy detection module, the distance between their optical centers should be as small as possible. In this embodiment, the specific standard for the distance between the two optical centers of the visible light imaging module and the gas tunable semiconductor laser absorption spectroscopy detection module is as follows:

[0076] The distance between the optical center of the visible light imaging module and the optical center of the gas tunable semiconductor laser absorption spectroscopy detection module It should be less than the nominal working distance of the gas tunable semiconductor laser absorption spectroscopy detection module. The radius and distance of the generated light spot The following conditions must be met:

[0077] ;

[0078] in, The width of the laser beam waist, Rayleigh distance for laser; This is an empirical value, taken as 10. For example, for L=10m, =5mm, wavelength is 1um, then .

[0079] The signal synchronization acquisition module has both software and hardware synchronization capabilities. During synchronous data acquisition, the deviation between the time the visible light imaging module acquires the image and the time the gas tunable semiconductor laser absorption spectroscopy detection module acquires the concentration should be controlled within an acceptable range. Inside, and that relative to nominal working distance angular velocity of the device Related, can be expressed as:

[0080] ;

[0081] in, The angular velocity of the gas leak detection and rapid tracing device; This is an empirical value, taken as 1. For example, when L = 10m and B = 0.05m, When = 10° / s, =0.029.

[0082] The data processing unit is composed of ARM or DSP, and its function is to complete scene modeling, concentration field fitting and projection, which is achieved by embedding the algorithm and program described in this application.

[0083] Example 2

[0084] This embodiment provides a calibration method for a gas leak detection and rapid source tracing device, with the included angle... Calibration can be performed using a calibration method, eliminating the need for secondary calibration during use. The calibration process utilizes an additional broadband camera whose spectral range covers the spectral range of TDLAS. For example, when the wavelength range of the laser used by TDLAS is 1.6µm, a short-wave infrared camera can be used for auxiliary calibration.

[0085] This embodiment provides an innovative calibration method. During calibration, the spectral range of the broadband camera needs to cover the spectral range of the gas tunable semiconductor laser absorption spectroscopy detection module. The specific calibration steps are as follows:

[0086] Step S1-1: Fix the broadband camera and visible light imaging module.

[0087] Step S1-2: Calibrate the intrinsic parameters of the broadband camera to the visible light imaging module using a custom target. and extrinsic parameter matrix .

[0088] Steps 1-3, at a distance of 2 from the broadband camera A white plate with good laser reflection for the gas tunable semiconductor laser absorption spectroscopy detection module is placed at a position. Four marker positions are marked on the four corners of the white plate. The plane of the white plate in the coordinate system of the visible light imaging module is calculated based on these four marker positions. The equation of this white plate plane can be expressed as:

[0089] ;

[0090] To simplify the calculation, the position of the whiteboard can be adjusted so that its plane is perpendicular to the optical axis of the visible light imaging module. In this case, the plane equation of the whiteboard is (L=10m):

[0091] .

[0092] Steps 1-4, by At a distance of 2 Below, when the whiteboard plane is perpendicular to the optical axis of the visible light imaging module, the coordinates of the laser spot of the gas tunable semiconductor laser absorption spectroscopy detection module in the coordinate system of the visible light imaging module are ( The following constraints must be met:

[0093] ;

[0094] .

[0095] Based on the information from steps 1-3, when the whiteboard plane is perpendicular to the optical axis of the visible light imaging module, the coordinates (X,Y,20) of the laser spot of the gas tunable semiconductor laser absorption spectroscopy detection module (TDLAS) in the camera coordinate system of the visible light imaging module need to satisfy the following constraints:

[0096] .

[0097] Steps 1-5: Based on the constraints obtained in Step 1-4, and combined with the intrinsic parameters obtained in Step 1-2... and extrinsic parameter matrix The coordinate range of the constraint range projected onto the image plane of the broadband camera is calculated using the following formula:

[0098] ;

[0099] .

[0100] When the two intrinsic parameter matrices are equal, and the rotation matrix R is a labeling element matrix, , When the camera focal length is 25mm and the pixel size is 12um, and the x-axis is the line connecting the optical centers of the broadband camera and the visible light imaging module, the specific constraints are as follows:

[0101]

[0102] That is, its effective imaging range is within a circle with a center (27.13, 0) and a radius of 5.21. The specific effect is as follows: Figure 2 As shown.

[0103] Steps 1-6: Use a broadband camera to image the laser spot of the gas tunable semiconductor laser absorption spectroscopy detection module.

[0104] Steps 1-7: Calculate the centroid of the laser spot and adjust the optical axis of the gas tunable semiconductor laser absorption spectroscopy detection module. When the centroid of the laser spot meets the limitations of steps 1-5, the calibration and adjustment are completed.

[0105] The formula for calculating the centroid of the laser spot is as follows:

[0106] ;

[0107] ;

[0108] in, This represents the value located at coordinates (i, j) in image I. Indicates the image height. Indicates the image width.

Claims

1. A calibration method for a gas leak detection and rapid source tracing device, characterized in that: It includes a gas leak detection and rapid source tracing device and a broadband camera. The gas leak detection and rapid source tracing device includes a visible light imaging module, a gas tunable semiconductor laser absorption spectroscopy detection module, a signal synchronous acquisition module, and a data processing unit. The visible light imaging module is used to image the leaked gas scene, providing the background and basic coordinate system for leak location; The gas tunable semiconductor laser absorption spectroscopy detection module is used to collect the gas leakage concentration at the leakage point in the scene. The signal synchronization acquisition module is used to synchronize the data acquisition of the visible light imaging module and the gas tunable semiconductor laser absorption spectroscopy detection module. The data processing unit is used to perform gas leakage modeling, concentration field fitting, and projection. There is an angle between the optical axis of the visible light imaging module and the optical axis of the gas tunable semiconductor laser absorption spectroscopy detection module. and included angle Satisfying Relationship: ； ； in, The upper limit of the angle, This refers to the distance between the optical center of the visible light imaging module and the optical center of the gas tunable semiconductor laser absorption spectroscopy detection module. This refers to the nominal working distance. The broadband camera's spectral range covers the spectral range of the gas tunable semiconductor laser absorption spectroscopy detection module, and the included angle... The calibration steps are as follows: Step S1-1: Fix the broadband camera and visible light imaging module; Step S1-2: Use a target to calibrate the intrinsic parameters of the broadband camera to the visible light imaging module. and extrinsic parameter matrix ; Steps S1-3: Place a white plate with good laser reflection for the gas tunable semiconductor laser absorption spectroscopy detection module, and calculate the white plate plane in the coordinate system of the visible light imaging module based on the four mark positions marked on the four corners of the white plate. Step S1-4: When the whiteboard plane is perpendicular to the optical axis of the visible light imaging module, the coordinates of the laser spot of the gas tunable semiconductor laser absorption spectroscopy detection module in the coordinate system of the visible light imaging module need to satisfy the constraints. Step S1-5: Based on the constraints obtained in step S1-4, and combined with the intrinsic parameters obtained in step S1-2... and extrinsic parameter matrix Calculate the range of image plane coordinates projected onto the constrained range in the broadband camera; Steps S1-6: Use a broadband camera to image the laser spot of the gas tunable semiconductor laser absorption spectroscopy detection module; Steps S1-7: Calculate the centroid of the laser spot and adjust the optical axis of the gas tunable semiconductor laser absorption spectroscopy detection module. When the centroid of the laser spot meets the limitation of step S1-5, the calibration and adjustment are completed.

2. The calibration method for a gas leak detection and rapid source tracing device as described in claim 1, characterized in that: In steps S1-3, at a distance of 2 from the broadband camera A white board with good laser reflection for the gas tunable semiconductor laser absorption spectroscopy detection module is placed at a position. Four marker positions are marked on the four corners of the white board. The plane of the white board in the coordinate system of the visible light imaging module is calculated based on the four marker positions.

3. The calibration method for a gas leak detection and rapid source tracing device as described in claim 2, characterized in that: In steps S1-4, by At a distance of 2 Below, when the whiteboard plane is perpendicular to the optical axis of the visible light imaging module, the coordinates of the laser spot of the gas tunable semiconductor laser absorption spectroscopy detection module in the coordinate system of the visible light imaging module are ( The following constraints must be met: ； 。 4. The calibration method for a gas leak detection and rapid source tracing device as described in claim 1, characterized in that: In step S1-5, according to the constraints obtained in steps 1-4 and combined with the internal parameters obtained in steps 1-2 and the external parameter matrix , calculate the image plane coordinate range of the constraint range projected onto the wide-spectrum camera. The specific calculation formula is as follows: ； 。 5. The calibration method for a gas leak detection and rapid source tracing device as described in claim 1, characterized in that: In a gas leak detection and rapid source tracing device, the frame rate of the visible light imaging module... Sampling frequency of the gas tunable semiconductor laser absorption spectroscopy detection module The following conditions must be met: ； ； ； ； in, This represents the minimum image frame rate. This represents the minimum TDLAS sampling rate. The angular velocity of the gas leak detection and rapid tracing device; This is an empirical value, set to 1.

6. The calibration method for a gas leak detection and rapid source tracing device as described in claim 1, characterized in that: In a gas leak detection and rapid tracing device, when installing a visible light imaging module and a gas tunable semiconductor laser absorption spectroscopy detection module, the distance between the optical center of the visible light imaging module and the optical center of the gas tunable semiconductor laser absorption spectroscopy detection module is... The following conditions must be met: ； in, The width of the laser beam waist, Rayleigh distance for laser; This is an empirical value, set to 10.

7. The calibration method for a gas leak detection and rapid source tracing device as described in claim 1, characterized in that: In a gas leak detection and rapid tracing device, during synchronous data acquisition, the deviation between the time the visible light imaging module acquires the image and the time the gas tunable semiconductor laser absorption spectroscopy detection module acquires the concentration is controlled within a certain range. Inside, and that Represented as: ； in, The angular velocity of the gas leak detection and rapid tracing device; This is an empirical value, set to 1.

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