Calibration method of gas leakage detection and rapid traceability device

Abstract

The invention discloses a calibration method of a gas leakage detection and rapid traceability device, which belongs to calibration of an included angle between optical axes of a visible light imaging module and a spectrum detection module in the gas leakage detection and traceability device, and comprises the gas leakage detection and rapid traceability device. The calibration method comprises the following steps: firstly calibrating an internal reference matrix and an external reference matrix, then constraining the coordinate of a laser spot in a coordinate system of the visible light imaging module, finally calculating the mass center of the spot, adjusting the optical axis of the tunable semiconductor laser absorption spectrum detection module, and completing adjustment and calibration after the mass center accords with the limitation. By using the calibration method, the spatial misalignment of the concentration data of the gas tunable semiconductor laser absorption spectrum detection module and the radiation value of the central point of the visible light imaging module can be reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of gas detection, relates to the detection and tracing of gas leakage, and in particular to a calibration method for a gas leakage detection and rapid tracing device. Background Art

[0002] Gas leak detection technology has extensive and important applications in the fields of air pollution control, petrochemicals, industrial process monitoring, etc. For example, in the petrochemical industry, there are a large number of methane gas storage or transportation equipment with complex structures. Effective monitoring of the leakage of these equipment is an important prerequisite for ensuring safe production.

[0003] For gas leaks, contact leak detection equipment is currently widely used. The sensor of the equipment needs to come into contact with the target gas to detect leaks. However, some leaks may be leaking, but most potential leaks have not yet leaked. Therefore, operators must personally check and detect each potential leak, which is inefficient and poses a hazard to the health and safety of inspectors. In addition, traditional gas leak detection technology can only achieve single-point concentration measurement, while the gas leak infrared imaging technology developed for methane gas leak detection uses an infrared focal plane detector to image the leaking gas. It has the advantages of large-scale monitoring and rapid tracing, but it cannot achieve quantitative measurement of the leak concentration and cannot provide accurate situation analysis for subsequent accident assessment and remedial disposal.

[0004] The invention patent application with application number 202010443190X discloses an infrared imaging and concentration detection device and method for methane gas leakage. The device includes an infrared thermal imager and a laser methane detection module. The infrared thermal imager is used to perform infrared imaging of the required monitoring area to find the methane gas leakage point; the laser methane detection module is aligned according to the leakage point found by 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 direction of the infrared thermal imager, and the two communicate with each other to realize data interaction. The infrared thermal imager can detect a large area of ​​the window to determine whether there is a natural gas leak in the window. The laser methane detection module can perform long-distance non-contact measurement of the methane leakage point and obtain accurate methane gas concentration information. The infrared thermal imaging technology for methane gas leakage detection is combined with the laser methane detection technology, and non-contact large-area rapid search for methane leakage points and quantitative detection of methane gas concentration are realized at the same time, realizing more efficient and accurate quantitative comprehensive detection than the existing single detection device.

[0005] In the above-mentioned invention patent application of infrared imaging and concentration detection device and method, although it realizes the quantitative detection of methane leakage point and methane gas concentration. However, firstly, like the traditional gas leakage detection technology, it can only realize single-point concentration measurement, and cannot obtain the step-by-step concentration field; secondly, traditional gas leakage tracing mostly uses infrared sensors for gas imaging, but the price of infrared sensors is relatively high, which is not conducive to promotion and application; thirdly, the existing visible light images only provide on-site evidence collection functions, and do not have the ability to quickly trace the source. Therefore, in order to reduce costs and promote application, how to use visible light imaging for gas leakage tracing and realize rapid tracing of gas leakage is particularly important. It is necessary to provide a gas leakage detection and rapid tracing device and method based on visible light imaging, and provide a method for calibrating the optical axis angle in the tracing device. Summary of the invention

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

[0007] In order to achieve the above-mentioned purpose, the present invention specifically adopts the following technical solutions: A calibration method for a gas leakage detection and rapid source tracing device, comprising a gas leakage detection and rapid source tracing device and a wide spectrum camera, wherein the gas leakage detection and rapid source tracing device comprises a visible light imaging module, a gas tunable semiconductor laser absorption spectrum detection module, a signal synchronization acquisition module and a data processing unit; The visible light imaging module is used to image the leaking gas scene and provide the background and basic coordinate system for leak positioning; The gas tunable semiconductor laser absorption spectrum 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 spectrum detection module; The data processing unit is used to realize 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 spectrum detection module , and the angle Satisfaction relationship: ; ; in, is the upper limit of the angle, is the distance between the optical center of the visible light imaging module and the optical center of the gas tunable semiconductor laser absorption spectrum detection module, is the nominal working distance; The spectral range of the wide spectrum camera covers the spectral range of the gas tunable semiconductor laser absorption spectrum detection module, and the angle The calibration steps are: Step S1-1, fixing the wide spectrum camera and the visible light imaging module; Step S1-2, using the target to calibrate the internal reference of the wide spectrum camera to the visible light imaging module and the external parameter matrix ; Step 1-3, placing a white board that reflects the laser of the gas tunable semiconductor laser absorption spectrum detection module well, and calculating the plane of the white board in the coordinate system of the visible light imaging module according to the positions of the four marks on the four corners of the white board; Step 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 spectrum detection module in the coordinate system of the visible light imaging module need to satisfy the following constraints: Step 1-5, based on the constraints obtained in step 1-4, combined with the internal parameters obtained in step 1-2 and the external parameter matrix , calculate the image plane coordinate range projected onto the wide spectrum camera by the constraint range: Step 1-6, using a wide spectrum camera to image the laser spot of the gas tunable semiconductor laser absorption spectrum detection module; Step 1-7, calculate the centroid of the laser spot, adjust the optical axis of the gas tunable semiconductor laser absorption spectrum detection module, and when the centroid of the laser spot meets the restrictions of step 1-5, the adjustment and calibration are completed.

[0008] Further, in step 1-3, at a distance from the wide spectrum camera 2 A white board with good laser reflection for the gas tunable semiconductor laser absorption spectrum detection module is placed at the position, and four marking 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 according to the four marking positions.

[0009] Further, in steps 1-4, Get at distance 2 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 spectrum detection module in the coordinate system of the visible light imaging module are ( ) needs to satisfy the following constraints: ; .

[0010] Furthermore, in step 1-5, according to the constraints obtained in step 1-4, combined with the internal parameters obtained in step 1-2 and the external parameter matrix , calculate the image plane coordinate range projected onto the wide spectrum camera by the constraint range. The specific calculation formula is: ; .

[0011] Furthermore, in step 1-7, when calculating the centroid of the laser spot, the calculation formula is: ; ; in, represents the value at coordinate (i, j) in image I, Indicates the image height, Indicates the image width.

[0012] Furthermore, in the gas leak detection and rapid source tracing device, the frame rate of the visible light imaging module and the sampling frequency of the gas tunable semiconductor laser absorption spectroscopy detection module The following conditions are met: ; ; ; ; in, is the lower limit of the visible light image sampling frame rate, is the lower limit of TDLAS data sampling rate, The moving angular velocity of the gas leak detection and rapid source tracing device; It is an experience value, take 1.

[0013] Furthermore, in the gas leak detection and rapid source tracing device, when the visible light imaging module and the gas tunable semiconductor laser absorption spectrum detection module are installed, the distance between the optical center of the visible light imaging module and the optical center of the gas tunable semiconductor laser absorption spectrum detection module is The following conditions are met: ; in, is the laser beam waist width, is the laser Rayleigh distance; It is the experience value, take 10.

[0014] Furthermore, in the gas leak detection and rapid source tracing device, when the signal synchronization acquisition module is synchronously acquiring data, the deviation between the time when the visible light imaging module acquires the image and the time when the gas tunable semiconductor laser absorption spectrum detection module acquires the concentration is controlled within the range within, and the It is expressed as: ; in, The moving angular velocity of the gas leak detection and rapid source tracing device; It is an experience value, take 1.

[0015] The beneficial effects of the present invention are as follows: In the present invention, the gas leakage concentration field model established in the tracing device is subject to spatial physical constraints and fluid mechanics physical constraints, and its spatial distribution has certain rules. Through scene understanding and fluid mechanics models, mathematical models such as Gaussian feathering models can be used to simplify the spatial distribution of gas concentration; by combining the concentration values ​​of multiple spatial positions collected by the tunable semiconductor laser absorption spectrum detection module, the spatial distribution of gas concentration is fitted, and the spatial distribution is projected into the visible light image coordinate system to achieve rapid positioning of the gas leakage source with high positioning accuracy, thereby achieving the rapid tracing capability of gas leakage that cannot be achieved by visible light wireless in traditional methods, and using lower-cost visible light imaging modules to replace higher-cost infrared sensors, effectively reducing the cost of gas leakage and tracing, which is conducive to the large-scale promotion and application of the gas leakage and tracing technology. In addition, an angle is also provided. A calibration method is proposed, which first calibrates the internal and external parameter matrices and then constrains the coordinates of the laser spot in the visible light imaging module coordinate system, and finally calculates the center of mass of the spot and adjusts the optical axis of the tunable semiconductor laser absorption spectrum detection module. The adjustment and calibration are completed only after the center of mass meets the constraints; the calibration method can reduce the spatial misalignment of TDLAS concentration data and the radiation value of the center point of the visible light imaging module. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the structure of the present invention; The dotted boxes are optional functional modules; Figure 2 It is a schematic diagram of the light spot limiting area in the calibration whiteboard in the present invention. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0018] Therefore, based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0019] Example 1 This embodiment provides a gas leak detection and rapid source tracing device, which tightly integrates visible light imaging and gas tunable semiconductor laser absorption spectroscopy detection module (ie, TDLAS), designs TDLAS leakage concentration collection trajectory, and combines the spatial perception of visible light images with the fluid mechanics constraints of gas leakage to achieve large-scale leakage concentration field estimation and rapid source tracing. Figure 1 As shown, it includes a visible light imaging module, a gas tunable semiconductor laser absorption spectrum detection module, a signal synchronization acquisition module and a data processing unit.

[0020] Among them, the visible light imaging module is used to image the leaking gas scene and provide the background and basic coordinate system for leak positioning.

[0021] The gas tunable semiconductor laser absorption spectroscopy detection module is used to collect the gas leakage concentration at the leakage point in the scene.

[0022] The signal synchronization acquisition module is used for synchronizing the data acquisition of the visible light imaging module and the gas tunable semiconductor laser absorption spectrum detection module.

[0023] The data processing unit is used to realize gas leakage model building, concentration field fitting and projection.

[0024] In addition, a display screen, a battery, and a motion actuator can be selected as needed. The display screen is used to display the process and results of detection and tracing, the battery is used to provide power to the entire device, and the motion actuator is used to control the imaging and detection direction of TDLAS, including horizontal rotation and vertical rotation. The above-mentioned display screen, battery, and motion actuator can directly adopt existing technologies without creative work.

[0025] 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 spectrum detection module , and the angle Satisfaction relationship: ; angle It can be solved by the following formula: ; in, is the upper limit of the angle, is the distance between the optical center of the visible light imaging module and the optical center of the gas tunable semiconductor laser absorption spectrum detection module, is the nominal working distance. When L=10m, B=0.05m, the angle .

[0026] The angle The calibration method can be used for calibration and fixing, and no secondary calibration is required during use. The calibration can be performed by using an existing angle calibration method or an innovative calibration method (the innovative calibration method will be recorded and protected in another patent filed together with this application). In this embodiment, the existing calibration method can be used.

[0027] Frame rate of visible light imaging module and the sampling frequency of the gas tunable semiconductor laser absorption spectroscopy detection module The following conditions are met: ; ; Should and Both with nominal working distance and the angular velocity of the device Related, specifically: ; ; in, is the lower limit of the visible light image sampling frame rate, is the lower limit of TDLAS data sampling rate, The moving angular velocity of the gas leak detection and rapid source tracing device; It is an empirical value, and is taken as 1. For example, when L=10m, B=0.05m, =10° / s, = =35.

[0028] When installing the visible light imaging module and the gas tunable semiconductor laser absorption spectrum detection module, the distance between the optical centers of the two is required to be as small as possible. In this embodiment, the specific standard for the distance between the optical centers of the visible light imaging module and the gas tunable semiconductor laser absorption spectrum detection module is: The distance between the optical center of the visible light imaging module and the optical center of the gas tunable semiconductor laser absorption spectrum detection module Should be less than the nominal working distance of the gas tunable semiconductor laser absorption spectrum detection module The radius of the light spot generated, the distance The following conditions should be met: ; in, is the laser beam waist width, is the laser Rayleigh distance; is an empirical value, take 10. For example, for L=10m, =5mm, wavelength is 1um, then .

[0029] The signal synchronization acquisition module has software synchronization and hardware synchronization acquisition functions. When the signal synchronization acquisition module is used to synchronize data acquisition, the deviation between the time when the visible light imaging module collects images and the time when the gas tunable semiconductor laser absorption spectrum detection module collects concentrations should be controlled within an acceptable range. within, and the Nominal working distance , the angular velocity of the device It can be expressed as: ; in, The moving angular velocity of the gas leak detection and rapid source tracing device; It is an empirical value, and is taken as 1. For example, when L=10m, B=0.05m, =10° / s, =0.029.

[0030] The data processing unit is composed of ARM or DSP, and the function of the data processing unit is to complete scene modeling, concentration field fitting and projection, which is achieved by implanting the algorithm and program described in this application.

[0031] Example 2 This embodiment provides a calibration method for a gas leakage detection and rapid source tracing device, wherein the angle The calibration method can be used for calibration and fixation, and no secondary calibration is required during use; the calibration process uses an additional wide-spectrum camera, the spectral range of which covers the spectral range of TDLAS; for example, when the wavelength range of the laser used by TDLAS is 1.6um, a short-wave infrared camera can be used for auxiliary calibration.

[0032] This embodiment provides an innovative calibration method. During calibration, the spectral range of the wide spectrum camera needs to cover the spectral range of the gas tunable semiconductor laser absorption spectrum detection module. The specific calibration steps are as follows: Step S1-1, fixing the wide spectrum camera and the visible light imaging module.

[0033] Step S1-2, use the customized target to calibrate the internal reference of the wide spectrum camera to the visible light imaging module and the external parameter matrix .

[0034] Steps 1-3, at a distance from the wide spectrum camera 2 A white board with good laser reflection for the gas tunable semiconductor laser absorption spectrum detection module is placed at the position, and four marking positions are marked on the four corners of the white board. The white board plane in the coordinate system of the visible light imaging module is calculated according to the four marking positions. The equation of the white board plane can be expressed as: ; In order to simplify the calculation, the position of the whiteboard can be adjusted so that the plane of the whiteboard is perpendicular to the optical axis of the visible light imaging module. At this time, the plane equation of the whiteboard is (L=10m): .

[0035] Steps 1-4 are Get at distance 2 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 spectrum detection module in the coordinate system of the visible light imaging module are ( ) needs to satisfy the following constraints: ; .

[0036] Combined with the information in 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 (ie, TDLAS) in the visible light imaging module camera coordinate system need to meet the following constraints: .

[0037] Step 1-5, based on the constraints obtained in step 1-4, combined with the internal parameters obtained in step 1-2 and the external parameter matrix , calculate the image plane coordinate range projected onto the wide spectrum camera by the constraint range. The specific calculation formula is: ; .

[0038] When the two intrinsic parameter matrices are equal and the rotation matrix R is a standard unit matrix, , ,When the camera focal length is 25mm, the pixel size is 12um, and the x-axis direction is the optical center line of the wide spectrum camera and the visible light imaging module, the specific constraints are:

[0039] That is, its effective imaging range is within a circle with a center of (27.13, 0) and a radius of 5.21. The specific effect is as follows Figure 2 shown.

[0040] Step 1-6, using a wide spectrum camera to image the laser spot of the gas tunable semiconductor laser absorption spectrum detection module.

[0041] Step 1-7, calculate the centroid of the laser spot, adjust the optical axis of the gas tunable semiconductor laser absorption spectrum detection module, and when the centroid of the laser spot meets the restrictions of step 1-5, the adjustment and calibration are completed.

[0042] When calculating the centroid of the laser spot, the calculation formula is: ; ; in, represents the value at coordinate (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 leakage detection and rapid source tracing device and a wide spectrum camera. The gas leakage detection and rapid source tracing device includes a visible light imaging module, a gas tunable semiconductor laser absorption spectrum detection module, a signal synchronization acquisition module and a data processing unit; The visible light imaging module is used to image the leaking gas scene and provide the background and basic coordinate system for leak positioning; The gas tunable semiconductor laser absorption spectrum 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 spectrum detection module; The data processing unit is used to realize 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 spectrum detection module , and the angle Satisfaction relationship: ； ； in, is the upper limit of the angle, is the distance between the optical center of the visible light imaging module and the optical center of the gas tunable semiconductor laser absorption spectrum detection module, is the nominal working distance; The spectral range of the wide spectrum camera covers the spectral range of the gas tunable semiconductor laser absorption spectrum detection module, and the angle The calibration steps are: Step S1-1, fixing the wide spectrum camera and the visible light imaging module; Step S1-2, using the target to calibrate the internal reference of the wide spectrum camera to the visible light imaging module and the external parameter matrix ; Step 1-3, placing a white board that reflects the laser of the gas tunable semiconductor laser absorption spectrum detection module well, and calculating the plane of the white board in the coordinate system of the visible light imaging module according to the positions of the four marks on the four corners of the white board; Step 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 spectrum detection module in the coordinate system of the visible light imaging module need to satisfy the following constraints: Step 1-5, based on the constraints obtained in step 1-4, combined with the internal parameters obtained in step 1-2 and the external parameter matrix , calculate the image plane coordinate range projected onto the wide spectrum camera by the constraint range: Step 1-6, using a wide spectrum camera to image the laser spot of the gas tunable semiconductor laser absorption spectrum detection module; Step 1-7, calculate the centroid of the laser spot, adjust the optical axis of the gas tunable semiconductor laser absorption spectrum detection module, and when the centroid of the laser spot meets the restrictions of step 1-5, the adjustment and calibration are completed.

2. The calibration method of a gas leak detection and rapid source tracing device according to claim 1, characterized in that: In step 1-3, at a distance from the wide spectrum camera 2 A white board with good laser reflection for the gas tunable semiconductor laser absorption spectrum detection module is placed at the position, and four marking 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 according to the four marking positions.

3. A calibration method for a gas leak detection and rapid source tracing device as claimed in claim 2, characterized in that: In steps 1-4, Get at distance 2 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 spectrum detection module in the coordinate system of the visible light imaging module are ( ) needs to satisfy the following constraints: ； 。 4. The calibration method of a gas leakage detection and rapid source tracing device according to claim 1, characterized in that: In step 1-5, based on the constraints obtained in step 1-4, combined with the internal parameters obtained in step 1-2 and the external parameter matrix , calculate the image plane coordinate range projected onto the wide spectrum camera by the constraint range. The specific calculation formula is: ； 。 5. The calibration method of a gas leakage detection and rapid source tracing device according to claim 1, characterized in that: In step 1-7, when calculating the centroid of the laser spot, the calculation formula is: ； ； in, represents the value at coordinate (i, j) in image I, Indicates the image height, Indicates the image width.

6. The calibration method of a gas leakage detection and rapid source tracing device according to claim 1, characterized in that: Frame rate of visible light imaging module in gas leak detection and rapid source tracing device and the sampling frequency of the gas tunable semiconductor laser absorption spectroscopy detection module The following conditions are met: ； ； ； ； in, is the minimum image frame rate, is the minimum TDLAS sampling rate, The moving angular velocity of the gas leak detection and rapid source tracing device; It is an experience value, take 1.

7. The calibration method of a gas leakage detection and rapid source tracing device according to claim 1, characterized in that: In the gas leak detection and rapid source tracing device, when installing the visible light imaging module and the gas tunable semiconductor laser absorption spectrum 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 spectrum detection module The following conditions are met: ； in, is the laser beam waist width, is the laser Rayleigh distance; It is the experience value, take 10.

8. The calibration method of a gas leakage detection and rapid source tracing device according to claim 1, characterized in that: In the gas leakage detection and rapid source tracing device, when the signal synchronization acquisition module is synchronously acquiring data, the deviation between the time when the visible light imaging module acquires the image and the time when the gas tunable semiconductor laser absorption spectrum detection module acquires the concentration is controlled within the range within, and the It is expressed as: ； in, The moving angular velocity of the gas leak detection and rapid source tracing device; It is an experience value, take 1.

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