Calibration Method for an Infrared Imaging Concentration Inversion Device for Gas Leakage

Abstract

The present invention discloses a calibration method for a gas leakage infrared imaging concentration inversion device, which relates to the calibration of the included angle between the optical axes of a spectrometer and an imager in the gas leakage infrared imaging concentration inversion device. This calibration method first calibrates the internal and external parameter matrices, then obtains the spatial coordinates of the optical axis intersection point A according to the projection relationship, and then calculates the image plane coordinates of the intersection point A projected onto the wide-spectrum camera based on the internal and external parameter matrices. Next, the optical axis angle is adjusted and the centroid of the projected light spot is calculated, and whether the centroid coincides with the pixel plane coordinates is used as the standard for completing the calibration.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas detection, and relates to the detection and inversion of gas leakage. In particular, it relates to a calibration method for a gas leakage infrared imaging concentration inversion device, that is, calibrating the angle between the optical axis of the spectral detector and the optical axis of the gas infrared imager in the inversion device. Background Art

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

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

[0004] The invention patent application with the 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 on the area to be monitored to discover methane gas leakage points; the laser methane detection module is aligned according to the leakage points found 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 direction of the infrared thermal imager, and the two communicate with each other to achieve data interaction. Through the infrared thermal imager, a large-area window can be detected to judge whether there is natural gas leakage in the window. Through the laser methane detection module, a long-distance non-contact measurement of the methane leakage point is carried out and accurate methane gas concentration information is obtained. By combining the methane gas leakage detection infrared thermal imaging technology with the laser methane detection technology, non-contact large-area rapid search for methane leakage points and quantitative detection of methane gas concentration are achieved simultaneously, realizing a more efficient and precise quantitative comprehensive detection than existing single detection devices.

[0005] In the above-mentioned invention patent application of the infrared imaging and concentration detection device and method, although it realizes the quantitative detection of the methane leakage point and the methane gas concentration, it only realizes the concentration measurement at a single point and does not realize the comprehensive large-scale concentration measurement within the scene. At the same time, since 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, this will also cause a large deviation between the observation point of the laser methane detection module and the center point of the infrared image within the effective distance, and the radiation value detected at the image center is not aligned with the concentration value detected by TDLAS. Therefore, it is necessary to provide a detection device in which the optical axis of the spectral detector forms an angle with the optical axis of the gas infrared imager, and a method for calibrating this angle. Summary of the Invention

[0006] The purpose of the present invention is to provide a calibration method for a gas leakage infrared imaging concentration inversion device, which is used to calibrate the angle between the optical axis of the spectral detector and the optical axis of the gas infrared imager.

[0007] In order to achieve the above purpose, the present invention specifically adopts the following technical solutions:

[0008] A calibration method for a gas leakage infrared imaging concentration inversion device includes a gas leakage infrared imaging concentration inversion device and a wide-spectrum camera. The gas leakage infrared imaging concentration inversion device includes a gas leakage infrared imager, a gas tunable diode laser absorption spectrometer, and a core operation unit; the spectral range of the wide-spectrum camera covers the spectral range of the gas tunable diode laser absorption spectrometer;

[0009] The gas leakage infrared imager is used to image the leaked gas to obtain the radiation distribution within the scene;

[0010] The gas tunable diode laser absorption spectrometer is used to collect the gas leakage concentration at the leakage point within the scene;

[0011] The core operation unit is used to perform inversion calculations based on the radiation distribution and gas leakage concentration within the scene;

[0012] There is an angle between the optical axis of the gas tunable diode laser absorption spectrometer and the optical axis of the gas leakage infrared imager , and the angle is not equal to 0;

[0013] The calibration steps for the angle are as follows:

[0014] Step S1-1, use a target to calibrate the internal parameters , and the external parameter matrix of the wide-spectrum camera to the gas leakage infrared imager;

[0015] Step S1-2, according to the farthest observation distance and the central coordinates of the gas leakage infrared imager , use the projection relationship to obtain the spatial coordinates of the intersection point A of the optical axes of the gas tunable semiconductor laser absorption spectrometer and the gas leakage infrared imager;

[0016] Step S1-3, according to the internal parameters , and the external parameter matrix , calculate the pixel plane coordinates of the intersection point A projected onto the wide-spectrum camera;

[0017] Step S1-4, according to the pixel plane coordinates, adjust the optical axis of the gas tunable semiconductor laser absorption spectrometer so that the wide-spectrum camera images the projection spot of the gas tunable semiconductor laser absorption spectrometer;

[0018] Step S1-5, calculate the centroid of the projection spot. When the centroid coincides with the calculated pixel plane coordinates, the calibration is completed.

[0019] Further, in step S1-2, use the projection relationship to obtain the spatial coordinates of the intersection point A of the optical axes of the gas tunable semiconductor laser absorption spectrometer and the gas leakage infrared imager; this projection relationship is:

[0020]

[0021] Among them, ( , , ) represents the spatial coordinates of the intersection point A, and ( , ) represents the central coordinates of the gas leakage infrared imager.

[0022] Further, in step S1-3, calculate the pixel plane coordinates of the intersection point A projected onto the wide-spectrum camera. The projection relationship is:

[0023]

[0024] Among them, represents the internal parameter, represents the external parameter matrix, ( , , ) represents the spatial coordinates of the intersection point A, and ( , , 1) represents the pixel plane coordinates after calculating the projection of the intersection point A.

[0025] Further, the calculation formula for the included angle is:

[0026]

[0027] Among them, is the distance between the optical center of the gas leakage infrared imager and the optical center of the gas tunable semiconductor laser absorption spectroscopy detector, which is the nominal observation distance.

[0028] Furthermore, the distance between the optical center of the gas leakage infrared imager and the optical center of the gas tunable semiconductor laser absorption spectroscopy detector is less than the radius of the light spot generated by the gas tunable semiconductor laser absorption spectroscopy detector at the nominal observation distance L.

[0029] Furthermore, the calculation formula for the radius of the light spot is:

[0030]

[0031] Among them, represents the laser beam waist width, represents the nominal observation distance under nominal working conditions, represents the laser Rayleigh distance.

[0032] The beneficial effects of the present invention are as follows:

[0033] 1. In the present invention, in the parallel optical axis type, the distance between the point corresponding to the image center and the TDLAS measurement point is D; however, in this application, the optical axis direction of the gas tunable semiconductor laser absorption spectroscopy detector is not consistent with the optical axis direction of the gas leakage infrared imager, and there is an included angle between the two optical axis directions; After introducing the included angle , the distance between the two (the distance between the point corresponding to the image center and the TDLAS measurement point) is d. Compared with the previous distance D, the distance d is greatly reduced, that is, the deviation between the observation point of the laser methane detection module and the infrared image center point within the effective distance is reduced, and the misalignment between the amplitude value corresponding to the image center and the TDLAS detection concentration is reduced, which is more suitable for realizing large-scene concentration measurement. In addition, a calibration method for the included angle

[0034] 2. In the present invention, the inversion device is further provided with a core operation unit. The core operation unit can perform inversion calculations based on the radiation distribution and gas leakage concentration within the scene, and finally obtain the concentration distribution throughout the scene, thereby being able to more intuitively display the distribution of the gas leakage concentration within the scene. Description of the Drawings

[0035] Figure 1 is a schematic flowchart of the calibration method in the present invention

[0036] Figure 2 is a schematic diagram of the inversion device in the present invention;

[0037] Figure 3 is a schematic diagram of the optical axis orientation of the gas leakage infrared imager and the gas tunable diode laser absorption spectrometer in the present invention. Detailed Embodiments

[0038] To make the objectives, 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 accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention.

[0039] Therefore, based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention.

[0040] Embodiment 1

[0041] This embodiment provides a calibration method for a gas leakage infrared imaging concentration inversion device, including a gas leakage infrared imaging concentration inversion device and a wide-spectrum camera. As Figure 2 shown, the gas leakage infrared imaging concentration inversion device includes a gas leakage infrared imager, a gas tunable diode laser absorption spectrometer, and a core operation unit; the spectral range of the wide-spectrum camera covers the spectral range of the gas tunable diode laser absorption spectrometer.

[0042] The gas leakage infrared imager is used to image the leaked gas to obtain the radiation distribution within the scene. The gas leakage infrared imager utilizes the absorption characteristics of the gas for the infrared spectrum, and it mainly consists of an optical filter and an infrared camera. The infrared camera includes a lens, an infrared focal plane detector, and a backend acquisition and processing circuit. The optical filter is adjusted according to the absorption peak of the detected gas.

[0043] The gas tunable semiconductor laser absorption spectroscopy detector is used to collect the gas leakage concentration at the leakage point in the scene. It consists of two parts: laser modulation emission and laser reception. The laser emission and acquisition link also has the ability of spectral selection, which is determined by the spectral passband and the absorption peak of the gas to be detected; for the gas to be detected, it is required that the absorption peak characteristics meet those of the infrared imager.

[0044] The core operation unit is used to perform inversion calculations based on the radiation distribution and gas leakage concentration in the scene. The core operation unit is composed of ARM or DSP, and mainly completes the concentration inversion algorithm.

[0045] There is an included angle between the optical axis of the gas tunable semiconductor laser absorption spectroscopy detector and the optical axis of the gas leakage infrared imager , and the included angle is not equal to 0. As Figure 3 shown, the gas leakage infrared imager and the gas tunable semiconductor laser absorption spectroscopy detector intersect at the nominal distance. Therefore, within the effective distance, the deviation d between the observation point of the gas tunable semiconductor laser absorption spectroscopy detector and the center point of the gas leakage infrared imager is less than the deviation D of the optical axis parallel type.

[0046] Among them, the calculation formula for the included angle is:

[0047]

[0048] Among them, is the distance between the optical center of the gas leakage infrared imager and the optical center of the gas tunable semiconductor laser absorption spectroscopy detector, is the nominal observation distance. When L = 10m and B = 0.05m, the included angle = 0.29°. The included angle can be calibrated and fixed by the calibration method, and no secondary calibration is required during use; an additional wide-spectrum camera is used in the calibration process, and the spectral range of the wide-spectrum camera covers the spectral range of the gas tunable semiconductor laser absorption spectroscopy detector; for example, when the wavelength range of the laser used by the gas tunable semiconductor laser absorption spectroscopy detector is 1.6um, a short-wave infrared camera can be used for auxiliary calibration. For the specific calibration method, reference can be made to another patent application for the calibration method submitted on the same day as this application.

[0049] During installation, it is required that the optical centers of the gas leakage infrared imager and the gas tunable diode laser absorption spectrometer be as close as possible. The specific standard is that the distance between the optical centers of the gas leakage infrared imager and the gas tunable diode laser absorption spectrometer is less than the radius of the light spot generated by the gas tunable diode laser absorption spectrometer at the nominal observation distance L. Among them, the calculation formula for the radius of the light spot is:

[0050]

[0051] Among them, represents the laser beam waist width, represents the nominal observation distance under nominal working conditions, represents the laser Rayleigh distance.

[0052] included angle Use an innovative method for calibration and fixation, so that secondary calibration is not required during use. As Figure 1 shown, the specific calibration steps are:

[0053] Step S1-1, use a target to calibrate the internal parameters , and the external parameter matrix ;

[0054] Step S1-2, according to the farthest observation distance and the central coordinates of the gas leakage infrared imager, use the projection relationship to obtain the spatial coordinates of the intersection point A of the optical axes of the gas tunable diode laser absorption spectrometer and the gas leakage infrared imager;

[0055] Step S1-3, according to the internal parameters , and the external parameter matrix , calculate the pixel plane coordinates of the intersection point A projected onto the wide-spectrum camera; The projection relationship here is expressed as:

[0056] ;

[0057] Step S1-4, according to the pixel plane coordinates , adjust the optical axis of the gas tunable diode laser absorption spectrometer so that the wide-spectrum camera images the projection light spot of the gas tunable diode laser absorption spectrometer;

[0058] Step S1-5, calculate the centroid of the projection light spot. When the centroid and the calculated pixel plane coordinates If they coincide, the calibration is completed.

[0059] Embodiment 2

[0060] Since the existing detection device does not further utilize the correlation model between gas radiation and concentration in infrared gas imaging. Therefore, based on Embodiment 1, a signal synchronization circuit is newly provided in this embodiment. The signal synchronization circuit is used to control the gas leakage infrared imager and the gas tunable diode laser absorption spectrometer to synchronously collect data.

[0061] The signal synchronization circuit has software synchronous acquisition and / or hardware synchronous acquisition functions; where:

[0062] Software synchronous acquisition is used to automatically match the timestamps when the gas leakage infrared imager collects data with the timestamps when the gas tunable diode laser absorption spectrometer collects signals. According to the speed of the two signal acquisition cycles, the matching relationships are many-to-one, one-to-one, and one-to-many respectively; for example, when the acquisition frame rate of the gas tunable diode laser absorption spectrometer is 50 times per second and the gas leakage infrared imager is 25 frames / s, then each frame of image corresponds to 2 concentration acquisitions.

[0063] Hardware synchronous acquisition is used to trigger the gas leakage infrared imager and the gas tunable diode laser absorption spectrometer to perform synchronous acquisition using a synchronous hardware clock. By using the synchronous hardware clock to trigger the acquisitions of the gas leakage infrared imager and the gas tunable diode laser absorption spectrometer, synchronous acquisition of the two signal sources is achieved; of course, the external trigger clock of the infrared focal plane of the gas leakage infrared imager and the sampling clock of the gas tunable diode laser absorption spectrometer can also be used to achieve the function of this synchronous acquisition.

Claims

1. A calibration method for a gas leakage infrared imaging concentration inversion device, characterized in that: It includes a gas leakage infrared imaging concentration inversion device and a wide-spectrum camera. The gas leakage infrared imaging concentration inversion device includes a gas leakage infrared imager, a gas tunable semiconductor laser absorption spectroscopy detector, and a core operation unit. The spectral range of the wide-spectrum camera covers the spectral range of the gas tunable semiconductor laser absorption spectroscopy detector. The gas leakage infrared imager is used to image the leaked gas to obtain the radiation distribution within the scene. The gas tunable semiconductor laser absorption spectroscopy detector is used to collect the gas leakage concentration at the leakage point within the scene. The core operation unit is used to perform inversion calculations based on the radiation distribution and gas leakage concentration within the scene. There is an angle between the optical axis of the gas tunable semiconductor laser absorption spectroscopy detector and the optical axis of the gas leakage infrared imager , and the angle is not equal to 0; The distance between the optical center of the gas leakage infrared imager and the optical center of the gas tunable semiconductor laser absorption spectroscopy detector is less than the radius of the light spot generated by the gas tunable semiconductor laser absorption spectroscopy detector at the nominal observation distance L. Included angle The calibration steps are as follows: Step S1-1, use a target to calibrate the internal parameters of the wide-spectrum camera to the gas leakage infrared imager , and the external parameter matrix ; Step S1-2, according to the farthest observation distance and the central coordinates of the gas leakage infrared imager , use the projection relationship to obtain the spatial coordinates of the intersection point A of the optical axes of the gas tunable semiconductor laser absorption spectrometer and the gas leakage infrared imager; Step S1-3, according to the internal reference , and the external reference matrix , calculate the pixel plane coordinates of the intersection point A projected onto the wide-spectrum camera; In step S1-4, according to the pixel plane coordinates, adjust the optical axis of the gas tunable semiconductor laser absorption spectroscopy detector so that the wide-spectrum camera images the projected light spot of the gas tunable semiconductor laser absorption spectroscopy detector. In step S1-5, calculate the centroid of the projected light spot. When the centroid coincides with the calculated pixel plane coordinates, the calibration is completed.

2. The calibration method of a gas leakage infrared imaging concentration inversion device according to claim 1, characterized in that: In step S1-2, use the projection relationship to obtain the spatial coordinates of the intersection point A of the optical axes of the gas tunable semiconductor laser absorption spectroscopy detector and the gas leakage infrared imager. This projection relationship is: Among them, ( , , ) represents the spatial coordinates of intersection point A, and ( , ) represents the center coordinates of the gas leakage infrared imager.

3. The calibration method of a gas leakage infrared imaging concentration inversion device according to claim 1, characterized in that: In step S1-3, calculate the pixel plane coordinates of the intersection point A projected onto the wide-spectrum camera. The projection relationship is: Among them, represents the internal parameter, represents the external parameter matrix, ([[]] , , ) represents the spatial coordinates of intersection point A, ([[]] , , 1) represents the pixel plane coordinates after calculating the projection of intersection point A.

4. The calibration method of a gas leakage infrared imaging concentration inversion device according to claim 1, characterized in that: included angle The calculation formula is as follows: wherein, is the distance between the optical center of the gas leakage infrared imager and the optical center of the gas tunable diode laser absorption spectroscopy detector, is the nominal observation distance.

5. The calibration method of a gas leakage infrared imaging concentration inversion device according to claim 1, characterized in that: The calculation formula for the radius of the light spot is: Among them, represents the laser beam waist width, represents the nominal observation distance under nominal operating conditions, represents the laser Rayleigh range.

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