Hydrocarbon gas leakage infrared imaging detection system and detection method

Abstract

The invention discloses a hydrocarbon gas leakage infrared imaging detection system and a detection method. The system comprises a front end and a monitoring terminal. The front end comprises an infrared optical lens, an uncooled IRFPA assembly and a video processing and system control device. The infrared optical lens comprises a medium-wave infrared objective optical lens and a long-wave infrared objective optical lens; the transmittance of the uncooled IRFPA assembly at the infrared band of 6.5-8.5 [mu] m is greater than 90%; the video processing and system control equipment comprises an infrared acquisition module and an infrared image processing module, and the infrared image processing module is configured to acquire an image acquired by the infrared acquisition module through the infrared optical lens and the uncooled IRFPA assembly, and at least process the image through a non-uniform correction algorithm to form a gas signal for the monitoring terminal to call. The system can be simultaneously suitable for detection of various alkane gases.

Description

Technical Field

[0001] The invention relates to the field of infrared detection technology, and in particular to an infrared imaging detection system and a detection method for hydrocarbon gas leakage. Background Art

[0002] In recent years, with the development of infrared imaging detection technology, the current gas leakage infrared imaging detection device based on uncooled IRFPA has realized leakage imaging detection of some gases such as ethylene, sulfur hexafluoride, ammonia, etc. in the long-wave infrared band. The typical characteristics of these gases are high absorption coefficient or large absorption bandwidth, and they are located in the conventional long-wave infrared band (8-12μm). Summary of the invention

[0003] The inventors have found that the current gas leakage infrared imaging detection device based on non-refrigerated IRFPA has the following main disadvantages:

[0004] On the one hand, the detection capability of alkane gases such as methane and butane is insufficient, or even difficult to detect. For example, the imaging effect of FLIR Tau2 detector on methane, butane, ethylene and sulfur hexafluoride gas (gas temperature 20.5℃, background temperature 25.5℃, gas flow rate 1l / min) is compared. Figure 1 , FLIR Tau2 can detect ethylene and sulfur hexafluoride gases with good uniformity and sensitivity, but it cannot effectively detect methane and butane gases.

[0005] On the other hand, the detection of hydrocarbon leakage requires natural daylight or lamps of suitable color temperature to provide a light source, otherwise it will not work. For example, the hydrocarbon leakage imaging and quantitative sensor disclosed in the Chinese patent (CN109154538A) is suitable for monitoring the emission of natural gas and other hydrocarbon gases, liquids, emulsions, solids and particles, as well as greenhouse gases such as methane and carbon dioxide. Gas leakage is detected by differential absorption imaging spectroscopy in the range of 1.0 to 2.6 microns, using a short-wave infrared (SWIR) detector array sensitive to the hydrocarbon spectral feature range in the short-wave infrared (SWIR) region provided by natural daylight or lamps of suitable color temperature. The detector does not require cryogenic cooling, and is combined with two or more selected spectral filters to produce core and wing spectral bands relative to hydrocarbon feature complexes near 2.3 microns.

[0006] Thirdly, there is still room for improvement in the simultaneous detection of multiple alkane gases.

[0007] Fourthly, while being applicable to the detection of a variety of alkane gases, the detection capability of gases with high absorption coefficients or wide absorption bandwidths, such as ethylene and sulfur hexafluoride, may be reduced.

[0008] In summary, the current gas leakage infrared imaging detection device based on non-cooled IRFPA has at least the following technical problems: first, it cannot effectively detect alkane gases such as methane and butane; second, it cannot obtain leakage images of alkane gases such as methane and butane with high imaging contrast when no light source is provided at night; third, it cannot be applied to the detection of multiple alkane gases at the same time; fourth, while being applicable to the detection of multiple alkane gases, the detection capability of gases with high absorption coefficient or large absorption bandwidth will be reduced.

[0009] In order to enrich products and methods to be applicable to more application scenarios, the present invention proposes a hydrocarbon gas leakage infrared imaging detection system and detection method, which can be simultaneously applicable to the detection of multiple alkane gases.

[0010] In a first aspect, an embodiment of the present invention provides a hydrocarbon gas leakage infrared imaging detection system, including a front end and a monitoring terminal;

[0011] The front end includes an infrared optical lens, an uncooled IRFPA component, and a video processing and system control device; the infrared optical lens includes a medium-wave infrared objective optical lens and a long-wave infrared objective optical lens; the uncooled IRFPA component has a transmittance greater than 90% in the infrared band of 6.5 to 8.5 μm;

[0012] The video processing and system control device includes an infrared acquisition module and an infrared image processing module. The infrared image processing module is configured to: obtain the image collected by the infrared acquisition module through the infrared optical lens and the non-cooling IRFPA component, and form a gas signal after at least processing it with a non-uniform correction algorithm for the monitoring terminal to call.

[0013] In some embodiments, the non-uniformity correction algorithm includes gain coefficient and offset coefficient calculation, non-uniformity correction and blind pixel compensation and single point correction.

[0014] In some embodiments, the gain coefficient calculation includes calculating high and low temperature two-point correction coefficients with a high temperature image and a low temperature image as processing objects, wherein the high temperature image is a uniform background image collected in advance in a first temperature environment higher than a standard temperature, and the low temperature image is a uniform background image collected in advance in a second temperature environment lower than the standard temperature;

[0015] The gain coefficient calculation also includes calculating a two-point integration time correction coefficient with a long integration image and a short integration image as processing objects, wherein the long integration image is an image pre-captured at a first integration time that is longer than a standard integration time, and the short integration image is an image pre-captured at a second integration time that is shorter than the standard integration time.

[0016] In some embodiments, the high temperature image is collected by:

[0017] The images in the first temperature environment are collected at set intervals and stored in RAM1. The current stored image and the previous stored image are read from RAM1 to obtain the average image of the two and store it in RAM1. Until the collection is completed, the high temperature image is obtained according to the m frames of images stored in RAM1 by the following formula:

[0018]

[0019] Among them, P sd is the pixel value of the image after weighted average; P i is the pixel value of the i-th frame image, i=1,2,...,m; P1 is the pixel value of the first frame image;

[0020] Accordingly, the low temperature image is collected in the following manner:

[0021] Images in the second temperature environment are collected at set intervals and stored in RAM2. The currently stored image and the previous stored image are read out from RAM2 to obtain an average image of the two and store it in RAM2. Until the collection is completed, the low-temperature image is obtained according to the above formula based on the m frames of images stored in RAM2.

[0022] In some embodiments, after the gain coefficient and the offset coefficient are calculated, the method further includes:

[0023] If the calculated gain coefficient and / or offset coefficient is a floating point number, the corresponding floating point number is converted into a logical integer.

[0024] In some embodiments, the gain coefficient calculation includes:

[0025] Multiply the input divided fixed-point number by 2 before calculating the gain factor n , n is an integer greater than 9 and less than 15.

[0026] In some embodiments, the gain coefficient and the offset coefficient are calculated in parallel, and after the calculation is completed, the pixel values ​​covered in the corresponding image are refreshed.

[0027] In some embodiments, the non-uniformity correction and blind pixel compensation include:

[0028] Increase the gain factor by 2 18 The pixel is multiplied by the amplified gain coefficient, shifted right by 8 bits, and divided by 2046. The resulting data is summed with the offset coefficient, the offset coefficient itself is subtracted, and then 1000 is added.

[0029] In some embodiments, the single point correction implementation step includes:

[0030] Capture two frames of images after two-point correction, calculate the average pixel value of the first frame image, add the set pixel value to the second frame image and then find the difference between the average pixel value, sum the obtained difference and the offset coefficient read from the specified cache space at the same time, subtract the set pixel value from the sum and store it in the cache space.

[0031] In some embodiments, before the non-uniform correction algorithm is processed, the following enhancement processing is performed on the acquired image:

[0032] The image is filtered using a filter to obtain the background layer of the image.

[0033] Performing histogram equalization processing on the background layer, and determining a difference image between the image and the processed background layer as a detail layer;

[0034] Performing self-gain enhancement processing on the detail layer;

[0035] The image after self-gain enhancement is reconstructed according to the weights to obtain the final enhanced image.

[0036] In some embodiments, the infrared acquisition module includes an infrared imaging circuit FPGA; the infrared imaging circuit is used to control the performance of infrared imaging and the signal-to-noise ratio of the gas imaging image, and the infrared imaging circuit includes a transmitter-follower circuit, a high input impedance single-ended to differential converter, a precision reference source, a power supply, an analog-to-digital conversion, and a layout design module.

[0037] In a second aspect, an embodiment of the present invention provides a hydrocarbon gas leakage infrared imaging detection method, comprising using any of the above-mentioned hydrocarbon gas leakage infrared imaging detection systems to perform hydrocarbon gas leakage detection.

[0038] The beneficial effects of the above technical solution provided by the embodiment of the present invention include at least:

[0039] (1) The hydrocarbon gas leakage infrared imaging detection system provided by the embodiment of the present invention includes a front end and a monitoring terminal; the front end includes an infrared optical lens, an uncooled IRFPA component and a video processing and system control device; the infrared optical lens includes a medium-wave infrared objective optical lens and a long-wave infrared objective optical lens. Compared with the traditional detection system based on the uncooled IRFPA component, better imaging contrast and imaging effect of methane gas can be obtained.

[0040] (2) The hydrocarbon gas leakage infrared imaging detection system provided by the embodiment of the present invention has an uncooled IRFPA component with a transmittance greater than 90% in the infrared band of 6.5 to 8.5 μm. The use of a band that matches the long-wave absorption spectrum of methane can obtain better imaging contrast and imaging effect, which is completely different from the conventional methane gas detection using a cooled medium-wave IRFPA. Therefore, the detection system solves the technical problem that the existing technology cannot effectively detect methane and butane gases, that is, the conventional uncooled IRFPA (such as the FLIRTau2 detector) has insufficient detection capability for alkane gases such as methane and butane, or even has difficulty in detecting them.

[0041] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description, claims, and drawings.

[0042] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0044] Figure 1 This is the imaging effect of the FLIR Tau2 detector;

[0045] Figure 2 A schematic diagram of the structure of an infrared imaging detection system for hydrocarbon gas leakage in an embodiment of the present invention;

[0046] Figure 3 A schematic diagram of a control circuit of a video processing and system control device in an embodiment of the present invention;

[0047] Figure 4 A schematic diagram of the structure of an online imaging detection system in an embodiment provided by the present invention;

[0048] Figure 5 The imaging process of the test example provided by the present invention;

[0049] Figure 6 The effect diagram of the LWIR imaging system of the test example provided by the present invention on methane gas at each imaging processing stage;

[0050] Figure 7 This is an imaging effect diagram of an embodiment provided by the present invention. DETAILED DESCRIPTION

[0051] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0052] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0053] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which the invention belongs. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0054] In the description of the present invention, it should be noted that the terms "include", "including", "have", "contain" and the like are open terms, meaning including but not limited to.

[0055] First, the terms in the relevant technical field involved in this specification are explained:

[0056] IRFPA, or infrared focal plane array, includes any multi-element planar array infrared detection device that can correspond each pixel of the scene in the entire field of view to a sensitive element.

[0057] The term "uncooled IRFPA" includes any infrared focal plane array that does not require cryogenic cooling and is suitable for operation in an environment close to room temperature.

[0058] The term "MWIR" refers to the mid-wave infrared band, and the term "LWIR" refers to the long-wave infrared band.

[0059] The term "signal-to-noise ratio" in this specification refers to a statistical analysis value of the brightness change of each pixel, specifically including the ratio of the optical signal power to the noise power within the limited bandwidth of the optical signal.

[0060] The term "noise equivalent temperature difference" NETD refers to thermal sensitivity, which is obtained by dividing the instantaneous noise by the responsivity. This value is a function of the camera's f-stop, integration time, and the specific temperature at which the measurement is made.

[0061] The term "minimum detectable leak rate" is defined as the leak rate of a gas at which an observer can just observe a leak rate of the gas when the gas flow rate is gradually reduced for a given background and gas temperature.

[0062] The term "slave computer" refers to a computer that can directly issue control commands.

[0063] Example

[0064] The embodiment of the present invention provides a hydrocarbon gas leakage infrared imaging detection system, referring to Figure 2 As shown, it includes a front end 1 and a monitoring terminal 2.

[0065] The front end 1 includes an infrared optical lens 11 , an uncooled IRFPA component 12 , and a video processing and system control device 13 .

[0066] The infrared optical lens 1 comprises a medium-wave infrared objective lens MWIR optical lens (medium-wave infrared lens) and a long-wave infrared objective lens LWIR optical lens (long-wave infrared lens).

[0067] Furthermore, the long-wave infrared objective lens LWIR optical lens includes a short-focus LWIR lens and a long-focus LWIR lens, and the parameters are shown in Table 1 below:

[0068] Table 1 Parameters of short-focus LWIR lens and long-focus LWIR lens

[0069] Parameter name Short-throw LWIR lens MWIR Lenses Long focal length LWIR lens focal length 25mm 35mm 40mm F# 0.8 0.75 0.9 Back intercept 20.2 21.3 20.7 Working band 6.5～14 3～5 6.5～14 Average transmittance >90%(7.3~8.3μm) 90%(3.2~3.4μm) 90%(7~12μm) Field of view 35.5×28.7 15.62×11.75 15.49×12.4 Interface (diameter x pitch) M45×0.75~6g M64×0.75~6g M45×0.75~6g

[0070] Both the medium-wave infrared objective MWIR optical lens and the long-wave infrared objective LWIR optical lens can be composed of three lenses. The embodiment of the present invention does not specifically limit the material of the lens. For example, a combination of single crystal germanium and KIRO-CG1 chalcogenide glass material (As40Se60) is used to perform optical athermal design of MWIR lens and LWIR lens. Single crystal germanium is the most commonly used long-wave infrared lens material, with good surface hardness and high transmittance at 2 to 14 μm; KIRO-CG1 chalcogenide glass material (As40Se60) has high transmittance at 1.0 to 14 μm, and has a lower refractive index temperature coefficient than single crystal germanium material, which can reduce the effect of temperature changes on the refractive index of the lens material, and has good processability and mature processing technology among chalcogenide glasses.

[0071] It is also applicable to the detection of four alkane gases (methane, ethane, propane, butane), and the transmittance of the uncooled IRFPA component is greater than 90% in the infrared band of 6.5-8.5 μm. The embodiment of the present invention does not specifically limit the technical principle and structure of the uncooled IRFPA component, and the uncooled IRFPA component includes but is not limited to Pico of ULIS of France, Pico640E-BB of SCD of Israel, MICROXCAM-384i-MLWIR of DRS of the United States and INO of Canada, and GWSP 02 02X1AF-W of Guangwei of Northern China.

[0072] In some embodiments, a corresponding narrowband film system design and film layer preparation are performed on a filter in the 6.5-8.5μm band range, and the specific process is as follows: within the 6.5-8.5μm wavelength range, an anti-reflection film is plated, and the average transmittance in the 6.5-8.5μm band range is greater than 90%; the absolute value of the transmittance at 4.8-5.5μm is ≤5%, and the average transmittance at 3-4.8μm is ≤1%; the absolute value of the transmittance at 9.5-10.2μm is ≤5%, and the average transmittance at 10.2-12μm is ≤1%.

[0073] In some embodiments, an uncooled IRFPA component is prepared by using an optimized detector pixel structure and preparation process. By continuing to make two layers of suspended structures on the microbridge support structure of the traditional detector to improve the response of other bands, it not only has a high absorption rate at a wavelength of 6.5 to 12 μm, but also has a greatly improved absorption rate at 3 to 5 μm. Main performance parameters: detector material VOx, response band: 7 to 8.5 μm, array size 640×512, pixel size 17 μm, noise equivalent temperature difference (NETD) 30 mK, signal transfer function (SITF) adjustable within the range of 15 to 30 mV / K, and can select 14-bit digital video CameraLink serial, low-voltage differential signal (LVDS) serial or low-voltage complementary metal oxide semiconductor (LVCMOS) parallel output. The average response in the long-wave infrared band of 6.5-8.5 μm required for alkane gas detection is about 88.5%, which can meet the gas imaging detection needs of the petrochemical industry.

[0074] The video processing and system control device 13 includes an infrared acquisition module 131 and an infrared image processing module 132. The infrared image processing module 132 is configured to: obtain the image (i.e., spectral data) acquired by the infrared acquisition module 131 through the infrared optical lens 11 and the uncooled IRFPA component 12, and form a gas signal after at least processing by a non-uniformity correction algorithm for the monitoring terminal 2 to call. The monitoring terminal can be a lower computer.

[0075] Specifically, the non-uniformity correction algorithm includes:

[0076] (1) Calculation of gain coefficient and offset coefficient

[0077] Since the system may use different optical lenses and spectral bands each time, the response of the detector will change greatly. If the default correction coefficient matrix is ​​used, the residual non-uniformity noise will be relatively large, and phenomena such as four-corner heat will be prone to occur. Therefore, some implementation methods of infrared image processing modules use a scene-based non-uniformity correction algorithm in the post-processing algorithm to recalibrate the correction coefficients for the specific optical system involved in each application.

[0078] The gain coefficient calculation includes the high and low temperature two-point correction coefficient calculation with the high temperature image and the low temperature image as the processing objects. The calculation process includes the high and low temperature image acquisition stage and the coefficient calculation stage.

[0079] The high temperature image is a uniform background image pre-collected in a first temperature environment (eg, 30 degrees) higher than the standard temperature, and the low temperature image is a uniform background image pre-collected in a second temperature environment (eg, 10 degrees) lower than the standard temperature.

[0080] High temperature images are collected by:

[0081] The images in the first temperature environment are collected at set intervals and stored in RAM1. The current stored image and the previous stored image are read from RAM1 to obtain the average image of the two and store it in RAM1 until the collection is completed. The high temperature image is obtained according to the m frames of images stored in RAM1 by the following formula:

[0082]

[0083] Among them, P sd is the pixel value of the image after weighted average; P i is the pixel value of the i-th frame image, i=1,2,…,m; P1 is the pixel value of the 1st frame image.

[0084] Low temperature images were acquired by:

[0085] Images in the second temperature environment are collected at set intervals and stored in RAM2. The currently stored image and the previous stored image are read out from RAM2 to obtain an average image of the two and store it in RAM2. Until the collection is completed, the low-temperature image is obtained according to the above formula based on the m frames of images stored in RAM2.

[0086] The gain coefficient calculation also includes the calculation of a two-point integration time correction coefficient with a long integration image and a short integration image as processing objects. The long integration image is an image pre-captured at a first integration time that is longer than the standard integration time, and the short integration image is an image pre-captured at a second integration time that is shorter than the standard integration time.

[0087] In some embodiments, after the gain coefficient and the offset coefficient are calculated, the method further includes:

[0088] If the calculated gain coefficient and / or offset coefficient is a floating point number, the corresponding floating point number is converted into a logical integer to reduce the required storage space and facilitate real-time imaging.

[0089] In some embodiments, the directly calculated gain coefficient is generally a decimal of about 1. To ensure the accuracy of the coefficient, the input fixed-point number to be divided is multiplied by 2 before the gain coefficient is calculated. n , n is an integer greater than 9 and less than 15. After experimental verification, select 2 12 Multiply and round down.

[0090] In some embodiments, the gain coefficient and the offset coefficient are calculated in parallel, and after the calculation is completed, the pixel values ​​covered in the corresponding image are refreshed, and spatial multiplexing does not require the development of more storage resources.

[0091] (2) Non-uniformity correction and blind pixel compensation

[0092] Including, amplify the gain factor by 2 18 The pixel is multiplied by the amplified gain coefficient, shifted right by 8 bits, and divided by 2046. The resulting data is summed with the offset coefficient, the offset coefficient itself is subtracted, and then 1000 is added.

[0093] The DSP66 multiplication and addition operator can be used to implement multiplication and addition operations between three data.

[0094] (3) Single point correction

[0095] The method includes collecting two frames of images after two-point correction, calculating the average pixel value of the first frame image, adding a set pixel value to the second frame image and then subtracting the difference from the average pixel value, summing the obtained difference with the offset coefficient read from the specified cache space at the same time, and subtracting the set pixel value from the sum and storing it in the cache space.

[0096] The set pixel value may be, for example, 2000. Adding the set pixel value can avoid negative values ​​appearing in the difference process.

[0097] In some embodiments, before the non-uniform correction algorithm is processed, the following enhancement algorithm is also performed on the acquired image:

[0098] (1) Use a filter to filter the image (layer processing) to obtain the background layer of the image

[0099] The guided filter can be used to filter the image to obtain the background layer of the image. The solution formula is as follows:

[0100]

[0101]

[0102] in,

[0103]

[0104]

[0105] (2) Perform histogram equalization on the background layer to determine the difference image between the original image and the processed background layer as the detail layer

[0106] Gaussian filter can be used for preprocessing:

[0107]

[0108] ▽ 2 I(i,j)=I(i+1,j)+I(i-1,j)+I(i,j+1)+I(i,j-1)-4×I(i,j)

[0109]

[0110] (3) Perform self-gain enhancement on the detail layer

[0111] I D (i,j)=I in (i,j)-I g (i,j)

[0112] G(i,j)=G min +[1-k(i,j)](G max -G min )

[0113] (4) Reconstruct the image after self-gain enhancement according to the weights to obtain the final enhanced image

[0114] I out (i,j)=q·ID (i,j)+(i-1)·I g (i,j)

[0115] The infrared image processing module processes the image collected by the infrared acquisition module through the above-mentioned non-uniform correction algorithm to form a gas signal. The monitoring terminal calls the gas signal and displays it through an image visualization method. A visual display method of gas leakage traces can be used.

[0116] Unlike general infrared target images, gas is an extremely weak signal, and the difference between it and the background is often only a dozen gray levels. Conventional processing algorithms tend to compress low-contrast gas details, causing the loss of gas targets or making them difficult to detect. Therefore, a detail enhancement processing algorithm based on gas infrared images and a visual display method for gas leakage traces are used to improve the sensitivity of the detection system. When gas leaks, it is a dynamic target that continues to change. If the application scenario is fixed-point monitoring, the inter-frame difference method can be used to eliminate most of the stray background. The continuous inter-frame difference method has obvious advantages in gas detection.

[0117] The hydrocarbon gas leakage infrared imaging detection system provided by the embodiment of the present invention includes a front end and a monitoring terminal; the front end includes an infrared optical lens, an uncooled IRFPA component and a video processing and system control device; the infrared optical lens includes a medium-wave infrared objective optical lens and a long-wave infrared objective optical lens. Compared with the traditional detection system based on the uncooled IRFPA component, better imaging contrast and imaging effect of methane gas can be obtained.

[0118] The hydrocarbon gas leakage infrared imaging detection system provided by the embodiment of the present invention has an uncooled IRFPA component with a transmittance greater than 90% in the infrared band of 6.5 to 8.5 μm. The use of a band that matches the long-wave absorption spectrum of methane can obtain better imaging contrast and imaging effect, which is completely different from the understanding that conventional methane gas detection uses a cooled medium-wave IRFPA. Therefore, the detection system solves the technical problem that the existing technology cannot effectively detect methane and butane gases, that is, the conventional uncooled IRFPA (such as the FLIRTau2 detector) has insufficient detection capability for alkane gases such as methane and butane, or even has difficulty in detecting them.

[0119] In some embodiments, the video processing and system control device 13 may use Figure 3 The circuit diagram shown in the figure. The control circuit structure block diagram of the video processing and system control device 13 selects CameraLink or LVDS output and transmits via differential signals.

[0120] Some specific embodiments of the control circuit of the video processing and system control equipment select the LVDS digital video interface, which has one pair of synchronization, two pairs of data and one pair of clock signals. These signals are received by the FPGA digital image processing platform through the GPIO interface and processed by the algorithm. The processing results are output to the ARM through the GPIO interface. The ARM receives the video signal from the FPGA and divides the video signal into two paths. One path is directly displayed through HDMI, and the other path is sent to the network port in the online system. The network port and the PC host computer communicate bidirectionally. The ARM receives the control signal sent by the PC, decodes the control signal and sends it to the FPGA through the serial port.

[0121] In some embodiments, the infrared acquisition module of the video processing and system control device 13 includes an infrared imaging circuit FPGA; the infrared imaging circuit is used to control the performance of infrared imaging and the signal-to-noise ratio of the gas imaging image, and the infrared imaging circuit includes a transmitter-follower circuit, a high input impedance single-ended to differential converter, a precision reference source, a power supply, an analog-to-digital conversion, and a layout design module.

[0122] The infrared acquisition module acquires the spectrum of the infrared region in real time, and the gases include but are not limited to methane and other alkane gases; the real-time acquisition meets the following parameters: the focal plane array is uncooled, the spectral range is 7-8μm, the pixel size is 12μm, the focal length is 40mm, and the resolution is 640×512 pixels.

[0123] In some embodiments, the infrared image processing module needs to implement the above-mentioned gas image enhancement algorithm and non-uniformity correction algorithm and system control functions on a hardware platform in order to realize embedded real-time processing of the imaging system.

[0124] Specifically, the hardware processing platform of the infrared image processing module can be divided into a field programmable gate array (FPGA) and an ARM processing platform. The FPGA platform uses Xilinx's Airtex-7 chip as the core processing device, equipped with SRAM and Flash storage space, three RS232 communication interfaces and digital video output (CameraLink outputs original 14-bit data) interfaces, mainly realizing non-uniform correction and enhancement processing of gas images, and can meet the basic processing capabilities of gas video images. The ARM platform mainly realizes image compression and communication or human-computer interaction interface with monitoring terminals.

[0125] In some embodiments, in order to meet different application requirements, two different imaging detection systems are designed, one is online, mainly to meet all-day monitoring needs; the other is handheld, mainly used in applications such as security inspections.

[0126] Structure for packaging online imaging detection system, see Figure 4 As shown, it includes three parts: a shell body, a top cover, and a front panel.

[0127] The whole is made of aluminum material, and the surface is black anodized, which is conducive to heat conduction heat dissipation. The main body of the prototype shell is in a "T" shape. The bulged part at the front end is used to ensure the installation space of components such as the thermal imager movement and lens; the rectangular part at the rear end is the installation space for the circuit board; the outer shell is designed with a grid to increase the surface heat dissipation area. The top cover and the shell body, the front panel and the main shell are fixed with screws. If it needs to be used outdoors, a sealing strip can be added to the inside of the joint to improve the protection level. The infrared lens is installed with a threaded flange. After focusing in place, it is locked and fixed with the top screw on the flange. The thermal imager movement assembly is installed with a bracket. The three-point positioning pins on the bracket ensure that the optical reference surface is installed correctly to ensure the overall imaging effect.

[0128] The housing structure used to encapsulate the handheld system includes: an upper housing, a lower housing, and a front panel. The front panel provides a mounting base for components such as the optical system, thermal imager, and filter wheel.

[0129] The prototype housing is camera-style. The front cavity is used to install the thermal imager movement, lens and other components. The rear cavity is the installation space for the circuit board and battery. The back panel is the touch screen installation position. The right side is the external socket position, which is protected by a protective cover. The bottom of the housing is designed with bracket installation holes and foot pads, which can be placed horizontally or bracket mounted. The recessed part of the side of the housing is used for hand-holding. The upper and lower main housings and the front panel and the main housing are installed by screw pressing to ensure their sealing. When used outdoors, a sealing strip is added to the inside of the joint to improve the protection level. The infrared optical lens is installed with a threaded flange. After adjusting it in place, it is locked and fixed with the top screw on the flange. The thermal imager movement assembly is installed with a bracket. The three-point positioning pins preset on the bracket ensure that the optical reference surface is installed correctly to ensure the overall imaging effect. The back slope of the housing is used as the touch screen control area, and there is a sunshade on the top for outdoor use. Below is the power switch and the charging port of the internal battery.

[0130] The hydrocarbon gas leakage infrared imaging detection system provided by the embodiment of the present invention can obtain a methane gas detection image with better imaging effect than the prior art, especially in the detection of methane leakage, it obtains an imaging contrast that exceeds expectations, and can select a suitable imaging filter bandwidth for different methane gas detectors and application backgrounds; in addition, the detection system not only has a good detection capability for gases such as sulfur hexafluoride and ethylene whose absorption peaks are located in the conventional long-wave infrared band, but also has a good detection effect for alkane gases whose absorption peaks are located in the unconventional long-wave infrared band near 7 microns. Finally, the relevant experiments of the present invention have verified its effectiveness in detecting oil and natural gas leaks, and improved the detection distance to a practical level.

[0131] Test example: Contrast test of methane gas detection imaging effect

[0132] In order to facilitate the control of variables, the measurement was carried out in a laboratory environment. Since the temperature control process of the gas is complicated and the control accuracy is not high, the background temperature is controlled to generate a gas background temperature difference when studying the contrast. The SR-800N-7D black body radiation source is selected for the control of the background temperature. The concentration of the gas can be adjusted by the mixing ratio of the reference gas without infrared absorption and the gas to be measured. The idea of ​​double gas chambers is adopted for contrast measurement. Because the actual working distance of the uncooled imaging detection system is short, a gas without infrared absorption can be selected as the reference gas. Nitrogen is selected in this test case. The gas coming out of the nitrogen bottle (nitrogen purity 99.99% vol) is divided into two paths, one enters the reference gas chamber, and the other enters the three-way interface with methane gas (methane gas purity 99.9% vol). The gas mixed with the three-way interface enters the target absorption gas chamber. The gas chamber is placed at the outlet of the black body radiation source and covers the radiation port. The radiation emitted from the black body radiation source is absorbed by the gas in the absorption gas chamber and enters the methane gas imaging system. The concentration is measured by a contact infrared densitometer and recorded in real time using a visible light camera. The measurement range of the densitometer is 0-50000ppm, and the measurement error is 1%. The detection performance of the methane gas detection system in different bands is determined by adjusting the methane gas concentration and background radiation temperature. When the external radiation enters the infrared imaging system, it is focused by the infrared optical system, photoelectrically converted, analog-to-digital converted and signal amplified, and finally converted into the output grayscale value. In order to measure the radiation contrast, the imaging system is calibrated to determine the quantitative relationship between the output grayscale value of the imaging system and the incident radiation.

[0133] For imaging process, see Figure 5 shown.

[0134] In order to intuitively compare the imaging performance of methane gas in MWIR and LWIR, the phenomenon of gas flowing into the absorption chamber at a certain speed from a pipe with a diameter of 8mm is observed. The collected original image is processed, and the processing process is mainly divided into four steps: 1) Since infrared images generally have noise, bilateral filtering is first used to reduce noise; 2) Since gas is an extremely weak signal in the entire infrared scene, the image is further enhanced by inter-frame difference, contrast stretching and other enhancement processing; 3) Since the noise may also be enhanced when the gas signal is enhanced, the block-matching and 3D filtering (BM3D) method is further used for noise reduction processing; 4) In order to facilitate human eye observation, the leakage position is estimated, the gas image part is extracted, and the gas is processed separately by pseudo color and superimposed on the original image.

[0135] After the imaging process, the measurement conditions are: methane gas temperature 19°C, background black body temperature 21°C, flow rate ≤ 0.2L / min, ambient relative humidity: 30%, gas absorption cell pressure 1atm, see Figure 6 The figure shows the effect of the LWIR imaging system on methane gas at each imaging processing stage. After video processing, the detectability of methane gas is significantly improved. This test case shows that although there is atmospheric infrared absorption in the LWIR band (7-8 microns) and the absorption intensity of methane gas is weaker than that of the MWIR band, the LWIR band is conducive to the detection of high background radiation and gas absorption bandwidth.

[0136] The test compared the imaging contrast and actual imaging effect of the uncooled infrared imaging system in two bands. The use of filters that match the long-wave absorption spectrum of methane can obtain better imaging contrast and imaging effect, which is completely different from the conventional understanding of using cooled medium-wave IRFPA for methane gas detection.

[0137] Embodiment 1:

[0138] This embodiment has developed online and handheld gas leak infrared imaging detection system prototypes based on the optimized designed non-cooled IRFPA components and infrared optical lenses.

[0139] The gas target and background radiation are focused and imaged on the wide-band uncooled IRFPA through the infrared optical lens and spectral selection filter. The imaging core is converted by 14-bit A / D and input into the FPGA image processing circuit as a digital signal. After non-uniform correction and detail enhancement, dynamic range compression, continuous frame difference and other algorithm processing, it is displayed on the monitor for human observation and judgment. The existing CameraLink video acquisition card with SDK development function (such as Pleora's iPORT CL-U3M-IND CameraLinkUSB conversion module, IMPERX's VCECLEX01ExpressCard / 54Camera Link image acquisition card) can be used to collect the original 14-bit data output by the infrared detector in real time, and perform preliminary algorithm verification on the host computer.

[0140] The technical effects of this embodiment are as follows:

[0141] The non-refrigerated gas leakage imaging system (40mm focal length infrared lens) proposed by the present invention can clearly observe the oil and gas leakage and the gas drift direction ( Figure 7 ).

[0142] The results of this embodiment prove that the methane gas leakage infrared imaging detection system can effectively detect gas leakage in petroleum and petrochemical equipment. It proves that the present invention can effectively detect leakage in the raw material tank area, can determine the leakage location and diffusion trend, and the effective detection distance is greater than 50m, meeting the practical application needs of the oil and gas industry.

[0143] It should be noted that for internal factors of the imaging system, the minimum detectable leak rate is mainly affected by the focal length of the optical lens and the temperature resolution of the detector. Usually, after the uncooled IRFPA assembly leaves the factory, the user cannot adjust the detector integration time. The focal length of the optical system can be changed by using a zoom optical lens. For external factors, MDLR is affected by factors such as gas background temperature difference, gas concentration, wind speed, observation distance, and leak port diameter.

[0144] In addition to those cited and discussed in detail above, the present invention can be used to detect and quantify other gases, liquids, emulsions, powders and solids by selecting appropriate spectral filters in the MWIR and / or LMIR. Therefore, the scope should not be determined by the illustrated embodiments, but by the appended claims and legal equivalents.

[0145] Based on the inventive concept of the present invention, an embodiment of the present invention further provides a hydrocarbon gas leakage infrared imaging detection method, comprising: using any of the above hydrocarbon gas leakage infrared imaging detection systems to perform hydrocarbon gas leakage detection.

[0146] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process can be rearranged without departing from the scope of protection of the present disclosure. The attached method claims present the elements of the various steps in an exemplary order and are not intended to be limited to the specific order or hierarchy described.

[0147] In the above detailed description, various features are grouped together in a single embodiment to simplify the disclosure. This method of disclosure should not be interpreted as reflecting an intention that the embodiments of the claimed subject matter require more features than are clearly stated in each claim. On the contrary, as reflected in the appended claims, the invention is in a state of having less than all the features of the disclosed individual embodiments. Therefore, the appended claims are hereby expressly incorporated into the detailed description, with each claim standing on its own as a separate preferred embodiment of the invention.

[0148] The above description includes examples of one or more embodiments. Of course, it is impossible to describe all possible combinations of components or methods for the purpose of describing the above embodiments, but it should be recognized by those skilled in the art that the various embodiments can be further combined and arranged. Therefore, the embodiments described herein are intended to cover all such changes, modifications and variations that fall within the scope of protection of the appended claims. In addition, with respect to the term "comprising" used in the specification or claims, the word is covered in a manner similar to the term "including", just as "including," explained as a transitional word in the claims. In addition, any term "or" used in the specification of the claims is intended to represent "non-exclusive or". The terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance.

Claims

1. A hydrocarbon gas leakage infrared imaging detection system, characterized in that: The system includes a front end and a monitoring terminal; The front end includes an infrared optical lens, an uncooled IRFPA component, and a video processing and system control device; the infrared optical lens includes a medium-wave infrared objective optical lens and a long-wave infrared objective optical lens; the uncooled IRFPA component has a transmittance greater than 90% in the infrared band of 6.5 to 8.5 μm; The video processing and system control device includes an infrared acquisition module and an infrared image processing module. The infrared image processing module is configured to: obtain the image collected by the infrared acquisition module through the infrared optical lens and the non-cooling IRFPA component, and form a gas signal after at least processing it with a non-uniform correction algorithm for the monitoring terminal to call.

2. The system according to claim 1, characterized in that The non-uniform correction algorithm includes gain coefficient and offset coefficient calculation, non-uniform correction and blind pixel compensation and single point correction.

3. The system according to claim 2, characterized in that The gain coefficient calculation includes calculating high and low temperature two-point correction coefficients with a high temperature image and a low temperature image as processing objects, wherein the high temperature image is a uniform background image collected in advance in a first temperature environment higher than a standard temperature, and the low temperature image is a uniform background image collected in advance in a second temperature environment lower than the standard temperature; The gain coefficient calculation also includes calculating a two-point integration time correction coefficient with a long integration image and a short integration image as processing objects, wherein the long integration image is an image pre-captured at a first integration time that is longer than a standard integration time, and the short integration image is an image pre-captured at a second integration time that is shorter than the standard integration time.

4. The system according to claim 3, characterized in that The high temperature image is collected by the following method: The images in the first temperature environment are collected at set intervals and stored in RAM1. The current stored image and the previous stored image are read from RAM1 to obtain the average image of the two and store it in RAM1. Until the collection is completed, the high temperature image is obtained according to the m frames of images stored in RAM1 by the following formula: Among them, P sd is the pixel value of the image after weighted average; P i is the pixel value of the i-th frame image, i=1,2,...,m; P1 is the pixel value of the first frame image; Accordingly, the low temperature image is collected in the following manner: Images in the second temperature environment are collected at set intervals and stored in RAM2. The currently stored image and the previous stored image are read out from RAM2 to obtain an average image of the two and store it in RAM2. Until the collection is completed, the low-temperature image is obtained according to the above formula based on the m frames of images stored in RAM2.

5. The system according to claim 2, characterized in that After the gain coefficient and the offset coefficient are calculated, the following is also included: If the calculated gain coefficient and / or offset coefficient is a floating point number, the corresponding floating point number is converted into a logical integer.

6. The system according to claim 2, characterized in that Gain factor calculation, including: Multiply the input divided fixed-point number by 2 before calculating the gain factor n , n is an integer greater than 9 and less than 15.

7. The system according to claim 2, characterized in that The gain coefficient and the offset coefficient are calculated in parallel, and after the calculation is completed, the pixel values ​​in the corresponding image are refreshed and covered.

8. The system according to claim 2, characterized in that The non-uniform correction and blind pixel compensation include: Increase the gain factor by 2 18 The pixel is multiplied by the amplified gain coefficient, shifted right by 8 bits, and then divided by 2046. The resulting data is summed with the offset coefficient, the offset coefficient itself is subtracted, and then 1000 is added.

9. The system according to claim 2, characterized in that The single point correction implementation steps include: Capture two frames of images after two-point correction, calculate the average pixel value of the first frame image, add the set pixel value to the second frame image and then find the difference between the average pixel value, sum the obtained difference and the offset coefficient read from the specified cache space at the same time, subtract the set pixel value from the sum and store it in the cache space.

10. The system according to claim 1, characterized in that Before the non-uniform correction algorithm is processed, the following enhancement processing is performed on the collected image: The image is filtered using a filter to obtain the background layer of the image. Performing histogram equalization processing on the background layer, and determining a difference image between the image and the processed background layer as a detail layer; Performing self-gain enhancement processing on the detail layer; The image after self-gain enhancement is reconstructed according to the weights to obtain the final enhanced image.

11. The system according to claim 1, characterized in that The infrared acquisition module includes an infrared imaging circuit FPGA; The infrared imaging circuit is used to control the performance of infrared imaging and the signal-to-noise ratio of gas imaging images. The infrared imaging circuit includes a transmitter-follower circuit, a high input impedance single-ended differential converter, a precision reference source, a power supply, an analog-to-digital converter and a layout design module.

12. A hydrocarbon gas leakage infrared imaging detection method, characterized in that: include: The hydrocarbon gas leakage infrared imaging detection system according to any one of claims 1 to 11 is used to perform hydrocarbon gas leakage detection.

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