Patent Publication Number: US-2018052072-A1

Title: Gas leak location estimating device, gas leak location estimating system, gas leak location estimating method and gas leak location estimating program

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present patent application is a U.S. National Phase application of International Application No. PCT/JP2016/057032, filed Mar. 7, 2016, which claims priority from Japanese Patent Application No. 2015-045658, filed Mar. 9, 2015, the entirety of which are incorporated herein by reference. 
    
    
     TECHNOLOGICAL FIELD 
     The present invention relates to estimation of a gas leak location. 
     DESCRIPTION OF THE RELATED ART 
     Heretofore, a system has been known to detect gas leaks in industrial plants with an infrared camera. 
     Patent Document 1 (Japanese Patent Application Laid-Open Publication No. Hei 09-021704) discloses a technique that involves selecting and displaying a pseudo color thermal image of an area having a temperature outside of a threshold based on an image signal acquired with the infrared camera to announce a gas leak and indicate the area having the temperature outside of the threshold due to the leaked gas. 
     Although the technique according to Patent Document 1 involves a process of displaying the area having the temperature outside of the threshold, it lacks the processing of analyzing and estimating the gas leak location and indicating and announcing the estimated gas leak location. Thus, users cannot accurately determine the gas leak location. 
     SUMMARY 
     An object of the present invention, which has been conceived in light of the issues of the traditional art, is to accurately estimate a gas leak location. 
     To achieve at least one of the abovementioned objects, according to an aspect of the present invention, there is provided: a gas leak location estimating device including: 
     an information processor which acquires image information on a plurality of frames from an infrared camera, the information processor being capable of executing:
         a block discrimination processing of dividing an image area of each of the frames into a plurality of blocks and discriminating whether each of the blocks is a gas area;   a count processing of counting a number of times each of the blocks is discriminated as the gas area, over the frames in chronological order, in the block discrimination processing; and   a leak location estimation processing of setting, among the blocks, a block whose counted value obtained in the count processing is equal to or larger than a predetermined value as an estimated gas leak location.       

     According to another aspect of the present invention, there is provided: a gas leak location estimating method acquiring image information on a plurality of frames from an infrared camera, the method including: 
     a block discrimination processing of dividing an image area of each of the frames into a plurality of blocks and discriminating whether each of the blocks is a gas area; 
     a count processing of counting a number of times each of the blocks is discriminated as the gas area, over the frames in chronological order, in the block discrimination processing; and 
     a leak location estimation processing of setting, among the blocks, a block whose counted value obtained in the count processing is equal to or larger than a predetermined value as an estimated gas leak location. 
     According to another aspect of the present invention, there is provided: a gas leak location estimating program causing a computer which acquires image information on a plurality of frames from an infrared camera, to execute: 
     a block discrimination processing of dividing an image area of each of the frames into a plurality of blocks and discriminating whether each of the blocks is a gas area; 
     a count processing of counting a number of times each of the blocks is discriminated as the gas area, over the frames in chronological order, in the block discrimination processing; and 
     a leak location estimation processing of setting, among the blocks, a block whose counted value obtained in the count processing is equal to or larger than a predetermined value as an estimated gas leak location. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The advantages and features provided by one or more embodiments of the invention can be fully understood from the detailed description given herein below. The appended drawings are not intended as a definition of the limits of the present invention. 
         FIG. 1  is a functional block diagram illustrating a gas leak location estimating system according to a first embodiment of the present invention. 
         FIG. 2  is a schematic diagram illustrating various processing carried out to image frames according to the first embodiment of the present invention. 
         FIG. 3  illustrates a first embodiment of the present invention and includes; schematic diagram Ga illustrating a result of a count processing carried out to an image frame and a block corresponding to the estimated gas leak location; schematic diagram Gb illustrating an example composite image for display. 
         FIG. 4  is a functional block diagram illustrating a gas leak location estimating system according to a second embodiment of the present invention. 
         FIG. 5  is a functional block diagram illustrating a gas leak location estimating system according to a third embodiment of the present invention. 
         FIG. 6  illustrates the third embodiment of the present invention and includes; schematic diagram Ga illustrating a result of a count processing carried out to an image frame, a block corresponding to the estimated gas leak location, and blocks as preset candidates of the gas leak location; and schematic diagram Gb illustrating an example composite image for display. 
         FIG. 7  is a schematic diagram illustrating various processing carried out to an image frame according to a fourth embodiment of the present invention. 
         FIG. 8  illustrates the fourth embodiment and includes; schematic diagram Ga illustrating a result of a count processing carried out to an image frame and a block corresponding to the estimated gas leak location; and schematic diagram Gb illustrating an example composite image for display. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Hereinafter, one or more embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the disclosed embodiments. 
     A device of estimating a gas leak location, a system of estimating a gas leak location, a method of estimating a gas leak location, and a program of estimating a gas leak location according to embodiments of the present invention will now be described with reference to the accompanying drawings. The embodiments described below should not be construed to limit the present invention. The gas leak location estimating system described below includes a gas leak location estimating device carrying out a gas leak location estimating method on the basis of a gas leak location estimating program, and an infrared camera. 
     According to the present invention, the gas leak location can be accurately estimated by processing based on a plurality of frames in chronological order because a gas leak location becomes constant regardless of passage of time. 
     First Embodiment 
     A gas leak location estimating system according to a first embodiment of the present invention will now be described. 
     The gas leak location estimating system  100  according to this embodiment includes an infrared camera  10 , a visible light camera  20 , and an information processor  30 . The information processor  30  is composed of a computer including a processor and storage. A gas leak location estimating program stored in the storage is executed by the processor to activate functional components. 
     The information processor  30  includes the following functional components: a gas detector  31 , a block divider  32 , a block discriminator  33 , a counter  34 , a leak location estimator  35 , and an image compositor  36 . 
     The infrared camera  10  detects infrared radiant energy emerging from a monitoring target and converts the energy to a digital image signal. The visible light camera  20  detects visible light radiating from the monitoring target and converts the visible light to a digital image signal. The infrared camera  10  and the visible light camera  20  have identical angles of view. The monitoring target is, for example, a piping facility for an industrial plant. 
     The infrared camera  10  and the visible light camera  20  execute consecutive imaging at a predetermined frame rate (for example, 30 fps), and the frame data is sequentially input to the information processor  30 . 
     The gas detector  31  detects a gas area in pixel unit from the infrared image signal input from the infrared camera  10  through any means, for example, temperature thresholding or motion detection method. The temperature thresholding is a method for discriminating a gas area, when a target to be detected is gas having a leakage temperature higher or lower than a temperature within a normal temperature range in the environment where the monitoring target is disposed, by using a threshold temperature for distinguishing from the temperature within the environment temperature range. The motion detection method is a method for discriminating a moving object area where differential signals of luminance signals of specific pixels in frames with respect to those of the respective pixels in a reference frame are higher than a predetermined threshold, to determine the moving object area as a gas area. The reference frame may be a one or more previous frame, or a past frame which has been still image as a whole in a certain period. 
     The block divider  32  divides each frame image of the infrared image signals into multiple blocks having a predetermined size. The size of a single block is, for example, 10×10 pixels. 
     The block discriminator  33  executes a block discrimination processing of discriminating whether each block in each frame is a gas area based on the results detected by the gas detector  31 . The block discriminator  33  discriminates the block of which more than a predetermined percentage (50%, for example) of the pixels is detected as the gas area by the gas detector  31 , and determines the block as the gas area. The block discriminator  33  assigns an identification value “1” to the block which is discriminated as the gas area, and an identification value “0” to the block which is not discriminated as the gas area. 
     The counter  34  executes a count processing of counting the number of times each block is discriminated as the gas area in the block discrimination processing, over chronological frames. 
     The leak location estimator  35  executes a leak location estimation processing of setting a block having a counted value which is obtained by the counter  34  and equal to or larger than a predetermined value, to an estimated gas leak location. 
     The image compositor  36  executes an image composition processing of defining a visible light image input from the visible light camera  20  as a back layer, extracting the pixels detected as the gas areas by the gas detector  31  from the infrared image signals input from the infrared camera  10 , converting the extracted pixels to the visible light range to obtain an infrared imaging visualization image, overlaying the infrared imaging visualization image on the back layer while setting a predetermined transmittance, and overlaying an image indicating the block set as the estimated gas leak location by the leak location estimator  35  thereon. The composite image prepared by the image compositor  36  is output and displayed on the display monitor. A user can grasp the gas distribution and the gas leak location from the displayed image. 
     The steps of the processing described above will now be described in detail with reference to  FIGS. 2 and 3 . For simplification, the processing of three frames will be described. 
     The gas detector  31  detects a gas area G 1  in a first frame F 1 , as illustrated in  FIG. 2  Ga 1 . 
     In response, the block discriminator  33  assigns an identification value “1” to the blocks which are discriminated as the gas area, and an identification value “0” to the blocks which are not discriminated as the gas area, as illustrated in  FIG. 2  Gb 1 . 
     The gas detector  31  then detects a gas area G 2  in a second frame F 2 , as illustrated in  FIG. 2  Ga 2 . 
     In response, the block discriminator  33  assigns an identification value “1” to the blocks which are discriminated as the gas area, and an identification value “0” to the blocks which are not discriminated as the gas area, as illustrated in  FIG. 2  Gb 2 . 
     The gas detector  31  then detects a gas area G 3  in a third frame F 3 , as illustrated in  FIG. 2  Ga 3 . 
     In response, the block discriminator  33  assigns an identification value “1” to the blocks which are discriminated as the gas area, and an identification value “0” to the blocks which are not discriminated as the gas area, as illustrated in  FIG. 2  Gb 3 . 
     The counted values of the respective blocks obtained by the counter  34  through the above process are illustrated in  FIG. 3  Ga. With reference to  FIG. 3  Ga, the leak location estimator  35  defines the block B 47  having a counted value equal to or larger than a predetermined value as an estimated gas leak location. In this case, the predetermined value is the maximum value. 
     The image compositor  36  defines a visible light image I 3  input from the visible light camera  20  as a back layer as illustrated in  FIG. 3  Gb, extracts the pixels detected as the gas area by the gas detector  31  from the infrared image signal input from the infrared camera  10 , converts the extracted pixels to a visible light range to obtain an infrared imaging visualization image (G 3 ), overlays the infrared imaging visualization image (G 3 ) on the back layer while setting a predetermined transmittance, and overlays an image indicating a block B 47  set as the estimated gas leak location by the leak location estimator  35  thereon, to generate a composite image. 
     The composite image of the visible light image and the infrared imaging visualization image is displayed as a still image of the most recent frame among the frames used in the above processing or a moving image of several most recent frames. 
     Second Embodiment 
     A gas leak location estimating system according to a second embodiment of the present invention will now be described. 
     With reference to  FIG. 4 , the gas leak location estimating system  101  according to this embodiment is identical to the gas leak location estimating system  100  according to the first embodiment except that the information processor  30  further includes a process termination determiner  37 . 
     The process termination determiner  37  determines whether the block set as the estimated gas leak location by the leak location estimator  35  remains unchanged over a predetermined number of times. For example, in the process described with reference to  FIG. 2 , the leak location estimator  35  executes the leak location estimation processing every three frames. In the case where the predetermined number of times is four, the process termination determiner  37  determines whether the block set as the estimated gas leak location by the leak location estimator  35  remains unchanged over four times. 
     If the block remains unchanged, the block discriminator  33  terminates the block discrimination processing. As a result, also the downstream steps by the counter  34 , the leak location estimator  35 , and the image compositor  36  are terminated. 
     The second embodiment described above can estimate a location of gas leak with certain reliability and reduce the load on the information processor  30 . 
     Third Embodiment 
     A gas leak location estimating system according to a third embodiment of the present invention will now be described. 
     With reference to  FIG. 5 , the gas leak location estimating system  102  according to this embodiment is identical to the gas leak location estimating system  100  according to the first embodiment except that the information processor  30  further includes a preset candidate selector  38 . 
     Multiple leak location candidates are preset by selection of positions in the frames captured by the infrared camera  10  and registered to the information processor  30 . 
     The preset candidate selector  38  selects the leak location candidates closest to the block set by the leak location estimator  35 . 
     For example, blocks C 42 , C 54 , and C 47  (see  FIG. 6  Ga) depicting flanged joints  51 ,  52 , and  53  are preliminarily set as the leak location candidates. This is because connections, such as joints, in the channel are prone to gas leakage. 
     The leak location estimator  35  estimates blocks B 14 , B 25 , B 35 , and B 36  having maximum values “2” to be the locations of gas leak, as illustrated in  FIG. 6  Ga. 
     The preset candidate selector  38  calculates the respective distances between the blocks B 14 , B 25 , B 35  and B 36  and the blocks C 42 , C 47  and C 54  and selects the leak location candidate having the smallest distance, i.e., the block C 47 . The distance should be the sum or average of linear distances calculated on the basis of the coordinates of the centers of the blocks. 
     With reference to  FIG. 6  Gb, the image compositor  36  composes the image indicating the blocks B 14 , B 25 , B 35  and B 36  set by the leak location estimator  35  as in the first embodiment, and also composes the image indicating the block C 47  selected by the preset candidate selector  38 . 
     It should be noted that the image indicating the block C 47  selected by the preset candidate selector  38  may be composed without composition of the image indicating the blocks B 14 , B 25 , B 35  and B 36  set by the leak location estimator  35 . 
     According to the third embodiment described above, the gas leak location can be accurately estimated on the basis of preliminarily registered preset candidates, even if an obstacle N 1 , such as a tree, appears between the infrared camera  10  and the piping facility or monitoring target, as illustrated in  FIG. 6  Gb.  FIG. 3  Gb illustrates a case that the obstacle N 1  does not exist in  FIG. 6  Gb. In this case, the block set by the leak location estimator  35  matches the block selected by the preset candidate selector  38 . When the blocks match in this way, it is preferred to display, in addition to the display of the matched blocks, the fact that the block set as the estimated gas leak location on the basis of the image processing matches the block selected as the preset gas leak candidate in a discriminable manner. 
     Fourth Embodiment 
     A gas leak location estimating system according to a fourth embodiment of the present invention will now be described. 
     The gas leak location estimating system according to this embodiment has a configuration identical to that according to the first embodiment illustrated in  FIG. 1  and executes the following process. 
     In this embodiment, the block divider  32  divides each frame image of an infrared image signal into 12×14 blocks. 
     The gas detector  31  detects a gas area G 1  in a first frame F 1 , as illustrated in  FIG. 7  Ga 1 . 
     In response, the block discriminator  33  assigns an identification value “1” to the blocks which are discriminated as the gas area, and an identification value “0” to the blocks which are not discriminated as the gas area, as illustrated in  FIG. 7  Gb 1 . 
     The gas detector  31  then detects a gas area G 2  in a second frame F 2 , as illustrated in  FIG. 7  Ga 2 . 
     In response, the block discriminator  33  assigns an identification value “1” to the blocks which are discriminated as the gas area, and an identification value “0” to the blocks which are not discriminated as the gas area, as illustrated in  FIG. 7  Gb 2 . 
     Similarly, third to ninth frames are processed to assign an identification value “1” or “0” to every block in each frame. 
     The gas detector  31  then detects a gas area G 10  in a tenth frame F 10 , as illustrated in  FIG. 7  Ga 3 . 
     In response, the block discriminator  33  assigns an identification value “1” to the blocks which are discriminated as the gas area, and an identification value “0” to the blocks which are not discriminated as the gas area, as illustrated in  FIG. 7  Gb 3 . 
     The counted values of the respective blocks obtained by the counter  34  through the above process are illustrated in  FIG. 8  Ga. With reference to  FIG. 8  Ga, the leak location estimator  35  discriminates the blocks B 0611 , B 0612 , B 0613 , B 0614 , B 0711 , B 0712 , B 0713 , B 0714 , B 0813 , B 0814 , B 0913 , and B 0914  having counted values equal to or larger than a predetermined value as estimated locations of the gas leak. For example, the predetermined value is “9.” 
     The image compositor  36  defines a visible light image I 10  input from the visible light camera  20  as a back layer as illustrated in  FIG. 8  Gb, extracts the pixels detected as a gas area by the gas detector  31  from the infrared image signal input from the infrared camera  10 , converting the extracted pixels to a visible light range to obtain an infrared imaging visualization image (G 10 ), overlays the infrared imaging visualization image (G 10 ) on the back layer while setting a predetermined transmittance, and overlays an image indicating the blocks B 0611 , B 0612 , B 0613 , B 0614 , B 0711 , B 0712 , B 0713 , B 0714 , B 0813 , B 0814 , B 0913  and B 0914  to be the estimated locations of the gas leak by the leak location estimator  35  thereon, to generate a composite image. 
     The composite image of the visible light image and the infrared imaging visualization image is displayed as a still image of the most recent frame among the frames used in the processing or a moving image of several most recent frames. 
     If a maximum value or a value smaller than the maximum value (the average, for example) is selected to be the threshold of the counted values for determining the estimated gas leak location, values exceeding the threshold are always included even if these values have low absolute values. This might hinder accurate estimation of the gas leak location. 
     According to the fourth embodiment described above, the threshold of the counted values for determining the estimated gas leak location is a constant value. Thus, the gas leak location is not estimated if the maximum value is smaller than this constant value. In this way, the gas leak location can be more accurately estimated without effects of noise and other factors. 
     In the embodiments described above, three or ten frames are processed to estimate the gas leak location. Any other number of frames may be appropriately selected in consideration of frame rate, calculation load, and estimated accuracy. 
     In the embodiments described above, the visible light image I 3  captured by the visible light camera  20  is defined as the back layer, to emphasize the gas leak location estimated through image composition. Besides a captured image, the back layer may be a graphic image prepared in advance. 
     Although the embodiments described above include an image compositor  36 , the image compositor  36  may be omitted because the composite image is displayed for the viewing of a user and unnecessary if the gas leak location estimated by the system according to the present invention is to be announced to another system including a computer. 
     Although embodiments of the present invention have been described and illustrated in detail, it is clearly understood that those are mere examples, and the scope of the present invention should not be limited to the examples in the descriptions and the appended claims. 
     Industrial Applicability 
     The present invention can detect a gas leak, for example, in an industrial plant and specify the gas leak location. 
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
           10  infrared camera 
           20  visible light camera 
           30  information processor 
         F 1  frame 
         F 2  frame 
         F 3  frame 
         G 1  gas area 
         G 2  gas area 
         G 3  gas area 
         I 3  visible light image 
         N 1  obstacle