Quantifying gas leak rates using frame images acquired by a camera

Patent metadata

Field	Value
Publication number	US-10852208-B2
Application number	US-201716099648-A
Country	US
Kind code	B2
Filing date	Jun 21, 2017
Priority date	Aug 30, 2016
Publication date	Dec 1, 2020
Grant date	Dec 1, 2020

Abstract

A method of quantifying gas leak rate includes receiving image frames acquired with a camera and including a plume from a gas leak source, determining a real-world size that each pixel represents, identifying pixels corresponding to the plume in a first image frame, calculating gas concentration path lengths of the plume for the pixels in the first image frame, calculating, based on the first image frame and a second image frame, an image velocity field of the plume including displacement vectors for the pixels, identifying, within the first image, a closed boundary enclosing the gas leak source of the plume, and calculating a first gas leak rate in the first image frame by calculating a volume rate of the plume flowing across the closed boundary based on the image velocity field, the gas concentration path lengths, and a time interval between the first and the second image frames.

First claim

What is claimed is:

1. A method of quantifying gas leak rate, comprising:
receiving a first plurality of image frames acquired with a first camera and comprising a plume from a gas leak source;
identifying a plurality of pixels corresponding to the plume in a first image frame of the first plurality of images frames;
calculating a plurality of gas concentration path lengths of the plume for the plurality of pixels in the first image frame;
calculating, based on the first image frame and a second image frame, an image velocity field of the plume comprising a plurality of displacement vectors for the plurality of pixels;
identifying, within the first image, a plurality of pixels corresponding to the gas leak source and generating a closed boundary enclosing an entirety of the plurality of pixels corresponding to the gas leak source;
calculating a first gas leak rate in the first image frame by calculating a volume rate of the plume flowing across the closed boundary based on:
the image velocity field;
the plurality of gas concentration path lengths; and
a time interval between the first image frame and the second image frame,

wherein the method further comprises:
post-processing the first plurality of image frames prior to calculating of the image velocity field of the plume;
calculating the gas leak rate using the first gas leak rate, and
wherein the first plurality of post-processed image frames are concentration path length map images.

2. The method of claim 1 , further comprising:
calculating an average distance of the plurality of displacement vectors;
applying a sub-pixel flow correction method in response to the average distance being less than 1 pixel.

3. The method of claim 2 , wherein the sub-pixel flow correction method comprises:
scaling the calculated first gas leak rate by a factor of the average distance of the image velocity field at each of the plurality of pixels.

4. The method of claim 1 , further comprising:
calculating a second gas leak rate in the second image frame; and
calculating an average gas leak rate based on the first gas leak rate and the second gas leak rate.

5. The method of claim 1 , wherein calculating the volume rate comprises:
identifying, within the closed boundary, a first contributing pixel comprising a displacement vector that points from the first contributing pixel to outside the closed boundary;
identifying, within the closed boundary, a second contributing pixel comprising a second displacement vector that points from the second contributing pixel to outside the closed boundary;
calculating a first gas volume from the first contributing pixel by multiplying the concentration path length of the first contributing pixel by the real-world size of the first contributing pixel;
calculating a second gas volume from the second contributing pixel by multiplying the concentration path length of the second contributing pixel by the real-world size of the second contributing pixel; and
generating a total gas volume by summing the first gas volume and the second gas volume; and
dividing the total gas volume by the time interval between the first image frame and the second image frame.

6. The method of claim 1 , wherein the image velocity field of the plume is calculated by an optical flow method.

7. The method of claim 1 , wherein the image velocity field of the plume is calculated by a geometric flow method.

8. The method of claim 1 , further comprising:
obtaining a second plurality of image frames acquired by a second camera and comprising the plume from the gas leak source,
wherein the first camera and the second camera are at different viewing angles;
calculating a second gas leak rate using the second plurality of image frames; and
averaging the first gas leak rate and the second gas leak rate.

9. The method of claim 8 , wherein the viewing angle of the first camera is orthogonal to the viewing angle of the second camera.

10. A non-transitory computer readable medium (CRM) storing computer readable program code embodied therein that:
receives a first plurality of image frames acquired with a first camera and comprising a plume from a gas leak source;
identifies a plurality of pixels corresponding to the plume in a first image frame of the first plurality of images frames;
calculates a plurality of gas concentration path lengths of the plume for the plurality of pixels in the first image frame;
calculates, based on the first image frame and a second image frame, an image velocity field of the plume comprising a plurality of displacement vectors for the plurality of pixels;
identifies, within the first image, a plurality of pixels corresponding to the gas leak source and generating a closed boundary enclosing an entirety of the plurality of pixels corresponding to the gas leak source;
calculates a first gas leak rate in the first image frame by calculating a volume rate of the plume flowing across the closed boundary based on:
the image velocity field;
the plurality of gas concentration path lengths; and
a time interval between the first image frame and the second image frame;

post-processes the first plurality of image frames prior to calculating of the image velocity field of the plume;
calculates the gas leak rate using the first gas leak rate, and
wherein the first plurality of post-processed image frames are concentration path length map images.

11. The non-transitory computer readable medium (CRM) of claim 10 storing computer readable program code embodied therein that further:
calculates an average distance of the plurality of displacement vectors;
applies a sub-pixel flow correction method in response to the average distance being less than 1 pixel.

12. The non-transitory computer readable medium (CRM) of claim 10 storing computer readable program code embodied therein that further:
calculates a second gas leak rate in the second image frame; and
calculates an average gas leak rate based on the first gas leak rate and the second gas leak rate.

13. The non-transitory computer readable medium (CRM) of claim 10 storing computer readable program code embodied therein, wherein calculating the volume rate comprises:
identifying, within the closed boundary, a first contributing pixel comprising a displacement vector that points from the first contributing pixel to outside the closed boundary;
identifying, within the closed boundary, a second contributing pixel comprising a second displacement vector that points from the second contributing pixel to outside the closed boundary;
calculating a first gas volume from the first contributing pixel by multiplying the concentration path length of the first contributing pixel by the real-world size of the first contributing pixel;
calculating a second gas volume from the second contributing pixel by multiplying the concentration path length of the second contributing pixel by the real-world size of the second contributing pixel; and
generating a total gas volume by summing the first gas volume and the second gas volume; and
dividing the total gas volume by the time interval between the first image frame and the second image frame.

14. A system for quantifying gas leak rate, comprising:
a memory; and
a processor that:
receives a first plurality of image frames acquired with a first camera and comprising a plume from a gas leak source;
identifies a plurality of pixels corresponding to the plume in a first image frame of the first plurality of images frames;
calculates a plurality of gas concentration path lengths of the plume for the plurality of pixels in the first image fr

Assignees

• Konica Minolta Laboratory Usa Inc

Inventors

• Wang Leiming

Classifications

• H04N23/45

  for generating image signals from two or more image sensors being of different type or operating in different modes, e.g. with a CMOS sensor for moving images in combination with a charge-coupled device [CCD] for still images · CPC title

• H04N23/20

  for generating image signals from infrared radiation only · CPC title

• G01J2005/0077

  Imaging · CPC title

• G01N21/3504

  for analysing gases, e.g. multi-gas analysis · CPC title

• G01M3/007

  Leak detector calibration, standard leaks (G01M3/207 takes precedence) · CPC title