Thermography Camera Gas Leak Detection Contrast
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Passive thermography cameras face challenges in enhancing the visibility of gas plumes against non-reflecting backgrounds like sky or water, and in reducing signal noise while maintaining sufficient contrast, due to the limitations of narrow spectral bandwidth and increased sensor gain, which complicates the detection of gas leaks in industrial settings.
Innovation Solution
A portable infrared thermography camera system that uses a focal plane array image sensor and a spectral band pass filter to limit the spectral bandwidth, combined with temporal filtering and image differencing techniques to enhance the visibility of gas plumes by scaling and subtracting temporally filtered images from current images, thereby improving contrast without completely eliminating background elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a narrow spectral band pass filter is used to limit the spectral bandwidth to match the absorption band of the gas, then the ability to distinguish gas plumes from background elements is improved, but the total irradiance is significantly reduced requiring increased sensor gain which amplifies noise
Solution Approach 1:
The patent applies temporal filtering to previous video frames before subtracting them from the current frame. This preliminary processing of historical data allows the system to reduce noise in the difference image by comparing against a temporally filtered reference, rather than directly subtracting unprocessed frames which would amplify noise along with gas plume signals.
Solution Approach 2:
The patent extracts only the dynamic components (gas plumes) from the video signal by subtracting the temporally filtered reference image from the current frame. This extraction process separates the gas plume information from the static background and noise, allowing for enhanced detection without the noise amplification that would result from direct subtraction of raw frames.
2Illumination intensity
If sensor gain is increased to compensate for reduced irradiance from narrow spectral filtering, then the visibility of gas plumes is improved, but noise in the image signal is significantly amplified
Solution Approach 1:
The system performs temporal filtering on previous frames before the subtraction operation, preparing a noise-reduced reference image in advance. This preliminary action ensures that when the difference image is generated, the noise level is already reduced, allowing for adequate gas plume visibility without excessive gain amplification of noise.
Solution Approach 2:
The system uses feedback from multiple previous frames to create a temporally filtered reference that adapts to changing conditions. This feedback mechanism allows the system to maintain accurate background subtraction while reducing random noise, thereby improving gas plume detection without requiring excessive sensor gain that would amplify noise.
3Object-generated harmful factors
If temporal filtering is applied to reduce random signal noise, then the signal-to-noise ratio is improved, but dynamic or transient elements of the scene may be smoothed or blurred
Solution Approach 1:
The patent applies temporal filtering as a preliminary step before difference image generation. By filtering the reference frames in advance, the system reduces noise in the background subtraction process while the subsequent difference operation preserves the sharp edges of dynamic gas plumes, as the subtraction removes only the smoothed background components.
Solution Approach 2:
The patent segments the video signal into static background components (captured by the temporally filtered reference) and dynamic foreground components (gas plumes). This segmentation allows the temporal filtering to affect only the background without blurring the gas plume edges, as the difference image operation separates these components.
4Measurement precision
If difference imaging is used to enhance dynamic elements, then the visibility of gas plumes is improved, but non-varying background elements are completely removed which can be disorienting and eliminate contextual information
Solution Approach 1:
The patent applies partial temporal filtering by using a weighted combination of current and previous frames rather than complete subtraction. This partial action allows the difference image to emphasize gas plumes while retaining some background contextual information, avoiding the disorientation that would result from complete background removal.
Solution Approach 2:
The patent applies different processing characteristics to different parts of the image: dynamic regions (gas plumes) are enhanced through difference imaging while static regions (background) are partially retained. This local quality approach ensures that gas plume detection accuracy is improved without completely eliminating background contextual information that provides spatial orientation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The camera system effectively increases the visibility of gas plumes by reducing noise and maintaining background information, allowing for more accurate detection of gas leaks over various backgrounds, including sky and water, while reducing the complexity and cost associated with illuminator-based systems.
Implementation Method 1
A spectral band pass filter is disposed between the lens element and the image sensor to limit the spectral bandwidth of the scene image to a spectral bandwidth approximately corresponding with an absorption band of the gas to be detected
Implementation Method 2
each image sensor generates an analog image signal in proportion to an irradiance of the scene image at corresponding locations
Implementation Method 3
a lens element for collecting radiation from a survey scene and forming a scene image onto a focal plane array image sensor
Data Source
AI summary
A portable thermography camera system (100) renders a video image of a survey scene over a narrow spectral bandwidth corresponding with an absorption band of a gas to be detected in the video image. The camera system forms a scene image onto a focal plane array (108) and generates a corrected image signal (162) corresponding with irradiance values at a plurality of locations of the scene image. The camera system further generates a temporally filtered image signal (168) corresponding with a temporal characteristics of the image signal (162) over a selected number of prior image frames. A difference block (166) reduces the temporally filtered image signal (168) by a scaling factor and produces a difference image by subtracting the scaled temporally filtered image signal from the corrected image signal (162). The displayed difference signal improves the visibility of the gas to be detected.