Thermal Image Processing for Internal-Reflection Ghost Suppression
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Solution Overview
Problem
Thermal cameras suffer from ghost images caused by internal reflections, which are difficult to distinguish from actual objects and can obscure other objects of interest, and existing methods to reduce reflections either require additional optical elements or degrade image quality.
Innovation Solution
A method for thermal image processing that analyzes the frequency distribution of pixel intensities to determine if a hot object peak is separated from the thermal background by a threshold, and adjusts pixel intensities to suppress ghost images only when necessary, without adding optical elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If antireflective coatings are applied to optical elements, then internal reflections are reduced, but sensitivity in the wavelength range of the coating is reduced
Solution Approach 1:
The patent extracts and removes the harmful ghost image pixels from the thermal image through digital image processing. By identifying ghost image pixels based on their location relative to hot objects and their intensity characteristics, the system selectively removes only the harmful reflected radiation artifacts without affecting the sensitivity to actual thermal radiation in the scene.
Solution Approach 2:
The patent introduces an intermediary processing step between image acquisition and final display. A ghost image suppression module acts as a mediator that analyzes the thermal image, identifies ghost image pixels through frequency distribution analysis and spatial relationships, and selectively adjusts their intensities to eliminate reflections while preserving genuine thermal information.
2Object-affected harmful factors
If curved protective windows or filters are added to defocus or attenuate reflected radiation, then undesired reflections are reduced, but device complexity and manufacturing costs increase
Solution Approach 1:
The patent replaces the mechanical/optical approach of using curved windows or physical filters with a digital image processing system. Instead of modifying the optical path with additional elements, the system uses computational methods to identify and suppress ghost images after they are formed in the captured thermal image, thereby eliminating the need for complex additional optical components.
3Object-affected harmful factors
If additional optical elements are introduced in the imaging system, then reflections are suppressed, but image quality is degraded in situations without hot objects
Solution Approach 1:
The patent implements a dynamic ghost image suppression approach that adapts to the content of each thermal image. The system analyzes the frequency distribution of pixel intensities and spatial relationships to determine whether ghost images are present, and only applies suppression when hot objects are detected. This dynamic adaptation ensures that image quality is preserved in scenes without hot objects while effectively suppressing ghost images when they occur.
Solution Approach 2:
The patent applies ghost image suppression selectively to specific regions of the thermal image rather than uniformly across the entire image. By identifying the locations of hot objects and predicting where ghost images would appear based on optical path geometry, the system applies suppression only to the affected local regions, leaving the rest of the image quality intact.
4Object-affected harmful factors
If ghost image suppression is applied to all thermal images, then ghost images are reduced, but computational resources are wasted when no hot objects are present
Solution Approach 1:
The patent applies partial action by performing ghost image suppression only when necessary. The system first analyzes the thermal image to detect the presence of hot objects with temperatures significantly above the background, and only then proceeds with the computationally intensive ghost image suppression process. This selective application avoids wasting computational resources on images where no ghost images would be visible.
Solution Approach 2:
The patent performs preliminary analysis of the thermal image before applying ghost image suppression. By first examining the frequency distribution of pixel intensities and detecting hot objects, the system determines in advance whether ghost image suppression is needed, thereby avoiding unnecessary computational processing and optimizing resource utilization.
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
This approach effectively suppresses ghost images, improving image clarity and reducing false alarms, while maintaining image quality and computational efficiency.
Implementation Method 1
thermal cameras are used to monitor temperature for early fire detection and/or detecting over-heating of objects
Implementation Method 2
radiation received from the hot object may due to internal reflections in the thermal camera result in an image artefact
Data Source
AI summary
A method for thermal image processing, comprises: acquiring a thermal image depicting a scene; obtaining a frequency distribution based on pixel intensities of the thermal image; processing the frequency distribution to determine whether the frequency distribution comprises a peak, caused by a hot object in the scene, which is separated from a thermal background of the scene by more than an intensity threshold; and in response to determining that the frequency distribution comprises the peak, processing the thermal image to suppress a ghost image of the hot object in the thermal image, wherein the ghost image is caused by internal reflections of radiation from the hot object in the thermal camera, and wherein the processing of the thermal image comprises: estimating a location of ghost image pixels forming the ghost image; and suppressing the ghost image in the thermal image by adjusting intensities of the ghost image pixels.