Adaptive Gain Histogram Equalization for Thermal Imaging Contrast

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Solution Overview

Problem

Thermal imaging systems face challenges in efficiently allocating display levels to image data, particularly due to the disparity between high digital depth of thermal image data and limited display depth, leading to poor visual contrast and inefficient use of display levels.

Innovation Solution

The implementation of adaptive Histogram Equalization (HE) transfer functions that adjust the gain based on the properties of the source histogram, such as width, to optimize the allocation of display levels and improve visual contrast, allowing for efficient utilization of available display levels by modifying the HE transfer function on a frame-by-frame basis.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If Histogram Equalization (HE) transfer functions are used to convert image data to display levels, then the utilization of available display levels is improved, but the visual contrast deteriorates when the histogram width is narrow

Engineering Contradiction:

Improvedisplay level utilization efficiencyVSAvoidvisual contrast

Core Design Contradiction:

ProductivityVSIllumination intensity

Solution Approach 1:

The patent applies dynamics by making the HE transfer function adaptive rather than static. The gain parameter of the HE transfer function is dynamically adjusted based on the measured histogram width of the input image. When the histogram width is narrow, the gain is increased to expand the contrast; when the histogram width is wide, the gain is reduced to maintain natural contrast. This dynamic adaptation resolves the contradiction between efficient display level utilization and visual contrast preservation.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of the HE transfer function (specifically the gain parameter) based on the histogram properties of the input image. By measuring the histogram width and using it to adjust the gain parameter, the system optimizes both display level utilization and visual contrast. This parameter change approach allows the same HE algorithm to adapt to different image characteristics and resolve the contradiction between efficient display utilization and contrast quality.

Inventive Principle:

Principle #35Parameter changes

2Illumination intensity

If the gain of the HE transfer function is increased to improve visual contrast, then the image contrast is enhanced, but the display levels are wasted due to inefficient utilization

Engineering Contradiction:

Improveimage contrastVSAvoiddisplay level utilization efficiency

Core Design Contradiction:

Illumination intensityVSProductivity

Solution Approach 1:

The patent implements feedback by measuring the histogram width of the input image and using this measurement to adjust the gain parameter of the HE transfer function. This closed-loop approach ensures that the gain is increased only when necessary (when histogram width is narrow), and reduced when the histogram width is adequate. The feedback mechanism prevents unnecessary gain increases that would waste display levels, while still enhancing contrast when needed, thus resolving the contradiction between image contrast enhancement and display level utilization efficiency.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent adjusts the gain parameter of the HE transfer function based on the measured histogram width, changing the parameter adaptively rather than using a fixed high gain value. This parameter change strategy ensures that contrast enhancement is applied only when the histogram width indicates it is necessary, preventing display level waste while maintaining image contrast quality.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If a fixed HE transfer function is used for all images, then the system complexity is reduced, but the adaptability to different image characteristics deteriorates

Engineering Contradiction:

Improvetransfer function complexityVSAvoidadaptability to histogram properties

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The patent applies self-service by enabling the HE transfer function to automatically adapt to different image characteristics without requiring manual intervention or complex configuration. The system measures the histogram width of each input image and autonomously adjusts the gain parameter accordingly. This self-adjusting mechanism provides adaptability to different image types while maintaining relatively simple system architecture, resolving the contradiction between system complexity and adaptability.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent makes the HE transfer function dynamic by allowing its gain parameter to change based on the input image's histogram properties. Rather than using a single fixed transfer function for all images, the system dynamically selects appropriate gain values based on measured histogram width. This dynamic approach provides versatility and adaptability across different image types while keeping the underlying HE algorithm simple and efficient.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS11276152B2Adaptive gain adjustment for histogram equalization in an imaging system

Publication Date: 2022.03.15 SEEK THERMAL

AI summary

Systems and methods may be provided that improve the application of Histogram Equalization (HE) transfer functions for converting image system source data to display compatible image frames. Histograms developed from source data may be measured and depending on their properties, the gain of the HE transfer function may be adaptively adjusted. In some embodiments the property measured is a histogram width.