Image Processing Apparatus Using Lookup Tables for Dynamic Range Synthesis
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Solution Overview
Problem
Conventional image processing methods for expanding the dynamic range of images by synthesizing frames with different exposure values face challenges in maintaining pixel value continuity at boundaries without increasing circuit scale and arithmetic operation complexity, leading to cost and efficiency issues in real-time video processing.
Innovation Solution
An image processing apparatus and method that utilize a pixel value converter, synthesizing/weighting coefficient creator, difference creator, and parameter updater to match and adjust pixel values across frames, using conversion coefficients and weighting coefficients to synthesize images while minimizing circuit scale and arithmetic load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If histogram-based pixel value matching is used to synthesize images with different exposure values, then pixel value continuity at boundaries is improved, but circuit scale and arithmetic operation amount increase significantly
Solution Approach 1:
The patent changes the approach from using histogram-based arithmetic operations to using lookup tables (LUTs) for pixel value conversion. The pixel value converter uses LUTs to efficiently match pixel values between images with different exposure values, achieving continuous pixel values at boundaries while avoiding the complex arithmetic operations required by histogram-based methods.
Solution Approach 2:
The patent replaces complex arithmetic operations with table lookup mechanisms. Instead of performing heavy histogram calculations and arithmetic adjustments, the system uses pre-computed lookup tables to achieve pixel value matching, significantly reducing circuit scale and arithmetic operation requirements while maintaining pixel value continuity.
2Speed
If high-speed arithmetic operations are performed to match pixel values at boundary portions in real-time, then response speed to subject change is improved, but circuit scale and cost increase
Solution Approach 1:
The patent performs preliminary action by pre-computing and storing conversion coefficients and lookup tables in advance. The pixel value converter uses these pre-prepared LUTs to rapidly convert pixel values between different exposure conditions in real-time, achieving high response speed without requiring complex arithmetic operations during the actual image synthesis.
Solution Approach 2:
The patent substitutes real-time arithmetic operations with pre-computed table lookups. By using lookup tables stored in memory, the system achieves fast pixel value conversion and boundary matching in real-time video processing, eliminating the need for high-speed arithmetic circuitry and reducing overall circuit scale.
3Productivity
If conventional pixel value conversion methods are used, then processing speed is maintained, but pixel value discontinuity occurs at boundary portions
Solution Approach 1:
The patent introduces feedback through the parameter update unit, which evaluates the difference between synthesized images and original images to automatically adjust and optimize conversion coefficients. This feedback mechanism ensures that pixel values at boundaries are continuously refined and matched, eliminating discontinuities while maintaining processing speed through efficient LUT-based conversion.
Solution Approach 2:
The patent dynamically adjusts conversion coefficients based on feedback from image difference evaluation. The parameter update unit modifies the conversion parameters to optimize pixel value matching at boundaries, ensuring continuous pixel values while maintaining processing efficiency through the lookup table approach.
Data Source
AI summary
Based on pixel value conversion coefficients, a pixel value converter converts pixel values of image signals obtained by imaging a same subject a plurality of times while mutually differentiating an exposure value. A synthesizing/weighting coefficient creation unit creates a synthesizing/weighting coefficient. A difference creation unit creates short-time exposure image data and long-time exposure image data. A weighting/synthesizing unit synthesizes the short-time exposure image data and the long-time exposure image data by using the synthesizing/weighting coefficient. A controller evaluates the difference, and updates the pixel value conversion coefficient so that the difference becomes smaller.