CMOS Image Sensor Dynamic Range Expansion via Region-Based Synthesis
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Solution Overview
Problem
Existing image processing techniques struggle to accurately combine pixel signals from CMOS image sensors with different sensitivities, leading to false colors due to deviations in luminance ratios caused by blinking light sources.
Innovation Solution
An apparatus and method that obtain pixel signals from images captured with different sensitivities, calculate a conversion ratio to standardize sensitivity, and determine a synthesis ratio for each divided region or pixel to perform dynamic range expansion synthesis, thereby correcting luminance ratios and preventing false colors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If pixel signals from multiple images with different sensitivities are combined to expand dynamic range, then the dynamic range of the image is expanded, but false colors are generated due to deviations in luminance ratios caused by blinking light sources
Solution Approach 1:
The patent divides the pixel array into multiple divided regions (e.g., first divided region and second divided region) and calculates separate synthesis ratios for each region. This segmentation allows different parts of the image to use optimized synthesis parameters, preventing false colors in regions affected by blinking light sources while maintaining dynamic range expansion in other regions.
Solution Approach 2:
The patent determines whether to use a first synthesis ratio or a second synthesis ratio based on the maximum luminance value in each divided region. By applying different synthesis ratios to different regions with different luminance characteristics, the patent maintains local color accuracy while achieving global dynamic range expansion.
2Device complexity
If a single synthesis ratio is used for all pixels to simplify processing, then the processing complexity is reduced, but color balance is lost in regions with blinking light sources
Solution Approach 1:
The patent segments the pixel array into multiple divided regions and applies different synthesis ratios to each region based on its luminance characteristics. This segmentation approach maintains relatively simple processing within each region while achieving accurate color balance across the entire image.
Solution Approach 2:
The patent dynamically selects between a first synthesis ratio and a second synthesis ratio based on the maximum luminance value detected in each divided region. This dynamic adaptation allows the system to respond to varying lighting conditions and blinking light source effects without requiring complex manual intervention.
Data Source
AI summary
A processing apparatus obtains pixel signals of a plurality of images by shooting a subject with different sensitivities by a sensor having a plurality of pixels; obtains a conversion ratio for converting the pixel signals of the plurality of images into pixel signals with a same sensitivity and a synthesis ratio for synthesizing the pixel signals of the plurality of images with the same sensitivity for each pixel; and performs dynamic range expansion synthesis for each pixel using the pixel signals of the plurality of images using the conversion ratio and the synthesis ratio. The synthesis ratio is obtained for each divided region obtained by dividing the plurality of pixels.