Hierarchical Histogram for Automatic Exposure Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing automatic exposure control systems for CMOS imagers require significant hardware and processing resources to generate full histograms, which is inefficient and time-consuming, especially for high-resolution imaging applications.
Innovation Solution
The implementation of a hierarchical histogram that divides pixel values into multiple sub-histograms with varying resolutions, reducing the number of bins and storage requirements while maintaining effective exposure control, using only the most significant bits of pixel outputs and employing percentile schemes to determine optimal exposure settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If full histograms are generated for automatic exposure control, then exposure control accuracy is improved, but hardware resources and processing time increase significantly
Solution Approach 1:
The patent divides the full histogram into multiple sub-histograms, each covering a specific range of pixel values (e.g., shadows, midtones, highlights). Instead of processing all pixel values uniformly, the system segments the histogram generation task into smaller, manageable sub-histograms that can be processed independently with reduced hardware resources while maintaining overall exposure control accuracy.
2Measurement precision
If full histograms are generated for automatic exposure control, then exposure control accuracy is improved, but processing time increases significantly
Solution Approach 1:
By segmenting the histogram into sub-histograms, the processing time is reduced because each sub-histogram can be generated and analyzed independently and in parallel, rather than waiting to process the entire histogram sequentially. This segmentation enables faster exposure control decisions.
Solution Approach 2:
The patent applies partial action by generating only the necessary sub-histograms required for exposure control rather than processing the complete histogram. The system selectively processes specific pixel value ranges that are most relevant to exposure adjustment, reducing overall processing time while maintaining control accuracy.
3Loss of information
If full histograms are generated, then complete pixel value distribution is captured, but storage requirements increase
Solution Approach 1:
The patent segments the pixel value distribution into multiple sub-histograms, each storing only the relevant portion of the data. This segmentation reduces the total storage capacity required because each sub-histogram contains fewer bins and less data than a full histogram, while collectively they preserve the complete pixel value distribution information needed for exposure control.
Data Source
AI summary
An automatic exposure control circuit and a method for generating a hierarchical histogram for exposure control. The control circuit and the method result in the generation of a histogram with sub-histograms of differing resolutions. The sub-histograms are used to adjust an image exposure setting according to a distribution of pixel values determined from the histogram.