Image Sensor Exposure Control via Block Motion Analysis
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Solution Overview
Problem
Conventional image capturing devices lack precise exposure control, particularly when capturing moving objects, as they do not account for relative changes between objects and backgrounds, affecting image quality.
Innovation Solution
A circuit and method that calculate evaluated luminance values for each image block, determine motion values, and adjust exposure time or gain based on these values using a look-up table to differentiate between foreground and background, enabling more precise exposure control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional exposure control based on average luminance of entire image is used, then device complexity is low, but exposure control precision is insufficient
Solution Approach 1:
The image sensor array is divided into multiple blocks, and each block is further divided into multiple regions. This segmentation allows the control circuit to calculate luminance statistics separately for each block and region, enabling precise exposure control for different areas of the image while maintaining manageable circuit complexity through modular processing.
Solution Approach 2:
The patent implements different exposure control strategies for different regions within blocks. Moving regions use one exposure determination method while stationary regions use another, allowing each region to receive optimized exposure control tailored to its specific characteristics rather than applying a uniform approach across the entire image.
2Reliability
If exposure control does not consider motion detection, then processing speed is fast, but image quality deteriorates due to inadequate exposure adjustment for moving objects
Solution Approach 1:
The control circuit performs motion detection and luminance statistic calculation for multiple blocks and regions in advance before the actual exposure operation. By pre-processing the image data to identify moving regions and calculate their luminance characteristics, the system prepares exposure parameters proactively, reducing processing delays during actual image capture while ensuring high image quality through motion-aware exposure control.
3Measurement precision
If uniform exposure control is applied to entire image, then ease of operation is high, but measurement precision of luminance varies across different regions
Solution Approach 1:
The image is divided into multiple blocks with each block containing multiple regions, allowing luminance statistics to be calculated locally for each region rather than uniformly across the entire image. This segmentation enables precise luminance measurement for each block while the automated calculation process maintains operational simplicity.
Solution Approach 2:
Different luminance measurement and exposure control parameters are applied to different blocks and regions based on their specific characteristics. Each block's luminance statistics are calculated independently, and exposure parameters are adjusted locally according to motion detection results and luminance values of that specific region, achieving both precision and automated ease of operation.
Data Source
AI summary
A method for controlling an image capturing device includes: calculating luminance data of a first image to generate a plurality of first characteristic values, and calculating luminance data of a second image to generate a plurality of second characteristic values; calculating a plurality of motion values of a plurality of blocks of the second image according to the luminance data of the first image and the luminance data of the second image; determining a plurality of ratio parameters corresponding to the blocks of the second image according to the motion values; generating a plurality of adjusted second characteristic values according to the ratio parameters, the second characteristic values and the first characteristic values; and generating an adjustment signal for controlling the image capturing device according to the adjusted second characteristic values.