Imaging Device Flash Ratio Control for White Balance Accuracy
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Solution Overview
Problem
Existing imaging systems face inaccuracies in white balance adjustment due to abrupt changes in flash ratio caused by hand vibration or changes in ambient lighting, leading to pixel position disturbances in images.
Innovation Solution
An imaging device and method that calculates an optimal final white balance coefficient by limiting the effective range of the flash ratio value, using a flash contribution indicator processor to adjust the flash contribution indicator within calculated upper and lower limits, ensuring accurate white balance adjustment despite image content variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a low-pass filter is applied to the flash ratio for every pixel to suppress rapid changes, then pixel position disturbance is reduced, but the flash ratio becomes inaccurate due to over-smoothing of legitimate variations
Solution Approach 1:
The patent applies different processing strategies to different regions of the image based on local characteristics. By identifying regions with abnormal flash ratio changes (likely caused by hand vibration) versus regions with legitimate flash ratio variations, the system selectively applies correction only where needed, preserving local accuracy while maintaining global stability.
Solution Approach 2:
The patent changes the parameter being controlled from the raw flash ratio to a corrected flash ratio that compensates for hand vibration effects. By introducing a correction mechanism that adjusts the flash ratio based on detected vibration patterns, the system maintains measurement precision while improving reliability.
2Measurement precision
If the flash ratio is calculated by comparing flash image and non-flash image pixels, then the contribution of flash to each pixel can be determined, but hand vibration or ambient lighting changes cause inaccurate flash ratio values
Solution Approach 1:
The patent applies a preliminary correction to the flash ratio calculation by detecting hand vibration effects and ambient lighting changes before final white balance adjustment. By identifying and compensating for these interfering factors in advance, the system prevents them from corrupting the flash ratio measurement, thereby maintaining both precision and reliability.
Solution Approach 2:
The patent introduces a feedback mechanism where the system continuously monitors the flash ratio values and detects abnormal variations caused by hand vibration or lighting changes. This feedback information is then used to adjust subsequent flash ratio calculations, creating a self-correcting system that maintains accuracy despite external disturbances.
3Measurement precision
If the flash ratio changes abruptly between pixels to accurately reflect local flash contribution, then local white balance accuracy improves, but pixel position disturbance occurs in the final image
Solution Approach 1:
The patent applies different smoothing strategies to different spatial regions based on the local characteristics of flash ratio variation. In regions where abrupt changes are legitimate (indicating real local flash contribution differences), the system preserves these variations. In regions where abrupt changes are artifacts (caused by hand vibration), the system applies localized smoothing. This selective approach maintains both local accuracy and global color registration.
Data Source
AI summary
An imaging device includes a flash ratio calculator calculating a flash ratio based on a flash image and a non-flash image, a main subject flash ratio selector selecting a flash ratio of an area of a main subject, a preliminary white balance coefficient determination unit determining a preliminary white balance coefficient used in adjusting a white balance, a flash ratio range calculator calculating an upper limit value and a lower limit value of a range of the flash ratio based on the flash ratio of the main subject and the preliminary white balance coefficient, a flash ratio processor altering the flash ratio so that the flash ratio is in the calculated range, and a white balance coefficient calculator calculating a white balance coefficient based on the altered flash ratio.