Flash Band Detection Threshold Adjustment for CMOS Sensors
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Solution Overview
Problem
CMOS image sensors using the rolling shutter method often produce flash bands due to external flashes, which are not accurately detected when the flash intensity is low or exposure conditions change, leading to reduced detection accuracy.
Innovation Solution
A flash band determination device that dynamically adjusts the threshold level for detecting flash bands based on changing exposure conditions, such as aperture or gain adjustments, to ensure accurate detection across multiple frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed threshold level is used for detecting flash bands, then the detection process is simple, but the detection accuracy decreases when exposure conditions change or flash intensity is low
Solution Approach 1:
The patent applies the dynamics principle by making the threshold level variable rather than fixed. The threshold is dynamically adjusted based on exposure conditions (aperture, gain, shutter speed) and continuously updated using adaptive filtering of luminance values. This allows the detection system to maintain high accuracy across varying exposure conditions while managing complexity through systematic adaptation.
Solution Approach 2:
The patent implements parameter changes by modifying the threshold level parameter according to exposure condition parameters. When aperture, gain, or shutter speed changes occur, the threshold is recalibrated. Additionally, the threshold undergoes continuous parameter changes through adaptive filtering that adjusts based on the statistical properties of the luminance signal, ensuring optimal detection sensitivity.
2Measurement precision
If the threshold level is adjusted for changing exposure conditions, then the detection accuracy is maintained, but the device complexity increases
Solution Approach 1:
The patent employs feedback mechanisms where the detection system continuously monitors luminance values and exposure conditions, then feeds this information back to adjust the threshold level. The adaptive filtering process uses feedback from the statistical properties of the luminance signal to refine the threshold. Exposure condition changes are detected and fed back to trigger threshold recalibration, creating a closed-loop system that maintains accuracy.
Solution Approach 2:
The system implements self-service through automatic threshold adjustment based on detected exposure conditions. The device monitors its own operating parameters (aperture, gain, shutter speed) and autonomously recalibrates the threshold without external intervention. The adaptive filtering mechanism also operates autonomously, continuously refining the threshold based on the statistical characteristics of the incoming luminance signal.
3Speed
If a simple threshold comparison is used, then the processing speed is fast, but the reliability of flash band detection decreases when flash intensity is low
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing threshold values for different exposure conditions. When a specific aperture, gain, or shutter speed combination is detected, the corresponding pre-computed threshold is quickly retrieved and applied. This preliminary preparation allows the system to maintain fast processing speeds while ensuring reliable detection even for low-intensity flashes, as the appropriate threshold is already optimized for the current conditions.
Solution Approach 2:
The system maintains fast processing through dynamic threshold adjustment using adaptive filtering that operates efficiently on the luminance signal. The filtering process dynamically adapts to the signal characteristics without requiring complex computations, preserving processing speed. Simultaneously, the dynamic nature of the threshold allows it to be optimized for low-intensity flash detection by adjusting based on the actual luminance distribution in the image.
Data Source
AI summary
A flash band determination device that is capable of always detecting a flash band with high accuracy. It is determined whether or not there is a flash band caused by an external flash of light, which is an area having a luminance level higher than a threshold level, in a plurality of images which are continuously obtained. The threshold level is changed with respect to an image picked up with an exposure condition which is different from an exposure condition used in picking up a preceding image.