CMOS Flash Detection via Line Luminance Frame Differences
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Solution Overview
Problem
Conventional imaging devices face challenges in reliably detecting the influence of external flashes, particularly in cases where the flash affects only a small portion of the screen or when a high-luminance subject moves, leading to incorrect flash detection and increased circuit complexity.
Innovation Solution
An imaging device with a flash detection unit that calculates line luminance information values and frame differences to determine the presence and duration of external flash influence, using reference values to accurately identify changes in luminance across frames without requiring significant circuit scale increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional flash detection methods are used, then flash detection is performed, but detection reliability is low when flash affects only small portions or when high-luminance subjects move
Solution Approach 1:
The screen is divided into multiple regions (first region and second region) to independently analyze flash influence in different areas. This segmentation allows the system to detect flash effects even when they affect only small portions of the screen, improving detection reliability without requiring full-screen analysis.
Solution Approach 2:
Different evaluation methods are applied to different regions of the screen based on their specific characteristics. The first region uses one evaluation approach while the second region uses another, allowing optimized detection for local conditions such as small flash impacts or moving high-luminance subjects.
2Measurement precision
If complex flash detection algorithms are implemented, then detection accuracy improves, but device complexity increases
Solution Approach 1:
By dividing the screen into regions and applying simple comparison operations within each region, the system achieves accurate flash detection without requiring complex algorithms. Each region's luminance values are compared against reference values, providing a computationally efficient approach.
Solution Approach 2:
The system changes the evaluation parameters differently for different regions - using appropriate reference values and comparison thresholds for each region. This allows accurate detection using simple parameter comparisons rather than complex computational algorithms.
Data Source
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AI summary
When capturing images of a subject with an imaging device that uses a CMOS image sensor, a white band-shaped artifact appears in the imaging signal due to the influence of a rolling shutter operation performed when an external flash has been emitted. Manipulating or removing images in which such an artifact appears requires specifying the frames in which the artifact appears. A line averaging unit (11) calculates the average luminance level of each line in the imaging signal, the average luminance levels are temporarily stored by a storage unit (12), and thereafter a frame difference calculation unit (13) calculates the difference between the line average luminance levels and the line average luminance levels of the next frame. These frame difference values are compared with a reference value, and it is determined that the influence of an external flash is present if a portion of interest with high values is continuous for one frame period.