Flash Band Compensation in Rolling Shutter Image Pickup
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Solution Overview
Problem
Image pickup apparatuses with rolling shutter devices face challenges in flash band compensation when the flash band width is smaller than the number of rows in one frame, leading to uneven luminance and the appearance of rows insensitive to the flash in the image.
Innovation Solution
An image pickup apparatus with a detection unit to identify flash bands across multiple frames, a correction unit to interpolate missing rows to create a full-screen flash image, and a determination unit to assess the flash band width, ensuring that rows without the flash band are interpolated using adjacent rows to prevent horizontal lines in the corrected image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional flash band compensation technique is used where the flash band width is smaller than the number of rows in one frame, then the feedback circuit can be configured, but rows insensitive to the flash appear in the corrected image
Solution Approach 1:
The patent transitions from a one-dimensional feedback circuit approach to a two-dimensional interpolation approach by utilizing both temporal (multiple frames) and spatial (adjacent rows) dimensions. The determination unit detects flash band presence across multiple frames, and the correction unit interpolates affected rows using information from adjacent rows in the same frame and corresponding rows in previous/next frames, effectively resolving the compensation accuracy issue without relying on complex feedback circuits.
2Difficulty of detecting and measuring
If the flash band width is smaller than the number of rows in one frame, then the detection is simpler, but the compensation becomes insufficient and creates visible artifacts
Solution Approach 1:
The determination unit performs preliminary detection of flash band presence and characteristics across multiple frames before the correction unit applies interpolation. By预先 identifying which rows are affected by the flash band and using multiple frames for detection, the system ensures reliable compensation even when the flash band is narrower than one frame height, preventing visible artifacts in the final image.
3Productivity
If interpolation is not performed for rows without flash band, then processing is faster, but horizontal lines appear in the corrected image
Solution Approach 1:
The correction unit applies interpolation selectively based on local conditions detected by the determination unit. Only rows that are adjacent to flash-affected rows undergo interpolation processing, while other rows remain unchanged. This localized approach maintains high processing speed while preventing horizontal line artifacts, as the interpolation is applied only where necessary to maintain image continuity.
Data Source
AI summary
An image pickup apparatus which satisfactorily compensates for a flash band appearing due to an external flash and prevents a row insensitive to the flash from appearing in a corrected image. The flash band appearing in a plurality of frames consecutive in terms of time is detected based on an image signal output from an image pickup device which sequentially starts exposure and sequentially reads out signals for each row of pixels. An image in at least one of those frames is corrected to a full-screen flash image. When a width of the flash band is smaller than the number of rows in one frame, a row in which the flash band does not appear is interpolated using a row in which the flash band appears and which immediately precedes or immediately succeeds the row in which the flash band does not appear.