Image Processor Flash Band Compensation Using Pseudo-Flash Frames
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Solution Overview
Problem
Image processors using the rolling shutter technique often produce flash bands due to varying exposure times across image lines, which existing methods struggle to fully correct, especially when flash duration is shorter than the frame period or when flash bands are non-complementary.
Innovation Solution
An image processor with a determiner to identify flash band images and a compensator that generates a pseudo-flash image using non-affected frames, applying offset and gain processes to eliminate flash bands, regardless of shutter operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If rolling shutter technique is used for sequential line exposure, then imaging capability is improved, but flash bands appear in images when external flash is used
Solution Approach 1:
The patent applies preliminary action by detecting flash bands in the image signal before final output, and preparing a replacement image from a previous frame that does not contain the flash band. The determiner identifies flash band images and the compensator generates replacement images using non-affected frames, effectively preparing the correction in advance before the harmful flash band effect is finalized in the output.
Solution Approach 2:
The patent uses copying by creating a replacement image that copies the structure and content of a previous frame (which does not have the flash band) and applying the necessary adjustments to produce the corrected image. The compensator generates a third image by using a second image (non-affected frame) as a template, effectively copying the good parts and discarding the harmful flash band portions.
2Object-affected harmful factors
If existing flash band compensation methods are used, then some flash band reduction is achieved, but non-complementary flash bands cannot be fully corrected
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the compensation process based on detected flash band characteristics. The determiner identifies the specific frames affected by flash bands, and the compensator selects appropriate replacement frames and applies necessary parameter adjustments (such as blending ratios and timing corrections) to achieve accurate compensation for both complementary and non-complementary flash bands.
3Duration of action of moving object
If flash duration is shorter than frame period, then flash bands appear as bands rather than full-frame effects, but existing compensation techniques fail
Solution Approach 1:
The patent applies preliminary action by detecting the presence and position of flash bands in the image signal before final output. The determiner identifies which specific lines or regions are affected by the short-duration flash, and the compensator prepares replacement images from previous frames that do not contain the flash band, effectively addressing the compensation need in advance before the harmful effect is finalized.
Solution Approach 2:
The patent applies local quality by providing different treatment to different parts of the image. Instead of treating the entire frame uniformly, the compensator identifies specific local regions (lines or areas) where flash bands occur and applies targeted compensation only to those regions, while leaving the rest of the image unchanged. This localized approach is particularly important for short-duration flashes that affect only specific portions of the frame.
Data Source
AI summary
Disclosed is an image processor that reduces or eliminates the effects of a flash band regardless of performing a shutter operation or not. An imaging device includes a flash band detector configured to determine whether each image of the consecutive images shown by image signals output from an imager is a flash band image a part of which is affected by a flash, and a flash band compensator configured to, if a first image is determined as the flash band image, generate a third image which is supposed where the third image is fully affected by a flash by using a second image which is not determined as the flash band image, and output the third image instead of the first image.