Image Reading Streak Detection and Correction
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Solution Overview
Problem
Conventional image reading apparatuses face inaccuracies in dust image correction, particularly when dust images intersect with original content, leading to incomplete correction and residual streaks in the output images.
Innovation Solution
The apparatus employs a detecting unit to identify streaks parallel to the feeding direction and a correcting unit that continues correction for a predetermined number of sub-scanning positions even after the streak has been detected, using a string counter to ensure continuous correction and prevent incomplete removal of dust images, especially at intersections with original content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dust image detection is performed based on pixel correlation in the main scanning direction, then detection precision is improved for most cases, but detection accuracy deteriorates when dust images intersect with original content such as characters or lines
Solution Approach 1:
The patent segments the dust image detection process into two independent stages: first detecting candidate dust images based on pixel correlation in the main scanning direction, then verifying and confirming dust images by checking continuity in the sub-scanning direction. This segmentation allows the system to handle both cases (with and without original content intersection) effectively by applying different verification criteria at each stage.
Solution Approach 2:
The patent introduces an intermediary verification mechanism using sub-scanning direction continuity detection. This intermediary step acts as a mediator between the initial detection based on main scanning correlation and the final dust image confirmation, resolving the contradiction by providing an additional dimension of verification that works regardless of whether original content is present.
2Manufacturing precision
If dust image correction is performed only at detected positions, then correction precision is improved for isolated dust images, but correction completeness deteriorates when dust images intersect with original content
Solution Approach 1:
The patent performs preliminary detection of dust images using main scanning direction pixel correlation before proceeding to sub-scanning direction verification. This preliminary action identifies candidate dust images that may be intersecting with original content, allowing the system to prepare appropriate correction strategies in advance rather than reacting after the fact.
Solution Approach 2:
The patent ensures continuity of useful action by implementing continuous monitoring and correction along the sub-scanning direction. Once a dust image is detected at any position, the system continues to apply correction along the entire sub-scanning line, ensuring that intersecting dust images are fully corrected without interruption, even when original content is present.
Data Source
AI summary
When an auto document feeder feeds an original to an original image reading platen, a CCD line sensor reads the original along the main scanning direction perpendicular to the feeding direction of the original. A string detection circuit detects a streak parallel to the feeding direction in the image. A string correction circuit corrects the detected streak. In particular, for a predetermined number of sub-scanning positions that are located in the same main scanning position as the main scanning position at which the streak has been detected by the string detection circuit and that exist subsequent to the sub-scanning position at which the streak has been detected, correction is performed by the string correction circuit even when no streak is detected by the string detection circuit.