Zigzag CIS Scanner Roller Bending Correction
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Solution Overview
Problem
Conventional large format scanners using long conveyance rollers suffer from image reading inaccuracies due to roller axis bending, leading to deviations and discontinuities in image composition, especially when reading large originals.
Innovation Solution
An image reading apparatus with a correction method that employs a plurality of line-type reading sensors arranged zigzag, a conveyance roller, and a drive unit to detect and correct shifts in image positions using calibration sheet data, adjusting the reading timing of each sensor to compensate for roller angle deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a long conveyance roller is used to read large originals, then the reading coverage area is improved, but image reading accuracy deteriorates due to roller axis bending
Solution Approach 1:
The patent divides the long conveyance roller into multiple segments and uses multiple line-type reading sensors (CIS units) arranged at different positions along the roller axis. Each sensor reads a specific section of the original, and the readings are subsequently synthesized. This segmentation allows each sensor to operate within a smaller, more accurate range while collectively covering the entire large original, thus resolving the contradiction between coverage area and reading accuracy.
Solution Approach 2:
The patent introduces an intermediary correction process that detects and compensates for roller axis bending deviations. A correction unit measures the actual position deviations caused by roller bending and applies correction values to the image data. This intermediary correction mechanism acts as a mediator between the mechanical roller system and the final image output, maintaining accuracy despite the physical limitations of long roller usage.
2Area of stationary object
If multiple line-type reading sensors are arranged zigzag to expand reading width, then the reading coverage is improved, but image composition continuity deteriorates due to connection position deviations
Solution Approach 1:
The patent implements a feedback mechanism where the system detects actual reading position deviations at CIS connection portions and uses this information to correct subsequent readings. The correction unit continuously monitors position deviations and adjusts correction values accordingly, creating a closed-loop control system that maintains composition continuity despite the zigzag arrangement of multiple sensors.
Solution Approach 2:
The patent dynamically changes correction parameters based on detected position deviations. By adjusting correction values according to actual measured deviations at connection positions, the system adapts to varying conditions and maintains seamless image composition. This parameter adjustment allows the system to compensate for the inherent discontinuities introduced by zigzag sensor arrangement.
3Speed
If roller angle detection is used to control reading timing, then reading synchronization is improved, but reading accuracy deteriorates due to decentering variations along the roller axis
Solution Approach 1:
The patent applies local quality correction by determining specific correction values for different positions along the roller axis. Instead of using a single uniform correction approach, the system calculates position-specific correction values that account for local variations in roller decentering. Each CIS unit receives tailored correction values based on its specific position, thereby maintaining reading accuracy despite varying decentering conditions along the roller length.
Data Source
AI summary
In conventional image reading in a large-sized scanner using plural CIS sensors, overall linearity of an original is poor, and a shift occurs particularly at connection portions of the CIS sensors in the read image. To solve this, an image reading apparatus in which CISs are arranged zigzag, and an original is read while conveying the original by a conveyance roller in a direction different from an arrayed direction of the reading elements of the CIS sensors performs following correction. That is, a shift from an image position in a calibration sheet corresponding to a rotation angle of the conveyance roller for at each position of the CIS sensors is detected from image data obtained by reading the calibration sheet while conveying the calibration sheet by the conveyance roller. The shift is corrected.