Color Drift Correction in Image Forming Apparatus
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Solution Overview
Problem
In color image forming apparatuses, existing methods fail to accurately correct color drift errors, leading to suboptimal image quality due to positional deviations in the horizontal scanning direction, especially when the image formation line curves, resulting in significant color drift in the middle part of the image.
Innovation Solution
The method involves forming at least three mark-patterns on different portions of the transfer medium in the main scanning direction, detecting their positions, calculating color-drift amounts relative to a reference color, and correcting these drifts in the sub-scanning direction to ensure that virtual image lines for each color intersect with the reference color's virtual image line at multiple points, thereby correcting skew and positional deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mark-patterns are formed only on both ends of the intermediate transfer belt for position correction, then the positions at both ends can be corrected, but the middle part of the image formation line will be largely deviated when the line curves, causing color drift in the horizontal scanning direction
Solution Approach 1:
The patent divides the single correction operation into multiple segments by forming mark-patterns at three distinct locations (both ends and middle) of the intermediate transfer belt. This segmentation allows independent detection and correction of positional deviations at each location, ensuring that the curved image formation line is accurately corrected at all points rather than only at the ends.
2Device complexity
If position correction is conducted based on mark-patterns at both ends only, then the correction process is simple, but color drift occurs in the middle part when the image formation line curves
Solution Approach 1:
The correction system is segmented into three independent detection points along the intermediate transfer belt. Each mark-pattern location provides localized correction data, allowing the system to handle curved image formation lines without increasing overall system complexity significantly, while dramatically improving color alignment accuracy in the middle region.
Solution Approach 2:
The mark-patterns are formed preliminarily on the intermediate transfer belt before actual image formation. These pre-formed patterns serve as reference markers that enable the detection unit to measure positional deviations and allow the control unit to calculate correction amounts in advance, preventing color drift before it occurs.
3Productivity
If the image formation line curves due to optical device positioning errors, then the overall image can still be formed, but significant color drift occurs in the horizontal scanning direction without proper correction
Solution Approach 1:
The patent implements a feedback mechanism where the detection unit continuously monitors the positions of mark-patterns formed on the intermediate transfer belt. Based on detected positional deviations from the ideal image formation line, the control unit calculates correction amounts and adjusts the timing of toner transfer for each color, compensating for curved image formation lines and preventing color drift.
Solution Approach 2:
The system dynamically changes the timing parameter of toner transfer based on detected positional deviations. When the image formation line curves, the control unit adjusts the transfer timing for each color (Y, M, C, K) according to the specific deviation amount detected at each mark-pattern location, thereby maintaining accurate color registration despite the curved line.
Data Source
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AI summary
A color-drift correcting method in an image forming apparatus includes a first and a second color-drift correcting. The first color-drift correcting includes correcting the color-drift amount in a sub scanning direction and a skew relative to the reference color image being based on each color-drift amount of at least three mark-patterns, each of which mark-pattern is formed of color images, so as to decide a corrected-image line as a virtual image line for each color, assumed when the color images are superposed onto a transfer media. A second color-drift correcting includes correcting the color-drift amount in the sub scanning direction so that the virtual image lines corresponding to each of the colors other than the reference color intersect with the virtual image line of the reference color at at least two points.