Duplex Image Magnification Correction via Pixel Position Shifting
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Solution Overview
Problem
High-speed image forming apparatuses face challenges in maintaining image quality due to magnification differences between the front and back sides of printed sheets, leading to issues like uneven density and moiré patterns, especially when adjusting resolution for duplex printing.
Innovation Solution
An image forming apparatus and method that includes an acquiring unit for image data, a scaling-factor determining unit, a resolution converting unit, a position determining unit, and a correcting unit to adjust pixel positions and resolutions, allowing for precise scaling and correction across sub-scanning and main-scanning lines to address magnification differences and prevent banding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-speed duplex printing is performed with shortened time interval between first and second side printing, then productivity increases, but magnification difference between front and back sides occurs due to heat and humidity changes
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing correction data (magnification correction values and shift amounts) before the actual printing process. The correction data is prepared in advance based on predicted magnification differences, allowing the system to compensate for heat and humidity effects during high-speed duplex printing without real-time measurement delays.
Solution Approach 2:
The patent changes parameters by adjusting the magnification correction value and shift amount based on detected magnification differences. The system dynamically modifies printing parameters (magnification and position shift) to compensate for environmental changes caused by high-speed processing, thereby maintaining image quality despite increased productivity.
2Manufacturing precision
If sub-scanning magnification changing function is used to eliminate magnification difference, then magnification consistency improves, but image deterioration occurs due to line culling or adding
Solution Approach 1:
Instead of changing the magnification parameter itself, the patent changes the position parameter by shifting the image in the sub-scanning direction. This positional shift avoids the need to add or remove lines, thereby eliminating magnification differences without causing image deterioration from line culling or adding operations.
Solution Approach 2:
The patent replaces the mechanical approach of line culling or adding with a digital position shift method. By substituting the physical manipulation of image lines with a computational position adjustment, the system achieves magnification correction without the harmful effects of line removal or insertion.
3Manufacturing precision
If line culling or adding is performed to adjust magnification, then magnification difference is corrected, but banding appears due to interference between screen ruling and magnification ratio
Solution Approach 1:
The patent changes the approach from magnification ratio adjustment to position shift adjustment. By modifying the position parameter rather than the magnification parameter, the system avoids creating interference patterns between screen ruling and magnification ratio, thereby preventing banding while still achieving magnification correction.
Solution Approach 2:
The patent converts the potential harm of position shifting (which could cause misalignment) into a benefit by precisely calculating the shift amount to match the magnification difference. This careful parameter adjustment transforms what could be a source of error into an effective correction mechanism that eliminates magnification differences without creating banding.
Data Source
AI summary
An image forming apparatus includes: an acquiring unit; a resolution converting unit; a receiving unit; a position determining unit; a correcting unit; and a scaling unit. The acquiring unit acquires image data composed of a plurality of pixels; the scaling-factor determining unit determines a scaling factor of the acquired image data; the resolution converting unit converts a resolution of the acquired image data into a higher resolution than the resolution of the image data; the receiving unit receives a designation of a sub-scanning directional shift amount of a correction pixel to be corrected; a position determining unit performs a position determining process; and the scaling unit scales the image data at the determined scaling factor by causing the position determining unit and the correcting unit.