Image Forming Apparatus Registration Correction via Less-Than-One-Pixel Interpolation
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Solution Overview
Problem
Existing image forming apparatuses face challenges in correcting registration deviation due to non-uniformity in lens deflection scanners, leading to curvature and inclination issues, which result in registration deviations and degrade image quality, especially when interpolation processing is applied to continuous tone images with screen processing.
Innovation Solution
An image forming apparatus that employs less-than-one-pixel-basis correction by adjusting pixel density through pulse width modulation (PWM) to invert the density relationship before and after change points, ensuring uniformity in image density and minimizing level differences, even in situations where linearity with PWM is difficult to achieve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If one-pixel-basis correction is used to correct registration deviation, then the correction can be implemented with simple pixel offsetting, but unnatural level differences and smoothing artifacts arise at change point boundaries
Solution Approach 1:
The patent applies partial correction by using less-than-one-pixel-basis correction (interpolation) instead of complete one-pixel-basis correction. This partial approach adjusts pixel values continuously across change points rather than making discrete jumps, thereby eliminating level differences while maintaining correction effectiveness. The correction amount is calculated as a fractional value based on profile characteristics, enabling smooth transitions without artificial boundaries.
2Manufacturing precision
If less-than-one-pixel-basis correction is applied to continuous tone images with screen processing, then density uniformity can be maintained, but the correction becomes complex and requires interpolation processing
Solution Approach 1:
The patent performs preliminary correction by calculating the correction amount based on profile characteristics before the actual image formation. The profile characteristics (curvature and inclination) are measured and stored in advance, allowing the correction values to be pre-computed. During image processing, these pre-calculated correction amounts are simply applied through interpolation, avoiding complex real-time calculations while maintaining density uniformity.
3Manufacturing precision
If mechanical adjustment members are used to correct registration deviation, then physical alignment can be improved, but the apparatus size increases and assembly complexity increases
Solution Approach 1:
The patent completely replaces mechanical adjustment mechanisms with an electrical/software-based correction system. Instead of using physical adjustment members to realign the deflection scanner, the system measures profile characteristics and applies digital correction to the image data. This substitution eliminates all mechanical adjustment components, reducing apparatus size and assembly complexity while achieving the same registration accuracy through computational methods.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for effective correction of registration deviations without introducing unevenness in density or level differences at change points, maintaining image quality and density uniformity, even when linearity with PWM is challenging, thereby enhancing the overall image forming process.
Implementation Method 1
An electrophotography is known as an image recording system used in a color image forming apparatus such as a color printer or a color copying machine. The electrophotography is one which forms a latent image on a photoconductive drum by utilizing a laser beam
Implementation Method 2
The electrophotography is one which forms a latent image on a photoconductive drum by utilizing a laser beam, and develops it with a charged color material (hereinafter referred to as toner)
Implementation Method 3
Recording of an image is carried out by transferring and fixing the image developed using the toner onto a transfer paper
Implementation Method 4
Recording of an image is carried out by transferring and fixing the image developed using the toner onto a transfer paper
Data Source
AI summary
There exists a problem that, for registration correction, carrying out less-than-one-pixel-basis correction and one-pixel-basis correction for an image after half toning using screen processing causes unevenness in density when it is hard for linearity of image density against a PWM to come out. Processing of interpolation is carried out so that the way how a halfdot is formed may always becomes the same after the interpolation processing. By applying a matrix in consideration of a dot direction which may be broken by the interpolation processing at the time of the screen processing, conversion in which a way of locating the half dot maintains relation of vertical inversion in a subscanning direction is carried out, and less-than-one-pixel-basis correction is carried out.