Image Calibration for Color Shift Reduction

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Solution Overview

Problem

Image forming apparatuses using the electrophotographic process face challenges in maintaining high image quality due to slight curvatures or inclinations of scanning lines, which cause color shifts and affect the resolution of images formed on various-sized media.

Innovation Solution

The apparatus employs a halftone processing portion, calibration processing portion, image region dividing portion, and correction processing portion to calculate and correct color shifts by dividing the image formable width into imaginary adjustment regions, using common calibration data to adjust the position of image adjustment regions in the sub-scanning direction, thereby reducing color shifts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If common calibration data is generated for multiple image forming media sizes by dividing the image formable width into imaginary adjustment regions, then the color shift is reduced and image quality is improved, but the processing complexity increases due to the need to determine image boundary positions that match dither matrix boundaries

Engineering Contradiction:

Improvecolor shift reductionVSAvoidprocessing complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The image formable width is divided into multiple imaginary adjustment regions in the main scanning direction, allowing calibration to be performed separately for each region. This segmentation enables precise color shift correction for different areas of the image, particularly addressing the problem of color shifts at image boundaries while maintaining overall image quality across multiple media sizes.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the parameter of image boundary positioning by applying a rounding function to align image boundaries with dither matrix boundaries. This parameter adjustment ensures that calibration data can be consistently applied across different image forming media sizes while reducing color shifts, as the rounded boundary positions match the periodic structure of the dither matrices used in halftone processing.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If image boundary positions are determined by applying a rounding function to match dither matrix boundaries, then the color shift at boundaries is reduced, but the positioning precision may be compromised due to rounding

Engineering Contradiction:

Improveboundary color shift reductionVSAvoidboundary position precision

Core Design Contradiction:

Manufacturing precisionVSMeasurement precision

Solution Approach 1:

The invention converts the potential harm of rounding (loss of positioning precision) into a benefit by aligning image boundaries with dither matrix boundaries. The rounding operation, while reducing absolute positioning precision, creates a beneficial alignment that eliminates color shifts at boundaries by ensuring that calibration corrections are applied consistently with the halftone processing structure. The harm of rounding is offset by the benefit of boundary alignment with the periodic dither pattern.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Adaptability or versatility

If the apparatus supports multiple image forming media sizes with consistent image quality, then the versatility is improved, but the device complexity increases due to the need for calibration processing across different sizes

Engineering Contradiction:

Improvemulti-size media supportVSAvoidcalibration processing complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The invention creates universal calibration data that can be applied across multiple image forming media sizes. By dividing the image formable width into imaginary adjustment regions and generating calibration data that works for different media dimensions, the system achieves multi-functionality. The same calibration processing portion can handle various media sizes (A4, A3, B4, etc.) without requiring separate calibration procedures for each size, thereby reducing the overall complexity despite supporting versatility.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS11330144B2Image forming method with calibration processing, and non-transitory computer-readable recording medium having stored thereon image forming program of the same

Publication Date: 2022.05.10 KYOCERA DOCUMENT SOLUTIONS INC

AI summary

In one embodiment, an image forming apparatus includes an image region dividing portion which determines, within an image formable width, an image boundary position that matches with one of matrix boundaries corresponding to boundaries between dither matrices, and sets image adjustment regions. The image forming apparatus also includes a correction processing portion which uses common calibration data to determine imaginary adjustment regions positioned closest to the image adjustment regions, respectively, in a main scanning direction, and uses a correction amount for the determined imaginary adjustment region to correct the position in a sub-scanning direction, thereby reducing a color shift. The image region dividing portion determines the image boundary position by applying a rounding function to a value obtained by dividing the number of pixels constituting a width of the image adjustment region by the number of pixels in one cycle of the dither matrix in the main scanning direction.