Developing Bias Correction Using Straight Line Test Patterns

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Solution Overview

Problem

In image forming apparatuses with exposure heads having a small depth of focus, developing-bias correction tends to result in larger correction widths, leading to reduced reproducibility of isolated dots and thin lines due to defocusing issues.

Innovation Solution

The apparatus includes a control unit that forms a straight line image on the conveying member with a length equal to or larger than the second detection width of the concentration sensor, allowing for accurate developing bias correction and subsequent gamma correction by detecting the image with concentration sensors, thereby minimizing the influence of defocusing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If developing-bias correction is performed with concentration patches formed by LED exposure with a large amount of defocusing, then the correction width of developing biases becomes larger, but the reproducibility of isolated dots and thin lines deteriorates

Engineering Contradiction:

Improveconcentration detection accuracyVSAvoidisolated dots and thin lines reproducibility

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

The invention applies different image patterns (straight line parts vs. dot patterns) to different measurement needs. Straight line parts are used for developing-bias correction where broader coverage is needed, while dot patterns are used for gamma correction where localized precision is critical. This local differentiation of quality resolves the contradiction by matching the measurement pattern to the specific correction objective.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The correction process is segmented into two distinct stages: developing-bias correction using straight line images, and gamma correction using dot patterns. This segmentation allows each stage to use optimized patterns for its specific purpose, preventing the degradation of isolated dots and thin lines while maintaining accurate concentration detection.

Inventive Principle:

Principle #1Segmentation

2Productivity

If LED exposure head is disposed close to the photosensitive member, then the depth of focus becomes small, but defocusing occurs more frequently

Engineering Contradiction:

Improveexposure efficiencyVSAvoidimage formation consistency

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The invention changes the parameter of the measurement pattern from traditional dot patterns to straight line patterns for developing-bias correction. This parameter change makes the measurement less sensitive to defocusing effects, allowing the exposure head to operate at close distances for high productivity while maintaining reliable and consistent image formation correction.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention converts the harmful effect of defocusing (which occurs when the exposure head is disposed close to the photosensitive member) into a beneficial situation by using straight line patterns that are inherently more tolerant to defocusing. This allows the close disposal arrangement to be maintained for productivity while the defocusing issue is neutralized through the appropriate measurement pattern selection.

Inventive Principle:

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

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 effectively suppresses the increase in developing bias correction widths, ensuring accurate concentration detection and maintaining image quality reproducibility, especially in color printers with LED exposure heads.

Implementation Method 1

a concentration sensor configured to detect an image and has a first detection width which is a detection width in the conveyance direction and a second detection width which is a detection width in the axial direction of the photosensitive member

Methodology Applied

Scientific EffectOptical detection: Absorption (EM radiation)

Implementation Method 2

an exposure head disposed close to the photosensitive member and configured to form a latent image on the photosensitive member by performing exposure based on image data

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS8948632B2Image forming apparatus and image formation correcting method

Publication Date: 2015.02.03 BROTHER KOGYO KK

AI summary

An image forming apparatus including: a photosensitive member; a conveying member; an exposure head; a developing unit; an image forming unit; a concentration sensor having a first detection width in a conveyance direction and a second detection width in an axial direction of the photosensitive member; and a control unit, wherein the control unit controls the exposure head and the image forming unit to form a first image for correction, which includes a straight line part extending in the axial direction of the photosensitive member and having a length equal to or larger than the second detection width of the concentration sensor, on the conveying member, and wherein the control unit corrects a developing bias to be applied to the developing unit based on a detection result of the first image for correction by the concentration sensor.