Photoconductor Density Correction Using Segmented Test Data
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Solution Overview
Problem
Electrophotographic image forming apparatuses face non-uniformity in toner image density along the rotation axis of a photoconductor due to variations in light exposure and photoconductor sensitivity, with existing solutions failing to correct density outside the test image range.
Innovation Solution
An image forming apparatus with a photoconductor, exposure unit, developing unit, transfer unit, reading unit, and data generating unit that forms electrostatic latent images, develops them with toner, transfers images onto sheets, reads document images, and generates first and second correction data to adjust image density within and outside the test image area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a test image is formed on a sheet with a size smaller than that of a photoconductor in the rotation axis direction, then the density correction process is simplified and faster, but density is not corrected in areas outside the range in which the test image is formed
Solution Approach 1:
The photoconductor surface is divided into multiple areas: a first area corresponding to the test image formation range and a second area outside the test image range. Different correction strategies are applied to each segment, allowing efficient correction within the test area while extending correction coverage to the outer areas through extrapolation techniques.
Solution Approach 2:
A test image is formed in advance on a sheet before actual image formation. This preliminary test image is used to measure density characteristics and generate correction data that is then applied to subsequent images, enabling proactive correction rather than reactive adjustment.
2Manufacturing precision
If multiple test patterns are printed and read to adjust laser beam amount at each position, then density non-uniformity in the rotation axis direction is suppressed, but the process complexity increases
Solution Approach 1:
The density measurement and correction data generation functions are extracted from the main image formation process. A dedicated reading unit measures the test image density characteristics, and correction data is generated separately and then applied during image formation, separating the correction function from the primary imaging function.
Solution Approach 2:
The system forms a test image, reads it with a density sensor to obtain actual density values, compares these with target values, and uses the difference to generate correction data that adjusts the laser beam amount. This closed-loop feedback mechanism automatically optimizes density uniformity without manual intervention.
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
The apparatus effectively corrects density non-uniformity in both the rotation axis direction and outside areas where the test image is formed, ensuring uniform image quality across the entire image area.
Implementation Method 1
the exposure unit exposes the photoconductor to light and forms an electrostatic latent image on the photoconductor
Implementation Method 2
The developing unit develops the electrostatic latent image by using toner
Data Source
AI summary
Two types of correction data, first correction data and second correction data, are used to correct density on the basis of reading results obtained by a reading unit reading a test image formed on a sheet. The first correction data is data for correcting image density in the rotation axis direction of the photoconductor. The correction using the first correction data is performed in each of multiple areas on the photoconductor which correspond to an area in which a toner image of the test image is formed. The second correction data is data for correcting image density in the rotation axis direction of the photoconductor. The correction using the second correction data is performed in areas outside the area in which the toner image of the test image which is read by the reading unit is formed.