Tone Correction for Density Unevenness in Image Forming Apparatus
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Solution Overview
Problem
Existing image forming apparatuses face significant challenges in correcting density unevenness in the main scanning direction due to factors like environmental fluctuations, photosensitive member sensitivity, and lens aberrations, requiring a large number of test charts for effective correction.
Innovation Solution
An image forming apparatus that includes a converter to generate tone correction conditions based on measurement results from a limited number of test images, using a controller to form test images with varying tones and acquire feedback conditions, thereby reducing the need for numerous test charts and improving correction accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If test images corresponding to one page are formed at constant image density in main scanning direction and sub-scanning direction with stepwise image density change for each page, then density distribution detection results can be obtained for generating conversion condition for main scanning direction, but a large number of test charts are required
Solution Approach 1:
The patent segments the test chart into multiple regions with different image densities (first through fourth image densities) within a single test chart. Each region contains test images for detecting density distributions at different tone levels. This segmentation allows comprehensive measurement of density corrections across multiple densities without requiring multiple separate test charts, thereby resolving the contradiction between measurement precision and quantity of test charts required
Solution Approach 2:
The patent creates a universal test chart structure that serves multiple measurement purposes simultaneously. The test chart can detect density distributions for multiple image densities (first, second, third, and fourth densities) and multiple tones within a single chart. This multi-functional design eliminates the need to generate separate test charts for each density level, reducing the total number of test charts while maintaining comprehensive measurement capability
2Measurement precision
If the same number of test charts are output as the number of tones for which image densities are to be measured, then comprehensive tone measurement can be achieved, but measurement time and complexity increase
Solution Approach 1:
The patent segments different tone measurements into distinct regions (first through fourth image densities) within a single test chart. Each region is assigned specific tones for measurement, allowing comprehensive tone coverage across the entire measurement range while maintaining all measurements in one chart rather than requiring separate charts for each tone
Solution Approach 2:
The patent performs preliminary organization of measurement data by pre-assigning specific tones to specific image density regions before actual measurement. The controller is configured to selectively generate density distribution data based on predetermined tone assignments for each region, eliminating the need to process all tones uniformly and reducing measurement complexity and time
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 solution effectively corrects density unevenness in the main scanning direction by generating precise tone correction conditions, reducing the impact of unsteady unevenness and reading apparatus repetition accuracy, resulting in improved image quality with fewer test charts.
Implementation Method 1
an exposure device to irradiate the photosensitive member with laser light corresponding to the image to be formed
Implementation Method 2
a charger that charges the photosensitive member
Implementation Method 3
a developing sleeve that develops the electrostatic latent image on the photosensitive member
Data Source
AI summary
An image forming apparatus includes a converter configured to convert image data with use of a tone correction condition corresponding to a position in a main scanning direction of the image data, and an image forming unit, which includes a photosensitive member and an exposure portion configured to expose the photosensitive member to light based on the converted image data, and is configured to form an image on a recording medium. The image forming apparatus further includes a holding portion configured to hold a plurality of feedback conditions corresponding to a plurality of tones and a controller configured to control the image forming unit to form a plurality of test images, acquire measurement results for the plurality of test images, and generate the tone correction condition based on the measurement results and the plurality of feedback conditions.