Image Density Correction Using Inline Sheet Reference Sensing
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Solution Overview
Problem
Image forming apparatuses face issues with charging, exposure, and development unevenness, leading to image density unevenness in the main and sub-scanning directions, which are difficult to accurately correct due to reading errors from sensors and sheet fluttering during conveyance.
Innovation Solution
The apparatus includes a conveyance path, a reading sensor, and a controller that suppresses image density unevenness by reading pattern images at multiple positions and using two-dimensional linear interpolation to correct image density based on average values and luminance differences, accounting for sensor errors and sheet fluttering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a reading sensor is used to measure image density unevenness, then measurement capability is provided, but reading errors occur due to light amount unevenness, sensor sensitivity differences, and sheet fluttering
Solution Approach 1:
A bare surface part (intermediary reference region) is introduced on the sheet as a mediator between the reading sensor and the pattern image. This bare surface part serves as a stable reference that is not affected by image formation variations, allowing the system to distinguish between actual image density unevenness and reading errors caused by light amount variations or sensor sensitivity differences. The reading results from the bare surface part are used to correct the reading results from the pattern image, thereby improving measurement reliability.
2Manufacturing precision
If image density unevenness correction is attempted using conventional methods, then some correction capability is achieved, but accurate correction is difficult due to the mixing of reading errors with actual unevenness
Solution Approach 1:
The reading errors are extracted and separated from the actual image density unevenness by measuring a bare surface part that is free from image formation effects. The reading results from this bare surface part represent only the reading errors (light amount unevenness, sensor sensitivity variations). These extracted reading errors are then used to correct the pattern image reading results, enabling accurate measurement of true image density unevenness and从而实现 accurate correction.
3Productivity
If the sheet is conveyed through the conveyance path for reading, then inline measurement is enabled, but sheet fluttering causes unstable reading distance and additional reading errors
Solution Approach 1:
The bare surface part acts as an intermediary reference that is affected by the same sheet fluttering and reading distance variations as the pattern image. By comparing the pattern image reading results with the bare surface part reading results, the system can cancel out the effects of sheet fluttering and unstable reading distance, enabling accurate measurement during inline conveyance.
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
Accurate detection and correction of image density unevenness in both scanning directions, resulting in high-quality images with reduced sensor-induced errors and sheet conveyance fluctuations.
Implementation Method 1
a reading sensor configured to read the sheet having the pattern image formed thereon during conveyance of the sheet through the conveyance path
Data Source
AI summary
An image forming apparatus includes an image former configured to form an image on a sheet, a conveyance path through which a sheet having a pattern image formed thereon by the image former is to be conveyed, a reading sensor configured to read the sheet having the pattern image formed thereon during conveyance of the sheet through the conveyance path, and a controller configured to suppress image density unevenness in a conveying direction of an image to be formed by the image former, wherein the image density unevenness is suppressed based on a reading result of the pattern image read by the reading sensor and a reading result obtained by reading, by the reading sensor, a plurality of positions in the conveying direction of the sheet conveyed through the conveyance path.