Dither Matrix Exposure Control for Toner Adhesion Interference
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Solution Overview
Problem
The existing methods for background exposure in electrophotographic image forming apparatuses using pulse width modulation (PWM) can cause image defects due to interference between the emission periods for normal and background exposures, leading to unintended toner adhesion and image quality degradation.
Innovation Solution
The implementation of an image forming apparatus that utilizes multiple dither matrices to control the exposure of a charged photosensitive member, with specific matrices for different toner density levels, including a minute exposure area and a normal exposure area, and a non-light-emitting area between them, to prevent interference and ensure accurate toner adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If background exposure is performed using PWM method with emission period for background exposure placed in emission period not for normal exposure, then the potential of photosensitive member is controlled to prevent toner adhesion in white portions, but exposure light interferes with normal exposure light causing unintended toner adhesion and image defects
Solution Approach 1:
The patent segments the exposure control into multiple independent dither matrices, each corresponding to different density levels. This segmentation allows independent optimization of background exposure and normal exposure parameters without interference, resolving the contradiction between toner adhesion control and image quality by preventing light interference through separate control matrices.
Solution Approach 2:
The patent applies local quality by using different dither matrices for different density levels and spatial regions. Each matrix is optimized for its specific density level, allowing precise control of exposure characteristics in different areas of the image, thereby achieving both reliable toner adhesion control and high image quality without cross-interference.
2Manufacturing precision
If multiple dither matrices with different density levels are used, then image quality and toner adhesion precision are improved, but device complexity increases
Solution Approach 1:
The patent changes parameters by using multiple dither matrices with different density level parameters. Each matrix is configured with specific threshold values and exposure characteristics optimized for its density level. This parameter-based approach enables precise toner adhesion control across different image regions while maintaining manageable system complexity through systematic parameter organization.
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 reduces image defects by maintaining the potential of the photosensitive member at appropriate levels for toner adhesion, thereby improving image quality and preventing tone jumps in halftone images.
Implementation Method 1
an exposure device that forms a latent image by applying light generated based on a driving signal to the charged photosensitive member
Implementation Method 2
a developing device that attaches toner to the latent image formed on the charged photosensitive member
Data Source
AI summary
An image forming apparatus includes a signal generating unit that stores information on a plurality of dither matrices preset in correspondence with the density level of toner to be attached to the photosensitive member and converts input image data based on the dither matrices to generate a driving signal. The signal generating unit stores information on a first dither matrix corresponding to a first density level and a second dither matrix corresponding to a second density level higher than the first density level. The first dither matrix includes a minute exposure area in which the exposure device is caused to emit light to attain a potential at which no toner adheres to the photosensitive member, and the second dither matrix includes a normal exposure area in which the exposure device is caused to emit light to attain a potential at which toner adheres to the photosensitive member.