Photoreceptor Segment Slope Correction for Image Density Uniformity
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Solution Overview
Problem
Electrophotographic image forming apparatuses face challenges in achieving uniform image density due to uneven electrification and sensitivity on photoreceptors, leading to issues like uneven density and increased costs with additional exposure means, especially in tandem-style color image forming systems.
Innovation Solution
The image forming apparatus determines pixel gradation based on image data and transforms it into exposure amounts using slope information specific to each segment of the photoreceptor, allowing for individual exposure amount transformation without additional exposure means, thereby adjusting the electric potential to match a reference property and preventing uneven density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If additional exposure means are added to correct uneven electrification and sensitivity, then image density uniformity is improved, but device complexity and cost increase
Solution Approach 1:
The photoreceptor surface is divided into multiple segments, and slope information is individually determined for each segment. This segmentation allows the system to address local variations in electrification and sensitivity without requiring additional global exposure correction mechanisms, thereby maintaining image density uniformity while avoiding increased device complexity.
Solution Approach 2:
The invention changes the parameter of exposure amount based on segment-specific slope information. By individually adjusting the exposure amount for each segment according to its specific slope characteristics, the system corrects uneven density caused by uneven electrification and sensitivity variations without adding physical exposure correction apparatus.
2Manufacturing precision
If additional exposure means are added to correct uneven electrification and sensitivity, then image density uniformity is improved, but apparatus cost increases
Solution Approach 1:
The system uses the existing exposure means to perform correction by adjusting the exposure amount based on predetermined slope information for each segment. The exposure means serves dual purposes: normal image formation and correction of uneven density, eliminating the need for separate correction apparatus and reducing overall system cost.
3Device complexity
If common transformation information is used for pixel gradation transformation, then device complexity is reduced, but image density uniformity deteriorates due to uneven electrification and sensitivity
Solution Approach 1:
Instead of using uniform transformation information across the entire photoreceptor surface, the invention applies local transformation information by determining individual slope information for each segment. This allows the exposure amount to be optimized for local conditions of electrification and sensitivity, correcting uneven density while maintaining straightforward control logic.
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 prevents uneven image density by adjusting the exposure amount based on segment-specific slope information, ensuring uniformity without enlarging the apparatus or increasing costs, even in systems with significant uneven electrification and sensitivity.
Implementation Method 1
the surface of photoreceptor (generally, drum-shaped photoreceptor) uniformly electrified to a prescribed initial electric potential by an electrification apparatus (electrification means)
Implementation Method 2
exposing the aforesaid electrified photoreceptor's surface by exposure means (such as the means for scanning laser source and its beam, and LED array)
Implementation Method 3
each photoreceptor has a peculiar electric potential distribution, even if the surface of photoreceptor is uniformly electrified under a fixed condition by the electrification apparatus, since each photoreceptor has individual differences caused by unevenness of such as the film thickness and material property in its surface member
Implementation Method 4
the density developed with toner (development density) has the excess and deficiency against the proper density
Data Source
AI summary
Uneven image density produced by photoreceptors, in which uneven electrification and sensitivity coexist, is limited economically and space efficiently. For each segment of the surface of the photoreceptor, individual memorizing of slope information K1 defining the slope of when a pixel gradation is approximately linear-transformed into exposure amount and, based upon K1 per segment, individual transforming of pixel gradation into the exposure amount (individual exposure amount transformation) is performed. The slope information which, with a reference electric potential Vs1 , matches the electric potential after the exposure of when the exposure amount, obtained by transforming a reference pixel gradation Is1 by means of the individual exposure amount transformation, is applied to the approximately-linear exposure property excepting the converging region to a residual potential VL, or to the exposure property extended by extrapolation operation, among exposure property g01 showing correspondence between the exposure amount and the electric potential after exposure per segment.