Laser Pitch Correction for Image Density Uniformity
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Solution Overview
Problem
In image forming apparatuses using multiple laser light sources, variations in light paths and curvatures lead to non-uniform scanning line pitches, causing density irregularities in printed images due to the wideness and narrowness of scanning lines, resulting in moire patterns and uneven toner adherence.
Innovation Solution
An image forming apparatus with a laser pitch correction unit that adjusts the density of image data based on the distance between scanning lines by using profile data from light sources A and B to correct for deviations from ideal pitch, ensuring uniform toner adherence and image density through PWM signal processing and filter calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple laser light sources are used to trace scanning lines simultaneously, then printing speed and resolution are improved, but non-uniform scanning line pitches cause density irregularities and moire patterns
Solution Approach 1:
The patent applies local quality by adjusting the density of image data specifically in regions where scanning line pitch deviations occur. Instead of uniform processing, the system identifies local variations in pitch between adjacent scanning lines and applies selective density adjustments to those specific regions, making the correction targeted and precise rather than global.
Solution Approach 2:
The patent changes the density parameter of image data in response to detected pitch variations. By dynamically adjusting the density parameter based on the actual pitch between scanning lines, the system compensates for non-uniformities caused by multiple laser light sources, thereby maintaining uniform toner adherence and eliminating density irregularities.
2Measurement precision
If multiple laser light sources are used to trace scanning lines simultaneously, then high resolution is achieved, but curvatures and inclinations of laser beams vary causing pitch non-uniformity
Solution Approach 1:
The patent implements feedback by detecting the actual pitch between adjacent scanning lines and using this information to adjust image data density. The system continuously monitors the pitch uniformity and feeds this information back to the image processing stage, creating a closed-loop control system that automatically compensates for pitch variations caused by laser beam curvature and inclination differences.
Solution Approach 2:
The patent applies preliminary action by adjusting the density of image data before toner application. By pre-processing the image data to account for anticipated pitch variations, the system prepares corrected density values in advance, ensuring that when toner is applied, the non-uniform pitch regions receive compensated density adjustments, thereby achieving uniform toner adherence.
3Ease of operation
If scanning lines have non-uniform pitch, then laser beam path variations occur, but this causes density non-uniformity in page and background regions
Solution Approach 1:
The patent applies local quality by selectively adjusting density only in regions where pitch non-uniformity affects image quality. Rather than uniformly processing the entire image, the system identifies specific page and background regions where density irregularities occur due to pitch variations and applies targeted corrections to those local areas, preserving flexibility while maintaining precision.
Solution Approach 2:
The patent changes the density parameter of image data in response to pitch variations. By dynamically modifying the density parameter based on local pitch measurements, the system compensates for the effects of laser beam path variations, ensuring that both page and background regions maintain uniform density despite the underlying pitch non-uniformity.
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 for non-uniform scanning line pitches by adjusting image data density, reducing toner adherence variations and achieving uniform image density across the page, thereby eliminating moire patterns and ensuring consistent image quality.
Implementation Method 1
When the photosensitive member 708 is irradiated with laser in a state where a surface thereof is charged by a high negative voltage, a surface potential of the photosensitive member 708 is increased, and a latent image potential is formed.
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
An image forming apparatus includes a plurality of light sources (800, A, B) that emits a plurality of light beams in parallel to each other in the sub scanning direction via an optical system (801, 804, 805, 806), a filter calculation means (103) that performs filter calculation of increasing or reducing a density of image data according to wideness or narrowness between a plurality of scanning lines formed on a photosensitive member (708) when the light beams from the plurality of light sources (800, A, B) are scanned on the photosensitive member (708), and a drive circuit that causes light beam emission from the plurality of light sources (800, A, B) based on the image data to which the filter calculation is performed by the filter calculation means (103).