Image Correction Method for Laser Scanning Banding
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Solution Overview
Problem
Conventional image forming apparatuses face challenges in maintaining uniform image density and correcting positional deviations, leading to issues like banding and hue variations due to fluctuations in surface speed, rotation speed, and mirror angle variations, which affect image quality.
Innovation Solution
A correction method that involves storing positional deviation data, performing coordinate transformation to adjust pixel positions, and applying a convolution operation to determine pixel values, ensuring uniform scanning line intervals and correcting image data based on positional deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the exposure amount of the light scanning device is adjusted to correct banding, then uneven image density is reduced, but the correction becomes unstable when image forming conditions change
Solution Approach 1:
The patent changes the correction parameter from exposure amount to scanning line position. By detecting actual scanning line positions and comparing them with ideal positions, the system calculates positional deviations and corrects image data accordingly. This parameter change makes the correction stable against variations in exposure conditions while maintaining effectiveness in eliminating banding and uneven density.
2Productivity
If scanning line intervals are not equal due to speed fluctuations and mirror angle variations, then image formation is faster, but banding and moire patterns occur
Solution Approach 1:
The patent implements a feedback mechanism where the actual positions of scanning lines are detected and fed back to the correction unit. The system calculates the deviation between actual and ideal positions, then uses this information to correct image data. This feedback loop enables the system to maintain precision despite speed fluctuations and mirror angle variations during high-speed scanning.
3Adaptability or versatility
If positional deviation occurs in scanning lines, then image formation adapts to speed variations, but hue variations and image defects occur in color images
Solution Approach 1:
The patent segments the correction process into two distinct steps: coordinate transformation to adjust pixel positions based on scanning line deviations, and filtering to determine final pixel values. This segmentation allows independent optimization of position accuracy and color alignment, preventing hue variations while maintaining adaptability to speed variations.
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 method effectively corrects uneven image density and banding, maintaining image quality by ensuring uniform scanning line intervals and addressing positional deviations, resulting in improved image formation without hue variations.
Implementation Method 1
a laser beam collimated with use of a collimator lens is deflected by a rotary polygon mirror
Implementation Method 2
the deflected laser beam is formed into an image on a photosensitive member with use of an elongated fθ lens
Implementation Method 3
the deflected laser beam is formed into an image on a photosensitive member with use of an elongated fθ lens
Implementation Method 4
a photosensitive member configured to rotate in a first direction so that a latent image is formed on the photosensitive member with light beams emitted from the light source
Data Source
AI summary
A correction method for an image forming apparatus including a light source including a plurality of light emitting points, a photosensitive member configured to rotate in a first direction, and a deflection unit configured to deflect light beams emitted from the light source in a second direction orthogonal to the first direction to form scanning lines, the correction method including: a storing step of storing information on positional deviation of the scanning lines in the first direction; a conversion step of converting positions of pixels of an input image by performing coordinate transformation based on the information so that an interval of the scanning lines becomes a predetermined interval; and a filtering step of determining pixel values of pixels of an output image by subjecting pixel values of the pixels of the input image after the coordinate transformation to a convolution operation.