LED Line Head Density Correction via Halftone Masking
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Solution Overview
Problem
Conventional image forming apparatuses with LED line heads face challenges in maintaining uniform light amounts across light emitting devices, leading to density unevenness and streaks, which require complex correction circuits and increased memory capacity, especially at high print resolutions.
Innovation Solution
The solution involves measuring and storing light amount information for LED line heads, generating mask patterns based on this data, and performing density correction on halftone image data to prevent density unevenness and streaks, while allowing for position correction after halftone processing to maintain image quality and reduce circuit complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If density correction is performed on multi-value image data at print resolution, then light amount uniformity is improved, but memory capacity requirements increase
Solution Approach 1:
The patent performs position correction on halftone image data before density correction. By pre-aligning the halftone data with the light amount property data at a lower resolution stage, the system avoids the need to store and process high-resolution multi-value image data during density correction, thereby reducing memory capacity requirements while maintaining correction effectiveness
Solution Approach 2:
The patent separates position correction and density correction into distinct processing stages. Position correction is performed first on halftone image data, followed by density correction on the position-corrected data. This segmentation allows each correction to be performed on appropriately scaled data, reducing overall memory requirements compared to performing both corrections simultaneously on full-resolution multi-value data
2Manufacturing precision
If position correction is performed on multi-value image data, then image position accuracy is improved, but circuit scale increases
Solution Approach 1:
The patent performs position correction on halftone image data before density correction rather than on the original multi-value image data. This preliminary action on already-processed halftone data reduces the complexity of position correction circuits while maintaining accuracy, as the data is already in a simplified binary format suitable for position alignment
Solution Approach 2:
Instead of performing position correction on the original multi-value image data and then converting to halftone, the patent inverts the sequence by first converting to halftone and then performing position correction. This inversion simplifies the position correction process and reduces circuit scale while achieving the same positional accuracy
3Manufacturing precision
If high print resolution is used, then image quality is improved, but memory capacity for correction data increases
Solution Approach 1:
The patent performs position correction on halftone image data at a resolution lower than the final print resolution. By establishing positional accuracy at this intermediate stage, the system avoids the need to store and process full-resolution multi-value data during correction operations, thereby reducing memory capacity requirements while maintaining high final print quality
Solution Approach 2:
The patent applies density correction based on light amount property data that is specific to each pixel position. By using position-corrected halftone data that aligns with the spatial characteristics of the LED line head, the system achieves high local quality correction without requiring full high-resolution correction data to be stored in memory
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 suppresses the need for large memory capacity and complex circuits, ensuring uniform image density and preventing streaks and moiré issues, while allowing for accurate position correction and maintaining image quality even at high resolutions.
Implementation Method 1
LED line head in which a plurality of light emitting devices are arranged in a line
Implementation Method 2
exposure device that selectively exposes the outer peripheral surface of the uniformly charged photosensitive member, and forms an electrostatic latent image
Data Source
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AI summary
An image forming apparatus comprising a printer unit that prints an image on a sheet using a line head in which a plurality of light emitting devices are arranged, and a storage that stores information regarding light amounts corresponding to the light emitting devices of the line head. The image forming apparatus generates a mask pattern based on the information regarding the light amounts obtained from the storage and a target light amount, and executes mask processing on halftone image data that is in positional correspondence with the light emitting devices, using the generated mask pattern.