Dither Matrix Threshold Arrangement for Print Density Uniformity
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Solution Overview
Problem
Existing image processing systems face challenges in maintaining target image quality due to variations in print characteristics among printing elements, leading to uneven density in printed images, particularly when using dither matrices for quantization.
Innovation Solution
An image processing apparatus and method that corrects image data based on print characteristics of printing elements and uses a dither matrix with thresholds arranged such that the number of pixels and processing units are not coprime, ensuring consistent dot formation across processing units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a dither matrix with spiral or Bayer type threshold arrangement is used to achieve target image quality, then image quality is improved, but the number of dots varies significantly across processing units causing density unevenness
Solution Approach 1:
The patent changes the parameters of the dither matrix by setting the number of pixels N to be an integral multiple of the processing unit width M (N = k × M where k is an integer). This parameter relationship ensures that each processing unit contains the same number of threshold values, resulting in consistent dot counts across all processing units while maintaining the spiral or Bayer threshold arrangement for image quality.
2Adaptability or versatility
If the number of pixels in dither matrix and processing unit width are made coprime to achieve flexible threshold arrangement, then threshold arrangement flexibility is improved, but dot number variation across processing units increases causing density unevenness
Solution Approach 1:
The patent establishes a specific parameter relationship where the number of pixels N in the dither matrix is an integral multiple of the processing unit width M. This constraint transforms the coprime relationship into a divisible relationship, ensuring that threshold values are evenly distributed across processing units while still allowing flexibility in choosing different dither matrix sizes and processing unit configurations.
3Extent of automation
If correction is performed based on patch density measurement with conventional dither matrix, then correction capability is improved, but measurement precision deteriorates due to density unevenness from varying dot numbers
Solution Approach 1:
By setting the dither matrix size N as an integral multiple of processing unit width M, the patent ensures uniform dot distribution across all processing units. This uniformity eliminates the density unevenness that previously contaminated patch density measurements, thereby enabling accurate measurement of print characteristics and precise correction parameter generation.
Data Source
AI summary
As viewed for each processing unit in head shading (HS) processing, a processing unit width is more than one pixel, so that a threshold arrangement corresponding to a target quality of an image intended by a dither matrix is kept while a possibility of avoiding zero dots from being generated can be enhanced. Moreover, the threshold arrangement is kept while a possibility of generating the same number of dots in processing units can be enhanced. Consequently, the threshold arrangement corresponding to a predetermined target quality of an image intended by a dither matrix is kept while it is possible to reduce occurrence of uneven density caused by the HS processing. Thus, it is possible to prevent the threshold arrangement from being limited by the HS processing according to the degree of the reduction.