Multi-Scan Dot Pattern Phase Inversion for Graininess Suppression
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Solution Overview
Problem
Existing image forming technologies using error diffusion and dither matrix methods for converting multi-valued input images to binary images often result in unwanted emphasis of low frequency components, leading to visually obtrusive graininess, especially with increasing numbers of scans.
Innovation Solution
An image forming apparatus and method that applies N-ary processing based on predetermined constraining condition information to each main scan, ensuring the phase of the dot pattern generated has an opposite phase relationship with the dot pattern already printed on the medium in the low frequency region, thereby suppressing graininess and improving image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If error diffusion method or dither matrix method is used for converting multi-valued input image data to binary image data, then pseudo tone expression is achieved, but low frequency components are unwantedly emphasized causing visually obtrusive graininess
Solution Approach 1:
The patent changes the phase relationship parameter of dot patterns between adjacent main scans. By setting the phase of dot patterns in adjacent main scans to have an opposite phase relationship in the low frequency region, the low frequency components that cause graininess are suppressed while maintaining pseudo tone expression quality
Solution Approach 2:
Instead of using the same phase relationship for dot patterns across multiple main scans (conventional approach), the patent inverts the phase relationship by setting adjacent main scans to have opposite phases. This inversion approach specifically targets and suppresses the low frequency components that cause visually obtrusive graininess
2Manufacturing precision
If multiple main scans are used to form an image, then dispersiveness of dot allocations is improved and density nonuniformity is reduced, but low frequency components are emphasized more with increasing number of scans
Solution Approach 1:
The patent modifies the phase relationship parameter of dot patterns across multiple main scans. By setting the phase to have an opposite phase relationship in the low frequency region for adjacent main scans, it suppresses the cumulative effect of low frequency components that would otherwise be emphasized with increasing scan numbers
Solution Approach 2:
The patent implements a periodic alternation of phase relationships between adjacent main scans. This periodic action creates a systematic pattern where low frequency components are consistently suppressed across multiple scans, preventing their cumulative emphasis while maintaining the benefits of multiple scan dispersiveness
Data Source
AI summary
In order to form a high-quality image, upon execution of multi-pass printing using a printing head with a plurality of nozzles, an image processing apparatus calculates, using a scan duty setting unit (105), scan duty data for respective nozzles for each scan of the printing head in accordance with input image data. A halftone processor (108) generates a dot pattern to be formed by applying N-ary processing. The constraining condition information is set so that the phase of spatial frequencies of a next dot pattern to be generated has an opposite phase relationship in a low frequency region with respect to the already printed dot pattern.