Print Head Dither Mask Layout for Uniform Overlap Regions
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Solution Overview
Problem
Existing printing technologies face challenges in maintaining image quality when multiple print heads overlap, leading to graininess and density variations due to deviations in dot formation positions, especially in mixed regions where different dither masks are used for each overlapping region.
Innovation Solution
A printing apparatus and method that employs a dither mask with a specific arrangement of heads and nozzles, utilizing blue or green noise characteristics to enhance dot dispersibility, and divides pixels into groups to minimize correlation between dot formation positions, ensuring consistent image quality across single and mixed regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple print heads are arranged with overlapping nozzle rows to increase printing width, then printing productivity is improved, but dot formation position deviation occurs causing graininess and density variation
Solution Approach 1:
The printing system is divided into multiple independent print heads (first, second, and third print heads) with overlapping nozzle rows. Each print head operates independently with its own dither mask, allowing precise control of dot formation positions in each segment while collectively achieving wide printing coverage.
Solution Approach 2:
Different dither masks are applied to different print heads to locally optimize dot formation characteristics. The first dither mask is used for the first print head, the second dither mask for the second print head, and the third dither mask for the third print head, ensuring that each local region maintains proper dot dispersibility despite positional deviations.
2Device complexity
If a single dither mask is used for all print heads to simplify the system, then device complexity is reduced, but image quality deteriorates in mixed regions where multiple nozzle rows overlap
Solution Approach 1:
Different dither masks are assigned to different print heads based on their specific positional relationships and overlapping patterns. This local optimization ensures that each print head produces dots with appropriate dispersibility characteristics for its specific operating conditions, maintaining high image quality across the entire printing width.
Solution Approach 2:
Multiple dither masks are created based on the same base dither mask pattern (with 4×4 elements), but with different threshold value arrangements tailored to each print head's specific configuration. This allows systematic generation of appropriate dither masks for each head without entirely redesigning the pattern.
3Manufacturing precision
If the dither mask size is increased to improve dot dispersibility in mixed regions, then image quality is improved, but processing time and computational load increase
Solution Approach 1:
Instead of using a single large dither mask covering the entire printing width, the system uses multiple smaller dither masks (each 4×4 elements) that are applied locally to each print head. This partial action approach achieves the necessary dot dispersibility in each local region without the computational overhead of processing a single large mask.
Data Source
AI summary
A printing apparatus includes a halftone processing section that uses a dither mask to determine whether or not to form a dot in each of a plurality of pixels constituting an output image based on an input gradation value of an original image, and a head unit that forms the output image on a medium based on a processing result of the halftone processing section, the output image includes a mixed region and a single region, a length of the mixed region is a first length, a length of the single region is a second length, and the number of elements of the dither mask is N times or 1/N times a total number of the number of pixels corresponding to the first length and the number of pixels corresponding to the second length.