Inkjet Head Dot Pattern Control for Banding and Granularity
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Solution Overview
Problem
Inkjet recording apparatuses face challenges in achieving high-definition image output with good granularity and reduced band-shaped non-uniformities, particularly at high-speed printing, due to nozzle redundancy and ejection characteristics fluctuations, which worsen granularity and banding issues.
Innovation Solution
An image processing apparatus and method that employs a two-dimensional nozzle arrangement with multiple value conversion to generate image data representing a dot pattern with blue noise characteristics in one direction and green noise characteristics in a perpendicular direction, optimizing dot placement to suppress granularity and banding non-uniformities by adjusting dot frequency and size distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-speed printing is carried out with a two-dimensional head, then productivity is improved, but granularity deteriorates due to short landing time difference causing deposited droplets to combine together
Solution Approach 1:
The patent applies dynamics by making the dot formation pattern variable based on printing conditions. Specifically, it switches between single-dot and multiple-dot patterns depending on the printing speed, allowing the system to adapt dynamically to high-speed conditions where granularity would otherwise deteriorate due to droplet combination
Solution Approach 2:
The patent changes the dot pattern parameters (single-dot vs. multiple-dot patterns) based on printing speed conditions. At high printing speeds, multiple-dot patterns are used to compensate for granularity deterioration caused by short landing time differences, while at lower speeds, single-dot patterns are sufficient
2Object-generated harmful factors
If dot size is increased to cover gaps between dots, then banding is reduced, but granularity becomes worse and ink volume increases
Solution Approach 1:
The patent applies local quality by using different dot patterns in different regions or conditions. Instead of uniformly increasing dot size everywhere, it selectively applies multiple-dot patterns in specific areas or under specific printing conditions (high speed) where banding is problematic, while maintaining finer dot patterns elsewhere to preserve granularity
Solution Approach 2:
The patent uses composite dot patterns combining multiple dots of different sizes or densities within the same image formation region. This composite approach allows coverage of gaps to reduce banding while maintaining overall granularity through the distributed nature of multiple smaller dots rather than one large dot
3Manufacturing precision
If multiple scanning method is used to complete image formation, then image quality is improved, but productivity decreases due to multiple scanning actions required
Solution Approach 1:
The patent applies preliminary action by pre-planning and pre-determining the optimal dot pattern (single-dot or multiple-dot) for each pixel position based on expected printing conditions before actual image formation. This allows the system to achieve high-quality results in a single pass without requiring multiple scanning actions, as all necessary dot pattern decisions are made in advance
Data Source
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AI summary
An image processing apparatus (72, 74) for generating binary or inultiple-value image data for forming an image on a recording medium (124) by ejecting droplets from nozzles (251) of nozzle rows of a recording head (14) while relative movement between the recording medium (124) and the recording head (14) is caused, the nozzles (251) serving as ejection ports for ejecting the droplets, includes a multiple value conversion means (74) which carries out quantization processing of original image data having multiple tones (M values) so as to convert the original image data to image data of N values having fewer tones than the original image data (where M and N are integers satisfying M> N≥ 2), wherein: the recording head (14) has a two-dimensional nozzle arrangement in which the nozzle rows are arranged in a first direction (S) which is a direction of the relative movement between the recording head (14) and the recording medium (124), and the multiple value conversion means (74) generates the image data of N values representing a dot pattern having blue noise characteristics in the first direction (S) and green noise characteristics in a second direction (M) which is a direction perpendicular to the first direction (S) on the recording medium (124) so as to achieve tonal representation based on the dot pattern having these frequency characteristics.