Image Processor Dot Overlap Control for Inkjet Density and Graininess
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Solution Overview
Problem
Inkjet printing devices face issues with density unevenness and graininess due to deviations in dot printing position, which are not effectively addressed by existing multipass printing methods that divide image data into uncorrelated binary planes, leading to irregular dot distribution and increased graininess.
Innovation Solution
An image processor that generates and quantizes density data to control the dot overlap rate based on image characteristics, adjusting the ratio of overlapping dots to maintain a balance between density uniformity and graininess by correlating dot data across multiple scans or printing element groups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If image data is divided into uncorrelated binary planes for multipass printing, then density unevenness is reduced, but graininess worsens due to irregular dot distribution
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing optimal threshold values in a threshold value table before the actual printing process. The image processing unit references this pre-prepared table to determine dot formation thresholds for each pass, ensuring that dot overlap rates are controlled in advance rather than reacting to density issues during printing. This proactive approach allows the system to prevent graininess while maintaining density uniformity.
Solution Approach 2:
The patent implements feedback by using the previously printed pass data to influence subsequent printing passes. The image processing unit calculates threshold values for each pass based on the dot formation results of previous passes, creating a feedback loop where each pass adapts to the cumulative dot coverage. This feedback mechanism ensures that dot overlap rates remain within optimal ranges, simultaneously achieving density uniformity and reducing graininess.
2Manufacturing precision
If dot overlap rate is increased to suppress density unevenness, then density uniformity improves, but graininess worsens due to excessive dot accumulation
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the threshold values for dot formation in each printing pass based on the cumulative dot overlap rate. The image processing unit modifies these parameters (threshold values) to maintain the dot overlap rate within a predetermined optimal range. This allows the system to achieve density uniformity without excessive dot accumulation that would cause graininess, as the parameters are continuously optimized rather than fixed.
Solution Approach 2:
The patent implements dynamics by making the dot formation process adaptive and variable across multiple passes. Instead of using fixed threshold values, the system dynamically adjusts thresholds based on real-time feedback from previous passes and the current dot overlap rate. This dynamic adjustment ensures that the dot overlap rate remains within optimal ranges, balancing density uniformity and graininess suppression throughout the multipass printing process.
3Object-affected harmful factors
If dot overlap rate is decreased to reduce graininess, then graininess is suppressed, but density unevenness increases due to insufficient dot coverage
Solution Approach 1:
The patent applies parameter changes by adjusting threshold values for each printing pass to maintain dot overlap rates within an optimal range that prevents both graininess and density unevenness. The image processing unit modifies these parameters based on cumulative dot coverage, ensuring sufficient dot coverage for density uniformity while preventing excessive overlap that would cause graininess.
Solution Approach 2:
The patent implements feedback by using cumulative dot coverage information from previous passes to adjust subsequent pass parameters. The system monitors the actual dot overlap rate and uses this feedback to modify threshold values in later passes, ensuring that density uniformity is maintained without creating graininess through excessive dot accumulation.
Data Source
AI summary
Provided is an image processor and image processing method that are capable of suppressing both density unevenness and graininess that occur due to deviation of the printing position of dots that are printed by a plurality of relative movements (or a plurality of printing element groups). In order to accomplish this, the dot overlap rate of an image characteristic in which density unevenness stands out is made higher than the dot overlap rate of an image characteristic in which other defects stand out more than the density unevenness. By doing so, it is possible to suitably adjust the dot overlap rate according to an image characteristic, and to output an image having no density unevenness or graininess.