Inkjet Image Processing Corrects Nozzle Defects by Gradation-Dependent Discharge
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Solution Overview
Problem
Existing image processing techniques for inkjet printers fail to adequately reduce the visibility of streaks caused by defective nozzles, particularly in mixed colors, as they either leave white streaks in single colors or reduce coloring efficiency, leading to concentration differences and visible streaks in both high and low gradation ranges.
Innovation Solution
An image processing device that acquires image data from an inkjet head with multiple nozzles, specifies defective nozzles, and divides the image data into specific pixel rows to adjust the generation rate and ink discharge amount based on gradation values, ensuring that defective nozzles do not discharge ink and adjacent nozzles adjust their discharge accordingly to maintain concentration equality across regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If concentration in the vicinity of the defective nozzle is increased to suppress white streaks, then visibility of white streaks is reduced, but black streaks occur
Solution Approach 1:
The patent applies different correction strategies to different regions: in highlight regions (low concentration), adjacent nozzles increase ink discharge to fill white streaks, while in shadow regions (high concentration), adjacent nozzles reduce ink discharge to prevent black streaks. This localized quality adjustment resolves the contradiction by adapting the correction method to the specific region's characteristics.
Solution Approach 2:
The patent changes the correction parameters based on the gradation value (concentration level). When the gradation value indicates a highlight region, the correction increases ink discharge from adjacent nozzles. When the gradation value indicates a shadow region, the correction decreases ink discharge from adjacent nozzles. This dynamic parameter adjustment resolves the contradiction between suppressing white streaks and preventing black streaks.
2Object-affected harmful factors
If correction region is expanded to suppress black streaks, then visibility of black streaks is reduced, but banding remains due to different image structure
Solution Approach 1:
The patent applies partial correction by limiting the correction to only those pixels where banding is actually generated, rather than expanding correction to a large region. The correction is applied selectively based on whether the pixel is adjacent to a defective nozzle and whether it falls in a highlight or shadow region, thus avoiding the banding caused by excessive correction while still suppressing black streaks.
Solution Approach 2:
The patent applies different correction amounts to different pixels based on their local characteristics. Pixels adjacent to defective nozzles in highlight regions receive different correction than pixels in shadow regions. This localized quality approach allows suppression of black streaks without creating banding from uniform expansion of the correction region.
3Object-affected harmful factors
If dot size is increased to fill voids in single color, then visibility of streaks is reduced, but coloring efficiency is reduced leading to concentration differences in mixed color
Solution Approach 1:
The patent changes the correction parameters based on the color mode. In single-color printing, the patent increases ink discharge from adjacent nozzles to fill white streaks. In multi-color printing, the patent adjusts the correction to maintain proper concentration balance across all colors, preventing both streaks and concentration differences. This dynamic parameter adjustment resolves the contradiction between streak visibility and concentration uniformity.
Solution Approach 2:
The patent makes the correction dynamic by adjusting it based on the printing conditions (single-color vs. multi-color). The correction amount and method change dynamically according to the color mode being used, allowing optimal performance in both single-color and multi-color printing scenarios without the trade-off present in static correction methods.
Data Source
AI summary
The image processing device divides image data into regions corresponding to a first pixel row, a second pixel row, a third pixel row, and a fourth pixel row, and generate output data, in which a generation rate of an ink droplet with a relatively large size, a generation rate of an ink droplet with a relatively small size, and the amount of ink discharged per unit area vary depending on a gradation value of the image data, for each of the divided regions. At the time of the generation of the output data, different output data items are generated for a third nozzle corresponding to the third pixel row when the first gradation value indicates a relatively high gradation and when the first gradation value indicates a relatively low gradation.