Modified Dither Matrix for Inkjet Print Uniformity
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Solution Overview
Problem
Inkjet printers face challenges in printing high-speed images with uniformity due to variations in droplet ejection amounts from multiple outlets, leading to unevenness in printed images, and require specialized circuits for shading compensation, increasing manufacturing costs.
Innovation Solution
A modified dither matrix is generated and used in conjunction with a printer head having outlets arranged in a specific pattern to control ink ejection, where element values are adjusted based on print density variations, allowing for high-speed image printing with reduced unevenness without the need for additional circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a density measurement part and shading compensation circuit are provided to correct ejection amount variation, then unevenness in printed image is suppressed, but device complexity and manufacturing cost increase
Solution Approach 1:
The dither matrix is pre-modified during the printing preparation stage to incorporate shading compensation data. This preliminary action embeds the correction information into the printing data itself, eliminating the need for real-time calculation circuits and density measurement parts in the printer hardware.
Solution Approach 2:
The invention introduces a modified dither matrix as an intermediary that carries shading compensation information. This matrix serves as a mediator between the original image data and the final printed output, encoding correction factors that compensate for ejection variation without requiring additional hardware circuits.
2Manufacturing precision
If pixel values are modified on the basis of print density in outlet before halftoning, then unevenness caused by ejection variation is suppressed, but calculation operation time increases and high-speed printing becomes difficult
Solution Approach 1:
The modification of pixel values and the multiplication by correction coefficients are performed in advance during the dither matrix generation stage, not during real-time printing. This preliminary calculation eliminates the need for complex real-time arithmetic operations, enabling high-speed printing while maintaining uniformity.
Solution Approach 2:
The shading compensation calculation is performed beforehand to create the modified dither matrix. By completing the computationally intensive operations in advance, the actual printing process only requires simple comparison and ejection control, maintaining high printing speed.
3Manufacturing precision
If a special shading compensation circuit is provided to perform real-time correction, then unevenness is suppressed, but manufacturing cost increases
Solution Approach 1:
The invention extracts the shading compensation function from the hardware circuit domain and relocates it to the data processing domain. By taking out the correction logic from the physical circuit and embedding it in the software-generated dither matrix, the need for expensive specialized hardware is eliminated.
Solution Approach 2:
Instead of implementing physical correction circuits, the invention uses a software-generated copy of the correction data embedded in the dither matrix. This virtual copy of the correction information achieves the same functional effect without the cost of physical circuit implementation.
Data Source
AI summary
A printer has a head where outlets are arranged in a width direction perpendicular to a predetermined scan direction, and a printing paper moves under the head in the scan direction. In a basic dither matrix which is an array where element values are arranged in a column direction corresponding to the scan direction and a row direction corresponding to the width direction and positions in the row direction are associated with the outlets in the head, respectively, the element values are modified on the basis of variation in print densities with respect to the width direction caused by ejection from the outlets. In the printer, printing is performed with the modified dither matrix, it is therefore possible to print an image at high speed and easily, where unevenness caused by variation in ejection amounts of droplets from the outlets or the like is suppressed.