Inkjet Printer Control Device for Multi-Pass Dot Placement
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Solution Overview
Problem
Conventional inkjet printers face issues with banding in printed images due to irregularities in sheet conveyance, leading to potential gaps between dots and decreased image density caused by deviations in dot positions during main scans.
Innovation Solution
A control device for an inkjet printer that reciprocally moves a print head with nozzles in a main scanning direction, intermittently conveying the printing medium in a sub scanning direction, and executing multiple forming processes to ensure accurate dot placement based on target image data, adjusting dot formation to maintain image density by overlapping scanning ranges and using specific conditions for dot formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If multiple main scans are employed to complete a single raster, then banding in printed images is avoided, but gaps between dots occur due to deviation in relative positions of dots, decreasing image density
Solution Approach 1:
The control device performs preliminary calculations to determine corrected conveying amounts based on detected conveyance amounts from previous passes. By pre-calculating the necessary adjustments, the system compensates for positional deviations before they affect dot placement accuracy, ensuring that dots are formed at correct positions despite variations in sheet conveyance.
Solution Approach 2:
The system incorporates feedback mechanisms by detecting actual conveyance amounts during each pass and using this information to calculate corrected conveying amounts for subsequent passes. This closed-loop approach continuously adjusts the conveying process to maintain precise dot positioning and eliminate gaps while preventing banding.
2Ease of manufacture
If conventional single-pass printing is used, then dot placement is simple, but banding occurs due to irregularities in sheet conveyance
Solution Approach 1:
The printing process is segmented into multiple passes, with each pass responsible for forming dots in specific regions of the raster. By dividing the overall printing task into smaller, manageable segments (passes), the system can handle irregularities in sheet conveyance more effectively, as each pass operates with more controlled and predictable conveyance characteristics.
Solution Approach 2:
The system employs periodic action by repeating the forming process multiple times with adjusted conveying amounts. Each pass is a periodic repetition of the dot formation process, but with modified parameters (corrected conveying amounts) to compensate for accumulated errors and maintain image quality throughout the printing process.
Data Source
AI summary
In a control device, a controller is configured to perform: acquiring target image data; and controlling a printer to execute a first forming process forming dots on a first scanning range and a second forming process forming dots on a second scanning range. The first scanning range overlaps the second scanning range at an overlapping area. The overlapping area includes a first position corresponding to a first pixel and a second position corresponding to a second pixel. In a case where both a first pixel value and a second pixel value indicate forming a dot and the target image data satisfies a condition requiring that density in a region including the first pixel is equal to or more than a reference, the first forming process forms a dot at the first position and the second forming process forms a dot at both the first position and the second position.