Multi-pass Image Processing Apparatus for Density Fluctuation Control
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Solution Overview
Problem
Existing multi-pass printing methods face challenges in controlling dot overlap and maintaining image quality due to fluctuations in printing medium conveyance, leading to density unevenness and increased graininess, while also incurring high processing loads.
Innovation Solution
An image processing apparatus and method that selectively processes multi-valued image data by dividing and quantizing it based on detected printing positions, allowing for controlled dot overlap and reduced processing load by generating common quantized data for multiple scans.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multi-pass printing is performed to reduce density unevenness and stripes, then image quality is improved, but dot position shift occurs due to conveyance fluctuation causing density fluctuation
Solution Approach 1:
The patent applies preliminary action by dividing multi-valued image data into scan-specific data before the actual printing process. This pre-processing step allows the system to prepare separate data sets for each printing scan, enabling subsequent independent quantization and processing that compensates for conveyance fluctuations and maintains stable dot positioning across multiple passes.
Solution Approach 2:
The patent segments the multi-valued image data into distinct portions corresponding to different printing scans. By dividing the data into scan-specific segments and processing each independently through quantization, the system can optimize dot placement for each pass while maintaining overall image quality consistency despite conveyance variations.
2Manufacturing precision
If multi-valued image data is divided and independently quantized for each scan, then complementarity between scans is reduced and overlapping dots increase, but this causes excessive graininess or insufficient density fluctuation suppression
Solution Approach 1:
The patent applies parameter changes by adjusting the quantization process dynamically based on the divided data portions. Instead of uniform quantization, the system modifies quantization parameters for different data segments, controlling the degree of dot overlap and graininess while maintaining sufficient density fluctuation suppression. This allows optimization of the balance between density uniformity and graininess control.
3Reliability
If data division and quantization processing is performed for all printing positions, then density fluctuation is suppressed, but processing load increases
Solution Approach 1:
The patent applies local quality by detecting the specific printing position on the printing medium and selectively applying data division and quantization processing only where necessary. For printing positions with low conveyance precision (such as near the boundaries), the full processing is applied to suppress density fluctuation, while positions with high conveyance precision may use simplified processing, thereby reducing overall processing load while maintaining density stability where most needed.
Data Source
AI summary
In image processing, it is possible to suppress density fluctuation and keep graininess low as well as obtain a good balance of the processing load. More specifically, when dividing multi-valued data and generating two-pass multi-pass printing data, divided multi-valued data that is common to the two passes is generated in addition to the divided multi-valued data for each of the two passes. Moreover, quantized data of that common multi-valued data is reflected on the quantized data for each pass. Furthermore, when generating quantized data, a process of generating common data by the aforementioned data division, or a process of performing quantization first without dividing the multi-valued data and then dividing the quantized 2-pass data is selectively performed according to the printing position on printing medium.