Printer Defect Camouflage via Grey Level Redistribution
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Solution Overview
Problem
Existing methods for camouflaging defective print elements in printers, such as ink jet printers, often result in image information loss due to the inability to print pixels when a nozzle is defective, especially in single-pass mode, and are inefficient in multi-pass modes, leading to degraded print quality.
Innovation Solution
A method that represents image information as a multi-level pixel matrix, transfers grey levels from defective nozzles to neighboring non-defective nozzles, and converts the matrix into a bitmap using algorithms like error diffusion or dithering to maintain image quality, allowing for flexible distribution of grey levels and adaptation to various printer capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a defective nozzle is bypassed by substituting pixels to neighbouring lines, then the defect is camouflaged and average optical density is conserved, but image information is lost when the neighbouring pixel position is already occupied by a black pixel
Solution Approach 1:
The patent transitions from binary bitmap manipulation to multi-level pixel matrix processing, adding a dimensional aspect of grey level values. This allows defective pixel information to be redistributed across multiple neighbouring pixels with adjusted grey levels, rather than simple binary substitution, thereby preserving image information while camouflaging defects
Solution Approach 2:
The patent changes the parameter representation from binary (0 or 1) to multi-level grey values (0-255). By modifying the grey level parameters of neighbouring pixels to accommodate transferred defect information, the system preserves image data while maintaining visual quality, avoiding information loss that occurs with binary substitution
2Reliability
If a defective nozzle is backed-up by a non-defective nozzle in multi-pass mode, then the defect is compensated, but productivity decreases
Solution Approach 1:
The patent performs defect compensation in advance by processing the pixel matrix before actual printing. The grey level redistribution and defect camouflage are calculated and prepared in the digital domain, allowing the printer to maintain single-pass operation without requiring additional correction passes, thus preserving productivity while achieving defect compensation
3Device complexity
If binary bitmap manipulation is used to bypass defective nozzles, then the processing is simple, but image quality degrades due to information loss
Solution Approach 1:
The patent enhances the data representation from binary to multi-level grey values, allowing richer information to be processed and redistributed. This parameter expansion enables quality preservation during defect compensation, as the additional grey level information provides more flexibility in maintaining image fidelity while managing processing complexity
Data Source
AI summary
A printer, a computer program and a method are provided for camouflaging defective print elements in the printer having a printhead with a plurality of print elements. The method includes (a) representing the image information to be printed by a multi-level pixel matrix wherein a grey level of each pixel is indicated by a number, (b) transferring the grey levels of pixels that are assigned to a defective print element, to neighboring pixels in the pixel matrix, and (c) converting the pixel matrix having the transferred grey levels, into a bitmap to be printed.