Digital Printing Nozzle Malfunction Compensation via Luminance-Debt
Solution Overview
Problem
Digital printing systems face issues with malfunctioning ink nozzles, which result in reduced print quality due to incomplete or misdirected ink droplets, and existing compensation techniques leave unwanted visual artifacts.
Innovation Solution
A method is introduced to modify the half-toned digital image by increasing droplet sizes in neighboring columns of a malfunctioning nozzle's column, using a pre-print digital processor to compute a modified version based on a cumulative luminance-debt function, iteratively adjusting droplet sizes to compensate for the missing ink, and printing the modified image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If simple compensation techniques are used to compensate for malfunctioning nozzles, then print quality is improved, but unwanted visual artifacts appear in the printed image
Solution Approach 1:
The patent applies local quality by differentiating the compensation approach based on the specific characteristics of each malfunctioning nozzle and its location. The system analyzes the half-toned digital image and applies targeted droplet size adjustments only to specific neighboring columns affected by each malfunctioning nozzle, rather than applying uniform compensation across the entire image. This localized approach maintains print quality while minimizing visual artifacts.
Solution Approach 2:
The patent changes the parameter of droplet size in neighboring columns to compensate for malfunctioning nozzles. By iteratively adjusting the droplet size parameter based on the luminance-debt function, the system redistributes the missing ink quantity to adjacent columns, achieving visual compensation without creating obvious artifacts that would result from simpler compensation methods.
2Manufacturing precision
If droplet sizes are increased in neighboring columns to compensate for missing ink, then the negative impact of malfunctioning nozzles is reduced, but the complexity of the printing process increases
Solution Approach 1:
The patent applies preliminary action by performing the compensation calculation and modifying the half-toned digital image before the actual printing process. The pre-print digital processor computes the modified droplet sizes based on the luminance-debt function, so that when printing occurs, the system simply executes the pre-calculated droplet size adjustments without real-time complexity.
Solution Approach 2:
The system performs self-service by automatically detecting malfunctioning nozzles and computing the necessary compensation adjustments without requiring manual intervention. The pre-print digital processor autonomously analyzes the image data, identifies affected columns, and calculates the iterative droplet size modifications needed to compensate for each malfunctioning nozzle.
3Measurement precision
If an iterative computation procedure is used to compute compensation values, then compensation accuracy is improved, but computation time increases
Solution Approach 1:
The patent applies partial action by implementing a convergence-based iterative procedure that stops when the luminance-debt function reaches an acceptable threshold or after a predetermined number of iterations. This approach achieves sufficient compensation accuracy without performing an excessive number of iterations, thereby balancing computation time with compensation precision.
Data Source
AI summary
Printing an image, using a printing system having a malfunctioning or inoperative nozzle corresponding to a column of affected positions in a half-toned digital image, includes modifying the half-toned digital image, using a pre-print digital processor of the printing system to compute a modified version of the half-toned digital image, such that droplet sizes are increased only in the two neighboring columns and according to a value of a compensation function, and printing the modified half-toned digital image on the target surface. Values of the threshold-based compensation function are based on a luminance-debt function defined by an iterative row-by-consecutive-row computation procedure, where for each iteration step the luminance-debt function is re-calculated according to data representing the ink values of affected positions and data representing the instant value of the compensation function.