Variable Beam Delays for Halftone Banding Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Reprographic printing systems face challenges in eliminating periodic density variations known as banding errors, which are difficult to reduce to imperceptible levels due to various noise sources, especially when halftone interactions with raster output scanner (ROS) variations occur, leading to visually perceptible banding in printed outputs.
Innovation Solution
The implementation of variable beam delays in multibeam raster output scanners to compensate for banding errors by adjusting beam timing values, allowing for selective actuation of light sources to produce modulated light outputs that counteract halftone pattern interactions and process direction density variations, thereby reducing banding to acceptable levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional banding compensation techniques are used, then some banding errors are reduced, but halftone-interaction banding remains visually perceptible
Solution Approach 1:
The patent changes the timing parameter of light source actuation by introducing variable beam delays. Each beam is delayed by a specific amount (e.g., 0-10 nanoseconds) to shift the interaction frequency between ROS variations and halftone patterns, moving the banding frequency out of the visually perceptible range and thereby resolving the contradiction between reducing banding errors and achieving visual acceptability.
2Productivity
If ROS modules with errors are used to maintain productivity, then printing speed is maintained, but banding errors increase
Solution Approach 1:
The patent converts the harmful effect of ROS module variations into a beneficial compensation mechanism. By measuring the actual banding characteristics produced by each ROS module and applying customized beam delays, the system transforms the presence of error-prone ROS modules into an opportunity for targeted compensation, allowing high-speed printing with error-prone modules while maintaining density uniformity through the beam delay compensation.
3Manufacturing precision
If beam timing is adjusted to compensate for banding, then image quality improves, but system complexity increases
Solution Approach 1:
The patent implements a feedback mechanism where banding characteristics are measured from test prints produced by each ROS module, and these measurements are used to determine the optimal beam delays for that specific module. This closed-loop feedback approach allows the system to automatically compensate for module-specific variations without requiring manual calibration, thereby improving image quality while managing system complexity through automated measurement and configuration.
Data Source
AI summary
Disclosed are methods and systems for compensating for process direction banding associated with a document processing system including a ROS. According to one exemplary embodiment, a ROS driver uses a plurality of beam delay/advance values to compensate for banding caused by an interaction of a halftone pattern and process direction density variations associated with the ROS.