Pitch-to-Pitch Gray Balance Calibration via Margin TRCs
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Solution Overview
Problem
Color printers face challenges in maintaining consistent gray balance across pitches due to variations in color pigments and internal processes, leading to inaccuracies in process gray production.
Innovation Solution
Generating customized tone reproduction curves (TRCs) for each pitch, both in the digital front end and image path of the marking engine, using target patch patterns printed in the substrate margins, which allows for real-time adjustments and frequent updates to balance gray levels, reducing paper waste and process interruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If customized tone reproduction curves (TRCs) are generated for each pitch using target patch patterns printed in substrate margins, then gray balance consistency across pitches is improved, but device complexity increases
Solution Approach 1:
The calibration process is segmented by creating separate TRCs for each pitch of the photoreceptor. Target patch patterns are printed in the margin areas of each pitch, allowing individual measurement and calibration of each pitch's gray balance characteristics. This segmentation enables precise compensation for pitch-to-pitch variations without requiring complete system redesign.
Solution Approach 2:
Target patch patterns are printed in the substrate margins during the normal printing process before actual measurement and calibration occur. This preliminary placement of calibration targets allows the system to capture gray balance data from each pitch without interrupting the printing workflow, and the TRCs are generated in advance for subsequent color correction.
2Measurement precision
If target patch patterns are printed in substrate margins for each pitch, then calibration accuracy is improved, but paper waste increases
Solution Approach 1:
The calibration function is extracted from the main printing area by placing target patch patterns in the margin areas of each pitch. This extraction allows calibration data to be collected from non-printable or less critical regions of the substrate, preserving the quality of the main image area while still obtaining accurate gray balance measurements from each pitch.
Solution Approach 2:
The calibration information is moved from the traditional separate calibration substrate approach to the margin dimension of the production substrate. By utilizing the margin areas—spaces that would otherwise be wasted or used for non-critical content—the system achieves calibration accuracy without requiring additional dedicated calibration materials or increasing overall paper consumption.
3Manufacturing precision
If frequent updates of TRCs are performed, then color accuracy is improved, but productivity decreases
Solution Approach 1:
The calibration process is made continuous by printing target patch patterns in the margins during normal production printing operations. Instead of stopping the press to perform calibration, the system continuously captures gray balance data from each pitch as it prints, allowing frequent TRC updates without interrupting the printing workflow. This maintains color accuracy while preserving productivity.
Solution Approach 2:
The system performs periodic calibration updates by analyzing target patch patterns printed at regular intervals in the substrate margins. Rather than requiring continuous interruption for calibration, the periodic inclusion of target patches in the margin areas allows the system to update TRCs at optimal intervals, balancing color accuracy requirements with maintaining high printing productivity.
Data Source
AI summary
A printer or other marking engine includes a marking material transfer device, such as a photoreceptor drum or belt, that includes a plurality of pitches. Each pitch receives an individual color of marking material and conveys the marking material to a substrate. The marking engine forms a desired image in a main image area of the substrate using marking material from one or more of the pitches, and produces a target patch pattern for each of the pitches in a margin area located outside the main image area. A measuring device such as a spectrophotometer is used to measure each target patch pattern, and based on the measured values, an individual color calibration is performed for each pitch for use in a subsequent marking operation. The color calibration may include generating or modifying a tone reproduction curve for each pitch based on the measured values. The margin area may be later trimmed off, thereby removing the portion of the substrate on which the target patch pattern is formed.