Digital Imaging Device Calibration via Spectrophotometry
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Solution Overview
Problem
Existing methods for calibrating digital color imaging devices, such as printers, are non-reliable and require specialized knowledge, leading to inconsistent and inaccurate results due to reliance on trial and error and density-based measurements that fail to ensure proper gray balance and are not optimized for inkjet and laser printers.
Innovation Solution
The use of colorimetric and spectrophotometric techniques to determine total colorant limits, per-channel colorant limits, and channel linearization tables, along with distribution functions for multi-hue colorants, to calibrate digital imaging devices accurately and repeatably, using test patterns and measurement devices like spectrophotometers to provide accurate colorimetric data for processor-generated calibration data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If density-based measurements are used for calibration, then the calibration process is simple, but the accuracy and reliability of color reproduction deteriorates
Solution Approach 1:
The patent replaces density-based measurement methods with colorimetric and spectrophotometric measurement systems. This substitution enables accurate measurement of colorimetric values (L*, a*, b*) and spectral reflectance, directly resolving the contradiction by providing both precision and reliability in calibration while maintaining processability through automated measurement and processing.
2Ease of operation
If trial and error methods are used for calibration, then the calibration process is easy to perform, but the reliability and consistency of results deteriorates
Solution Approach 1:
The patent implements a feedback-based calibration process where colorimetric measurements of printed test patterns are fed back to automatically adjust and determine optimal colorant limits and linearization tables. This eliminates trial-and-error methods while maintaining ease of operation, as the system automatically iterates to optimal calibration parameters based on measured colorimetric data.
Solution Approach 2:
The calibration system performs self-calibration by automatically measuring printed test patterns, processing colorimetric data, and determining calibration parameters without requiring specialized operator knowledge. The system serves itself by integrating measurement, analysis, and parameter determination into an automated workflow that reliably produces consistent results.
3Measurement precision
If colorimetric and spectrophotometric techniques are implemented, then measurement precision and calibration accuracy improve, but device complexity increases
Solution Approach 1:
The patent employs a multi-functional calibration system that integrates both colorimetric measurement (for L*, a*, b* values) and spectrophotometric measurement (for spectral reflectance) capabilities into a single calibration apparatus. This universal approach allows the system to perform multiple measurement functions, enabling accurate determination of both colorimetric characteristics and spectral properties without requiring separate dedicated devices, thus managing complexity while maintaining high measurement precision.
4Productivity
If automated calibration with colorimetric data is implemented, then productivity and repeatability improve, but the complexity of measurement and processing increases
Solution Approach 1:
The patent implements preliminary action by pre-defining test pattern structures and measurement protocols that automatically capture the necessary colorimetric data for calibration. The system is configured in advance to measure specific patches and compute calibration parameters systematically, which simplifies the measurement and processing steps during actual calibration execution while maintaining high productivity and repeatability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach ensures repeatable and accurate calibration of digital imaging devices, maintaining the gamut of proofing printers similar to commercial presses, without requiring specialized knowledge, and provides precise gray balance and accurate color reproduction.
Implementation Method 1
The use of colorimetric and spectrophotometric techniques to determine total colorant limits, per-channel colorant limits, and channel linearization tables
Data Source
AI summary
Methods and apparatus are provided for calibrating a digital color imaging device to a printing press by determining a total colorant limit, per-channel colorant limits, and channel linearization tables using calorimetric and/or spectrophotometric techniques. In addition, for digital color imaging devices that use multi-hue colorants, methods and apparatus are provided for determining distribution functions for the multi-hue colorants as a function of input values.