Printer Calibration Using Limited Range Reflective Scanners
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Solution Overview
Problem
Existing printer calibration methods rely on expensive and cumbersome instruments like densitometers and spectrophotometers, which are not suitable for all printers due to their high cost, calibration requirements, and limited applicability, especially when using reflective scanners with smaller density measurement ranges that drift over time.
Innovation Solution
A novel calibration algorithm that characterizes the limitations of a reflective scanner's density measurement range, allowing for weighted combinations with an initial lookup table to generate a corrected lookup table, effectively calibrating the printer even when the scanner's range is limited, by blending scanner data with factory defaults to minimize discontinuities and ensure accurate output within the printer's critical density range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If densitometers or spectrophotometers are used for printer calibration, then measurement precision and calibration accuracy are improved, but device cost and operational complexity increase significantly
Solution Approach 1:
The patent replaces expensive, complex calibration instruments (densitometers and spectrophotometers) with inexpensive, readily available reflective scanners. The scanner, though less precise, is used in conjunction with a calibration target and algorithm to achieve adequate calibration results without the high cost and complexity of professional measurement devices.
Solution Approach 2:
The patent introduces a calibration target with known density values as an intermediary between the scanner and the printer calibration process. This target serves as a reference that allows the scanner's limited measurements to be transformed into accurate calibration data through mathematical algorithms, bridging the gap between the scanner's capabilities and the calibration requirements.
2Device complexity
If reflective scanners are used for printer calibration, then device cost and accessibility are improved, but measurement precision and reliability deteriorate due to limited density range and drift
Solution Approach 1:
The patent performs preliminary characterization of the scanner's density measurement range and drift characteristics before using it for calibration. By pre-determining the scanner's operational limits and applying appropriate corrections or weightings in the calibration algorithm, the system compensates for the scanner's inherent inaccuracies and extends its effective measurement capability.
Solution Approach 2:
The patent transforms the scanner's raw measurements into corrected density values by applying mathematical transformations that account for the scanner's limited range and drift. The calibration algorithm adjusts measurement parameters and applies corrections based on the known characteristics of the scanner, effectively expanding its usable measurement range and improving accuracy.
3Device complexity
If the calibration algorithm uses only scanner measurements, then device simplicity is improved, but calibration accuracy deteriorates when scanner density range is limited
Solution Approach 1:
The patent merges scanner measurements with factory default lookup table data in a weighted combination. By combining the actual scanner measurements (which capture current printer state) with the factory defaults (which provide a complete density range reference), the algorithm produces an accurate corrected lookup table even when the scanner's measurement range is limited.
Solution Approach 2:
The patent uses partial scanner measurements within the scanner's limited density range and supplements them with factory default data for the remaining density ranges. This partial action approach allows the system to utilize the scanner's available measurements while compensating for its limitations through the weighted combination with factory defaults, achieving complete calibration coverage.
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 enables effective printer calibration using less costly reflective scanners, producing better printed results than without calibration, while accounting for scanner drift and limitations, ensuring optimal output within the printer's accurate density range.
Implementation Method 1
scanning the plurality of printed patches on the target with the reflective scanner to obtain a set of reflectance values
Data Source
AI summary
A method of calibrating a printer using a reflective scanner is disclosed. Because the reflective scanner used for calibration may only be able to accurately measure a limited density range that is less than the full density range of the printer, some information from the reflective scanner is disregarded or deemphasized during the calibration process. A calibration page is printed and scanned. Lookup tables (LUTs) that comprise the printer calibration values are updated based on adjustments calculated from the scanner for density regions where the scanner produces relatively accurate measurements, but updated based on the preexisting settings for density regions where the scanner produces relatively inaccurate measurements. In transitions regions between accurate and inaccurate regions, the LUTs are adjusted based on a combination of measurements from the scanner and the preexisting settings.