Printer Chart Marker Alignment for Colorimetric Accuracy
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Solution Overview
Problem
Existing color adjustment techniques for inkjet printers face challenges in obtaining stable colorimetric values, particularly when the marker position and chip module boundaries do not coincide, leading to density steps and errors in sensor reading values.
Innovation Solution
The proposed solution involves an image processing apparatus that includes a printing unit for printing a chart image with a patch and a marker, a scanning unit for reading the chart image, and a correction unit for correcting reading characteristics based on the reading results. The marker is arranged in the main scanning direction to account for unevenness in the printing or scanning unit, allowing for accurate colorimetric value determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the marker position is arbitrarily set in the chart image, then the chart can be printed and scanned, but density steps occur when marker position and chip module boundaries do not coincide, leading to inaccurate colorimetric values
Solution Approach 1:
The marker position is predetermined and set in advance based on the chip module boundary positions before printing the chart image. This preliminary positioning ensures that when the chart is printed and scanned, the marker aligns with the chip module boundaries, preventing density steps and ensuring accurate colorimetric measurements.
Solution Approach 2:
The chart image is designed with different regions having different functions: the marker region is specifically positioned at chip module boundaries to serve as a reference point, while other regions contain test patches for colorimetric measurement. This local differentiation ensures that the marker provides accurate positional reference without interfering with the uniformity of test patches.
2Measurement precision
If the interval between markers does not match the sensor unevenness period, then the chart can be scanned, but reading errors occur in the sensor values within patches, preventing accurate colorimetric value determination
Solution Approach 1:
The marker interval is specifically set to match the sensor unevenness period (a critical parameter of the scanning system). By changing the marker spacing parameter to align with the sensor's periodic characteristics, the method eliminates reading errors that would otherwise occur when sampling at mismatched intervals, thereby improving measurement accuracy.
3Reliability
If calibration is performed with a white reflection standard, then illumination and sensors can be calibrated, but variations in sensor reading characteristics remain due to angle dependence and spectral characteristics differences
Solution Approach 1:
A chart image with specifically designed markers and uniform density patches serves as an intermediary calibration target. This intermediary provides known reference points that allow the system to characterize and correct sensor reading variations, bridging the gap between the white reflection standard calibration and actual printing measurements.
Data Source
AI summary
The image processing apparatus according to the present disclosure has: a printing unit configured to print a chart image including a patch extending in a main scanning direction intersecting a conveyance direction of a sheet and having a uniform density and a marker for identifying a position in the main scanning direction; a scanning unit configured to read the chart image printed by the printing unit; and a correction unit configured to correct reading characteristics of the scanning unit based on reading results read by the scanning unit, wherein the marker is arranged in the main scanning direction based on information relating to unevenness in the main scanning direction of the printing unit or the scanning unit.