Inkjet Printer Head Shading Correction via Target Color Specification
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Solution Overview
Problem
Conventional head shading correction techniques in inkjet printers are inadequate in correcting color differences caused by variations in nozzle ejection characteristics due to reader errors or variations in light source characteristics, leading to unsatisfactory image density uniformity.
Innovation Solution
An inkjet printer system that calculates color specification values for nozzle regions, sets target color specification values, and applies correction amounts to image data based on these values to correct for variations, thereby reducing the influence of reader errors and ensuring uniform image density across the print medium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional head shading correction technique is used to correct nozzle ejection variations, then color difference correction is attempted, but reader errors and light source variations cause read value variations that influence correction values and prevent adequate correction
Solution Approach 1:
The patent divides the correction process into multiple independent measurement stages: initial patch reading to determine correction values, and subsequent verification reading to detect reader errors. By segmenting the correction workflow, the system can identify and exclude erroneous readings without compromising the overall correction accuracy.
Solution Approach 2:
The patent implements a feedback mechanism where the system reads patches multiple times, compares the read values, and uses statistical analysis to detect and correct reader errors. The correction values are refined based on feedback from repeated measurements, allowing the system to distinguish between actual nozzle variations and reader errors.
2Measurement precision
If multiple patches are read to calculate correction values for each nozzle region, then color specification accuracy is improved, but processing time increases
Solution Approach 1:
The patent performs preliminary measurements by reading multiple patches before final correction value determination. This preliminary action allows the system to establish baseline correction values and detect reader errors in advance, preventing the need for time-consuming re-corrections later in the printing process.
Solution Approach 2:
The patent changes the measurement parameters by reading patches at different positions and under different conditions to calculate comprehensive correction values. By varying the measurement parameters and taking multiple samples, the system achieves higher accuracy without requiring excessive measurement time, as the correction values are derived from statistical analysis of multiple readings.
Data Source
AI summary
In the present invention, a first calculation unit calculates, based on image data obtained by reading with a reading unit a plurality of patches formed on a printing medium by a plurality of nozzle regions constituting nozzle array of a printing head, respective color specification values of a plurality of correction regions corresponding to a plurality of nozzle regions constituting the nozzle array. Then, a target value setting unit sets, based on the calculated color specification values of the plurality of correction regions, a target color specification value of the patch. Further, a second calculation unit calculates a difference between each of the color specification values of the plurality of correction regions and the target color specification value as a correction amount. After that, based on the correction amount calculated, image data corresponding to an image printed by each of the plurality of nozzle regions are corrected.