Test Pattern Reading Angle to Suppress Inkjet Moire Errors
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Solution Overview
Problem
Inkjet printing apparatuses experience moire errors in reading test patterns due to periodic density variations, leading to inaccuracies in density unevenness correction values.
Innovation Solution
The printing apparatus and method involve forming a test pattern with a controlled inclination angle (0°<θ<90°) between the scanning and reading directions to reduce moire interference, using a reading unit that reads the test pattern in units of reading resolution in intersecting directions, and optionally inclining the medium or using a guide to align the reading direction accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the reading unit reads the test pattern in the same direction as the scanning direction, then the reading process is simple and efficient, but moire occurs causing errors in density correction values
Solution Approach 1:
The patent introduces a new dimension by inclining the reading direction at an angle θ relative to the scanning direction. This angular offset breaks the periodic alignment between reading pixels and printing nozzles, eliminating moire patterns while maintaining measurement accuracy for density correction
2Measurement precision
If the reading direction is inclined by an angle θ relative to the scanning direction, then moire is reduced and reading accuracy is improved, but the reading process becomes more complex
Solution Approach 1:
The patent changes the operational parameter of reading direction from parallel to inclined at angle θ. This parameter modification effectively suppresses moire interference and improves reading accuracy, while the control unit manages the complexity through automated coordinate transformation and image processing
Data Source
AI summary
A printing apparatus includes a printing head, a control unit, a reading unit, and a storage unit, forms a test pattern for correcting a printing characteristic onto a medium, and corrects the printing characteristic based on a reading result of the test pattern by the reading unit. The reading unit reads a density of a printing surface on the medium in units of reading resolution in a first reading direction and a second reading direction intersecting the first reading direction. The storage unit stores an inclination angle θ (0°<θ<90°) along the printing surface of a reading direction that serves as a reference of inclination from a scanning direction intersecting an alignment direction of a plurality of nozzles of the first reading direction and the second reading direction and the scanning direction. The control unit causes the reading unit to read the test pattern in a state where the reading direction is inclined by the inclination angle θ from the scanning direction.