Inkjet Printer Calibration Using Spread Spectrum Patterns
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Solution Overview
Problem
Existing methods for calibrating ink jet printers are unreliable due to variations in dot shape, size, and position, making precise alignment and displacement measurements challenging, especially for high-quality color reproduction and resolution.
Innovation Solution
A method involving printing a chart with spread spectrum patterns using different nozzle sets, imaging the chart, and calculating the accuracy of the print mechanism by determining the positions of these regions, allowing for precise displacement measurements between them.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If visual inspection methods are used for printer calibration, then the process is simple and intuitive, but the measurement precision is insufficient due to variations in dot shape, size, and position
Solution Approach 1:
The calibration chart is divided into multiple regions, each printed by different nozzle sets, allowing independent analysis of each nozzle group's performance and displacement characteristics
Solution Approach 2:
The patent transforms the calibration target from simple geometric shapes to spread spectrum patterns with specific statistical properties, changing the parameter space from visual geometry to frequency domain characteristics that are invariant to dot variations
2Reliability
If sparse dot arrays are used for measurement, then the chart is simple to print, but the reliability of dot position localization is poor due to large variations in dot shape, position and size
Solution Approach 1:
The patent transitions from spatial domain dot positioning to frequency domain analysis by applying spread spectrum patterns, enabling reliable position determination through spectral correlation rather than direct dot detection
Solution Approach 2:
The patent replaces direct geometric measurement of individual dots with a statistical signal processing approach using spread spectrum sequences, substituting mechanical/optical dot positioning with mathematical correlation methods
3Measurement precision
If overlapping dot patterns are used for calibration, then the measurement can be performed with simple optical sensors, but the measurement precision is affected by sensitivity to displacement variations in optical density
Solution Approach 1:
The patent changes the measurement parameter from optical density to spatial correlation of spread spectrum patterns, making the measurement invariant to optical density variations while maintaining simplicity of optical sensing
Data Source
AI summary
A method (300) is described of determining characteristic of an ink jet printer (15). A chart containing multiple regions or patches is printed (320) on a print medium (115) using the ink jet print (15). The chart includes at least a first region printed using a first set of nozzles, and at least a second region printed using a second set of nozzles. The first and second sets of nozzles are a predetermined distance apart in the printer head of the printer (15). The printing of the first and second regions is also separated by a print medium advance operation equal to the predetermined distance. This causes the first and second regions to be aligned in the direction of the print medium advance operation. The chart is then imaged using scanner (16) chart to form a chart image. The positions of the regions appearing in the chart image are next determined (340). The spatial alignment characteristic of the printer is calculated from the distance, in the medium advance direction, between said first and second regions.