Inkjet Printer Linefeed Calibration via Head Sensor
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Solution Overview
Problem
Existing printer calibration methods are unreliable due to variations in dot shape, size, and position, and require complex computations or costly equipment, failing to correct linefeed errors in real-time.
Innovation Solution
The Relative Shift Measurement (RSM) method uses a print head sensor to measure the relative shift between a reference image and the actual printed image during printing, compensating for thermal and other effects, to determine the error between nominal and actual linefeed distances and calibrate the print head position in real-time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If individual dot positions are measured for calibration, then the experimental set-up is simple and result analysis is straightforward, but the measurement is unreliable due to large variations in dot shape, position and size
Solution Approach 1:
The patent segments the printed image into multiple swaths and uses a head sensor to capture and compare each swath independently to a reference image. This segmentation allows real-time measurement of linefeed errors without relying on individual dot positions, thereby improving measurement reliability while maintaining simple experimental setup.
Solution Approach 2:
The patent replaces mechanical/optical scanning systems with a head sensor integrated into the print head. This substitution enables real-time capture of printed swaths during the printing process itself, eliminating the need for separate scanning equipment and improving measurement reliability through direct comparison of printed output.
2Reliability
If Fourier analysis is used to measure print head position through specially designed test charts, then the method is robust to noise, but complex computation is required and real-time measurement is not achieved
Solution Approach 1:
The patent uses the print head's own sensor to measure the quality of its printed output in real-time. The head sensor captures swaths during printing and compares them to reference images, enabling self-diagnosis and calibration without external scanning equipment or complex Fourier analysis, thus reducing computation complexity while maintaining noise robustness.
Solution Approach 2:
The patent performs measurement continuously during the printing process rather than in separate pre- or post-processing steps. The head sensor captures swaths in real-time as they are printed, allowing continuous monitoring and calibration without interrupting the printing workflow, thereby reducing computation complexity and enabling real-time operation.
3Measurement precision
If optical sensor is used to position print head in service station, then accurate positioning is achieved, but separate measurement of sensor relative position is required beforehand
Solution Approach 1:
The patent performs preliminary calibration by printing a reference swath and capturing it with the head sensor before actual printing begins. This preliminary action establishes the reference image for comparison, enabling real-time measurement during subsequent printing without requiring separate sensor positioning measurements, thus reducing calibration time while maintaining positioning accuracy.
4Manufacturing precision
If optical sensor measures and corrects print density error, then density correction is achieved, but the printing area must be covered by sensor field of view and considerable computational power is required
Solution Approach 1:
The patent makes the head sensor multi-functional by using it for both linefeed error measurement and print quality monitoring. The same sensor that captures swaths for linefeed calibration also detects density variations and other print defects, eliminating the need for separate measurement systems and reducing computational power requirements through unified processing.
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 provides accurate and efficient real-time calibration of the print head position, improving the quality of printed images by compensating for variations and errors, without the need for separate scanning or costly equipment.
Implementation Method 1
a print head sensor to measure, in real-time during printing, the relative shift (displacement) between a reference image to be printed and the image actually printed
Data Source
AI summary
Regarding an image forming apparatus for printing an input image and including a print head having a head sensor configured to sense information from the input image printed on a print medium, there is a method of determining a head sensor position parameter in the image forming apparatus. The method includes printing a first swath of the input image on the print medium and determining the head sensor position parameter by performing a sub-method. The sub-method includes capturing, via the head sensor, a target image from the printed first swath, comparing the target image to a reference image for the first swath based upon the input image, and determining the head sensor position parameter based on a relative shift between the target image and the reference image.