Inkjet Printhead Image Registration via Sensor Feedback
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Solution Overview
Problem
Inkjet printers are slower than laser printers due to the need for numerous carriage passes across the page, and achieving accurate image registration on media is challenging, especially when using multiple printhead modules that require precise positioning to avoid print defects at the edges of printed portions.
Innovation Solution
A method of calibrating image registration by determining relative distances between sensors and printheads along the X and Y axes, using optical sensors and a printer controller to adjust the imaging process, ensuring accurate media positioning and printhead firing positions based on measured distances and encoder positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple printhead modules are used to increase print swath width, then print speed is improved, but image registration accuracy deteriorates due to positioning difficulties at the edges of printed portions
Solution Approach 1:
The patent employs sensors to detect the actual position of media sheets and provides feedback signals to the controller. The controller uses this feedback to dynamically adjust the positioning of multiple printhead modules, ensuring accurate image registration across the entire page width while maintaining high print speed.
Solution Approach 2:
The patent replaces purely mechanical positioning systems with a hybrid system that incorporates optical sensors and electronic control. Instead of relying solely on mechanical precision of printhead mounting, the system uses sensor detection and electronic adjustment to achieve accurate registration, substituting mechanical complexity with sensor-based feedback control.
2Manufacturing precision
If numerous carriage passes are used to cover the entire page, then image registration can be achieved, but print speed deteriorates
Solution Approach 1:
The patent divides the printing system into multiple independent printhead modules, each capable of printing a portion of the page simultaneously. This segmentation allows the system to cover the entire page width in a single carriage pass or fewer passes, dramatically improving print speed while maintaining registration accuracy through individual sensor control for each module.
Solution Approach 2:
The patent transitions from a single-dimension (single carriage pass) printing approach to a multi-dimensional approach by arranging multiple printhead modules across the page width. This spatial dimensionality change allows simultaneous printing across the entire page, eliminating the need for numerous sequential carriage passes.
3Length of moving object
If printheads are positioned to cover wider page width, then print swath increases, but positioning precision deteriorates at the edges
Solution Approach 1:
The patent introduces sensors as intermediary devices between the printheads and the media. These sensors detect media position and provide reference signals that enable the controller to calculate and adjust the precise positioning of each printhead module, maintaining edge-to-edge registration accuracy across wide page widths.
Solution Approach 2:
The patent dynamically adjusts positioning parameters for each printhead module based on sensor feedback. Instead of using fixed mechanical positions, the system changes positioning parameters (offsets, corrections) in real-time to compensate for variations in media loading and printhead placement, maintaining precision across the entire print swath.
Data Source
AI summary
A method of registering an image onto a sheet of media on an imaging surface of a printer having a printhead for imaging onto the sheet, comprising: detecting a position of said sheet of media being advanced onto the imaging surface using a first sensor positioned along said media path upstream of the printhead; and firing the printhead at a time based on the detected position and a calibrated distance between the sensor and the printhead.