Ejector activation scheduling system for an ink-jet printhead
AssigneeXerox Corporation
InventorsJuan J. Becerra, Christopher R. Morton, Thomas A. Tellier, David A. Mantell, Eduardo M. Freire
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Abstract
An ink-jet printhead accepts a series of digital addresses as image data. Each digital address causes an individual ejector in the printhead having the particular address to be activated. The frequency of operation of the printhead can be directly related to the frequency at which addresses are submitted to the printhead. A scheduler polls image data for spot placements which require simultaneous activation of a plurality of ejectors in a set of interdependent ejectors, and then reschedules the activation of ejectors to avoid conflicts.
Claims18
An ink-jet printing apparatus;
- comprising:
- a printhead, defining therein a plurality of ejectors;
- each ejector including an energy-imparting portion being selectably actuable by application of a signal thereto;
- a decoder, operatively connected to an energy-imparting portion of each of the plurality of ejectors, the decoder accepting as inputs a list of digital addresses of individual ejectors to be activated, the decoder activating the energy-imparting portion of an ejector in response to receiving a digital address of the ejector;
- means for selectably activating each of a set of ejectors within a cycle of predetermined duration, the cycle being divided into N time slots for a set of N ejectors in the printhead;
- means for moving the printhead in a process direction at a process velocity relative to a sheet on which an image is formed in accordance with image data;
- and
- a scheduler for selecting a time slot within the cycle for activating each selected ones of said ejectors in the set to create a mark on the sheet with each of a series of cycles as the printhead is moving, whereby each selected ones of said ejectors in the set is activated at a unique time slot to approximate a desired image configuration of marks.
The apparatus of claim 6, the scheduler further including
- means for detecting in the image data cycles having combinations of pixel areas to be marked which require a plurality of ejectors to be activated within a single time slot;
- and
- means for iterating through each time slot for the image data in the detected cycle in a forward order, and for conflict time slots having a plurality of ejectors to be activated with no ejector to be activated in a subsequent time slot, rescheduling one of the ejectors in the conflict time slot to the subsequent time slot in the cycle.
A method of operating a printhead including a linear array of ejectors, comprising the steps of:
- providing, for a set of N ejectors in the printhead, means for selectably activating each of the ejectors in the set within a cycle of predetermined duration, the cycle being divided into N time slots;
- moving the printhead in a process direction at a process velocity relative to a sheet;
- and
- with each cycle as the printhead is moving, selecting a time slot within the cycle for activating each selected ejector in the set to create a mark on the sheet, whereby each selected ejector in the set is activated at a unique time slot to approximate a desired image configuration of marks, where the desired configuration of marks would have required a plurality of ejectors to be activated within a single time slot.
Dependencies are inferred from the claim text.