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US 2003/0117484 A1Published application
Adaptive light emitting diode bar equalization
AssigneeXerox Corporation
InventorShahriar Vazan
Life of this patent
Estimating the term…
Abstract
Uniformity of light output from an LED printbar is achieved by current sensing or image sensing of auxiliary LEDs on the LED printbar. A photodetector measures the light output from the auxiliary LEDs and a comparator will compare the auxiliary LED data to determine if the entire LED printbar has to be compensated to make the light output more uniform.
Claims6
A method for correcting exposure non-uniformities in a printbar having a plurality of individual LEDs, said method comprising:
- calibrating said printbar by determining a first set of correction values for each corresponding one of the individual LEDs, storing said first set of correction values and a plurality of sets of correction values in a correction memory, each said correction value being a digital value for causing output of light of a substantially predetermined light intensity from the corresponding one of said individual LEDs;
- measuring the light intensity from a predetermined set of individual LEDs of said printbar,
- comparing said measured light intensity with a uniform light intensity, determining a difference between said measured light intensity and said uniform light intensity, and
- loading one of said plurality of sets of correction values into said printbar, when the determined difference between said measured light intensity and said uniform light intensity exceeds a predetermined maximum difference.
1 more element
An LED printbar comprising:
- a plurality of individual LEDs;
- said plurality of individual LEDs having a first plurality of LEDs to image a photoreceptor and a second plurality of LEDs to image a photodetector, said first plurality of LEDs being larger in number than said second plurality of LEDs;
- a current driver having a control input, said current driver for applying a drive current to said plurality of individual LEDs, wherein first drive current is controlled by said control input;
- a correction memory for storing a plurality of sets of correction values, said correction memory for applying one of said sets of correction value to said control input;
- sensing means for comparing the light output from said second plurality of LEDs at said photodetector to a predetermined light output for loading the appropriate one of said plurality of sets of correction values from said correction memory to said control input.
2 more elements
Dependencies are inferred from the claim text.