Patent ID: 7375740

Claim:
A method of adjusting print uniformity for a xerographic device having an LED printbar, the method comprising: (a) printing lines test pattern on a first target media in a process direction of the xerographic device, each test pattern line being associated with an individual LED of the LED printbar; (b) printing halftone strips test pattern on a second target media in the process direction of the xerographic device, each halftone test strip including an arrangement of dots, each dot being associated with designated LEDs of the LED printbar and each halftone strip being associated with a halftone gray level i; (c) scanning the first and second target media with the test patterns; (d) measuring an LED line metric of each test pattern line and reflectance uniformity of each test halftone strip; (e) concurrently calculating a lines uniformity difference profile, and a set of halftone strips uniformity difference profiles, including: calculating first differences between each LED line metric and a first target value, and calculating second differences between each halftone strip uniformity profile and a second target value; and (f) adjusting current value supplied to each LED associated with the test patterns to make corresponding partial corrections to the first and second differences respectively, to simultaneously optimize the print uniformity as a composite of the lines test pattern and the halftone strips test pattern wherein the partial corrections are proportional to sensitivities of the line uniformity profile difference metric and the halftone uniformity profile difference metric to the adjusting of the LED current value.