Patent ID: 7471420

Claim:
A method of correcting a uniformity profile in an electrostatographic printing apparatus, comprising: measuring a sample image and generating multiple tone reproduction curves along a dimension of actuation, each tone reproduction curve having a plurality of patch values, each patch value having a corresponding tone reproduction curve level; subtracting a reference patch density for each tone reproduction curve level from all tone reproduction curve patch values at the corresponding tone reproduction curve level to obtain a difference profile for each tone reproduction curve level; converting the difference profiles to a raster output scanner intensity profile; converting the difference profiles to a laser intensity profile; printing on the printing apparatus, according to a resulting correction; and repeating the steps of measuring, subtracting, converting to a raster output scanner intensity profile, converting to a laser intensity profile, and printing on the printing apparatus wherein the difference profiles are presented as a linear equation ΔD NN %,i =S LP@NN %,i *ΔLP i +S LED@NN %,i *ΔLED i where index NN % represents the tone reproduction curve level measured, index i is an index of the sample image measured along the dimension of actuation, ΔLP i is a change in the raster output scanner intensity at index i relative to an intensity at a reference tone reproduction curve, ΔLED i is a change in the laser intensity at index i relative to the intensity at the reference tone reproduction curve, S LP@NN %,i is a change in a measured density per unit change in ΔLP i for index i of tone reproduction curve level NN %, and S LED@NN %,i is a change in a measured density per unit change in ΔLED i for index i of tone reproduction curve level NN %, and the steps of converting the difference profiles are performed by simultaneously solving the following equations for ΔLED i and ΔLP i for each patch i from 1 to last ΔD 1,i =S LP@1,i *ΔLP i +S LED@1,i *ΔLED i ΔD 2,i =S LP@2,i *ΔLP i +S LED@2,i *ΔLED i ΔD last,i =S LP@last,i *ΔLP i +S LED@last,i *ΔLED i.