Method of uniformity correction in an electrostatographic printer by using a second actuator
View Patent ↗Various exemplary embodiments include an electrostatographic printing apparatus and a method of correcting one or more associated uniformity profiles. In various exemplary embodiments the apparatus includes first and second actuators. In various exemplary embodiments the method includes measuring an image and generating at least one corresponding TRC, generating a charge profile, subtracting a reference patch density from a patch value to obtain a difference profile, converting the difference profile to a ROS intensity profile and an LED intensity profile, and iteratively repeating the steps of measuring, generating, subtracting and converting until within an acceptable range.
1. 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.
2. The method according to claim 1 , wherein the steps of measuring, subtracting, converting to a raster output scanner intensity profile, and converting to a laser intensity profile, are performed for only a subset of all tone reproduction curve levels.
3. The method according to claim 1 , wherein S LP@NN %,i is constant for all values of index i.
4. The method according to claim 1 , wherein S LED@NN %,i is constant for all values of index i.
5. The method according to claim 1 , wherein the steps of measuring, subtracting, converting to a raster output scanner intensity profile and converting to a laser intensity profile are repeated until the uniformity correction reaches a desired threshold.
6. The method according to claim 1 , wherein S LP@NN %,i is constant for all values of index i and for all values of index NN %.
7. The method according to claim 1 , wherein S LED@NN %,i is constant for all values of index i and for all values of index NN %.
8. The method according to claim 1 , further comprising modulating the laser intensity profile to produce a charge profile.
9. The method according to claim 8 , wherein the charge profile operates in conjunction with the raster output scanner intensity profile.
10. The method according to claim 1 , wherein a reference tone reproduction curve corresponds to a predetermined color target.
11. The method according to claim 1 , wherein the steps of measuring, subtracting, converting to a raster output scanner intensity profile and converting to a laser intensity profile are performed continuously as part of a closed process control loop.