Patent ID: 7988252

Claim:
A method of estimating the alignment in a printing medium direction between a first pen and a second pen of a printing system, comprising: printing a first pattern using a first pen; printing a second pattern using a second pen; wherein the first pattern and the second pattern are substantially aligned along a scan axis; wherein the first pattern comprises a plurality of first marks printed by one or more nozzles associated with a first primitive group of the first pen, wherein the first pattern also comprises a plurality of second marks printed by one or more nozzles associated with a second primitive group of the first pen; wherein the second pattern comprises a plurality of third marks printed by one or more nozzles associated with a third primitive group of the second pen, wherein the second pattern also comprises a plurality of fourth marks printed by one or more nozzles associated with a fourth primitive group of the second pen; wherein the plurality of first marks and the plurality of second marks are staggered in relation to one another, and wherein the plurality of third marks and the plurality of fourth marks are staggered in relation to one another; scanning along the scan axis over the first pattern and the second pattern; outputting an optical sensor output, wherein the optical sensor output comprises a series of peaks, wherein each peak is associated with a mark and a height of each peak is dependent on the area of a mark detected by an optical sensor; and computing at least one ratio between the height of one of the series of peaks and at least another height of a different one of the series of peaks, and determining an amount of misalignment based on the at least one ratio.