Patent ID: 7997680

Claim:
A method for forming a printed pattern from a pattern layout using a printing system, the printing system comprising a print head including a plurality of ejectors and a camera rigidly connected to the print head, the camera having an imaging sensor including an alignment target, the method comprising: performing a first alignment operation to achieve a specified orientation between the print head and a first set of alignment marks on a substrate using first image data generated by the imaging sensor of the camera; performing a first print operation after the first alignment operation to print a first portion of the pattern layout on the substrate to generate a first portion of the printed pattern, wherein performing the first print operation includes making a plurality of printing passes across the substrate in a first print direction; performing a second alignment operation to orient the print head relative to a second set of alignment marks on the substrate using second image data generated by the imaging sensor of the camera; and performing a second print operation to print a second portion of the pattern layout on the substrate to generate a second portion of the printed pattern, wherein performing the second print operation includes making a plurality of printing passes across the substrate in a second print direction that is non-parallel to the first print direction, wherein the imaging sensor of the camera comprises an alignment target, and wherein performing the first alignment operation comprises: determining a relative position between the alignment target and each of the plurality of ejectors; positioning the print head over the substrate; printing a spot onto the substrate from each of the plurality of ejectors, each of the spots printed by the plurality of ejectors having an actual location with reference to a horizontal axis and a vertical axis parallel to the substrate; determining a vertical offset between an expected location of each spot along the vertical axis and the actual location of the spot along the vertical axis; calculating a linear fit line for the vertical offset of each spot plotted against an expected location of the spot along the horizontal axis; calculating the slope of the linear fit line; and rotating the print head relative to the substrate according to an angle defined by the slope of the linear fit line.