A method of detecting an alignment error includes the steps of controlling a first portion of one or more imaging units to image on a substrate a first plurality of substantially parallel lines extending along a first direction and a second plurality of substantially parallel lines extending along a second direction and controlling a second portion of one or more imaging units to image a third plurality of substantially parallel lines extending along the first direction and a fourth plurality of substantially parallel lines extending along the second direction. One or more distances between adjacent lines of the second plurality of lines are varied and one or more distances between adjacent lines of the fourth plurality of lines are varied. Further, the lines imaged by the first and second portions form an alignment pattern. The method further includes the steps of collecting data relating to the alignment pattern and analyzing the collected data to determine an alignment error between the first and second portions of the one or more imaging units.