Method of controlling print registration in an electrophotographic machine

摘要

A method of aligning print images of an electrophotographic machine on a print medium includes providing a plurality of rotating photoconductive drums in the electrophotographic machine. Each of a plurality of laser beams is reflected off of a respective one of a plurality of reflectors. Each reflector rotates relative to the respective laser beam to thereby scan the laser beam across a respective one of the photoconductive drums to produce a scan line in a scan direction. The relative rotation between the laser beams and the respective reflectors is cyclically repeated to thereby produce a plurality of substantially parallel scan lines on each photoconductive drum. Each scan line is displaced from an adjacent scan line by a scan line separation distance in a process direction perpendicular to the scan direction. Toner is applied to each scan line on the photoconductive drums. A moving toner transfer medium contacts each photoconductive drum at a respective toner transfer nip. A first toner transfer nip is associated with a first reflector. A second toner transfer nip is associated with a second reflector. A length of the toner transfer medium between at least the first toner transfer nip and the second toner transfer nip is a non-integer multiple of the scan line separation distance. The length of the toner transfer medium has an integer portion and a fractional portion when expressed in units of the scan line separation distance. A speed of the rotation of the second reflector is temporarily increased or decreased dependent upon the fractional portion of the length. The toner is transferred from the photoconductive drums to the toner transfer medium. The toner is transferred from the toner transfer medium to the print medium. The machine controller provides raster image data to the respective laser printheads after accounting for the relative phase relationships between the respective reflectors. Raster scan data is synchronized in both scan and process directions to produce scans on the transfer medium that overlay those deposited at an earlier photoconductive drum.