HIGH SECURITY COPYING PROCESS WITH PLYWOODING PHOTORECEPTOR
Original Publication Date: 1996-Apr-30
Included in the Prior Art Database: 2004-Apr-07
Xerox Disclosure Journal
A defect of laser printers using coherent light, known as plywooding, is the appearance of interference artifacts in the photoreceptor for grey images. These patterns are specific to a particular photoreceptor and can be used to "fingerprint" or identify the photoreceptor that made a particular copy. By deliberately adjusting a copier to produce this plywood effect in a light grey background region, copiers in secure installations can produce uniquely identifiable copies, and allow auditing of copy generation or verification that copies were made on a particular "authorized" machine.