Patent ID: 8146498

Claim:
A method for determining a position of a mechanical edge of a reference edge of a sheet of recording media relative to a first edge of a drum slot in a cylindrical surface of an imaging drum, the method comprising: a) mounting the sheet of recording media on the imaging drum in an orientation wherein the reference edge extends along the cylindrical surface of the imaging drum in a substantially axial direction and wherein the reference edge extends over the first edge of the drum slot; b) illuminating a reflective layer in the slot using at least three illumination sources and casting a shadow of a second edge of the drum slot on the reflective layer, at least part of the perimeter of the shadow being non-parallel with the first edge of the drum slot wherein position of the shadow can be changed by using a different illumination source from the at least three illumination sources or a combination thereof; c) capturing at least one digital camera image of the reference edge and at least one acute reflective apex in the slot; and d) determining from the at least one digital camera image a location of at least one point on the mechanical edge.