Abstract: In color printing with a color registration system for the registration of plural color images on an image bearing surface, such as a photoreceptor belt of a color printer, registration marks are imaged on the image bearing surface, which registration marks correspond to the color images and are sensed by a registration marks sensor. In an initial gross registration mode the system first automatically images first registration marks, in the form of expanded chevron targets, which are greatly expanded in the process direction so as to avoid overlapping marks even if there is initial gross misregistration, to thus provide wider initial misregistration latitude for the sensor. When an acceptable initial registration is achieved, the system automatically switches to imaging more closely spaced and more frequent second registration marks, preferably regular chevron targets, providing higher registration accuracy.

Abstract: There is provided a method for use with a printing machine having a movable imaging member and a projecting system for modulating a beam and projecting an image into the movable imaging member. The printing machine further includes a developer for application of developer material to the image projected onto the movable imaging member for transfer of the image to a print media sheet.

Abstract: A sheet detector having an emitter (lamp), detector (phototransistor), operational amplifier and an RC network. As contamination is deposited on the emitter or detector, a feedback loop provides more drive to the lamp providing sufficient drive to hold the emitter of the phototransistor at its desired stage. As a first copy paper is passed between the emitter and detector, the RC network of a common mode operational amplifier detects a change and generates an output. As a subsequent sheet enters the system, the transmissibility abruptly changes again causing the common mode operational amplifier to provide a subsequent pulse indicating the presence of a multiple feed.