Laser printer with apparatus to reduce banding created by uneven separation of succeeding scan lines

摘要

A print apparatus includes a photoconductor (10) and a mechanical system (12, 14) for moving the photoconductor (10) past a scan line exposure station. The print apparatus includes a sensor device (20) for providing outputs indicative of the movement of the photoconductor (10). A first comparator (70) produces a first position error signal that is derived from a difference between a reference signal (74) and a position error signal output, such position error signal indicating that the position of the photoconductor (10) differs from a predetermined print position that is determinable with respect to the reference signal (74). The print apparatus further includes a laser beam scanner (24, 30) and a beam detector (18, 102) for producing a scan position signal. A second comparator (72) is responsive to the scan position signal and the position error signal from the first comparator (70) to produce a beam deflection control signal that is applied to a beam deflector (28). The beam deflector (28) moves the laser beam (26) in a direction which reduces the beam deflection control signal and positions the laser scan at a position closer to a predetermined print position.