Compensation for process direction photoreceptor motion in a Raster Output Scan system is provided by moving the cylinder lens located between the laser source and a rotating spot scanning mechanism, e.g., a polygon. The cylinder lens is moved in the process direction in response to error signals generated by a SOS detector and timing marks on the photoreceptor drum surface, or an encoder on the drum shaft. The lens movement is obtained by sending motion error signals to a piezoelectric actuator which increases in length to impart the desired motion to the cylinder lens.