Abstract: This optical system permits larger tolerances in mirror facet pitch angles for rotating mirror line scanning apparatus without the use of expensive lenses having toroidal and like complex surfaces or lenses employing elements that have one cylindrical surface whose center of curvature lies on or very near the axis of the scanned surface. A lens system having a negative cylindrical element with its axis perpendicular to the plane of deflection is employed in a rotating mirror scanning arrangement. The lens system images the rotating mirror surface on the scan line in an azimuth perpendicular to the plane of deflection of the beam while ringing the collimated rays of the light source in the plane of deflection of the beam to focus in the one scan line.