Method and apparatus for generating optical scans

摘要

A system is disclosed for transforming a collimated beam of light, such as that generated by a laser, into a beam of light which repetitively scans a fixed path by utilizing a mirror which is repetitively rotated through a predetermined angular displacement. The angle between the mirror axis of rotation and the mirror position relative to the axis varies between subsequent mirror rotations and defines a scanning beam rotational axis error which is eliminated by the present invention. An input beam of collimated light is directed onto the rotating mirror along a first path to produce a first scanned reflected output beam for each rotation of the mirror. A second scanned reflected output beam is generated by redirecting the first scanned reflected output beam through a prism and back onto the mirror along a second path. The second path is vertically displaced from the first path by a distance related to the mirror rotational axis error. Each point at which the second scanned output beam intercepts the mirror is laterally offset from a corresponding point at which the input beam intercepts the mirror by a distance related to the relative angle between the mirror and the input light beam. The second scanned reflected output beam is reflected from the mirror to generate a third scanned reflected output beam for each deflection of the mirror. The repetitive deflections of the mirror produce a plurality of third scanned reflected output beams which define a grouping of non-coincident surfaces which are also nonintersecting with respect to the input beam. The third scanned reflected output beams are converged onto the fixed path such that the optical output beam repetitively scans the fixed path without any perceptible deviations caused by the mirror rotational axis error.