Abstract: Bow can be minimized by an auxiliary grating in a post deflection path of the diffracted beam from the hologon which is disposed in non-parallel relationship to the plane of rotation of the hologon. The ellipticity of the spot which generates the scan line and intensity variation in the scan beam can be minimized by using a dispersive element, preferably a prism, between the hologon and the bow compensation grating with its dispersion in a direction opposite to the direction of the dispersion of the hologon and of the auxiliary grating. Another grating before the hologon can be used to correct for wavelength shift induced cross-scan error associated with the dispersion in the hologon and a bow compensation grating following the hologon.

Abstract: Centered monofacet deflector systems having a dipole laser beam scanning pattern (dual scanning beams which propagate in opposite directions) enables both the scan rate and the scan duty cycle of the scanning system to be doubled over deflectors which produce only one beam. The deflector may be a non-disc plane diffraction grating (NPDG) deflector or a dual reflecting cube (DRC) deflector having polarization sensitive beam splitting characteristics. The input beam polarization contains or is generated to contain orthogonally polarized components which are reflected or diffracted to produce one of the dual scanning beams and a transmitted beam through the element and retroreflected with the proper polarization to be deflected at the element to produce the other scanning beam thereby providing the capability of two simultaneous or sequential scan lines for every revolution of the deflector element.

Abstract: A dual reflection unpolarizing monofacet (DRUM) scanner or beam deflector is made up of two essentially identical 45.degree. right angle prism elements with their hypotenuse faces together to form a body which may be rectangular or cylindrical and may be contained in a housing which provides for aerodynamic stability when the scanner rotates at high speed. The hypotenuse faces have a partially reflective surface on which an incident beam, collinear with the rotational axis, is incident. This beam is transmitted and reflected to provide dual beams, one of which is absorbed by light absorbing material, preferably a coating, on a surface of the body and the transmitted beam is retroreflected by a mirror on another surface of the body, back to the partially reflective surface. An output beam is provided by the retroreflected beam.

Abstract: Laser beam scanners having a polarization sensitive beam deflecting surface (specifically a monofacet nondisc plane diffraction grating (NPDG) monofacet deflector and a dual reflection monofacet polarization sensitive deflector that incorporates a polarizing beam splitter cube) achieve essentially 100% radiometric throughput efficiency while also achieving a scan beam intensity that stays constant over the total range of scan angles by using a circularly polarized incident beam and a quarter-wave retardation plate at the entrance aperture of the scanner assembly so that the quarter-wave plate rotates with the assembly. The quarter-wave plate has its optical axis oriented with respect to the incident beam so that it converts the incident circularly polarized beam into a linearly polarized beam having a polarization direction that maximizes the radiometric throughput efficiency of the scanner assembly.

Abstract: An adjustable, resettable fixed mount for a hologon laser scanner disc or spinner provides perpendicular angular orientation of the hologon disc relative to the motor rotation axis within about 5 to 10 arc seconds and corresponding wobble angles as compared to 20 to 40 arc seconds for hologon discs mounts in dynamic mounts or rigidly with fixed, hard mounts which have heretofore been proposed and used. The improved mount is a fixed hard mount which is nevertheless adjustable. It may be implemented by a connecting assembly having a hub with a spherical bearing which allows perpendicular angular orientation of the hologon about a plane perpendicular to the motor drive shaft on which the spherical bearing is mounted. A retainer cap has a plurality of angularly spaced adjusting screw members which change the perpendicular angular orientation of the disc relative to the motor rotation axis. Alignment is performed while the hologon is not rotating.

Abstract: A dual, simultaneous beam scanning system for simultaneously scanning two individually modulated adjacent scan lines on an internal drum imaging surface uses a deflector which varies the angular orientation between combined orthogonally polarized beams so that one of the beams rotates about the other in synchronism with the angular position (the distance between start of scan) along the scan lines around the drum imaging surface. Signals from both a beam position sensing photodetector array and from a shaft encoder on the deflector unit, such as a Hologon deflector, controls the deflection of one of the orthogonally polarized beams so as to maintain the spacing and prevent crossovers of the adjacent scan lines and also reduce differential bow. Differential bow may be corrected both in the internal drum configuration and in a flat field imaging system using plural beam scanning. The scan lines can overlap so as to provide high resolution imaging at a rate of the order of hundreds of scan lines per second.

Abstract: A dual, simultaneous beam scanning system for simultaneously scanning two individually modulated adjacent scan lines on an internal drum imaging surface uses a deflector which varies the angular orientation between combined orthogonally polarized beams so that one of the beams rotates about the other in synchronism with the angular position (the distance between start of scan) along the scan lines around the drum imaging surface. Signals from both a beam position sensing photodetector array and from a shaft encoder on the deflector unit, such as a Hologono deflector, controls the deflector of one of the orthogonally polarized beams so as to maintain the spacing and prevent crossovers of the adjacent scan lines and also reduce differential bow. Differential bow may be corrected both in the internal drum configuration and in a flat field imaging system using plural beam scanning. The scan lines can overlap so as to provide high resolution imaging at a rate of the order of hundreds of scan lines per second.

Abstract: A hologon scanning system which provides two sequential scans across an image plane per revolution of the hologon. The hologon is a disc having a single facet with a planar linear diffraction grating in a surface which is perpendicular to the axis of rotation of the disc and which is centered on the axis of rotation. An incident laser beam which preferably overfills the facet is diffracted and scanned by the rotation of the facet. The facet is preferably elliptical in shape with its major axis perpendicular to the facet grating lines. The diameter of the disc can be made only slightly larger than the profile of the incident beam on the disc so as to minimize inertia and enable the disc to be rotated at very high speeds without failure due to centrifugal force induced stress. Four sequential scans per revolution can be produced by using a pair of superimposed centered facets with their grating lines oriented orthogonally to each other.

Abstract: Bow can be minimized by an auxiliary grating in the post deflection path of a diffracted beam from the hologon which is disposed in non-parallel relationship to the plane of rotation of the hologon. The ellipticity of the spot which generates the scan line and intensity variation in the scan beam can be minimized by using a dispersive element, preferably a prism, between the hologon and the bow compensation grating with its dispersion in a direction opposite to the direction of the dispersion of the hologon and of the auxiliary grating.Another grating before the hologon can be used to correct for wavelength shift induced cross-scan error associated with the dispersion in the hologon and a bow compensation grating following the hologon.

Abstract: A hologon scanning system which generates an essentially bow-free scan line or lines across a surface using a planar, and preferably a holographic, grating disposed in a holding assembly which is rotated about an axis. The surface of the grating is at a constant angle of incidence with respect to a collimated beam of laser light propagating along the axis of rotation. The grating period for the wavelength of the laser beam and for the coordinate system associated with the rotating grating provides a diffraction angle from the grating which is constant with rotation angle; the diffracted beam being perpendicular to the rotation axis. An essentially bow-free, straight scan line is obtained across the receptor surface which may be a flat image plane or a cylindrical image plane having its axis along the axis of rotation of the grating.

Abstract: A hologon scanner system in which a pair of laser beams which are collinear with each other are deflected by a common hologon scanner. The beams are initially linearly polarized in orthogonal directions and are combined in a polarization sensitive beam combiner so that they are collinear. The combined beams are passed through a quarter wavelength plate (the laser beams both being of the same wavelength) so as to circularly polarize them in opposite hands. The combined circularly polarized beams may be modulated to change their intensity. Such modulation may be provided by an acousto-optic diffraction grating modulator. The modulated beams are then directed to the hologon deflector and are scanned across the image surface. The modulator is also part of a closed loop feedback system with a detector which responds to positional variations of the image surface due to its transport system and deflects the beam to compensate for such position variations.

Abstract: A hologon scanner system in which a pair of laser beams which are collinear with each other are deflected by a common hologon scanner. The beams are initially linearly polarized in orthogonal directions and are combined in a polarization sensitive beam combiner so that they are collinear. The combined beams are passed through a quarter-wave plate (the laser beams both being of the same wavelength) so as to circularly polarize them in opposite hands. The combined circularly polarized beams may be modulated to change their intensity. Such modulation may be provided by an acousto-optic diffraction grating modulator. The modulated beams are then directed to the hologon deflector and are scanned across the image surface. The modulator is also part of a closed loop feedback system with a detector which responds to positional variations of the image surface due to its transport system and deflects the beam to compensate for such position variations.

Abstract: An integrated laser scanning system for scanning a modulated beam across an image surface, which may be a receptor on which the image is scanned, is provided by a rigid housing having a central plate and walls which define a plurality of cells on opposite sides of the central plate, some of which may extend through the central plate. A deflector, preferably having a rotatable hologon, a laser and optical components, including an assembly of components for processing and modulating the laser beam, are mounted in different ones of the cells and define a beam path which is folded and extends in one direction over the central plate and in an opposite direction out of the housing toward the image surface.

Abstract: A unitary assembly of a hologon scanner disc or spinner, a motor for rotating the disc and a lens for focusing the deflected laser beam on an image surface. A housing including a base plate and a cover removably mounted on the base plate, encloses the hologon disc. The base plate has a surface with respect to which the position of the hologon disc and lens is referenced. The cover has a platform on which lenses are interchangably mounted, such that, each lens has the correct position and orientation with respect to the entrance pupil of the scanner system. The hologon disc is also removably mounted on the shaft of the motor and referenced against a shoulder of the shaft which is precisely spaced with respect to the reference surface of the base plate of the housing. The hologon deflector facets of different discs which are mounted on the shaft always have the same alignment with respect to the lens and the laser beam which is incident thereon.

Abstract: A hologon scanner system in which a laser beam is scanned across a receptor surface with an essentially bow-free scan. A focusing lens comprised of symmetrical, nonanamorphic optical elements is positioned in the scanned beam between the hologon deflector and the image plane. The focusing lens is provided with barrel or pincushion distortion and is tilted with respect to the scanned beam and bends the beam to correct for the bow introduced by the hologon deflector.