Holotek, LLC

Xerox Corporation

Other

Ecrm Incorporated

Halotek Ltd.

Charles J Kramer

Mehdi N Araghi

Joachim A Ritter

Christopher R Snelling

Martin Edward Banton

David B Kay

Tibor S Fisli

Ned J Seachman

Kwok-Leung Yip

Joseph J Daniele

Alan F McCarroll

Geoffrey B Gretton

Joahim A Ritter

An optical wavelength selection device containing an optical beam source, a device for collimating the optical beam to produce a collimated optical beam, a diffraction grating assembly for diffracting the collimated optical beam to produce a collimated optical diffracted beam, a device for modifying the polarization state of the collimated optical beam, and a lens assembly for focusing the collimated optical diffracted beam. The device for modifying the polarization state of the collimated optical beam is located within the diffraction grating assembly in one embodiment and before the diffraction grating assembly in another embodiment.

Diffraction grating-based wavelength selection unit having improved polarization dependent performance

A process for preparing a printing plate. In this process a photopolymer printing plate is exposed to a source of actinic radiation, and this exposure causes the photopolymer to change at least one of its physical properties. Thereafter, a portion of the photopolymer is removed. The developed printing plate is then irradiated with deep ultraviolet radiation with a wavelength of from about 170 to about 290 nanometers.

Process for preparing a printing plate

An optical wavelength selection apparatus containing a surface-relief transmission diffraction grating, a collimating lens for collimating a beam incident to the diffraction grating, and a focusing lens for focusing the beams diffracted by the diffraction grating. The diffraction grating, after having been subjected to a test condition of 85 degrees centigrade and a relative humidity of 85 percent for at least 500 hours, has diffraction efficiency performance within 6 percent of that achieved before being subjected to these test conditions.

Diffraction grating-based wavelength selection unit

A surface-relief transmission diffraction grating which, after having been subjected to a test condition of 85 degrees centigrade and a relative humidity of 85 percent for at least 500 hours, has diffraction efficiency performance within 6 percent of that achieved before being subjected to these test conditions.

Surface-relief diffraction grating

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. A hologon deflector system may incorporate two identical prism elements of essentially the same shape and which are supported on the same body so that scan beam tracking errors associated with movement (vibration) of one of the prisms is compensated by the movement or vibration of the other.

Hologon deflector system having dispersive optical elements for scan

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. The deflector systems are useful for imaging applications, especially on recording media mounted on the internal surface of a drum.

Deflector system which produces dual, oppositely directed scanning beams

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. The DRUM deflector may be part of a system which provides a tracking beam of a wavelength different from the scanning beam which is reflected from the partially reflecting surface, then acting as a dichroic beam splitter. A dichroic beam combiner combines light of both wavelengths and directs the light to be incident on the dichroic, partially reflecting surface of the DRUM deflector. A spherical mirror with a clock grating reflects the tracking beam to a photodectector to provide an output signal from which in-scan tracking errors can be derived.

Rotationally symmetric dual reflection optical beam scanner and system

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. The polarization direction of the converted linearly polarized beam stays constant relative to the deflecting surface, as a result of using the circularly polarized incident beam and the quarter-wave plate which rotates with the deflecting surface.

Optical beam scanners for imaging applications

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. The adjusting screws from the retainer cap have tips which are inserted into the hologon disc assembly and preferably a balancing disc of soft metal which is opposed to and spaced from the retainer cap. Then the rotational angular position of the hologon is locked to the rotational position of the retainer cap which in turn is locked to the motor shaft. The improved mount maintains the hologon alignment position even after many hours of use and starts and stops of the motor rotation. Readjustment may readily be accomplished by resetting the adjusting screws.

Adjustable fixed mount for a hologon deflector

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.

Simultaneous multibeam scanning system

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.

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. This monograting disc deflector provides a cost-effective scanner solution for high resolution, flat field imaging applications.

Hologon scanner system

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. A hologon deflector system may incorporate two identical prism elements of essentially the same shape and which are supported on the same body so that scan beam tracking errors associated with movement (vibration) of one of the prisms is compensated by the movement of vibration of the other.

Hologon deflection system having dispersive optical elements for scan

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. The beam scan angle across the receptor surface is equal to the angle of rotation of the grating, rather than being related to the angle of rotation by a factor approximately equal to the ratio of wavelength of the laser light to the grating period.

Hologan scanner system

A multi-wavelength (color--red(R)--blue(B)--green(G)) scanner system using diffraction grating deflector elements. A plurality of elements are used. Each has a different grating period. The elements all have the same lambda/D (wavelength to grating period) ratio. The elements are moved serially to intercept a composite, multi-wavelength beam. A preobjective lens is used to focus the successive, different wavelength beams to a single composite spot on an image surface. Since each element has the same lambda/D value, for a different wavelength, the spots from each wavelength will overlap and scan essentially colinear lines, successively, on the image surface. By moving the image surface an image area can be scanned. The composite spots and lines are used to read color images by measuring the spectrum of reflected light from the scanned image or may be used to generate color images by independently modulating individual sources of light comprising the beams and which make up the scanning spot.

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Pittsford, NY, United States of America

Charles J Kramer