Xerox Corporation

Other

William L Lama

Robert P Loce

James D Rees

John A Durbin

Martin Edward Banton

Thomas J Hammond

Susan E Feth

Stephen T Avery

Ned J Seachman

Stephen C Corona

Melvin E Swanberg

Michael S Cianciosi

Girmay K Girmay

Karl A Northrup

Kevin J Garcia

Peter K Wu

Robert P Siegel

James J Appel

David B Kay

Michael E Harrigan

Richard F Lehman

Cyril G Edmunds

Gary A Dir

Ronald E Jodoin

Jeffrey David Kingsley

Michel J Denber

Kenneth W Altfather

Randall C Ryon

Peter R Watson

Susan E Dunn

Clark I Bright

Gregory B Swistak

Paul H Stiebitz

Donna U Ozern

David L Cole

Paul H Steibitz

Warren H Woolley

Donald A McTarnaghan

Martin Pepe, Jr

Douglas W Story

Eleanor Whitte

Antje B Parker

Per S Nylen

Abd-El-Fattah A Ibrahim

An apparatus for correcting color images in an electrophotographic printing machine in which a first image is developed on a photoconductive surface, the second and subsequent images are superimposed over the first developed image. The apparatus includes an input device for inputting an image signal having a plurality of color components. An image processing unit processes the inputted signal. The image processing unit includes an adaptive exposure processor that modulates the exposure level of a raster output scanner (ROS) for a given pixel as a function of toner previously developed at the pixel site, thereby allowing toner layers to be made independent of each other.

Adaptive exposure color correction

A hybrid halftone cell selection method enables selection of gray levels in halftone printing algorithms to minimize the effects of noise resulting in nonuniformities, such as, for example, halftone banding. The method requires selection of hybrid halftone cells possessing structures wherein the total number of gray pixels are limited. The number of gray pixels having any given intermediate reflectance level in any halftone cell is also limited. The cell selection method thus reduces the number of TRC gray steps to some minimum required number by eliminating the most noise sensitive cells (i.e. those cells having the highest percentage of gray level pixels). The intermediate reflectance values of the gray pixels in the selected cells are then selected to produce uniform gray steps and reduce variability in the TRC.

Method of hybrid halftone printing by limiting the number of gray pixels

Improvements in bit-image quality in printing systems is achieved by providing several different pattern matching processors. Each pattern matching processor comprises a lookup table of patterns and corresponding replacement image patterns. A source image is modified by replacing areas in the source image that match patterns with the corresponding image patterns. Pattern matching processors are chosen depending on: the type of image being processed, input from the operator (user), feedback from the xerographic processor, and the color of the image. A user interface is provided which allows a user to download template and pattern data for each pattern matching processor. Pattern matching can be used to correct single-bit, half-bit, line-growth, xerographic effects and aliasing errors, and to provide control of print quality to the user.

Bitmap-image pattern matching apparatus for correcting bitmap errors in

A pulsed imaging, facet tracked, Raster Output Scanner utilizes pulse width modulation in conjunction with spatial filtering to form three exposure levels at the surface of a charged photoreceptor medium, one of the levels associated with a specific color. This type of scanner with a nominal video rendering experiences a color line growth in the process direction. The line growth problem is caused by a coherent optical effect. The resultant output print has bolded color lines in the process direction. Several techniques are set forth to compensate for this line growth. In a preferred technique, the video data stream is modified by locating or positioning video pulses representing white information at the start of an associated pixel time period. When the color pixel is imaged, it will therefore, always abut an adjoining white pulse and will be inhibited from spreading into the adjacent pixel period. Other techniques rely upon inversion of white pulses, or separation of white pulses into two signals, each segment moved to the beginning and the end of the associated pixel period. According to another technique, the input data stream is buffered and pixel groups examined to identify neighboring white and color signals. These signals are then either narrowed or in the case of a sequence of color signals, the lead and trail edge of the color signals are trimmed.

Pulsed imaging, pulse width modulation scanner for a tri-level highlight

A pulsed imaging Raster Output Scanner utilizes pulse width modulation in conjunction with spatial filtering to form three exposure levels at the surface of a recording medium, one of the levels associated with a specific color.

Pulsed imaging, pulse width modulation raster output scanner for

A multiple diode laser array used in a ROS scanning system is modified to reduce the effects of undesirable spatial exposure variation at the surface of certain type of layered, semi-transparent photoreceptors. The spatial absorption variation is later manifested as a 'plywooding' pattern formed on output prints derived from the exposed photoreceptor. The laser array is modified to form a merged scanning beam at the photoreceptor surface of two or more diode outputs, each output operating at a different wavelength than the other. In one embodiment, a plurality of diodes, each at a different wavelength, are sequentially addressed, and an image of each diode is scanned across the photoreceptor which results in an exposure distribution that would be similar to that formed by an incoherent beam.

Plywood suppression in ROS systems

A multi-beam laser ROS print system is described which is adapted to minimize banding in output prints. Multiple beams from a laser source are separated by a distance which causes the beam to scan consecutive lines in a non-consecutive scan; e.g., according to a particular beam interlacing sequence. It has been found that as a general proposition, banding decreases with increasing interlacing orders and, furhter, that once a print system error frequency, or another frequency of interest has been identified, there are a number of interlacing orders, each an optimum value, which can be introduced to reduce banding which would ordinarily result from the particular frequency error.

Multi-beam scanning system compensated for banding

A document feeder is provided for presenting documents to the platen of a copier for copying with a vacuum belt platen transport system having document transporting belts movable under a substantially planar vaccum plenum backing. Also included is a vacuum system for applying a partial vacuum to a document sheet being transported by the movable belts over the platen. Show-through and show-around problems are reduced by optically mtching the belts and the plenum backing. In the preferred embodiment, the background surface is slightly roughend and made to be approximately 92% reflective to light during image exposure. The belts are composed of a urethane material which is approximately 16% transmissive but provides a 91% reflectance when moving along the plenum surface.

Plural belt document feeder with optimum optical properties

A printing system employing a raster output scanning device is compensated for the effects of motion of the medium upon which an image is being printed. An amplitude transmittance spatial filter is positioned either in an exit pupil of the 'slow scan' optics of the system or in the first Fourier transform plane of a lens positioned between the scanning device and the recording medium. Several preferred transmittance functions are provided.

Printer compensated for vibration-generated scan line errors

Trinary and quaternary halftone reproduction systems for electronic printers in which discrete combinations of either three or four reflectance level pixels having optimum intermediate levels form halftone cells to provide an increased number of gray steps for processing image signals, yielding an optimum Tone Reproduction Curve.

Image halftoning system for printers

In an electronic printer which utilizes an image write bar, a control circuit is provided to compensate for the effects of vibration in a rotating photoconductive member, typically a photoreceptor drum. In one embodiment an encoder is positioned so as to detect spatial displacements of indicia affixed to the photoconductor surface, Correction signals are generated and sent to control circuits which adjust the on/off timing of the write bar operation and/or the intensity of the image bar output. This adjustment results in compensation for the effects of photoconductor vibration.

Image bar printer compensated for vibration-generated scan line errors

An electrophotographic reproduction device is described which is capable of forming images of an original document modified by information added to or replacing information of the original. A latent image of the document is formed on a photosensitive surface and a portion of the image, in a first embodiment, is maintained at the original charge level. This fully charged section is subsequently discharged in an image-wise pattern by a compact annotator device. The annotator includes an illumination source, an addressable light modulator device such as a liquid crystal panel and a lens array for forming the modulated light pattern onto the photosensitive surface.

Apparatus for forming composite images

A gradient index lens array having improved stray light characteristics is enabled by coating the surfaces of the fibers comprising the array with a low transmittance, low viscosity material. The index of this material is matched to that of the fiber surface to prevent Fresnel reflection. The interstitial areas of the lens array comprises a light absorbing material. In another embodiment, stray light caused by light scattering at the end faces of the lens array is reduced by masking the end face with a mask having apertures overlying the fiber faces. The mask apertures have slightly smaller diameters to mask out the rough outer edge of the fibers.

Gradient index lens array with improved image quality due to stray light

Exposure modulation (strobing) at a photoreceptor surface due to mechanical vibration of the photoconductor is eliminated by placing a filter with appropriate transmission characteristics in the optical path. The transmission characteristics necessary to achieve zero strobing include an incidence profile having a zero Fourier transform at the vibration frequencies.

Method and apparatus for eliminating exposure strobing effects in a

An imaging device is disclosed which comprises a noble metal photosensitive glass having formed on the surfaces a plurality of raised spherical surfaces which form an array of thick lenses. The array can be positioned between an object and image plane to project images from the object plane onto the image plane. Lens spherical aberrations are reduced and lens array imaging performance is optimized by an optimum lens aperture radius or an optimum lens numerical aperture.

Short focal length imaging device

Growing community of inventors

Webster, NY, United States of America

William L Lama