Hewlett-packard Company

Hewlett-packard Development Company, L.P.

Victor D Loewen

Mark John Wibbels

Kurt Robert Bengtson

Jan Philip Allebach

Mark Edward Shaw

David Alan Johnson

Steve A Jacob

Thomas Camis

Kenneth Eugene Heath

George Henry Kerby

Kenneth A Lindblom

Seong Jun Park

A method for creating an image to be printed is provided. A first halftone pattern and a second halftone pattern for respective first and second periodic clustered dot halftone regions of the image are selected. The regions have respective frequencies and one of the frequencies is higher than the other frequency. A transition region is determined. The transition region includes a boundary between the two regions and includes additional portions of the two regions beyond the boundary. The two halftone patterns are blended with each other in the transition region based on a blending ratio of the two halftones where the blending ratio changes as a function of distance between the edges of the transition region.

Creating an image to be printed using halftone blending

A method for reducing edge effect (white gapping) between objects formed on a photoconductive member of an imaging device includes, during processing of a given color plane, partially exposing the photoconductive member for all image data that specifies a color to be developed on at least one color plane but that specifies no color to be developed on the given color plane. As such, the partial exposing does not enable development of that image data during image processing of the given color plane. By partially exposing objects that do not include a color to be developed on the color plane currently being processed, and while normally exposing adjacent objects that include a color to be developed on the current color plane, the lateral electric field effects between the objects is reduced and, thus, toner development for the given color plane is more edge precise for reduced white gapping between the objects.

Color plane partial exposure for reducing edge effect

A method for reducing edge effect (white gapping) between objects formed on a photoconductive member of an imaging device includes, during processing of a given color plane, under exposing (partially exposing) the photoconductive member for image data that specifies a color to be developed on at least one color plane but specifies no color to be developed on the given color plane. Under exposing occurs relative to a development threshold for the image processing of the given color plane. As such, the under exposing does not enable development of that image data during image processing of the given color plane. The under exposing occurs relative to a high frequency halftone screen for minimizing contamination (unwanted development) during the partial exposure. A half tone screen switching process enables appropriate halftone exposure for objects embodying the given color plane, and enables the necessary under exposure (utilizing the high frequency halftone screen) for objects not embodying the given color plane. By partially exposing objects that do not include a color to be developed on the color plane currently being processed, and while normally exposing adjacent objects that include a color to be developed on the current color plane, the lateral electric field effects between the objects is reduced and, thus, toner development for the given color plane is more edge precise for reduced white gapping between the objects.

Color plane under exposure for reducing edge effect

A method of aligning duplex images on an imaging device such as a printer or copier includes duplex imaging a test sheet having indicia on each side of the sheet that communicate, when observed in a single visual context, duplex imaging adjustment parameters for the imaging device. The method further includes modifying imaging parameters of the imaging device based on the duplex imaging adjustment parameters communicated. The indicia on each side of the sheet are seen in a single visual context by observing certain of the indicia through the media, as when the media is held up to a light source. In a preferred embodiment, the indicia on each side of the sheet includes respective portions of a vernier scale. The imaging parameters are modified by entering the adjustment parameters at a control panel of the imaging device. Imaging parameters modified include timing parameters associated with the process of writing data on the imaging device. In addition to the method, an imaging device includes components, data and executable instructions necessary for implementing the above described method.

Duplex image alignment

A color table calibration system produces multiple color samples for each target color point in a color table. Each sample is offset from the target color within the color space by a random amount that is equal to a fixed offset plus a random interval. In the preferred implementation, the fixed offset is equal to a distance approximately equal to the color excursion caused by noise and the random interval is constrained to not exceed the fixed offset. The color table calibration system prints a set of multiple samples for each color point. The color samples are measured using conventional measuring devices and then averaged. The color table calibration system uses the sample average to derive a calibrated color table. The pseudo random supersampling and averaging for each color point reduces errors introduced by mechanical and environmental variations.

System and method for constructing calibrated color tables in color

A single pass EP color printer includes a photoreceptor web having multiple layers and including a charge transport layer and a charge generation layer. Four exposure devices (e.g. either laser-based or thin film electroluminescent edge emitting (TFEL) devices) are serially arrayed along the photoreceptor web and act to expose the photoreceptor web in accordance with cyan, magenta, yellow and black color image pixel data. A liquid toner developer module is associated with each exposure device and includes a liquid toner reservoir, a developer roll for carrying the liquid toner to a transfer point and a squeegee roll. Each developer module is fixed so as to position its developer roll at a constant prescribed distance from the photoreceptor web at the toner transfer point and to create a fluid interfacial layer between its developer roll and the photoreceptor web. In addition, each squeegee roll is maintained in constant contact with the photoreceptor web. Erasure devices and corona charging devices are positioned between the respective developer modules to enable preparation of the photoreceptor web for a subsequent exposure/development operation. A drying roll is positioned after a last developer module for fixing the imaged toner on the photoreceptor web. The exposure devices operate from either the lower side of the photoreceptor web or from the upper side; however, in the latter instance, the photoreceptor web is comprised of a transparent support and ground plane layer. Additional embodiments of the invention are disclosed which employ a dielectric powder toner and a liquid toner four pass system.

Single pass, in-line color electrophotographic printer with interspersed

This invention is concerned primarily with scanning at multiple vertical resolutions using an essentially single speed scanner (11, 12) without having to use complex digital image processing to do resolution conversions. The invention accomplishes the multiple resolution scanning by a combination of rejecting certain lines of data and making relatively small adjustments to the paper velocity, V'.sub.p.

Method and an apparatus for limited variable speed scanning

Disclosed are apparatus and methods for transducing mechanical movement into electrical signals indicative of the movement. The apparatus is an improved optical encoder of the type having a source of light, a code wheel for modulating the light according to movement of the object whose position is being measured and a photo detector for receiving the modulated light. The code wheel modulates the light from the light source into spiral-shaped beams of light separated by columns of spiral-shaped dark areas. Photo detectors are oriented to receive the modulated light.

Apparatus for and methods of optical encoding having spiral shaped light

An optical shaft angle encoder has a code wheel with alternating reflective and non-reflective areas in a circumferential path on one face of the wheel. A light emitting diode is spaced apart from the reflective areas on the wheel. Four photodetectors are also spaced apart from the same face of the wheel so that, as the wheel rotates, the photodetectors are alternately illuminated or not illuminated by light from the light emitting diode that is reflected from the reflective areas. Preferably the light emitting diode is relatively nearer the shaft axis than the photodetectors and is in a radial direction from the shaft axis which bisects the array of photodetectors.

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Eagle, ID, United States of America

Victor D Loewen