Xerox Corporation

Mark A Gwaltney

Connie F Purdum

Robert P Loce

Jeffrey J Folkins

Charles H Tabb

Zhao-zhi Yu

Beilei Xu

Meng H Lean

Martin Sidney Maltz

Jon S McElvain

Charles Michael Hains

Kenneth W Pietrowski

Robert E Grace

David Jordan Lieberman

Roger Lee Bullock

James R Beachner

Paul M Butterfield

John F O'Brien

Carlos O Alva

Thomas J Fleck

Kevin M Sheridan

David R Wyble

Shirley Cheng

Disclosed herein is an image processing method for producing enhanced halftone edges, particularly suited to those edges which only lie upon the background as apposed to those edges which abut other halftone screens. It utilizes a step of defining border pixels and a step of halftoning those border pixels in a different manner than the halftoning applied to the interior region of the tint or image segment. The preferred halftone for the border pixels will be related to the interior halftone by some number of common spatial frequency harmonics. Examples of common-harmonic screening for an edge include, but are not limited to: (a) same screen with different tone reproduction characteristics (boosted edge values); (b) same screen angles and frequencies with a different spot function, possibly phase shifted; (c) a dot screen whose frequency vectors can be generated by the frequency vectors of the interior screen; (d) a line screen whose frequency vectors can be generated by the frequency vectors of the interior screen. This generation process is directed to ensuring that the two screens will be 'harmonically matched' where at least one of the fundamental frequency vectors and harmonics of the first screen will equal at least one of the fundamental frequency vectors and harmonics of the second screen.

Tinted edge enhancement using harmonic halftones for the boundary pixels

Test image data is introduced into the image processing path of a marking device, at various points prior to the marking engine. Comparison of output of the marking engine from various sources of image data is made to diagnose imaging path component failure. Imaging data at various points in the image processing path is captured for analysis as part of component failure diagnosis. Various memory devices are used to both introduce test data at various points in the image processing path and capture data at various points of the image processing path.

Memory for diagnosing imaging component failure

Method, system and computer-readable medium containing instructions for performing halftone gamma correction in a printing environment to achieve and maintain high print quality. The system includes one or more subsystems, including a tone reproduction subsystem that creates one or more print calibration pages, each having a tone curve defining a relationship between a plurality of input color levels, output color levels and a level of measured darkness. A pixel adjustment subsystem associates each input color level with one of the output color levels based on a desired percentage change in the level of measured darkness. Further, a gamma correction system performs gamma correction on a selected tone curve of one of the print calibration pages by associating each input color level with one of the output color levels based on the desired percentage change in the level of measured darkness in a substantially flat region of the selected tone curve.

System and method of performing halftone gamma correction in a printing environment

A method is disclosed for reducing halo print defects occurring in printed/copied color images. The method includes detecting a boundary between a first image object and a second image object within a color separation of the color document, and modifying the video values of a plurality of pixels within the color separation so that the video values slope toward the boundary, the plurality of pixels being located within a transition zone adjacent the boundary. In the case where toner black is used, the video values of a plurality of pixels within a transition zone of a toner black color separation are modified so that the video values ramp or slope down toward the boundary, and the video values of a plurality of pixels within transition zones of a cyan color separation, a magenta color separation, and a yellow color separation are modified so that the video values ramp or slope up toward the boundary. In effect, the process increasingly replaces toner black with process black (i.e. equal parts of cyan, magenta, and yellow toner particles) in the transition zone in a direction toward the boundary. As a result the electrostatic interactions on the photoreceptor are reduced and halo print defects are eliminated.

Method for reducing halo print defects associated with color images

An improved method for estimating toner usage in digital xerographic printers and copiers. The method is characterized by taking into account digital image dot spreading which results in the area of a pixel not being developed fully and some areas outside of the pixel being developed. Thus, the improved method takes into account the departure of a developed image from an ideal shape (i.e. square). To this end, the improved method compensates for departure of a developed image from an ideal shape. In carrying out the method estimated toner usage is based on pixel groupings rather than simple pixel counting.

Method for estimation of toner usage in digital xerographic copiers and

Apparatus and method for glossing certain areas of a substrate. In particular, highlight images are created by incorporating in some of the images on a substrate a clear polymer material thereby providing them with a larger mass thereby resulting in a higher gloss than those images on the same substrate which do not contain the additional clear polymer.

Highlight gloss for xerographic engine

In a multi-color imaging apparatus utilizing a recharge step between two image creation steps for recharging a charge retentive surface to a predetermined potential pursuant to forming the second of the two images, a first corona generating device recharges the charge retentive surface to a higher absolute potential than a predetermined potential, and then a second corona generating device recharges the charge retentive surface to the predetermined potential. An electrical charge associated with the first image is substantially neutralized after being recharged by the first and second corona generating device.

Split recharge method and apparatus for color image formation

In a multi-color imaging apparatus utilizing a recharge step between two image creation steps, a corona generating device is used to recharge the developed image areas and untoned areas of a charge retentive surface to a lower electrical potential than that associated with the developed image areas before recharge, so that the residual voltage associated with the developed image is substantially reduced and a minimal level of negative charge is driven through the toner layer(s). An electrical charge associated with any previously developed images is substantially neutralized prior to development of any subsequent images thereon.

Single positive recharge method and apparatus for color image formation

A developer control for enabling the use of developer and toner materials with widely varying At in high quality xerographic copying and printing. Pixel count data is combined with toner test patch reflectance data during a brief toner rundown to determine the rate of change of density per unit change in toner concentration. During toner rundown, dispensing of toner is suspended for a period of time for effecting toner concentration reduction by approximately 0.25%. The change in Toner Concentration (TC) is estimated using pixel counting. Additionally, toner test patches are created and the reflectance thereof is measured for determining the change in toner density. The estimated TC change and the change in toner density are processed using linear regression to find the average change in density sensor output for the estimated change in TC which is referred to as the rundown slope. The rundown slope is then compared to a target value. If it exceeds the target value by more than ? (a noise factor), the dispense setpoint is reduced by one unit. If the rundown slope is less than the target value by more than ?, the dispense point is increased by one unit. The noise factor, ? is attributable to errors in pixel count or reflectance sensor drift. According to the foregoing, the nominal control line and control band in TC-Tribo space is altered to produce a much wider usable At range.

Closed-loop developability control in a xerographic copier or printer

A printing machine of the type in which a latent image recorded on an image bearing surface is developed with toner to form a visible image thereof, includes a development apparatus for developing the latent image. The development apparatus includes a housing storing a supply of magnetically-attractable developer material containing toner. A moving flexible donor belt mounted within the housing spaced from the image bearing surface transports developer to a development zone adjacent the image bearing surface. A magnetic member attracts and transports the developer material within the housing to the donor belt. A plurality of selectively-actuable electrodes embedded within the donor belt are biased to create a powder-cloud of toner particles within the development zone. Within the development zone, the flexible donor belt moves over a pair of spaced apart support rollers defining the width of the development nip. The spacing between the support rollers is adjustable to inexpensively create different widths for development nips from a common structure development unit, thereby saving image bearing member real estate within the development zone and improving the quality of image development.

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Fairport, NY, United States of America

Mark A Gwaltney