Xerox Corporation

Robert P St John

William A Lloyd

Douglas N Curry

Sofia Filshtinsky

The contour fidelity of reproduction of images is enhanced by matching groups of pixels with templates based on a hierarchical set of patterns. This is accomplished by isolating a symmetrical window of pixels in the image including a central pixel and matching the groups of pixels in the window with hierarchical templates. Enhancement values for the central pixel are provided based on the results of the comparison. Windows are formed so that each pixel in the image is a central pixel for at least one window. The hierarchial set of patterns is developed so that each pattern in the hierarchy is a combination of an extension pattern and the pattern immediately below it in the hierarchy. This significantly reduces the hardware requirements for implementation of the technique. Templates are developed by creating horizontal, vertical, reversed and inverted permutations of each pattern in the set. Correctable pixel locations are identified for each template, and the central pixel receives enhancement values when it is in the correctable location of at least one template. In an microaddressable printer, overscanning and increased clock frequency provide multiple segments for representing each pixel, and spot width compensation allows multiple intensity levels for each segment.

Enhanced fidelity reproduction of images by hierarchical template

A color electrographic recording apparatus is provided to produce on a recording medium a composite color image comprising a plurality of superimposed component images of different colors, e.g., magenta, cyan, yellow and black. The apparatus includes means for transporting the recording medium in opposite directions along a predetermined path through the electrographic recording apparatus, a recording station in the path and having a recording head with electrode means for forming a latent image on the recording medium, control means operative to energize the electrode means to create a latent image on the recording medium, a plurality of developing means adjacent either one side or both sides of the recording station in the path, each of the developing means for developing a latent image produced on the recording medium at the recording station into a corresponding visible component image of a respective color. The transport means is operative to pass a section of the recording medium through the recording station to form a first component latent image followed by its respective color development and reverse the direction of medium transport to permit formation of a next component latent image followed by its respective color development and repeating this process until all component latent images and their respective color development have been completed to form a composite color image. The color electrographic recording apparatus also includes unique registration means associated with the transport of the recording medium and the apparatus control means to form each component latent image so that all the component color images will be superimposed on one another even in spite of any shrinkage or expansion of the medium during its multiple handling and processing by the electrographic recording apparatus.

Color electrographic recording apparatus

A web tracking system for a continuous web of material which is transported from a supply to a takeup means along a predetermined path via one or more processing stations and comprises aligned tracking indica along at least one edge of the web. Means are provided to observe the tracking indica as the web is transported along the system path and produce information either indicative of dimensional changes in the length and width of the web due to web shrinkage or expansion or indicative of a particular point along the length of the web useful at one or more of the processing stations in the system.

Web tracking system

Apparatus for controlling the rotational speed of a polygonal mirror adapted to scan a reflected light beam over a desired scanning area as each facet of the mirror is rotated into the path of an incident light beam. The apparatus comprises a poly-phase motor coupled to the mirror for driving same. The motor has a plurality of input terminals and a plurality of motor windings connected to the input terminals. First means responds to the reflected light beam for generating a first clock signal having a frequency proportional to the actual rotational speed of the mirror. Second means generates a second clock signal having a frequency proportional to a desired rotational speed of said mirror. Third means coupled to the first and second means responds to the first and second clock signals for generating a third clock signal having a frequency representative of the difference in phase or frequency between the first and second clock signals. A poly-phase generator is coupled to the third means and is responsive to the third clock signal for generating a plurality of mutually phase-displaced drive signals for respective application to the plurality of input terminals of the motor, whereby a plurality of mutually phase-displaced sinusoidal signals are respectively developed across the motor windings, each sinusoidal signal having a frequency proportional to the frequency of the third clock signal.

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Sunnyvale, CA, United States of America

Robert P St John