International Business Machines Corporation

Sherwood Kantor

Larry W Bassetti

Russell Alan Budd

Mikel J Stanich

Bruce David Gibson

Randall A Maddox

Larry L Wolfe

Paul S Yosim

Ross B Hooker, Iii

Wayne A Overby

Janis K Richert

Garry J Selby

Enhancement of text characters when converted to a higher resolution without degrading imbedded halftone images. Enhancement at the higher resolution is determined by comparing predetermined patterns to individual lower resolution pels and surrounding pels. The predetermined patterns are selected as occurring in text data and not in half-tone images according to the rules described.

Pel resolution addressing conversion

This is an electronic scheme for correcting for mechanical misalignment and chromatic aberrations from laser beam to laser beam in the scan direction of a multiple beam laser scanning system for use in an electrophotographic machine. Each beam is first corrected for mechanical misalignment and thereafter for chromatic aberrations. A reference laser beam produces two pulses near the start of scan (SOS) and two pulses near the end of scan (EOS). A non-reference laser beam then produces SOS and EOS pulses from which the mechanical misalignment is calculated. A gated clock is energized by the reference pulse and a tapped delay line is used for nanosecond resolution. After accomplishing correction for mechanical misalignment, chromatic aberrations are corrected by measuring the amount of total pel displacement of the non-reference scan line relative to the reference scan line and inserting appropriate delays at selected intervals throughout the non-reference scan in order to maintain pel placement accuracy to a desired tolerance.

Chromatic and misalignment compensation in a multiple beam laser

In an electrophotographic printer or the like, compensation is provided for environmental effects (temperature, humidity, photoconductor aging, etc.) which would otherwise affect print quality. Analyzing print data allows identification of compensation locations; those are locations at which compensation is most critical, such as single pel lines. A series of clock pulses of varying phase displacement are employed, and selected based on environmental variations, so as to modify the print data at the identified compensation locations. The print data comprises a series of pulses. Compensation to control the width of lines perpendicular to the scan direction is effected by selectively advancing the leading edge of pulses defining a white/black transition and delaying the trailing edge of pulses defining the black/white transition. This control then affects the duration of the print pulses. For lines which are parallel to the scan direction width control is effected by adding gray pulses, both the leading and trailing edges of these gray pulses are controlled in accordance with environmental variations. Accordingly, the duration of the gray pulse is also controlled.

Compensation for fine line prints

Print enhancement circuits for an electrophotographic printing machine are placed between the character generator and the printhead to modify drive signals for the printhead. Modifications include smoothing the digitized edges of slanted lines; broadening single pel width lines in the direction perpendicular to the scan direction as well as in the direction parallel to scan. Inhibiting circuits are provided to prevent passage of enhancement signals under certain conditions. Generally, leading and trailing edge gray signals are provided next to all black data in a direction parallel to scan while expanded black signals are provided for the single pel data in a direction perpendicular to scan by adding to the black signal on both its leading and trailing edges. When a single picture element (pel) area contains two added black signals, both are passed; when a single pel area contains one added black signal and one gray signal, both are passed; when a single pel area contains two gray signals, only the leading gray signal is passed; and when a single pel area contains two added black signals and a gray signal, only the gray signal is passed.

Interacting print enhancement techniques

This discloses an electrophotographic printing machine with circuits to enhance the printing of fine lines, such as lines of a single picture element (pel) in width. Provision is made for broadening such lines in one dimension by adding small 'black' areas to each edge of the fine line in order to broaden it. In a second dimension, perpendicular to the first dimension, lines are broadened by placing gray pels next to black pels. The disclosure also discusses specific cases in which it may be considered desirable to inhibit the enhancement signals.

Fine line print enhancement

This invention relates to enhancing the apparent resolution of electrophotographic printers. This is accomplished by writing a gray of half-tone halo along the periphery of images written on the photoconductor. When the image with its half-tone halo is developed, transferred and fixed by steps in the electrophotographic process, the printed image has a substantially smooth contour. In effect, the gray halo placed around the image merges with the black interior of the image when the image is developed, transferred and fixed. To prevent the image from appearing to be too thick after its contour has been smoothed by the use of the half-tone halo, the number of black picture elements used to write the image on the photoconductor are reduced. Also, the width of image segments making up the image may be adjusted by changing the level of gray used to write the half-tone halo.

Method and apparatus for enhancing the resolution of an

Dimensional variations, such as skew, alignment and abutment, in an array scanner are corrected by scanning and storing into a storage means an uncorrected electronic image generated from a test pattern. Correctional factors are generated from the stored electronic image. The correctional factors are used to correct the dimensional variations in the electronic image of the test pattern and/or dimensional variations in subsequent electronic image outputted from the scanner.

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Boulder, CO, United States of America

Sherwood Kantor