International Business Machines Corporation

Larry W Bassetti

Sherwood Kantor

Ross B Hooker, Iii

Janis K Richert

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.

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Boulder, CO, United States of America

Larry W Bassetti