Process and arrangement for generating high-quality matrix print

Details Process and arrangement for generating high-quality matrix print Process and arrangement for generating high-quality matrix print

1995-08-10

1998-06-16

Wong, Peter S.

Incremental printing of symbolic information

Electric marking apparatus or processes

Electrostatic

347131, 358298, 358296, 358459, 399 55, 399 56, 399 47, 399 48, G01D 1514, G03G 2100, H04N 121

Patent

active

057678880

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
Process and arrangement for generating high-quality matrix print using electrophotographic printing equipment.
2. Description of the Related Art
The invention relates to an electrophotographic process and an arrangement for generating a macro-charge zone that is inkable by toner applicators and delimited by an inking limit having an adjustable contour on a photoconductor of a printing or copying machine, using at least one exposure-variable and a position-variable controllable light source.
In electrophotographic printing equipment, it has previously been common to represent characters and half-tone images by means of point matrices which comprise individual inked points of predetermined size. Gray gradations are achieved by means of a matrix arrangement, for example in the form of a dither matrix or other matrix. Matrices of this type, however, have an unfavorable relation of resolution and gray gradation and run the risk of forming matrix contours and Moire fringes, which limit the achievable printing quality.
Although it is known from U.S. Pat. No. 4,809,021 to achieve an increase of printing quality by generating points of varied size by means of variation of the intensity or the diameter of the laser beam, the shape of the points is, however, predetermined. As a result of this predetermined shape of the matrix points, in conjunction with the predetermined point size, it has not been possible until now, using electrophotographic printing equipment, to achieve offset-like printing quality both with respect to the representation of half-tones and also with respect to the representation of characters and printed lines.


SUMMARY OF THE INVENTION

It is therefore an object of the invention, for electrophotographic printing equipment, to provide a process and an arrangement which enables a high printing quality, both with respect to a representation of half-tones and with respect to characters and printed lines.
It is a further aim of the invention to design the process and the arrangement such that a finely graded offset-like matrix print is possible.
These and other objects and advantages of the invention are achieved by an electrophotographic process for generating a macro-charge zone which is inkable by toner applicators and is delimited by an inking limit having an adjustable contour on a photoconductor of a printing or copying machine, using at least one exposure-variable and position-variable controllable light source, the process having the following features:
a) for forming the macro-charge zone delimited by the inking limit, by controlling the exposure of the light source and the radiation position on the photoconductor and by controlling a bias voltage which can be applied between photoconductor and toner applicator, an electrostatic potential relief made of individual adjacent micro-charge zones of exposure-dependent size is generated on the photoconductor, and the inking limit is defined, the contour of which is determined by the bias voltage level on the potential relief;
b) the light emitted by the light source per micro-charge zone onto the photoconductor has an exposure distribution which is dimensioned in such a manner that, proceeding from a center of high exposure, the exposure falls off homogeneously to the outside.
The electrophotographic process is further defined wherein, to represent an area of a half-tone image, a matrix of macro-pixels having inking areas assigned to gray steps is used, the magnitude of which areas lies in the integration range of the human eye and each macro-pixel is in turn constructed from a matrix of micro-pixels and wherein a macro-charge zone, which is delimited by the inking limit, is generated on the photoconductor for each macro-pixel, using this inking area, the macro-charge zone being composed of adjacent micro-charge zones assigned to the micro-pixels. The micro-charge zones used for the formation of a macro-charge zone are generated on the photoconductor by means of light sources whose exposure di

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