Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1996-02-13
1998-04-14
Bost, Dwayne
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
395109, 395114, 395115, 395101, 358448, G06K 1500
Patent
active
057403317
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a system and a process for converting image information in matrix form and suitable for positive image generation into image information suitable for inverse image generation for an electrographic printer or copier.
European reference EP 0 403 476 B1 discloses an optical character generator for an electrophotographic printer, using which printing information present in the form of electronic data is converted into an optical image. The optical image is then transmitted to a photoconductive layer, for example a continuously circulating charge storage drum of the printer, by means of exposure, in order to generate a latent charge image. This charge image is developed in a known way and transfer printed, for example on paper.
Advantageous for this application are optical character generators which expose the charge storage drum line by line over its complete length, since the exposure process, in contrast to exposure by means of a laser, can then be carried out without mechanical movement. Such a line by line construction of the optical character generator requires a dedicated light source for each imaging point within one line. Light-emitting diodes are preferably used as light sources, since these components offer the possibility of a very compact arrangement.
In the case of the known character generator, the pixels of the matrix are exposed by means of the light-emitting diodes on the charge storage drum, on which pixels toner particles are intended to be deposited during the image development. The pixel is therefore identical to the toner point. The point diameter of an exposed pixel is determined by the focusing of the light-emitting diode, that is to say by its cone of light incident on the photoconductive layer.
The pixels are arranged at a defined spacing from one another. The spacing between two pixels is defined as the grid size. In the case of the prior art, the point diameter is greater than the grid size. For this reason, in the case of the exposure of two adjacent pixels, overlapping of the toner points occurs. This overlapping leads to improved representation of the image to be reproduced. The ratio of the point diameter to the grid size is defined as the degree of overlap. The degree of overlap commonly lies in the range between 1.4 and 2.
Apart from this first development method, as is used in the case of the cited prior art, that is to say the inking of the discharged areas (=DAD Discharged Area Development), there is a second development method: the inking of the charged areas (=CAD Charged Area Development).
Whereas, in the case of the first development method, the discharged surface areas of the photosensitive layer correspond to the information to be printed, in the case of the second development method the charged surface area corresponds to the information to be printed. In order to provide the precondition for this second development method, the background of the information to be printed is exposed on the photosensitive layer. This exposure can be carried out, as in the case of the first development method, optionally by means of a laser beam, a laser diode beam, a line of light-emitting diodes or the like.
Since the first-named development method is normally used in electrographic printers or copiers, there are for this process on the market a corresponding number of partially standardized character sets in the form of so-called "bit maps". A bit map designates a defined matrix in which, to generate a character or an image, specific pixels are set in a binary fashion.
Such bit maps are disclosed, for example, by U.S. Pat. No. 4,635,081. The individual character elements to be represented are stored in a memory in character fields (bit maps) of equal size in the form of binary characters. A character field for one character of a size 1/10.times.1/6 inch has 18 columns and 24 lines and hence 432 points of intersection. Each point of intersection, which corresponds to a pixel, is allocated one digital memory location.
It has now bee
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patent: 4251821 (1981-02-01), Kimura
patent: 4396928 (1983-08-01), Abe et al.
patent: 4584573 (1986-04-01), Ito
patent: 4635081 (1987-01-01), Wiedemer
patent: 4700201 (1987-10-01), Sato
patent: 5282057 (1994-01-01), Mailloux et al.
Goldmann Gerd
Lobel Markus
Bost Dwayne
Legree Tracy M.
Oce Printing Systems GmbH
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