Patent
1990-05-29
1992-05-26
Herndon, Heather R.
G06F 1562
Patent
active
051173719
DESCRIPTION:
BRIEF SUMMARY
Character storage process and arrangement for reducing the redundancy of characters for matrix printers with multipass printing.
The invention relates to a process for the runtime-optimized and code-optimized storage of characters in matrix printers with multipass printing according to the preamble of patent claim 1.
In the case of matrix printers, which can be fitted either with a needle print head or an ink print head, in contrast with daisywheel printers, which print the characters as a whole, the letter or the character to be printed is composed of a large number of individual small dots. The print quality of these characters depends to a considerable extent on the resolution. This is determined by the number of individual dots per character, i.e. by the number of lines and columns of the character matrix. In the case of a mosaic printing process, the number of printer needles or the number of ink nozzles determines the number of lines of the character matrix within which the characters are built up.
If such a matrix printer is equipped, for example, with an ink printing mechanism, the latter includes a large number of writing nozzles, to each of which is assigned an individually actuable transducer element. The writing nozzles are in connection with an ink supply system, which is equipped with an ink bottle. This ink bottle contains either ink of black color for black printing and/or the customary printing colors in the case of three-color printing, cyan, yellow and magenta, in three separate chambers of the ink bottle. The writing nozzles end at the side facing a recording carrier of a so-called nozzle plate in outlet openings, which are arranged there in one or more rows.
For the actuation of the transducer elements, and thus for the ejection of individual ink droplets, an item of character information is taken from a character generator and transferred to an image dot memory, in which the character to be printed is, so to speak, electronically depicted. Via a printer electronics, the transducer elements are actuated in dependence on the relative movement of the head with respect to the recording carrier and according to the information in the image dot memory and the characters are built up in matrix form on the recording carrier. In this case, the build-up takes place in the character matrix, the horizontally running lines of which are also referred to as tracks, the vertically running columns of which are also referred to as print columns.
Matrix printers with added features are usually able to represent the characters with different print quality. A distinction is made here essentially between a so-called draft quality (DQ) and a near letter quality (NLQ).
In order to obtain a good print image in both print modes, the text lines are not completely applied to the recording carrier in a single printing run, but with the aid of a multipass process. In this case, the characters to be depicted are printed matrix line by matrix line in a plurality of chronologically successive printing runs.
Such a multipass printing process requires a filing or storage of the image dots in the print buffer (image dot memory), adapted to the print head's geometry, i.e. the arrangement of the needles or of the nozzle openings. This leads to a considerable memory requirement for the character set within the character generator and to relatively long processing times. These reasons give rise to the necessity of reducing the image dot storage capacity by a redundancy-reducing coding of the character information.
German patent specification No. 3,132,842 discloses a process for reducing the redundancy of binary character strings for matrix printing processes. This process is based on the fact that only a part of the altogether existing matrix dots of a character matrix is required for the representation of alphanumeric characters. Therefore, to reduce the complexity required for the dot-by-dot representation of the characters in the character matrix, details on the difference between the image dot coordinates according to
REFERENCES:
patent: 4125829 (1978-11-01), Kayashima
patent: 4513299 (1985-04-01), Lee et al.
patent: 4554637 (1985-11-01), Kuntze
IBM Technical Disclosure Bulletin, vol. 25, No. 9, Feb. 1983, J. E. Bresenham et al.: "Font compression in high resolution printers", pp. 4582-4584.
Patent Abstracts of Japan, vol. 11, No. 213 (M-605) (2660), 10 Jul. 1987 & JP, A, 62030052 (Tokyo Electric Co. Ltd), 9 Feb. 1987.
IBM Technical Disclosure Bulletin, vol. 23, No. 12, May 1981, P. R. Spivey: "Data compression technique for APA printer (change block skipping)", pp. 5464-5467.
Kristen Franz
Traute Martin
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