Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1996-05-14
1998-10-13
Lee, Thomas D.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
382199, 382106, H04N 140, G06K 948
Patent
active
058220860
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to graphic arts, facsimile and publishing technologies and, more specifically, to those image reproduction systems characterized by the possibility of providing merely two levels of optical parameter (such as optical density, brightness, reflection, absorption, transmission coefficients, etc.). The invention can be used in graphic arts scanners, in the input/output units of electronic graphic data processing systems, facsimile and copier equipment.
PRIOR ART
In graphic arts technology, in electrography, thermography, matrix and ink-jet printing, liquid crystal indicators, etc., use is made of the so called screening for tonal range reproduction. This consist in varying the relative surface areas taken up in a copy by printed elements (half-tone dots) and blank elements, i.e. by the dark and light elements. The minimum sizes of steadily reproducible half-tone dots and blanks have a finite value dependent on the noise level in a system, which level is in turn dependent on the properties of the substrate on which to reproduce the image, as well as on ink, plate, toner, etc. With due account taken of said finite sizes, the density of arrangement of half-tone dots on a substrate should not be excessively high because their relative surface areas should be free to vary within sufficiently large margins to thereby assure the desired number of gradations that can be reproduced. At the same time, insufficient screen frequency (screen ruling) will limit image definition and sharpness while the screen elements themselves will wreck the finer details and contours of an image.
To simultaneously satisfy the contradictory requirements for better definition and better tone rendition, an optimal screening principle may be employed, wherein screening will change its properties selectively, with due account taken of the nature of individual image areas, to meet on of said requirements to a greater or lesser extent (Yu. V. Kuznetsov and V. A. Uzilevski. Electronic Screening in Graphic Arts (Russ.). "Kniga", Moscow, 1976). As in a number of optimal coding solutions for continuous-tone (CT) images when transmitted through communication channels, the psycho-visual premise for an adaptive approach here lies in the well known relation between the contrast or threshold sensitivity of vision and the spatial frequency of a pattern.
There are known prior-art methods for adaptive screening (SU 832771, 1288934 and 1246408), wherein screen ruling is increased with increasing busyness in image areas, and tone rendition is assured not only by means on account of the half-tone dot size but also by increasing their number per unit image surface area. The incident decrease in the number of gradation reproducible in such areas is made up for by a noticeable increase in the brightness sensitivity threshold of vision with decreasing detail sizes. To assess the busyness of an area to be reproduced, the devices used to implement said methods comprise a video signal source with a main output, whose signal corresponds to the sampling value of the optical parameter of the area to be reproduced, and with supplementary outputs, whose signals correspond to the optical parameter values of the areas adjoining the one to be reproduced. Connected to the main and supplementary outputs of the source is a busyness analyzer to generate busyness signals based on the tonal values of the given and adjacent areas.
There are also known adaptive screening methods, wherein half-tone dots are formed of elements obtained by dividing a copy (substrate) area corresponding to the original area to be reproduced (U.S. Pat. Nos. 4,675,831 and 4,698,691). The half-tone dot shape is specified here for all gradations by a distribution matrix of weight values for the elements in one or several spatial periods of the screen. The dot size and the surface area printed within such a period are defined while forming the image based on the tonal value of the original area to be reproduced, and the position of printed and nonprint
REFERENCES:
patent: 4675831 (1987-06-01), Ito
patent: 4698691 (1987-10-01), Suzuki
patent: 5034990 (1991-07-01), Klees
patent: 5051844 (1991-09-01), Sullivan
patent: 5229867 (1993-07-01), Ershov et al.
Grant II Jerome
Lee Thomas D.
LandOfFree
Method and device for adaptive screening of continuous tone orig does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and device for adaptive screening of continuous tone orig, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and device for adaptive screening of continuous tone orig will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-318837