Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1979-06-11
1983-01-18
Martin, John C.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
H04N 521
Patent
active
043694659
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
Our present invention relates to a process and a device for suppressing interferences from spurious signals in a display system wherein pictures are composed of electronically generated image points in the form of luminous dots of different brightness.
BACKGROUND OF THE INVENTION
In such display systems, the pictures are defined on a viewing screen by an assembly of dots projected thereon by an electron beam whose intensity is controlled by a luminance signal of variable level. With television-type screen scanning for example, the location of a dot is given by an address P(i,j) in which i represents the order of a scanning line and j the position of the considered dot in that line. Associated with each impage point P(i,j) is a luminance signal of level S(i,j) normally specifying the brightness of a dot of given dimensions known in the art by the term "pixel".
The pictures obtained in this type of display system are subject to certain defects due to the existence of spurious phenomena interfering with the luminance signals. Known techniques permit the elimination of certain image defects if the latter are identified without ambiguity, that is to say in practice if their level is invariable and known. This is for example the case with mono-ionic or ionizing-particle noise in an image-intensifying-tube circuit and with interferences producing a black or a white dot in a vidicon tube. These techniques utilize the prior knowledge of the shape of the curve of the luminance histogram of the picture, the curve showing along the ordinate the number of dots of a given brightness level. The conventional way of interference suppression consists in replacing the luminance signal of any dot whose level is equal to or higher than the level of the interfering signal by a signal of the most probable level of the picture. This process is the more effective the narrower the histogram, i.e. the smaller the typical deviation of the number of dots along the curve from a peak representing the most probable brightness level. Still, there are drawbacks in particular if the interferences to be eliminated are in a range of very improbable levels. These dots consequently carry a great amount of information, in the statistical sense of the term, and their suppression results in a loss of overall information. This loss of information can only be evaluated with knowledge of the subjective degree of interest shown by the observer for the information conveyed by the image points subjected to this leveling procedure. Thus, if the level of the luminance signal of the spot to be eliminated is in the domain of brightness of the particular details looked for in the picture by the observer, the elimination of these levels by the aformentioned process in fact renders the corrected picture irrelevant.
OBJECT OF THE INVENTION
The object of our present invention is to provide an interference-suppressing process and device obviating the drawbacks referred to.
SUMMARY OF THE INVENTION
A process according to our invention, designed to suppress interferences in the display of a picture whose image points are electronically generated luminous dots projected onto a viewing screen such as that of a cathode-ray tube in a predetermined pattern of consecutive line scans, involves a comparison of two luminance signals whose levels determine the brightness of a given image point P(i,j) and of at least one adjacent image point P(i-k,j-p) where i indicates the order number of a scanning line and j indicates the dot position in that line. Thus, in a first step of our process, a luminance signal S(i,j) pertaining to image point P(i,j) is compared with a luminance signal S(i-k,j-p) pertaining to an adjacent image point or dot; the level of signal S(i-k,j-p) could also be the mean of the levels of luminance signals pertaining to several such adjacent dots. In order to define an adjacent dot, indices k and p may have any of the values +1, 0 and -1 except that, of course, the case k=p=0 must be excluded.
If the comparison reveals a lev
REFERENCES:
patent: 3979555 (1976-09-01), Opittek
patent: 3983320 (1976-09-01), Ketcham et al.
Blamoutier Michel
Fraleux Jean
"Thomson-CSF"
Martin John C.
Ross Karl F.
LandOfFree
Process and device for suppressing interferences in a picture co does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process and device for suppressing interferences in a picture co, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process and device for suppressing interferences in a picture co will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-139359