U.S. Philips Corporation

Pieter Homan

Ulf Rothgordt

Raymond G Schayes

In facsimile transmission the sequences of picture elements having the same luminance are transmitted in coded form. The code words have, in general, different lengths and no ambiguous beginning or end marking respectively. Consequently, in case of a disturbance during the transmission not only the luminance values are generally falsified but also the plurality of successive picture elements so that in situ of the receipt picture lines appear which are too long or too short. In accordance with the invention it is now proposed in the case of a picture line which was received in a disturbed manner to compare it to one or both adjacent picture lines respectively, to take-over the portions having an adequate correlation, and, as regards the place of the disturbed portion to shift the end of the disturbed picture line in such a way that the definite line gets the prescribed length and to replace the portions of insufficient correlation by the corresponding information of one of the two adjacent picture lines. This comparison can be done relative to the two ends of the disturbed picture line. It is particularly favorable for the comparison that the picture elements of each picture line are grouped in equal groups and to check if the ratio of the number of, for example, black picture elements having a corresponding position in adjacent lines relative to the total number of black elements in the groups of the two lines together, remains below a given threshold value (decorrelation).

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Hilversum, Netherlands

Pieter Homan