Patent US 3,980,812

The invention contemplates an improved method of electronic-image analysis within a field of raster-scanned subject matter in which each scanning line lying within the boundaries of an object to be evaluated supplies by means of a discriminator a binary signal corresponding to the line length between object-boundary intercepts for the particular line. The improvement involves production of a localized search signal synchronized with raster scanning such that the search signal is effectively located within at least part of the scan-line coverage of the object. The search signal is used to control for each scan line the delay time of the binary signal of the same scan line, said delayed binary signal starting an output signal, the delay time of said binary signal being so controlled that it lies between a scan line period T.sub.1 and a minimum time T.sub.2 and depends upon the time interval between the start of said binary signal and of said output signal. The output signal in each following scan line is started by the delayed output signal of the foregoing scan line or the output signal of the line just scanned, depending upon which signal starts earlier. The binary signal of each scan line is also separately delayed by one scan line period in order to produce an anticoincidence pulse when the thus-delayed binary signal and instantaneously produced binary signal fail to overlap. Finally, an evaluation-output signal is produced upon observation of coincidence as between the output signal and the anticoincidence pulse.