Optical Readout of Videodisc

At first sight optical readout of videosignal stored on a disc seems to be a difficult and critical task due to what is paradoxically one of its most interesting features: no mechanical contact between the readout "stylus" and the information carrying surface of the disc. Since the readout "stylus" used here is a light beam, it cannot be simply mechanically guided by a groove, the way it is accomplished, for example with conventional audio records.