Recording and reproduction of video data - using digital, phase modulated and amplitude modulated signals with modulated laser beams carrying additional information

摘要

To avoid the necessary summation and subsequent decoding of contrast and colour information for video recording, laser beams are modulated to carry the additional information. The main contrast information provides one of three discrete inputs to the video recorder. After analogue to digital conversion it switches five laser beams to record a five bit code on tape in the form of perforations. The second analogue signal deflects the five beams in line with tape movement and the third analogue signal amplitude-modulates the five beams. This has the effect of altering the width of the beams. Five laser beams are again used for reproduction. They are sensed by photodiodes. The three sources of information are recovered in the form of digital, pulse phase modulated and pulse amplitude modulated signals respectively.