Duplication process for video recording track - has coherent light projected through master track on to photosensitive track

摘要

A process is ued to duplicate information recorded on a track. The information of the track is stored in micro-elements providing variations of the track thickness. The process can use micro-densities of 105 points per square millimetre and is not sensitive to dust. The duplication is by means of a contactless method. The process consists of projecting a coherent light source (S) on a micro-element (P) of the track to be duplicated. It also uses a lens (L) to produce a beam on the phase modulated track (P). A photosensitive track (M) is placed parallel to the track (P). The photosensitive track (M) receives interference bands transmitted by the micro-elements (P). The photosensitive track (M) is then subjected to a chemical treatment to obtain local variations of light transmission.