MULTIPLE DATA SURFACE OPTICAL MEDIUM AND STORAGE SYSTEM

摘要

The optical data storage system comprises an optical medium comprising two spaced-apart substrates having the same material thickness, each substrate having a data layer. At least one of the substrates has a data layer which is at least partially transmissive. A light source is located near a first one of the substrates. A device directs light from the source to the medium, and includes a device for focusing the light to a discrete number of focusing positions. Each position defines an optical path between the light source and a corresponding one of the data layers. Each of the two optical paths includes a passage through substrate material having a total thickness equal to three substrate thicknesses.