An optical data storage system comprises a multiple data surface medium and optical head, The medium comprises a plurality of substrates separated by a light transmissive medium. Data surfaces are located on the substrate surfaces which lie adjacent a light transmissive medium. The data surfaces are...http://www.google.com.au/patents/US5615186?utm_source=gb-gplus-sharePatent US5615186 - Multiple data surface data storage system with holographic filter element
