Patent ID: 6341120
Filing Date: 2002-01-22
Classification: G11B

Abstract:
A three-dimensional optical memory, comprising:a recording medium, including a plurality of layers in a thickness direction thereof; a plurality of recording surfaces respectively formed on said layers, the recording surfaces each having data recording tracks; sample servo marks, onto which an optical beam is focused, provided respectively on said recording surfaces, wherein said sample servo marks each have at least two mark portions, wherein the at least two mark portions are arranged in a zig-zag manner in the thickness direction of said recording medium, thereby interposing one of said data recording tracks, wherein a difference in positions of the at least two mark portions in the thickness direction of the recording medium is set larger than a focus depth of the optical beam which is emitted from an optical head, and wherein said recording surfaces have a plurality of indication marks which are unique for each recording surface, and at least one of the indication marks is provided in close proximity to each of the sample servo marks on said data recording tracks.