Patent ID: 7697404

Claim:
An optical data storage medium, the medium comprising: a substrate configured to transmit a radiation beam with a first index of refraction and wherein the radiation beam has a specified wavelength; a first data surface configured to store digital data, the first data surface transmitting the radiation beam and having a land portion with pits of a specified pit depth disposed on the land portion, wherein the pit depth is the perpendicular distance between the plane of the land portion and the base of the pit; a second data surface configured to store digital data, the second data surface having a land portion with pits of the pit depth disposed on the land portion; and a spacer layer configured to maintain a spacing distance between the first and second data surfaces and to transmit the radiation beam with a second index of refraction such that the radiation beam passes through the substrate and focuses on either the first or second data surfaces, wherein the pit depth is substantially equal to the radiation beam wavelength divided by four times the average of the first and second indexes of refraction.