Optical data storage apparatus and method

Claim 1

An optical data storage apparatus for storing and retrieving digital information, comprising an optical data disc having a substrate whose surface defines a plurality of data-storage positions, a stable-resonator laser having a resonator cavity, for use in producing a coherent output light beam, means for focusing said output beam onto the surface of said disc, at each data-storage position on the surface of said substrate, reflecting means effective to reflect the focused coherent beam, when said beam is directed against said position, from a selected one of 2 N submicron displacement distances normal to the surface of the substrate, where N is an integer greater than 2, corresponding to a selected one of 2 N bits of information, back into the laser cavity, means for moving the focused output beam relative to the disc surface to selected data-storage positions thereon, at successive, known times, means for measuring the power of said output beam, as the focused primary beam is moved to such selected sites, and means operatively connected to said moving means and said measuring means for converting time-dependent changes in the measured power of said output beam to position-dependent displacement distances at the selected data-storage sites, for determining the selected one of the 2 N bits stored at each such site.

Claim 13

A method of retrieving digital information, comprising directing a focused laser beam onto the surface of an optical data disc whose surface defines (i) a plurality of data-storage positions, and (ii) at each such position, one of 2 N submicron displacement distances normal to the surface of the substrate, where N is an integer greater than 2, corresponding to a selected one of 2 N bits of information, moving the focused beam relative to the disc to a selected data-storage positions on the disc, at each such position, back reflecting at least a portion of the laser beam reflected from such positions, measuring the power of said output beam, as the focused primary beam is moved to each such selected position, and converting the measured power of said output beam at the selected data-storage positions to one of 2 N bits of information at that position.

Claim 14

A method of retrieving digital information, comprising directing a focused laser beam onto the surface of an optical data disc whose surface defines (i) a plurality of data-storage positions, and (ii) at each such position, one of 2 N submicron displacement distances normal to the surface of the substrate, where N is an integer greater than 2, corresponding to a selected one of 2 N bits of information, moving the focused beam relative to the disc to a selected data-storage positions on the disc, at each such position, back reflecting at least a portion of the laser beam reflected from such positions, measuring the power of said output beam, as the focused primary beam is moved to each such selected position, and converting the measured power of said output beam at the selected data-storage positions to one of 2 N bits of information at that position.