Medium for recording digital information using an array of equally

Abstract

A digital recording medium formed of a thermoplastic substrate having an array of parallel rows of equally-spaced microscopic optically-alterable mirrors each supported by a mesa projecting from one surface. A layer of transparent plastic over the mirrors provides dust protection. The medium can be formed also from a single transparent thermoplastic substrate with an array of indentations in a first surface. The bottom of each indentation is coated with a reflective material. When viewed from the opposite surface of the substrate, the indentations become mesas. The micromirrors are formed of a composite of gold and silicon dioxide. Recording is by exposure to a laser beam that reduces the reflectivity of selected mirrors. After exposure to the recording laser beam, the mirrors retain enough reflectivity to be distinguishable from the intervening valleys. The mirrors serve as timing and tracking markers prior to and during recording, and during read-out. The area and location of each information bit is determined prior to recording: not as a result of the recording process. Scanning may be accomplished by reciprocating movement of the medium.