Optical data storage.

摘要

A method of optical data storage is disclosed which comprises encoding data into a code of order M, where M is an integer of 3 or greater, and writing the encoded data onto a receptive optical data storage medium using a laser system capable of generating (M-1) distinguishable pits in the surface of the receptive optical data storage medium. With such a method, the resultant data storage medium contains M different states, these being the lands together with the (M-1) pit states. The invention may be practiced using a plurality of lasers in order to generate the (M-1) pit states; alternatively, a single adjustable laser may be employed, e.g. one in which the intensity and/or wavelength and/or polarisation state of the laser beam may be modulated. A writing system for effecting optical recordings is also disclosed, this sytem including a semi-conductor laser under control of an electronic circuit arranged to ensure that the current flowing through the semi-conductor laser is always greater than the threshold current at which light is emitted.