International Business Machines Corporation

Terry W McDaniel

Kurt A Rubin

Blair I Finkelstein

Hal Jervis Rosen

Timothy Carl Strand

Andrew A Gaudet

Hal A Rosen

Harris Anthony Notarys

An optical data storage system comprises an optical disk drive and a multiple data surface magneto-optical medium. The medium comprises a substrate, a first dielectric layer, a first magneto-optical data layer, a second dielectric layer, a transmissive member, a third dielectric layer, a second magneto-optical data layer, a fourth dielectric layer, and a reflector layer. The thicknesses of the magneto-optical and dielectric layers are selected to maximize the magneto-optical read out signal received from the data layers. The disk drive includes a phase retarder for improving the signal from the magneto-optical data layers.

Multiple data surface magneto-optical data storage system

A magnetooptical disk has two axially space-apart translucent recording layers. Each translucent recording layer is axially closer to an outer surface of the disk than to the other recording layer. This geometry enables closely axially disposing a magnetic field biasing means to each of the recording layers from opposite axial sides of the disk, respectively. Laser beams are axially introduced into the disk to pass through one of the translucent recording layers in a defocussed state to reach a second recording layer in a focussed state. In this manner, recording in the second layer is effected by a modulated magnetic bias field using a constant intensity laser beam. Two sets of laser beams and magnetic biasing means are provided for recording on both data in both of the recording layers.

Optical disk recorders using disks coatings close to outer surfaces with

Two-sided optical disks having recording layers disposed close to outer

A laser in a magneto optical recorder supplies a laser light beam to be used in processing signals to and from a magneto optical record member. The laser beam is split into two portions. A first portion is the data beam which is directed to impinge upon a magnetooptic storage member. A second portion is so-called wasted light which is directed away from the storage member. The wasted light is intercepted by a mirror and reflected into a beam splitter to phase-coherently combine with light reflected from the storage member for improving signal-to-noise ratio of the reflected storage member light beam. This action improves signal-to-noise ratio and enhances servo operation in the focusing position control of the optical head with respect to an optical storage medium. The focus control signal derived from the reflected light is not only used to control the focus of an objective lens in the system but also for positioning the mirror in synchronism with the movement of the storage member along the axis of the objective lens so that the phase-coherence of the wasted light beam and the data beam is maintained.

Utilizing wasted laser light in optical systems

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Morgan Hill, CA, United States of America

Terry W McDaniel