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Optical Disk Data Storage

IP.com Disclosure Number: IPCOM000131512D
Original Publication Date: 1982-Jul-01
Included in the Prior Art Database: 2005-Nov-11
Document File: 5 page(s) / 22K

Publishing Venue

Software Patent Institute

Related People

Richard F. Kenville: AUTHOR [+3]

Abstract

The deterioration-resistant optical disk, with its capacity for high-density data storage, could become the preferred digital recording medium of the future. Adapted from a paper originally published in Digest of Papers, Compcon Spring 82, pp. 288-292. Today s laser-ablated metal-film optical disks could be the digital data storage system of the future. They are made of materials that can be stored for many years without stringent environmental controls, and because diffraction- limited optical systems in combination with disks have high storage densities, they promise a lower cost per bit than any other medium.

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THIS DOCUMENT IS AN APPROXIMATE REPRESENTATION OF THE ORIGINAL.

This record contains textual material that is copyright ©; 1982 by the Institute of Electrical and Electronics Engineers, Inc. All rights reserved. Contact the IEEE Computer Society http://www.computer.org/ (714-821-8380) for copies of the complete work that was the source of this textual material and for all use beyond that as a record from the SPI Database.

Optical Disk Data Storage

Richard F. Kenville,

RCA

The deterioration-resistant optical disk, with its capacity for high-density data storage, could become the preferred digital recording medium of the future.

Adapted from a paper originally published in Digest of Papers, Compcon Spring 82, pp. 288- 292.

Today s laser-ablated metal-film optical disks could be the digital data storage system of the future. They are made of materials that can be stored for many years without stringent environmental controls, and because diffraction- limited optical systems in combination with disks have high storage densities, they promise a lower cost per bit than any other medium.

RCA has recently completed two systems that establish the feasibility of optical disks as a high data-rate digital recording medium. The results of these programs are being used to design operational data storage hardware. The systems can record 5 x 10~ bits of data on one side of an optical disk at rates exceeding 1 00M bits per second. They have provided a bit error rate of one in 108 and can access any block of data in less than 0.5 seconds. To achieve these results multiple laser spots were focused into a 0.4-pm diameter at half power and spaced on 1.25-pm centers. The disk's aerial density of 109 bits per square inch is an order of magniture greater than the generally accepted limit in magnetic recording of 108 bits per square inch.

The RCA optical disk system

The RCA system focuses a modulated laser beam onto a rotating disk, ablating the thin metal surface to form a series of "pits" in concentric tracks. This permanently stored information can be read out by lowering the laser power to inhibit ablation, removing the modulation, and sensing the reflected light from the disk's surface.

The system uses three servo controls. One keeps the laser beam focused on a diffraction- limited spot on the

disk when the surface is uneven. A track servo follows recorded tracks during readout, even when they are imperfectly centered. A motor servo maintains a constant disk speed to record and play back at a fixed data rate.

The data path.

As illustrated in Figure I, user data is fed into the input buffer, which allows it to flow into the system continuously and be transmitted for additional overhead information on demand. Data from the input buffer goes to the record formatters in bursts called subblocks, each of which passes through an error detection and correction encoder that adds parity bits for error protection during playback. The record formatter then group...