George Churchill Kenney

Bit oriented optical storage with thin tellurium films

We discuss here some of the basic issues involved in the development of an optical storage medium based on the laser micromachining of thin tellurium films. Results are presented in the areas of recording sensitivity, materials resolution, error statistics, and archival stability. It is shown that a medium using 20–30 nm of tellurium deposited on polymethyl methacrylate substrates is an extremely attractive choice.

Digital Optical Recorders At 5 Mbit/S Data Rate

Five optical disk recorder/readers were developed, each having an on-line user storage capacity of 101° user bits per disk side. The advantages of optical recording, as compared to magnetic-tape recording, are improved archival life, low cost media, and rapid random access capabilities. Recording at a 5 Mbit/s user data rate is done by laser machining of micron-sized holes in a thin tellurium alloy film allowing direct-read-after-write recording of information. Coding and error correction reduce the user error rate to 10-1°. The recorders have been interfaced to DEC PDP-11 minicomputers and for test purposes to a SEL 32/77 computer.

High Density Optical Recording Cartridge

For high density optical recording requiring a high numerical aperture objective, it has been found that substrate incident recording suffers from spherical aberration because of substrate thickness variations. To overcome this problem a novel protective cartridge-enclosed disc has been developed which provides the advantages of air incident recording without the presence of spherical aberration. This cartridge protects the disc from atmospheric dust and virtually eliminates the possibility of internal dust generation both during operation and during storage. In addition, all components, including dust seals, have an expected life of at least 10 years. Key optical and mechanical considerations are discussed as well as experimental results obtained from an operational prototype.

An Optical Disc Data Recorder

We discuss the development of an optical disc recorder with an on-line storage capacity of 1010 bits. Recording is done by laser machining of micro-sized pits in a thin tellurium film allowing direct-read-after-writing (DRAW) of the information. The recording format maps each bit of information to a recorded pit. The tellurium is deposited on a clear plastic disc configured to be self-protecting and easily handled. A major program objective was to demonstrate the feasibility of an inexpensive recorder and disc.