Browse Prior Art Database

Optical Servo Information on Magnetic Recording Disks

IP.com Disclosure Number: IPCOM000079784D
Original Publication Date: 1973-Sep-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Schneider, J: AUTHOR

Abstract

Magnetic disk production is accomplished by preparing a substrate which bears the magnetic recording layer. Before depositing the magnetic layer, the substrate is processed on the lathe for superfinishing the surface. The inconvenience of this process is that turning marks protrude from the surface of the substrate in the form of a spiral, from an inner to an outer radius of the turned area.

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Optical Servo Information on Magnetic Recording Disks

Magnetic disk production is accomplished by preparing a substrate which bears the magnetic recording layer. Before depositing the magnetic layer, the substrate is processed on the lathe for superfinishing the surface. The inconvenience of this process is that turning marks protrude from the surface of the substrate in the form of a spiral, from an inner to an outer radius of the turned area.

A cross section of magnetic disk configuration 6 shows a substrate 7 of aluminum, which is coated by a layer 8 of magnetic recording material. Layer 8 also covers cams 9 of the turning marks, limiting areas 12 that form a spiral of a data track from an inner to an outer radius of the magnetic disk surface.

Cams 9 are optically sensed for getting the servo information which guides magnetic head 3 over data track 12. Head slider 1 is supported by access arm 2. A first light beam 10a travels from a first laser 5a to an edge of a cam beside the data track, which reflects light beam 11a to a first photodiode 4a mounted in the head slider. A second light beam 10b travels from a second laser 5b to an edge of the other cam beside the data track, which reflects a light beam 11b to a second photodiode 4b mounted in the slider. Deviations of magnetic head 3 from the center of a data track 12 are detected by photodiodes 4a and 4b, which produce signal differences corresponding to track deviations of magnetic head 3.

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