Browse Prior Art Database

Optical or Capacitive Digital Servos for Record Members

IP.com Disclosure Number: IPCOM000087486D
Original Publication Date: 1977-Feb-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 3 page(s) / 43K

Publishing Venue

IBM

Related People

Cannon, MR: AUTHOR

Abstract

In many digital data record members, so-called sector servos are used for track location and track following purposes. A sector servo is a servo pattern that is interleaved among data signals for enabling time sampled head positioning. Such sector servo signals occupy substantial portions of the record medium area, thereby reducing the data capacity of the record storage disk. A way to obviate the reduction of storage capacity, in media having high linear densities, is to employ optical patterns on the surface of the record storage disk. Such optical patterns may have a thickness typically of 4 microinches and can be constructed by electroless plating on the record surface followed by selective chemical milling or etching.

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Optical or Capacitive Digital Servos for Record Members

In many digital data record members, so-called sector servos are used for track location and track following purposes. A sector servo is a servo pattern that is interleaved among data signals for enabling time sampled head positioning. Such sector servo signals occupy substantial portions of the record medium area, thereby reducing the data capacity of the record storage disk. A way to obviate the reduction of storage capacity, in media having high linear densities, is to employ optical patterns on the surface of the record storage disk. Such optical patterns may have a thickness typically of 4 microinches and can be constructed by electroless plating on the record surface followed by selective chemical milling or etching.

It is preferred that such optical patterns provide good contrast with the medium coating, such as ferrous oxide or chromium dioxide. For stability purposes the optical material should include vanadium or titanium. Alternatively, the optical patterns may be disposed in a guardband area intermediate adjacent data tracks, resulting in no degradation of the magnetic signal during readback operations because of the additional separation between head and medium caused by the optical patterns. There would also be no degradation in capacity.

Independence between magnetic and optical signals enables full use of the servo patterns during either erase, write or read. Accuracy is limited only by the photolithographic techniques employed. Further, the optical patterns can include address information for enabling absolute addressing of any of the tracks on the record storage disk. This addressing enables good error recovery procedures not found in indexed head seeked storage apparatus. The photolithographically produced metallic patterns provide a continuous servo signal multiplexed with continuous data transfer. This is preferable to the inter...