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Photonic Servo Tracking on Magnetic Disk Files

IP.com Disclosure Number: IPCOM000046850D
Original Publication Date: 1983-Aug-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Schedewie, F: AUTHOR

Abstract

The high data density on modern magnetic disks necessitates that the head be accurately positioned. Optimum accuracy is obtained by positioning the servo tracks on the data disk rather than on a separate disk. The great problem with magnetically coded servo tracks in the vicinity of data tracks is crosstalk between the data signal channel and the servo signal channel. The two channels may be decoupled from each other by combining the magnetic coding of data with the optical or photonic coding of the servo tracks, using a photonic signal for controlling the head position. It is proposed to print colored servo tracks on top of the magnetic layer. Especially ink jets are used to print narrow tracks. By different periodical droplet sequences, the several tracks can be differently coded, using in particular fluorescent ink.

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Photonic Servo Tracking on Magnetic Disk Files

The high data density on modern magnetic disks necessitates that the head be accurately positioned. Optimum accuracy is obtained by positioning the servo tracks on the data disk rather than on a separate disk. The great problem with magnetically coded servo tracks in the vicinity of data tracks is crosstalk between the data signal channel and the servo signal channel. The two channels may be decoupled from each other by combining the magnetic coding of data with the optical or photonic coding of the servo tracks, using a photonic signal for controlling the head position. It is proposed to print colored servo tracks on top of the magnetic layer. Especially ink jets are used to print narrow tracks. By different periodical droplet sequences, the several tracks can be differently coded, using in particular fluorescent ink. Successive tracks may be coded in different ways, to distinguish a track from adjacent inner and outer tracks or to identify a particular track. Tracks may be coded as described below. a) Color coding Different tracks emit different colors either by backscattering or fluorescence produced by a common white

light or UV light source. b) Frequency coding Different tracks are coded by two or more different ink jet dot densities along the track. Suitable

filter circuits are included in the detector electronics. c) Digital coding The index or number of a track is printed in binary form and periodically repea...