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Optical Position Signal for Magnetic Recording Head in a Disk File

IP.com Disclosure Number: IPCOM000040504D
Original Publication Date: 1987-Nov-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Beeken, PB: AUTHOR

Abstract

Precise positioning of a recording head slider over the recording medium track can be obtained by a servo system using a patterned disk and a modified air bearing slider. The slider is modified by adding a small lens much like those used for optical fiber couplers on its back. A small laser or light-emitting diode is then passed through a beam splitter, illuminating the lens. Light is then focused onto the disk surface which reflects some of the light back through the lens. The reflected beam then passes through the beam splitter and is imaged onto a photodetector. As the disk spins, variations in reflectivity due to the inscribed pattern are read by the photodetector and translated into electrical pulses.

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Optical Position Signal for Magnetic Recording Head in a Disk File

Precise positioning of a recording head slider over the recording medium track can be obtained by a servo system using a patterned disk and a modified air bearing slider. The slider is modified by adding a small lens much like those used for optical fiber couplers on its back. A small laser or light-emitting diode is then passed through a beam splitter, illuminating the lens. Light is then focused onto the disk surface which reflects some of the light back through the lens. The reflected beam then passes through the beam splitter and is imaged onto a photodetector. As the disk spins, variations in reflectivity due to the inscribed pattern are read by the photodetector and translated into electrical pulses. Depending on the type of mask used (usually a chevron pattern with a coded sequence at the start of each track), accurate position information can be made available to a servo controller for positioning the air bearing slider.

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