Browse Prior Art Database

Optical Readout for Magnetic Memory

IP.com Disclosure Number: IPCOM000096712D
Original Publication Date: 1963-Sep-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Barrekette, ES: AUTHOR [+2]

Abstract

This improves the signal to noise ratio, and therefore the bit discrimination, when using the Kerr effect to obtain nondestructive optical readout of a magnetic record. Magnetic drum 10 has magnetic spots 12 and non magnetic spots 14, i. e., there is no magnetic material on spots 14.

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Optical Readout for Magnetic Memory

This improves the signal to noise ratio, and therefore the bit discrimination, when using the Kerr effect to obtain nondestructive optical readout of a magnetic record. Magnetic drum 10 has magnetic spots 12 and non magnetic spots 14, i.
e., there is no magnetic material on spots 14.

Assume, e. g., that a magnetic spot represents a 1 bit and a nonmagnetic spot a 0 bit. The drum is placed in a high frequency magnetic field of frequency F created by electromagnet 16. Electrical energy of frequency F is applied to the electromagnet by signal source 18. The magnetic field causes the magnetization of magnetic spots 12 to oscillate at frequency F.

A light beam generated by light source 20 is applied through polarizer 22 and image lens 24 to the surface of drum 10. The light beam is reflected from the surface of drum 10 through collecting lens 26 and analyzer 28 onto photomultiplier tube 30. When the polarized light beam is reflected by non magnetic spot 14, there is DC output level from tube 30 which is blocked by band pass filter 32. However, when the polarized light beam is reflected by magnetic spot 12, the AC variation in the magnetization of the spot, causes a corresponding AC variation in the polarization of the light beam. The resulting output signal from tube 30 has an AC variation of frequency F superimposed on it. This signal is passed by filter 32 resulting in an output signal indicating that a 1 bit is detected.

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