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Browse Prior Art Database

Optical Transducer System

IP.com Disclosure Number: IPCOM000090196D
Original Publication Date: 1969-Mar-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

Alstad, JK: AUTHOR [+2]

Abstract

This system reads data from a record media. Transducer 1 consists of transparent substrate 2 and a substantially transparent, nonreflecting ferromagnetic film 3 coated on such substrate. Film 3 can be composed of, for example, garnet, magnetic glass, or of very thin magnetic metal or alloy. Substrate 2 is preferably of nonplanar configuration to encourage total internal reflection TIR of light and to control refraction effects on light entering and leaving transducer 1. When the magnetic portion of transducer 1 is placed in magneto-coupled relation with record medium 4 containing data, the latter is transferred to transducer 1 and remains there even after media 4 is moved out of coupled relation.

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Optical Transducer System

This system reads data from a record media. Transducer 1 consists of transparent substrate 2 and a substantially transparent, nonreflecting ferromagnetic film 3 coated on such substrate. Film 3 can be composed of, for example, garnet, magnetic glass, or of very thin magnetic metal or alloy. Substrate 2 is preferably of nonplanar configuration to encourage total internal reflection TIR of light and to control refraction effects on light entering and leaving transducer 1. When the magnetic portion of transducer 1 is placed in magneto- coupled relation with record medium 4 containing data, the latter is transferred to transducer 1 and remains there even after media 4 is moved out of coupled relation. Magnetic transfer is facilitated by medium 4 being of higher coercivity than the magnetic film on transducer 1 or by the use of an external idealizing field.

Light source 5 is positioned to direct light rays through circularly polarizing device 6 and then into substrate 2 of transducer 1. The angle of incidence of the light rays with film 3 of transducer 1 is selected in accordance with Snell's Law so that it is greater than the angle of TIR for, for example, positive circularly polarized light, but less than the angle of TIR for negative circularly polarized light. The critical angle for TIR can thus be varied by varying the direction of the magnetic field of film 3 in the longitudinal direction. Therefore, the sense of the magnetic data trans...