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公开(公告)号：DE1807486A1
公开(公告)日：1969-06-04
申请号：DE1807486
申请日：1968-11-07
Applicant: IBM
Inventor： EDWARD MCDONALD RONALD , DENIS MEE CHARLES , VOEGELI OTTO
Abstract: 1,223,916. Magnetic store read out arrangements. INTERNATIONAL BUSINESS MACHINES CORP. 1 Nov., 1968 [9 Nov., 1967], No. 51903/68. Heading H3B. In a read out arrangement for a magnetic store comprising a transparent plate 12 of magneto optical material, such as a garnet, in which remanent magnetic states as shown by arrows 14 are established in discrete zones 13 to represent digital information, a plane polarized light beam 10 from a source 11 is converted by the zone through which it passes into an elliptically polarized beam 10a having a direction of polarization (shown at 16 and 17 in Figs. 1 and 2 respectively) determined by the direction of zone magnetization, the polarization direction, and hence the magnetic direction of the zone, being identified by a detector 20. The detector comprises a compensator 21 which converts elliptical polarization 16, 17 to circular polarization 26a, 26b, followed by a quarter wave plate 22 which converts circular polarization to plane polarization, the orientation of plane polarization 28a, 28b being determined by the direction of circular polarization 16, 17. One orientation of plane polarization is rejected by an analyser 24, so that a light beam is detected by a photo-electric cell 25 only when the magnetic state of the zone in the light path is in a particular one of its two possible directions. The compensator 21 may selectively absorb a plane polarized component of the elliptically polarized light or may be a Babinet or solid compensator.
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公开(公告)号：DE1524875A1
公开(公告)日：1970-10-22
申请号：DEJ0034948
申请日：1967-11-02
Applicant: IBM
Inventor： DENIS MEE CHARLES , EDWARD MAC DONALD RONALD , VOEGELI OTTO
IPC: G11B11/105 , G11C11/14
Abstract: 1,133,919. Magneto-optical data storage. INTERNATIONAL BUSINESS MACHINES CORP. 19 Oct., 1967 [10 Nov., 1966], No. 47554/67. Heading H3B. Data stored in a magnetic garnet thin film is read by directing a beam of polarized light, having a wavelength less than 5000 A, on to the storage location and detecting changes in the polarization of the beam caused by the stored data. The film preferably consists of gadolinium iron garnet, less than 2 microns thick, and preferably 0À2 micron thick, mounted on a transparent substrate. The film is maintained at its compensation temperature in a magnetic field which is incapable of switching the magnetization direction of any part of the film at the compensation temperature. To store data polarized light, e.g. from a zinc oxide laser or from a gallium arsenide laser associated with a frequency doubler, is directed on to a selected region of the film by means of an optical deflector, and raises the temperature of this region. The magnetic field is then sufficient to switch the magnetization in this region to store a " 1," for example. If a " 0 " is to be stored either the light beam or the magnetic field is suppressed, or the field is reversed. During read out the magnetic field is switched off and the film is scanned more rapidly to reduce to heating of the storage sites. The reading process may utilize either the Faraday effect, whereby the plane of polarization of the beam is rotated, or the circular dichroism of the film, whereby one of the circularly polarized components of the incident beam is absorbed more than the other, depending on the direction of the remanent magnetization in the storage region.
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