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

IPC: G02F1/09 ,  G06K7/10

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.