Faraday effect page composer for holographic memory system

Claim 2

In a holographic memory system in which a page composer modulates a plane polarized, coherent, monochromatic light beam to store in a holographic storage medium in conjunction with a reference beam a hologram of the data that is carried in the modulated beam, the method of modulating said beam comprising: forming a thin planar layer of magnetizable material having Faraday effect rotation of an incident plane polarized, coherent, monochromatic light beam; initially, uniformly magnetically orienting the magnetization vector M of said layer in a first magnetization direction normal to its plane surface; secondly, switching selected portions of said layer for magnetically orienting the magnetization vector M of said selected portions of said layer in a second magnetization direction, opposite to thE first magnetization direction of the remaining portion of said layer, normal to its plane surface; directing a plane polarized, coherent, monochromatic light beam along a first transmission axis normally incident to a planar surface of said layer; rotating in a first angular direction the plane of polarization of said incident light beam in the area of said layer whose magnetization vector M is oriented in said first magnetization direction; rotating in a second angular direction, opposite to said first angular direction, the plane of polarization of said incident light beam in the areas of said selected portions of said layer whose magnetization vector M is oriented in said second magnetization direction; orienting a planar mirror on the back side of said layer to deflect said light beam back through said layer and along said first transmission axis for further rotating the planes of polarization of said once rotated planes of polarization in like first or second angular directions; directing said selectively plane polarized light beam incident to an analyzer for transmitting therethrough substantially only those portions of said beam whose plane of polarization has been twice rotated in said second angular direction; forming a plurality of parallel beams whose plane of polarization has been twice rotated in said second direction and whose spatial distribution in a plane normal to their transmission axis conforms to the spatial distribution of said selected portions of said layer.

Claim 3

A holographic memory system including a selectively alterable page composer for modulating a plane polarized, coherent, monochromatic light beam and storing in a holographic storage medium a hologram of the data that is carried in the modulated beam, the system comprising: means for generating a coherent, monochromatic light beam; means for plane polarizing said beam long a first polarization axis; means for forming an object beam and a reference beam from said plane polarized beam; page composer means including a thin planar layer of magnetizable material having a Faraday effect rotation of an incident plane polarized, coherent, monochromatic light beam and means for: uniformly magnetically orienting the magnetization vector M of said layer in a first magnetization direction normal to its surface; and, switching selected portions of said layer for magnetically orienting the magnetization vector M of said selected portions of said layer in a second magnetization direction, opposite to the first magnetization direction of the remaining portion of said layer, normal to its surface; means for directing said object beam along a first transmission axis normally incident to said page composer for: rotating in a first angular direction the plane of polarization of said object beam that is incident to the area of said layer whose magnetization vector M is oriented in said first magnetization direction; and, rotating in a second angular direction, opposite to said first angular direction, the plane of polarization of said object beam that is incident to the areas of said selected portions of said layer whose magnetization vector M is oriented in said second magnetization direction; means oriented on the back side of said page composer to deflect said light beam back through said layer along said first transmission axis for further rotating the planes of polarization of said once rotated planes of polarization in like first or second angular directions; means for transmitting substantially only those portions of said beam whose plane of polarization has been twice rotated in said second angular direction and forming a plurality of parallel beams; means for concurrently directing said reference beam and said plurality of parallel beams upon a selected area of a holographic storage medium for storing therein a hologram of the data carried in said plurality of parallel beams.

Claim 4

A holographic memory system including a selectively alterable page composer for modulating a plane polarized, coherent, monochromatic light beam and storing in a holographic storage medium a hologram of the data that is carried in the modulated beam, the system comprising: means for generating a coherent, monochromatic light beam; means for plane polarizing said beam long a first polarization axis; means for forming an object beam and a reference beam from said plane polarized beam; page composer means including a thin planar layer of magnetizable material having a Faraday effect rotation of an incident plane polarized, coherent, monochromatic light beam and means for: uniformly magnetically orienting the magnetization vector M of said layer in a first magnetization direction normal to its surface; and, switching selected portions of said layer for magnetically orienting the magnetization vector M of said selected portions of said layer in a second magnetization direction, opposite to the first magnetization direction of the remaining portion of said layer, normal to its surface; means for directing said object beam along a first transmission axis normally incident to said page composer for: rotating in a first angular direction the plane of polarization of said object beam that is incident to the area of said layer whose magnetization vector M is oriented in said first magnetization direction; and, rotating in a second angular direction, opposite to said first angular direction, the plane of polarization of said object beam that is incident to the areas of said selected portions of said layer whose magnetization vector M is oriented in said second magnetization direction; means oriented on the back side of said page composer to deflect said light beam back through said layer along said first transmission axis for further rotating the planes of polarization of said once rotated planes of polarization in like first or second angular directions; means for transmitting substantially only those portions of said beam whose plane of polarization has been twice rotated in said second angular direction and forming a plurality of parallel beams; means for concurrently directing said reference beam and said plurality of parallel beams upon a selected area of a holographic storage medium for storing therein a hologram of the data carried in said plurality of parallel beams.