A computer memory system is disclosed which includes a randomly and electrically accessible semiconductor "page" memory. The semiconductor page memory is conventional to the extent that it includes a planar array of electrically-accessible flip-flops for storing a corresponding number of binary information bits. In addition, each flip-flop is provided with a photosensor by which the flip-flop can be set in response to received light, and is provided with a light valve controlled by the state of the flip-flop. A laser light source, a light deflector and holographic optics are provided to create a hologram of the array of light valves at any one of many small areas on an erasable holographic storage medium. Subsequently, the hologram can be illuminated to recreate and project the image of the array of light valves onto the array of photosensors to return the information to the flip-flops in the semiconductor page memory. In this way, the semiconductor page memory serves as a page-at-a-time electrical input-output unit for a great many pages of information stored optically on the erasable holographic storage medium.
An electronic memory device is disclosed which utilizes silicon-on-sapphire SOS) transistors that exhibit binary states dependent upon the dose of ionizing radiation to which they are subjected. A memory utilizing such SOS transistors may have information written into it, permenently or for a short period of time, by electron-beam bombardment so that the memory operates as a PROM. The memory may also operate as a RAM when a scanning electron beam, in conjunction with appropriately applied biases, is used to read and write information at a high rate.
An electrically and optically accessible memory is disclosed in which binary information is stored in a holographic storage medium with a relatively high packing density by an organization in which lenses are eliminated and corner reflectors are used. A laser beam is directed to an illumination hologram to illuminate an array of controllable corner reflectors each of which reflects to represent a "1" and does not reflect to represent a "O". The reflected light returns as an object beam through the illumination hologram to the storage medium, where it interferes with laser light transmitted through the illumination hologram as a reference beam to form a hologram in the storage medium. The stored information is read out by directing the laser beam through the illumination hologram to the storage medium as a reference beam to cause the stored hologram to be read out through the illumination hologram to photosensors associated with the corner reflectors.
The invention provides a non-linear projection system, which includes a variable acuity non-linear holographic optical element (HOE), and an apparatus for creating the HOE. The projection system comprises a computer, a light valve which projects images generated by the computer, a lens train for focusing the images projected by the light valve, an HOE for the non-linear refraction of the focused images and a hemispherical viewing screen. The system additionally provides means for maintaining the center of the projected images in alignment with center of the field of view of an observer. The variation of the pixel size and spacing created by the system matches the variation of the human visual acuity of the observer permitting a realistic view to be presented while requiring a minimum of computer data to be generated and projected. The apparatus for creating the HOE utilizes a laser beam, three lens trains and a holographic recording medium. A procedure for utilizing the apparatus to record the HOE over a large portion of its surface area is also disclosed.
