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Holographic Store Using Noncoherent GaAs Injection Lasers

IP.com Disclosure Number: IPCOM000090331D
Original Publication Date: 1969-Apr-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Gamblin, RL: AUTHOR

Abstract

Because of their general characteristics, GaAs diodes are suited for use in intermediate size holographic stores in spite of their limited spatial coherence. This holographic store system employs an array of GaAs laser diodes that, by switches not shown, are selectively activated for reading information from selected areas of a hologram plate by directing the activated laser beam through a discrete area of the hologram plate and onto an array of receiving photodiodes. One of the requirements of the system is that the GaAs diode center spacing be geometrically similar to the center spacing of the hologram plate.

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Holographic Store Using Noncoherent GaAs Injection Lasers

Because of their general characteristics, GaAs diodes are suited for use in intermediate size holographic stores in spite of their limited spatial coherence. This holographic store system employs an array of GaAs laser diodes that, by switches not shown, are selectively activated for reading information from selected areas of a hologram plate by directing the activated laser beam through a discrete area of the hologram plate and onto an array of receiving photodiodes. One of the requirements of the system is that the GaAs diode center spacing be geometrically similar to the center spacing of the hologram plate.

Between the GaAs array and the hologram Plate is an optical system consisting of lenses L1 and L2, having focal lengths of f1 and f2 respectively, and an aperture located between the lenses. The components of the system are spatially oriented as shown. The aperture is selected to be the same diameter d as that chosen for the hologram. Light from the laser diodes is focused at the back focal plane of lens L2 providing plane parallel converging beams that are directed upon the receiving photodiode array. The latter is placed as close to the hologram plate as is consistent with the spatial frequency of 1000 lines/mm or less and with no overlapping in the zero order beams.

The width of the diode l determines the power output of an individual diode but l/f1 determines the spatial coherence of the hologra...