Mitsuhito Sakaguchi

A New Associative Memory System Utilizing Holography

A new associative memory utilizing holography is described, which has advantages such as higher density and larger capacity storage, simpler peripheral devices, and reciprocal translation between different kinds of information. The advantages of the holographic associative memory were achieved by use of associative translation function of a hologram and spatial logical operations. Two types of the holographic associative memory are explained; one uses a thin hologram, and the other a thick hologram. In the latter case, the ultimate bit density of 107bits/cm2is expected. A preliminary experiment of the memory system using a thin hologram (10 words x10 interrogation bits x20 information bits) was carried out and confirmed high signal-to-noise ratio in the interrogation and read out operations, associative translation function between different information, and high reliability in the memory operation.

Holographic disk with high data transfer rate: its application to an audio response memory

This paper describes a memory realized with a high data transfer rate using the holographic parallel-processing function and its application to an audio response system that supplies many audio messages to many terminals simultaneously. Digitalized audio messages are recorded as tiny 1-D Fourier transform holograms on a holographic disk. A hologram recorder and a hologram reader were constructed to test and demonstrate the holographic audio response memory feasibility. Experimental results indicate the potentiality of an audio response system with a 2000-word vocabulary and 250-Mbit/sec bit transfer rate.

Phase-Matched Electro-Optic Light Modulator

A new type of light modulator, in which incident light polarization is converted to perpendicular polarization by electro-optic effect of r51, was studied, using an a-cut LiTaO3 with a Li/Ta1.2 composition. A spatially periodic electric field for phase-matching between two crossed polarizations is generated by a pair of interdigital electrodes. The electrode period is changed along the light path so that phase-match condition can be satisfied over a wide temperature range. Birefringence inhomogeneity along the light path was found to contribute to wider operation temperature ranges. An extinction ratio of above 30 dB and 73% conversion with an applied voltage of 180 V were obtained in the modulator. Measured temperature characteristics were almost coincident with calculated values.

The hologram tablet: a new graphic input device

Graphic data tablets are input devices which digitize coordinate positions of topological patterns.

Generalized design consideration of holographic scanners with aberration corrections

Hologram generating method for laser scanners with aberration corrections has been proposed and demonstrated. Aberration correction consideration has led to the concept of the generalized holographic zone plate. To generate the holographic zone plate, the holographic technique for optical product operations, between a plurality of coherent spherical waves, has been applied. When spherical waves, N in number, are applied, aberration can be corrected in a scan length magnification equal to or less than N2. Experimentally, remarkable aberration correction effect of this method holograms has been verified for scan lengths over 50 cm.