Abstract

Optical card storage is one of the most compact form of data storage, which stores information on the plastic card of credit-card size. This method of storage has been intensively explored for commercial applications, although the capacity of this storage is strictly limited due to its small dimension of an optical data storage. The capacity (or the density in a unit area) is given by the total size of memory area divided by the extent of laser-beam spot. The minimum size of spot is as large as a half of light wavelength. This is due to the light-wave diffraction. To overcome this limitation, we developed a new type of optical card storage. In this card storage, bit data are three-dimensionally recorded inside volume medium, rather than on the surface of the medium.¹

© 1995 IEEE