Hitachi, Ltd.

Norio Murase

Motoyasu Terao

Hisataka Sugiyama

Akira Arimoto

Tetsuya Nishida

Kimio Tatsuno

Fumiyoshi Kirino

Masahiro Ojima

Keikichi Andoo

Masahiko Takahashi

Fumio Kugiya

Shigenori Okamine

Hiroshi Yasuoka

An information recording medium includes an information recording layer on which at least information is to be recorded by irradiating light, and a light transmission restricting layer which has a plurality of nonlinear transmission characteristics or nonlinear reflection characteristics for the intensity of the light irradiated and which has an optical material for restricting the transmission or reflection of the light according to the respective characteristics when the light is irradiated onto the information recording layer. An information recording and reproducing unit uses the information recording medium and includes an information recording position setting unit for deciding a position at which information is to be recorded on the information recording medium by detecting a direction of an easy magnetization axis. With the above arrangement, the spot diameter of the light can be distinguished between the one when information is reproduced and the one when information is recorded on the information recording medium respectively, to thereby ensure an accurate positioning of the head on the tracks of the recording medium.

Recording medium having a plurality of nonlinear transmission

A wavelength-multiple optical memory is provided which is capable of performing high density recording/reading at room temperature. A large number of cylindrical recording members, each of which is made up of plural portions along a central axis of the cylinder and plural sizes which vary slightly in a direction perpendicular to the central axis, are formed on a substrate. The cylindrical recording members may be of circular cylindrical or elliptical cylindrical shape. It is preferable that recording material layers of the cylindrical recording members have complex refractive indexes which are different from each other. A difference in size of the recording material layers of the circular or elliptical cylinders having sizes closest to each other is preferably in a range of 1/5000 to 1/5 of an average of the sizes, are even more preferably in a range of 1/500 to 1/10. Wavelength-multiple recording is performed by changing a wavelength of a light beam emitted from a light source within a very narrow range.

Wavelength-multiple optical recording medium

An optical information recording carrier which comprises an information recording film susceptible to a change in atomic arrangement upon exposure to a recording beam, a first transparent film for preventing diffusion of heat generated in the recording film upon exposure to the recording beam and provided on each side of the recording film, a second transparent film for diffusing the heat in the in-plane direction of the film and provided on at least one outside thereof, and an organic member further provided on at least one outside thereof, the recording beam being irradiated onto the recording film through the organic member has distinguished characteristics of repeated recordings and erasings.

Optical information phase change recording medium having double

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Kokubunji, Japan

Norio Murase