Nippon Telegraph and Telephone Corporation

Centre National De La Recherche Scientifique

Takaya Tanabe

Manabu Yamamoto

Yoshiaki Kurokawa

Hiroshi Yoshikawa

Toshifumi Ohkubo

Masahiro Ueno

Masahiro Endo

Shogo Yagi

Abel C Rousset

Philippe Tailhades

Masakatsu Senda

Laurence Bouet

Akinori Furuya

Corine Despax

Tokinobu Mitasaki

Kikuji Katoh

Hisanobu Dobashi

Yasuko Andoh

Keiichiro Itoh

A medium, that is a laminated holographic medium of the present invention is composed of two or more core layers; 3 or more cladding layersset so as to bind the core layers; one or more diffraction grating layersstoring information data and set at a boundary between a portion of the core layersand the cladding layersbinding the core layersor set inside the core layers; and one or more recording layersstoring information data as forms or a refractive index distribution and set at a boundary between a portion of the core layersand the cladding layersbinding the core layersor inside the core layersthrough or without a gap layer.

Laminated holographic medium, recording apparatus/method, reproduction apparatus/method for the same and design method of laminated hologram medium

An information coding apparatus, an information decoding apparatus, and a method and a program therefor are provided, which can represent a large amount of information with a small number of pixels. Information bits which are inputted are coded as a block of a two-dimensional image made up from m (where m is a natural number)&#xd7;n (where n is a natural number) pixels. Specifically, pixels which represent the information bits are arranged in a code area, which is an area of (m&#x2212;o)&#xd7;(n&#x2212;p) pixels within a code block of m&#xd7;n pixels (where o and p are natural numbers which satisfy 0&#x3c;o&#x3c;m and 0&#x3c;p&#x3c;n); and, no pixels which represent the information bits are arranged in a guide area, which is an area of the other pixels within the code block of m&#xd7;n pixels.

Information coding apparatus, information decoding apparatus, and method and program for the same

A magneto-optical recording medium has a recording layer and a reflective layer on a substrate. The recording layer has a layered structure in which at least one spinel ferrite (or rutile-type oxide or hematite) layer and at least one garnet ferrite layer are piled together. It is preferable that the layered structure is formed on tracks where data are recorded. A manufacturing method comprises the steps of heat treatment in the range of 500-700&#xb0; C., preferably 600-630&#xb0; C., after the formation of the recording layer. In the magneto-optical recording and playback device to record and play back data, the wavelength of light for recording data is different from that for reading data, which is preferable for a magneto-optical recording medium comprising a garnet ferrite layer.

Magneto-optical recording medium, manufacturing method thereof and magneto-optical data recording and playback device

In a two dimensional image recording and reproducing scheme, a position of a prescribed pattern in an information recording image that contains the prescribed pattern is detected by detecting a rough position of the prescribed pattern in the information recording image in units of pixel size, and then detecting a detailed position of the prescribed pattern in the information recording image in units less than the pixel size, according to the rough position and a center of gravity of a distribution of similarities between regions in the information recording image and a reference image of the prescribed pattern.

Two dimensional image recording and reproducing scheme using similarity distribution

A holographic medium is formed of an optical waveguide including at least one core layer positioned between at least one portion of a material having a lower refractive index, a diffraction grating layer formed at a boundary between the core layer and the material of lower refractive index or in the core layer, and a storage layer outside the optical waveguide. Upon storing information in the storage layer a reference beam and an object are input into the optical waveguide and in retrieving stored information the reference beam is emitted to an end face of the core layer and transmitted through the core layer to be transformed into a diffracted beam in a diffraction grating layer that is emitted outside the core layer and transmitted through the storage layer, where the object beam is retrieved as a retrieved beam.

Optical waveguide, holographic medium, holographic storage and retrieval method and system

This invention relates to magneto-optical recording media such as magneto-optical disks and cards, manufacturing methods of the medium and a magneto-optical recording and playback device to record and play back data using the magneto-optical recording media. The magneto-optical recording medium of the present invention has a recording layer and a reflective layer on a substrate, and the recording layer has a layered structure in which at least one spinel ferrite (or rutile-type oxide or hematite) layer and at least one garnet ferrite layer are piled together. It is preferable that the layered structure is formed on tracks where data are recorded. The manufacturing method of the present invention comprises the steps of heat treatment in the range of 500-700&deg; C., preferably 600-630&deg; C., after the formation of the recording layer. In the magneto-optical recording and playback device to record and play back data of the present invention, the wavelength of light for recording data is different from that for reading data, which is preferable for a magneto-optical recording medium comprising a garnet ferrite layer.

Opto-magnetic recording medium with a garnet ferrite recording layer, and opto-magnetic information recording/reproducing device

An information reading apparatus can detect the coupling state of the input light to a waveguide of a laminated recording medium in a simple manner, so as to enable to focus the input light on a target recording layer to access the information recorded in the target recording layer quickly. The apparatus is compact and is economical to produce. The apparatus has a light source for injecting a light on an input edge of a lamination recording section, assembled into the recording medium containing a lamination of recording layers. Each recording layer has data represented by scattering centers which diffract an input light generated by a converging lens. An input light directing device directs the light source and the converging lens as a unit to focus the input light on a desired location. An image recording device records an informational image generated by guided waves produced within a laminated waveguide. An optical power detector detects output light emitted from an output edge of a specific recording layer as well as scattered light generated from recording layers other than the specific recording layer. An optical power discrimination circuit determines whether an optical power detected by the optical power detector is associated with the output light or the scattered light. Data recorded in any specific recording layer can be accessed quickly and simply by focusing input light on a core layer of a multi-layered hologram recording data storage medium. Because the absolute positional information stored in the storage medium is minimized, data storage capacity of the storage medium is almost unaffected while making the apparatus compact and low cost.

Information reading apparatus and information recording medium

The present invention provides a data readout apparatus and method using optical beams by which high data-recording density for optical recording media and high transfer rate for regenerated data can be realized. The data readout method of the present invention comprises the steps of: making a first optical beam incident on an optical recording medium in a manner such that in three successive tracks n-1, n, and n+1, n being an integer of two or more, on the recording medium, the center of the beam spot of the first optical beam lies, in a transverse direction of the tracks, between the boundary point of tracks n-1 and n and the center of track n-1; making a second optical beam incident on the optical recording medium in a manner such that the center of the beam spot of the second optical beam lies, in the transverse direction of the tracks, between the boundary point of tracks n+1 and n and the center of track n+1; detecting reflected beams of the first and second optical beams from the optical recording medium; and regenerating data recorded on the three tracks in accordance with levels of the detected reflected beams. According to this, data sequences recorded on three successive tracks can be regenerated simultaneously by using two optical beams; thus, even if the track pitch is narrowed, it is possible to detect signals without the influence of crosstalk, and the data transfer rate can be increased. The apparatus for implementing this method allows simpler circuit arrangement.

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Tokorozawa, Japan

Takaya Tanabe