Pioneer Corporation

Pioneer Electronic Corporation

Other

National Institute for Materials Science

Pioneer Electronics Corporation

Takashi Yamaji

Hideki Hatano

Satoru Tanaka

Tomomitsu Kouno

Yoshihisa Itoh

Hajime Matsushita

Kenji Kitamura

Shunji Takekawa

Yasunori Furukawa

Myeongkyu Lee

Toshio Goto

Masayuki Iwasaki

Sakashi Ootaki

Masami Nishida

Masaru Nakamura

Fumitaka Kotaka

Akira Yokoi

Yoshihisa Ito

Hajime Matsushia

A description is provided of an optical information recording and reproducing apparatus having a volume holographic memory. The apparatus is capable of recording an interference pattern in the volume holographic memory in high density and can be made small-sized. The apparatus includes a comprises support portion for detachably supporting the volume holographic memory, which is made of a photorefractive crystalline material; a reference beam supplying portion for making a coherent reference beam of a first wavelength incident on the volume holographic memory; a signal beam generating portion for making a coherent signal beam of the first wavelength, which is modulated in accordance with image data, incident on the volume holographic memory, intersecting therein the signal beam with the reference beam, and generating a three-dimensional light interference pattern of the signal beam and the reference beam; and detecting a portion for detecting diffracted light from a refractive index grid of the light interference pattern in the volume holographic memory, due to irradiation of the reference beam. The signal beam and the reference beam are arranged in a plane having a normal line perpendicular to the symmetrical axis of rotation of the volume holographic memory.

Optical information recording and reproducing apparatus having volume holographic memory

A holographic recording medium exhibiting a high recording sensitivity without execution of reduction treatment. A system records information on the holographic recording medium by using a gating light within a wavelength band causing less optical damage to the holographic recording medium. The holographic recording medium includes a single crystal of lithium niobate (LiNbO) or lithium tantalate (LiTaO) containing Mn as a dopant.

Holographic recording medium and holographic recording/reproducing apparatus using the same

A description is provided of an optical information recording and reproducing apparatus. The apparatus comprises: a holographic memory made of a photorefractive crystalline material; a support portion for detachably supporting the memory; a reference beam supplying portion for supplying a coherent reference beam of a first wavelength incident on the memory; a signal beam generating portion for supplying a coherent signal beam of the first wavelength, which is modulated in accordance with image data, incident on the memory, intersecting therein the signal beam with the reference beam, and generating a three-dimensional interference pattern of the beams; a detecting portion for detecting a diffracted light from a refractive index grating of the interference pattern in the memory, due to irradiation of the reference beam; and a medium position adjusting portion for moving a position of the support portion in accordance with a signal corresponding to positioning images from the detection portion. The memory includes a nonvolatile refractive index grating corresponding to a three-dimensional interference pattern of a coherent reference beam and a coherent signal beam, the coherent signal beam being modulated in accordance with positioning images.

A photorefractive material provides a high photosensitivity without reduction. The material comprises a single crystal of terbium (Tb)-doped niobate or tantalate. The single crystal is a single crystal of lithium niobate (LiNbO ) whose molar fraction of &lsqb;Li O&rsqb;/(&lsqb;Li O&rsqb;&plus;&lsqb;Nb O &rsqb;) lies in a range of 0.482 to 0.505, or a single crystal of lithium tantalate (LiTaO ) whose molar fraction of &lsqb;Li O&rsqb;/(&lsqb;Li O&rsqb;&plus;&lsqb;Ta O &rsqb;) lies in a range of 0.482 to 0.505. The amount of terbium added in the photorefractive material ranges from 10 weight ppm to 1000 weight ppm.

Photorefractive material

A volume holographic memory for recording three-dimensional distribution of interference fringes generated owing to interference between signal light and reference light is provided, wherein the volume holographic memory is formed into a cylindrical shape. Also an optical information recording/reproducing apparatus is provided which incorporates an interference-fringe generating unit for generating interference fringes formed owing to interference between signal light and reference light; a storage unit for storing three-dimensional distribution of the interference fringes generated by the interference-fringe generating unit; a detecting unit for detecting diffracted light obtainable from the storage unit by irradiating the storage unit with reference light; and a reproducing unit for reproducing signal light from diffracted light detected by the detecting unit, wherein the storage unit is constituted by a volume holographic memory having a cylindrical shape.

Volume holographic memory and optical information recording/reproducing apparatus

Disclosed are a holographic memory medium for use in a holographic memory system, which can prevent generation of stray light of a gating beam at the time of recording information, and a recording apparatus which uses this memory medium. This memory medium records an information signal carried by a signal beam as a coherent reference beam and the signal beam enter the memory medium with a gating beam being present. The memory medium has at least a first surface and a second surface parallel to each other and comprises an antireflection coat, formed on the first surface, for preventing reflection of the gating beam. The recording apparatus records an information signal using a holographic memory medium and comprises a light absorbing member of absorbing the gating beam coming through the memory medium.

Holographic memory medium and recording apparatus using the same

An optical information recording and reproducing apparatus, which detachably supports a holographic memory formed of a photorefractive crystal, includes a portion for supplying a coherent reference light beam at a first wavelength into the holographic memory; a portion for supplying a coherent signal light beam at the first wavelength, modulated in accordance with image data, into the memory to produce an optical interference pattern with the reference light within the memory; a portion for supplying a gate light beam at a second wavelength into the memory for activating or deactivating an index grating in accordance with the presence or absence of the optical interference pattern to enhance a photo-sensitivity of the memory; a detector for detecting diffraction light from the index grating of the memory by the irradiation of the reference light beam; and a portion for changing and regulating a light intensity of the gate light beam.

Optical information recording and reproducing apparatus using a holographic memory

A two-color hologram recording/reproducing apparatus is capable of directing interferable signal light and reference light into a hologram recording medium to record an information signal carried by the signal light. The hologram recording medium is sensitive to a first light at a first wavelength in an ultraviolet or short-wavelength visible light band to develop light induced absorption. The apparatus includes a light source for irradiating the hologram recording medium with the first light, a laser light source for irradiating the hologram recording medium with signal light and reference light at a second wavelength longer than the first wavelength after the first light is irradiated, and a gate light source for directing gate light at a third wavelength into the hologram recording medium. The gate light causes the hologram recording medium to develop a recording sensitivity to activate or inactivate a refractive index grating in accordance with existence or non-existence of a light interference pattern formed by the signal light and the reference light.

Two-color hologram recording/reproducing apparatus

Digital signal sequences to be recorded in predetermined unitary recording areas are transformed into blocks, a plurality of bit data carrying all digit levels to be read and determined upon reproduction are included in the resultant blocks, and sequences of the data blocks are recorded in the recording medium in the unitary recording areas. Upon reproduction, the blocks of the read signals obtained from a recording medium are recognized, a threshold value is determined for each block on the basis of the values of read signals corresponding to bit data carrying all digit levels to be read and determined, and each digit level of bit data in the read signal are read and determined on the basis of the threshold values.

Digital signal recording/reproducing method

A description is provided of an optical information recording and reproducing apparatus which detachably supports a volume holographic memory formed of a photorefractive crystal. The apparatus includes a portion for supplying a coherent reference light beam at a first wavelength into the volume holographic memory; a portion for supplying a coherent signal light beam at the first wavelength, modulated in accordance with image data, into the memory to produce an optical interference pattern with the reference light within the memory; a portion for supplying a gate light beam at a second wavelength into the memory for activating or deactivating an index grating in accordance with the presence or absence of the optical interference pattern to enhances a photo-sensitivity of the memory; and a detector for detecting diffraction light from the index grating of the memory by the irradiation of the reference light beam. The apparatus includes a scanning portion for moving an intersecting region in which the gate light beam, the signal light beam and the reference light beam intersect with one another within the volume holographic memory along an optical axis of an optical path of the signal light beam within the volume holographic memory.

Optical information recording and reproducing apparatus using a volume holographic memory

A description is provided of an optical information recording and reproducing apparatus employing a holographic memory. The apparatus includes a mask disposed in an optical path of the signal light beam so as to cover a light intensity distribution of the signal light beam incident into the holographic memory at nearly a half portion thereof with respect to the center of the distribution of the zeroth-order diffracted light of the signal light beam. The center of a region of the holographic memory where the signal light beam and the reference light beam intersect with each other, is shifted by a distance substantially equal to twice the distance between peaks of the zeroth-order diffracted light or the first-order diffracted light of the signal light beam.

Holographic memory and optical information recording and reproducing apparatus using the same

A volume holographic memory-based optical information-recording/reproducing apparatus being capable of controlling an interference area formed by a reference beam and a signal beam within a recording medium more easily than by waveform shaping using a lens. A recording medium is installed in the apparatus for recording a three-dimensional optical interference pattern formed by at least two coherent light beams as spatial changes in refractive index of the recording medium. A signal beam optical system transmits a coherent signal beam to the recording medium through a Fourier transform lens. A reference beam optical system transmits a coherent reference beam to the recording medium. The reference beam intersects the signal beam within the recording medium, and an angle of intersection between the reference beam and the signal beam is changed. Diffracted light of the reference beam diffracted from the recording medium is detected. Light intensity distribution-offset element is arranged in both of optical paths of the signal and reference beam optical systems, for controlling a distribution of a light intensity of the signal beam and a light intensity of the reference beam, respectively, within an area in the recording medium in which the signal beam and the reference beam intersect with each other.

Volume holographic memory-based optical information-recording/reproducing apparatus

A volume holographic memory-based optical information-recording/reproducing apparatus is capable of enhancing density of spatial multiple recording. A recording medium is mounted in the apparatus for recording a three-dimensional optical interference pattern formed by at least two coherent light beams as spatial changes in refractive index of the recording medium. A signal beam optical system supplies a coherent signal beam to the recording medium through a Fourier transform lens. A reference beam optical system supplies a coherent reference beam to the recording medium. The reference beam is caused to intersect with the signal beam within the recording medium and an angle of intersection between the reference beam and the signal beam is changed. Diffracted light of the reference beam diffracted from the recording medium is detected. Spatial beam modulating means is arranged in the optical path of the reference beam optical system for limiting light intensity of the reference beam in a manner such that a cross section of the reference beam in the recording medium has a light intensity distribution opposite to a light intensity distribution of the signal beam in the recording medium.

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Tsurugashima, Japan

Takashi Yamaji