Tdk Corporation

Hideaki Miura

Tetsuro Mizushima

Jiro Yoshinari

Takuya Tsukagoshi

Tatsuya Kato

Hiroshi Shingai

Hironori Kakiuchi

Hideki Hirata

Kenji Yamaga

Hiroshi Chihara

Rie Ihara

Hideki Sunohara

The present invention provides a hologram recording material which attains high refractive index change, high flexibility, high sensitivity, low scattering, environment resistance, durability, low dimensional change and high multiplicity, and is suitable for volume hologram recording. Also, the present invention provides a hologram recording medium. A hologram recording material comprising: an organometallic compound at least containing at least two kinds of metals, oxygen, and an aromatic group and having an organometallic unit wherein two aromatic groups are bonded directly to one metal; and a photopolymerizable compound. One of the at least two kinds of metals is Si, and the metal(s) other than Si is/are preferably selected from the group consisting of Ti, Zr, Ge, Sn, Al and Zn. The organometallic unit is preferably a unit wherein two aromatic groups are bonded directly to one Si atom. A hologram recording medium () has a hologram recording material layer ().

Hologram recording material and hologram recording medium

The present invention provides a hologram recording material which is not required to be subjected to pre-exposure treatment at the time of recording, attains high refractive index change, high sensitivity, low scattering, environment resistance, durability, low dimensional change, and high multiplicity, and is suitable for volume hologram recording. Also, the present invention provides a hologram recording medium. A hologram recording material comprising a matrix material having a softening temperature of 50&#xb0; C. or higher, and a photopolymerizable monomer which is in a liquid phase state at room temperature. The matrix material is preferably contained in an amount of 50% by weight or more and 90% by weight or less of the whole of the hologram recording material. A softening temperature of the hologram recording material is preferably 0&#xb0; C. or higher.

It is an object of the present invention to provide an information recording method for recording information in a data rewritable type optical recording medium having a plurality of information recording layers, which can form recording marks having good shapes. In the information recording method according to the present invention, information is recorded in an optical recording mediumhaving at least a stacked L0 layerand L1 layerby projecting a laser beam thereonto whose power is modulated between a plurality of powers including at least a recording power (Pw) and an erasing power (Pe) via a light incidence plane. When information is recorded, &#x3bb;/NA is set to be equal to or shorter than 700 nm, where &#x3bb; is a wavelength of the laser beam and NA is a numerical aperture (NA) of an objective lens, and a ratio (Pe/Pw) of the recording power and the erasing power when information is to be recorded in the L0 layeris set to be smaller than that when information is to be recorded in the L1 layer

Method of recording information in optical recording medium, information recording, apparatus and optical recording medium

A holographic multiplex recording method which can keep a recording data rate constant and equalize nonuniformity in recording due to vibrations or the like, and a holographic recording apparatus and a holographic recording medium, which employ the method. In a process of multiplex-recording information, the time of exposure to a laser beam per data page is kept constant, and the laser output power of the laser beam is increased in accordance with a decrease in recording sensitivity of the holographic recording medium.

Holographic multiplex recording method, holographic recording apparatus and holographic recording medium employing the method using interference fringes

A holographic recording method, a holographic recording apparatus, a holographic recording and reproducing method, a holographic recording and reproducing apparatus, and a holographic recording medium for recording information in an angle multiplex fashion as a hologram in a first format in which either one of signal light and reference light branched out from a laser light source is made to cross the other in a recording layer at a predetermined incidence angle and the incidence angle is changed at a predetermined angular pitch, or in a second format of higher angular selectivity, wherein the incidence angle when recording information in the second format of higher angular selectivity can be adjusted to cover an incidence angle that satisfies the Bragg's condition when recording in the first format, thereby ensuring reproduction compatibility between media of different angular selectivities.

Holographic recording method, holographic recording apparatus, holographic recording and reproducing method, holographic recording and reproducing apparatus, and holographic recording medium

A holographic recording apparatusrealizes multilevel gray-scale recording by: controlling a reflection type spatial light modulator (DMDD) via a control unitso that an object beam in an object optical systemis reflected in an exposure direction so as to be incident on a holographic recording mediumor in a non-exposure direction so as not to be incident thereon selectively pixel by pixel in accordance with a data page to be recorded; and making (N+1) levels of gradation exposure with a single exposure time tgiven by dividing tby N, where tis an exposure time necessary for rendering a single pixel of the data page as an ON pixel, and N is an integer of not less than 2.

Holographic recording method and holographic recording apparatus

A multilayer holographic recording medium that improves recording density and data transfer rates. The multilayer holographic recording medium, from which information is reproduced by a multilayer holographic memory reproducing apparatus, includes a plurality of deposited holographic recording layers. During recording, a reference beam is common to those holographic recording layers and an incident angle of an object beam is modulated for each holographic recording layer. During reproduction, a laser beam for reproduction having the same condition as that of the reference beam used for recording is projected thereonto, so that diffraction beams are simultaneously generated in the respective holographic recording layers to directions that are the same as incident directions of the object beam used for recording.

Multilayer holographic recording medium and manufacturing method of the same, multilayer holographic recording and reproducing method, multilayer holographic memory reproducing apparatus, and multilayer holographic recording and reproducing apparatus

In a personal identification systemfor identifying a user on the basis of biometric information, a hologram is formed in a holographic recording portionof an optical information recording medium. The hologram is provided by the interference between a reference beam subjected to spatial light modulation by record cryptographic identification information based on the biometric information of the user obtained by a biological information sensorand an object beam. At the time of identification, an information processing devicemakes validation cryptographic identification information from the biometric information directly obtained from the user, and a spatial light modulatormodulates a hologram reproduction reference beam by the validation cryptographic identification information. The right or wrong of a reproduced image is detected, and the leakage of the identification information is prevented.

Personal identification method, personal identification system, and optical information recording medium

A method of recording data on a double-layer optical recording medium having a recording layer with high light transmittance is provided. A laser beam is modulated to emit a pulse series of laser including a write pulse of a write power and a cooling pulse of a bottom power, so as to encode and write data to be recorded as recording marks of a length nT along a track of the recording layer, where n is an integer and T is one clock cycle. An nT recording mark is formed using (n&#x2212;1) write pulse(s), and when forming a recording mark of 4 T or longer, a cooling pulse with a pulse width of 0.8 T to 2 T is inserted before the last write pulse. Recording marks are thereby accurately formed without heat interference between consecutive recording marks and cross erase between recording marks of adjacent tracks.

Method of recording data on optical recording media and optical recording device

Provided is a hologram retrieval method and a holographic recording and reproducing apparatus for preventing an increase in SNR, a decrease in retrieval accuracy, or the retrieval itself from being made impossible, which would otherwise occur because of a small size of data used for retrieval. Digital information is recorded on a holographic recording medium as data pages DP formed of a two-dimensional bit map image with each page being multiplexed. The data page DP is divided into a plurality of equal data blocks DBto, DBto DB, and DBto DB, and each data block DB is provided with a data image that is encoded by an encoding method for providing a certain number of ON pixels within each data block DB. A spatial light modulator allows the to-be-retrieved data image to be encoded by the encoding method and displayed as block information on a retrieval data block associated with the data block, and a signal beam to be thereby modulated. Of resulting diffracted beams, the diffracted beam of the maximum intensity is used to detect the target data image and the address of the reference beam.

Hologram retrieval method and holographic recording and reproducing apparatus

When recording on a holographic recording medium by using a recording beam, the time required for an asking servo control to recover is reduced to increase the data transfer rate. In the holographic recording apparatus, a laser beam from a laser light sourceis formed into a collimated beam having an expanded beam diameter and then is divided into an object beam and a reference beam. The divided object beam is modulated according to information to be recorded, and these object and reference beams are made incident on the reflective surface of a rotating polygon mirror, while maintaining collimated beam shapes and being adjacent to each other, through a condenser lenshaving a focal point behind the reflective surface of the polygon mirror. The object and reference beams are made incident on the holographic recording mediummoving in the same direction as their scanning direction with angles different from each other so as to interfere with each other within the holographic recording medium

Holographic recording method and apparatus

A holographic recording medium in which a thick holographic recording layer is formed without the use of multilayering and without accompanying thickness unevenness, scattering, and nonuniformity of dynamic range, and a method for manufacturing the same. The holographic recording mediumis configured by sandwiching a hybrid material layerand a photopolymer layerbetween first and second substratesand. The hybrid material layercontains an inorganic glass and a photopolymer as main ingredients. The photopolymer layersubjected to heat or ultraviolet curing is provided on the dried hybrid material layersuch that the combined thickness of this hybrid material layerand the photopolymer layeris uniform. The second substrateis bonded and fixed to this photopolymer layerserving as a bonding layer.

Holographic recording medium and method for manufacturing the same

A method for recording information on an optical recording medium is provided so that it is satisfied that 0.16&#x2266;(L&#xd7;T)/(&#x3bb;/NA)&#x2266;0.30 and 0.06&#x2266;(L&#xd7;T)/(&#x3bb;/NA)&#x2266;0.14, where &#x3bb; is a write wavelength of a laser beam used to irradiate the recording layer of a phase-change optical recording medium, NA is a numerical aperture of an objective lens used for irradiation with the laser beam, Lis a relative speed between the objective lens and the optical recording medium, Tis a pulse time of a cooling pulse inserted immediately following a leading write pulse, and Tis a leading write pulse time. The method allows for forming a record mark with a good shape and prevents fluctuations at the front edge of the record mark, which would be otherwise caused by the recrystallization of the recording film being held at a high temperature.

Method for recording information on optical recording medium

A holographic recording mediumis configured to have a recording layeron which information can be recorded as holograms; and first and second heat generating layersA andB provided in a pair so as to sandwich the recording layer. Then, the first and second heat generating layersA andB are allowed to generate heat by being irradiated with a heat generating laser beam LBhaving a wavelength that is different from that of a signal beam LBor a reference beam LBfor reproducing or recording information. The holographic recording medium and a method for recording and reproducing the same, and a recording and reproducing apparatus can compensate for shrinkage of the recording layer due to recording or variations in temperature, thereby allowing for reproduction of the holograms under optimum conditions.

Holographic recording medium, method for recording and reproducing the same, and reproducing apparatus

A method and apparatus for performing reproduction position servo-control without reducing the recording capacity of a holographic recording medium. Upon the reproduction of a holographic recording medium, part of a reproduction beam serving as a servo beam is projected onto a recording layerA of the holographic recording mediumfrom the side opposite to the side of the reproduction beam (a reference beam) along the same optical axis as that of the reproduction beam, and the diffraction beam thereof is detected by a photodetectorC through a polarizing beam splitterB.

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Tokyo, Japan

Hideaki Miura