Abstract: A hologram recording and reproducing apparatus preforms to record data on a recording medium and reproduce data from the recording medium. The recording medium is made of a photorefractive crystal having a parallel plate shape.

Abstract: 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.

Abstract: In a hologram recording method for forming a plurality of areas of a refractive index light interference pattern of a coherent signal light beam in accordance with information data within a recording medium having a shape of parallel flat plates, the signal light beam and the recording reference light beam cross each other within the recording medium, and a gate light beam having a second wavelength for revealing recording sensitivity of the recording medium is simultaneously irradiated to the recording medium so as to pass through a portion of the recording reference light beam and demarcate a volume smaller than that of this crossing portion.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: An optical information recording/reproducing system includes a support member for removably supporting a volume holographic memory formed of a photorefractive crystal, and has a shape of a rotary member having a rotational symmetry axis, with plane surfaces perpendicular to the rotational symmetry axis formed at respective opposite ends thereof. The system also includes a reference beam-irradiating member for irradiating the volume holographic memory with a coherent reference beam having a first wavelength. The system also includes a signal beam-irradiating member for irradiating the volume holographic memory with a coherent signal beam which has the first wavelength and is modulated according to image data, to cause the signal beam to intersect with the reference beam within the volume holographic memory and thereby generate a refractive index grating of a three-dimensional optical interference pattern between the signal beam and the reference beam.

Abstract: 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.

Abstract: A hologram recording medium can record an interference pattern to a volume holographic memory at high density. Therefore, the hologram recording medium is made of a photo refractive crystal of a uniaxial crystal having a shape of parallel flat plates, and has a plurality of areas of a refractive index grating corresponding to one portion of a three-dimensional light interference pattern of a coherent signal light beam and coherent reference light of a first wavelength modulated in accordance with information data, wherein the areas of the refractive index grating respectively have a spatially independent columnar shape and are juxtaposed in parallel with each other, and lattice vectors of the refractive index grating in the adjacent areas of the refractive index grating exist in directions different from each other.

Abstract: A hologram recording medium, a hologram recording method and a recording and reproducing apparatus are capable of recording an interference pattern onto a volume holographic memory at high density.

Abstract: 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.

Abstract: A hologram recording and reproducing apparatus preforms to record data on a recording medium and reproduce data from the recording medium. The recording medium is made of a photorefractive crystal having a parallel plate shape.

Abstract: 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.

Abstract: 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.

Abstract: An optical information recording/reproducing system includes a support member for removably supporting a volume holographic memory formed of a photorefractive crystal, and has a shape of a rotary member having a rotational symmetry axis, with plane surfaces perpendicular to the rotational symmetry axis formed at respective opposite ends thereof. The system also includes a reference beam-irradiating member for irradiating the volume holographic memory with a coherent reference beam having a first wavelength. The system also includes a signal beam-irradiating member for irradiating the volume holographic memory with a coherent signal beam which has the first wavelength and is modulated according to image data, to cause the signal beam to intersect with the reference beam within the volume holographic memory and thereby generate a refractive index grating of a three-dimensional optical interference pattern between the signal beam and the reference beam.

Abstract: The present invention relates to a method of preparing an alcohol by reducing a carboxylic acid or a derivative thereof, more particularly, a method of preparing an alcohol by a reduction reaction in the presence of a zirconium-titanium oxide catalyst. A carboxylic acid or a carboxylic acid derivative is converted into a corresponding alcohol by a reduction reaction in the presence of a zirconium-titanium oxide catalyst using an alcohol as a hydrogen source. An alcohol can be prepared in a high yield in the present invention. To be more specific, the method of the present invention can convert a higher fatty acid or a carboxylic acid derivative, which has given a corresponding alcohol in a low yield in the presence of a zirconium catalyst alone, into the corresponding alcohol in a high yield. Further, the reaction can be performed easily, and the product can be easily separated from the catalyst.

Abstract: After the lactone portion of trans-whiskey lactone is hydrolyzed with potassium hydroxide, this portion is reacted with isopropyl bromide and mixed with an alkyl group, thereby obtaining isopropyl (3S,4S)-4-hydroxy-3-methyloctanoate. Then, the isopropyl (3S,4S)-4-hydroxy-3-methyloctanoate is reacted with diethyl azodicarboxylate in the presence of triphenylphosphine and azodicarboxylate, thereby obtaining isopropyl (3S,4S)-4-(3',5'-dinitrobenzoyloxy)-3-methyloctanoate. The isopropyl (3S,4S)-4-(3',5'-dinitrobenzoyloxy)-3-methyloctanoate is hydrolyzed in 2% potassium hydroxide, and as a result, cis-whiskey lactone (A) represented by the following general formula is obtained. According to this method, cis-whiskey lactone, one of the perfume components of whiskey and wine, can be produced selectively and easily.

Abstract: The carbonyl group at the 2-position of levoglucosenone is reduced to obtain a hydroxyl group having a .beta.-configuration. The hydroxyl group having a .beta.-configuration is reversed to an .alpha.-configuration, and hydroxyl groups are added at the 3- and 4-positions in a cis-.alpha. form. Finally, the protective group of the hydroxyl group at the 2-position is eliminated. The reduction of the carbonyl group at the 2-position can be performed such that the levoglucosenone is reacted with aluminum lithium hydride or sodium boron hydride in an appropriate solvent. Reversion of the hydroxyl group having a .beta.-configuration can be performed by the Mitsunobu method or a method having a mesylation step and a step using cesium acetate. The addition of the hydroxyl groups to the 3-and 4-positions in the cis form can be performed by oxidizing the double bond across the 3- and 4-positions with an appropriate oxidizing agent.

Abstract: There is provided a method of preparing an epoxide (1a) or (1b) shown below: ##STR1## where R.sup.1, R.sup.2, R.sup.3, and R.sup.4 represent a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, an alkoxy group, an aryloxy group, an acyl group, an alkyloxycarbonyl group, an aryloxycarbonyl group, allalkyl group, a silyl group, and a silyloxy group; the groups may be bonded with each other to form rings in the case where these groups can be bivalent; these groups may be the same or different, may have substituting groups, or may be branched; and each form (isomer) has a structure in which one side of the plane constituted by double bonds, R.sup.1, R.sup.2, R.sup.3 and R.sup.4, is more seterically hindered in comparison with the other side;characterized in that:an olefin represented by the formula (2) below, is reacted with iodine in the presence of compound generating acyloxy ion, ##STR2## where R.sup.1, R.sup.2, R.sup.3 and R.sup.