Abstract: An optical information recording/reproducing apparatus for recording an interference pattern between signal light and reference light information-multiplexed as a hologram in an optical information recording medium and for reproducing information recorded in the optical information recording medium on the basis of the recorded hologram with use of the reference light. The apparatus includes a light source for emitting light and a coherency controller for controlling a coherency of the light source. The apparatus controls the coherency controller in such a manner as to switch between a coherency required in a recording mode and a coherency required in a reproducing mode.

Abstract: An optical information recording/reproduction device appropriately adjusting a recording condition and a method and a medium therefor are provided in order to cope with a problem that the signal-to-noise ratio (SNR) during reproduction decreases, unless the condition during recording is adjusted, because of variation in the environment during recording, variation of components such as laser output, variation of production of the device, and the like in the optical information recording/reproduction device using holography. In an optical information recording/reproduction device configured to record or reproduce information to an optical information recording medium by using holography, a recording condition is adjusted, before user data are recorded, in an adjustment area provided for recording condition adjustment in an optical information recording medium.

Abstract: A holographic optical pickup device includes an optical axis split element for splitting a reference beam into two light beams in different propagation directions having polarized states substantially orthogonal to each other, angular variable elements for changing incident angle of the reference beam for irradiating an optical information recording medium, an image sensor for detecting a diffracted beam generated from a recorded region upon irradiation of the optical information recording medium with the reference beam to form a reproduction signal, and photodetectors for detecting the diffracted beam generated from the recorded region upon irradiation of the optical information recording medium with the reference beam. An angular error signal is generated for controlling the angular variable element using signals detected by the photodetectors.

Abstract: An optical information recording/reproducing apparatus for recording an interference pattern between signal light and reference light information-multiplexed as a hologram in an optical information recording medium and for reproducing information recorded in the optical information recording medium on the basis of the recorded hologram with use of the reference light. The apparatus includes a light source for emitting light and a coherency controller for controlling a coherency of the light source. The apparatus controls the coherency controller in such a manner as to switch between a coherency required in a recording mode and a coherency required in a reproducing mode.

Abstract: A holographic optical pickup device includes an image sensor that detects a diffracted beam generated from the region to be reproduced when irradiating an optical information recording medium with a reference beam, and sets the detected diffraction beam as a reproduction signal, and a photodetector that is different from the image sensor, which detects the diffracted beam generated from a recorded region in the recording medium when irradiating the recording medium with the reference beam. A light receiver of the photodetector is divided into a plurality of light receiving planes so as to generate the position error signal indicating the positional shifting of the region to be recorded/reproduced of the recording medium with respect to the objective lens from a differential signal of a plurality of signals derived from the respective light receiving planes.

Abstract: An optical information recording/reproducing apparatus, to apply holograms of an angle multiplex recording method therein includes: a light source to emit a light beam; a divider unit to divide the light beam into a signal beam and a reference light; an angle variable unit to change an angle of the reference light incident upon an optical information recording medium; a spatial light modulator unit to add information to the signal beam; an objective lens to irradiate the signal beam on the medium; an image pickup unit to detect a diffracted light generating from a recording region, when the reference light is irradiated on the medium; and an optical element to shape a form of light flux of the reference light, so that a light flux diameter of the reference light in a multiplex direction becomes larger than the light flux diameter of the reference light in a pitch direction.

Abstract: Provided is an optical pickup device that suppresses a fluctuation of a tracking error signal caused by stray light when recording/reproducing information on/from an optical disc including a plurality of recording layers and attains size reduction. It includes a laser diode emitting laser light of about 405 nm in wavelength, an objective lens irradiating the optical disc with an optical beam emitted from the laser diode and having a numerical aperture of about 0.85, and a detector including a detection part receiving the optical beam reflected from the optical disc. An optical magnification from the optical disc to the detector is set within a range from about 10× to 15×.

Abstract: An optical pickup device includes a galvanometer mirror that changes an incident angle of a reference beam to an optical information recording medium, an image sensor that detects a diffracted beam from a region to be reproduced upon irradiation of the recording medium with the reference beam, and sets the detected diffracted beam to a reproduction signal, and a photodetector that detects the diffracted beam generated from a plurality of recorded regions upon irradiation of the recording medium with the reference beam. The photodetector includes a plurality of light receivers, and generates an angular error signal indicating positional shifting of the incident angle of the reference beam from a differential signal of a plurality of signals derived from the respective light receivers so as to control the angle of the galvanometer mirror.

Abstract: An optical information recording/reproducing apparatus, to apply holograms of an angle multiplex recording method therein includes: a light source to emit a light beam; a divider unit to divide the light beam into a signal beam and a reference light; an angle variable unit to change an angle of the reference light incident upon an optical information recording medium; a spatial light modulator unit to add information to the signal beam; an objective lens to irradiate the signal beam on the medium; an image pickup unit to detect a diffracted light generating from a recording region, when the reference light is irradiated on the medium; and an optical element to shape a form of light flux of the reference light, so that a light flux diameter of the reference light in a multiplex direction becomes larger than the light flux diameter of the reference light in a pitch direction.

Abstract: Disclosed is an optical disc device that provides a stable servo signal with a simple configuration during the use of an objective lens showing significant color aberration. At time T0, which is before the start of a write operation (time T2), a defocus application circuit 111 generates a defocus signal DF1 to be added to a focusing error signal FES. A tracking signal gain control circuit 113 changes a tracking signal gain correction amount to be given to a tracking error signal TES to TG1. The defocus signal generated from the defocus application circuit terminates at substantially the same time the write operation starts (time T2). After the focusing error signal FES is no longer offset (at time T3), the tracking signal gain correction amount generated from the tracking signal gain control circuit 113 is restored to a reference value.

Abstract: There is disclosed an optical information recording device using a multilayer optical disc as a recording medium, in which the number of components of the device is reduced. The optical disc has, e.g., one recording layer with prepits and a plurality of recording layer without prepits. An optical pickup included in the information recording device includes a switchable lens element to focus laser beams to be applied to the multilayer optical disc onto two adjoining recording layers. A tracking error signal offset obtained for a recording layer with prepits is stored. Recording an information signal into a recording layer from which a tracking error signal cannot be detected is performed, while maintaining the accuracy of positioning on track with respect to the prepits based on the stored offset. When reading out an information signal, tracking control based on the prepits of recorded information signals is exerted.

Abstract: A holographic optical pickup device includes an optical axis split element for splitting a reference beam into two light beams in different propagation directions having polarized states substantially orthogonal to each other, angular variable elements for changing incident angle of the reference beam for irradiating an optical information recording medium, an image sensor for detecting a diffracted beam generated from a recorded region upon irradiation of the optical information recording medium with the reference beam to form a reproduction signal, and photodetectors for detecting the diffracted beam generated from the recorded region upon irradiation of the optical information recording medium with the reference beam. An angular error signal is generated for controlling the angular variable element using signals detected by the photodetectors.

Abstract: In a small-sized optical pickup device for enabling to obtain a stable servo-signal, as well as, a focus error signal and a tracking error signal, without receiving ill influences of stray lights from other layers, when recording/reproducing a multi-layer optical disc, a reflection light from the multi-layer optical disc is divided into plural numbers of regions by a diffraction grating. And, it is divided into at least four (4) regions, by a division line in the tangential direction of the optical disc and a division line in the radial direction thereof. Light receiving parts, for detecting either one of grating diffraction lights, i.e.

Abstract: A holographic optical pickup device includes an image sensor that detects a diffracted beam generated from the region to be reproduced when irradiating an optical information recording medium with a reference beam, and sets the detected diffraction beam as a reproduction signal, and a photodetector that is different from the image sensor, which detects the diffracted beam generated from a recorded region in the recording medium when irradiating the recording medium with the reference beam. A light receiver of the photodetector is divided into a plurality of light receiving planes so as to generate the position error signal indicating the positional shifting of the region to be recorded/reproduced of the recording medium with respect to the objective lens from a differential signal of a plurality of signals derived from the respective light receiving planes.

Abstract: An optical pickup device includes a galvanometer mirror that changes an incident angle of a reference beam to an optical information recording medium, an image sensor that detects a diffracted beam from a region to be reproduced upon irradiation of the recording medium with the reference beam, and sets the detected diffracted beam to a reproduction signal, and a photodetector that detects the diffracted beam generated from a plurality of recorded regions upon irradiation of the recording medium with the reference beam. The photodetector includes a plurality of light receivers, and generates an angular error signal indicating positional shifting of the incident angle of the reference beam from a differential signal of a plurality of signals derived from the respective light receivers so as to control the angle of the galvanometer mirror.

Abstract: An optical pickup device includes a laser diode for emitting a laser beam, an objective lens for collecting the light beam emitted from the laser diode and irradiating an optical disc with the collected light beam, a diffraction element for making the light beam reflected from the optical disc diverge, and a detector having a plurality of detection parts for receiving the diverging light beams caused by the diffraction element. The diffraction element has first, second, and third divided areas, wherein a 0th-order diffracted light from the first divided area, the second divided area, and the third divided area is detected by at least four divided detection parts; and at least two detection parts for detecting the light beam diffracted at the first divided area into first or higher diffraction order are aligned in a direction generally perpendicular to the track of the optical disc.

Abstract: Optical pickup device including: semiconductor laser diode emitting optical flux; objective lens converging flux emitted from the diode and radiating flux to an optical disc; diffraction grating branching an optical flux reflected from the disc; and a photodetector receiving flux branched by the grating and has a plurality of light receiving parts, wherein: the grating has areas A, B and C; among diffracted beams diffracted by a track of the optical disc, only a 0-th order diffracted beam becomes incident upon area A, and 0-th and ±1-st order diffracted beams become incident upon area B; the photodetector detects a reproduction signal from optical fluxes diffracted in areas A, B and C; the plurality of light receiving parts which detect the +1-st order diffracted beam or the ?1-st diffracted beam diffracted in area A are aligned in a direction substantially perpendicular or parallel to a track direction of the disc.

Abstract: Disclosed are a module to detect a tracking error signal that is easy to be assembled and robust against variation in a track angle, a diffraction grating, an optical pickup, and an optical disc apparatus that enable the module to be realized, wherein a diffraction grating divided into at least three areas, first, second, and third areas, is used; the second area is an area that do not diffract light; and focusing positions of light diffracted by the first and third areas sandwiching the second area therebetween on an optical disc are arranged with a spacing of (2n?1)×t/2 in an optical disc radial direction, respectively, where n is a nonnegative integer and t is a spacing of guide grooves of the optical disc.

Abstract: For obtaining stable servo-signals without receiving ill influences of stray lights from other layers, on both a focus error signal and a tracking error signal, when recording/reproducing a multi-layer optical disc having small gap between layers thereof, a light beam is divided with using a first and a second diffraction gratings. The first diffraction grating is a polarization diffraction grating, and is mounted on an actuator. The second diffraction grating is disposed on a fixed portion. The first diffraction grating has a first region having a center of a light beam and other(s), and among signal lights reflecting from the disc, the light beam entering into the first region is diffracted, and the light beam entering into the second region transmits therethrough. The second diffraction grating transmits the light beam diffracting on the first region of the polarization diffraction grating therethrough, while diffracting the light beam diffracting on the second region.

Abstract: Provided is an optical pickup device that suppresses a fluctuation of a tracking error signal caused by stray light when recording/reproducing information on/from an optical disc including a plurality of recording layers and attains size reduction. It includes a laser diode emitting laser light of about 405 nm in wavelength, an objective lens irradiating the optical disc with an optical beam emitted from the laser diode and having a numerical aperture of about 0.85, and a detector including a detection part receiving the optical beam reflected from the optical disc. An optical magnification from the optical disc to the detector is set within a range from about 10× to 15×.