Abstract: A hologram recording device records holograms by interference between an recording beam and a reference beam. The device includes an objective lens exhibiting a predetermined aberration. It is supposed that the laser beam applied to the beam splitter has an light intensity of 1, the recording beam and the reference beam emitted from the beam splitter have light intensities of P and 1?P, respectively, the optical magnification for the recording beam traveling from the beam splitter to the objective lens is a, and N pixels are used for modulation of the recording beam in the spatial light modulator. When the recording beam at the predetermined region has an amplitude 1/k times the amplitude of the reference beam, and the amplitude of the recording beam is X times as great as when there is no aberration, the predetermined aberration of the objective lens is determined to satisfy the formula: 0 < X < a ? ( 1 - P ) 0.6 ? P × 1 kN .

Abstract: A holographic recorder can vary the optical distance between an object lens and a relay lens near the object lens. This arrangement allows defocus-multiplexing utilizing state variations in the laser beam when the beam reaches a storage medium.

Abstract: A hologram recorder is provided, in which coherent light from a light source is split into a signal beam and a reference beam, and the signal beam is modulated by a spatial light modulator to be directed to a hologram recording medium, while the reference beam is directed to the hologram recording medium to overlap with the signal beam for recording a hologram on the hologram recording medium. The hologram recorder includes a beam phase modulator provided with a plurality of optical devices (20p, 20p?) each configured to assume one of two modes such as ON mode and OFF mode, the ON mode for causing the reference beam to be passed or reflected in a predetermined direction toward the hologram recording medium, the OFF mode for causing the reference beam to be blocked or directed in another direction other than the predetermined direction. Each optical device (20p, 20p?) provides a phase difference 0 or ?.

Abstract: A disk-type hologram recording medium and a hologram recording and reproduction device utilizing such a recording medium are provided. The hologram recording and reproduction device includes a spatial optical modulator provided with a plurality of optical elements arranged in a grid-like form. These optical elements are divided into groups each associated with 1 bit of data for performing required light modulation. Thus, a special pattern exhibiting a greater S/N margin for 1 bit can be recorded in the recoding medium. During data recording or data reproduction, the special pattern is read from the recording medium, and based on the retrieved special pattern, fine adjustment by servo control is conducted for adjustment of tilting or focusing of the recording medium and for adjustment of the wavelength of the light emitted from the light source.

Abstract: A hologram recorder (A) which records holograms by causing a recording beam (P) and a reference beam (S) to interfere with each other in a hologram recording media (B), includes an incident-side and an emitting-side lenses (3a, 3b) provided as a compound lens disposed in a laser beam path between a light source (1) and a beam separator (7); and an aperture stop (5) provided to limit a light flux diameter between the incident-side and emitting-side lenses (3a, 3b). The aperture stop (5) is disposed at a position biased toward the incident-side lens (3a) as viewed from an incident-side focal position of the emitting-side lens (3b).

Abstract: A hologram recorder records a hologram in a hologram recording medium by interference of a recording beam irradiated at a predetermined incident angle to the medium via a spatial light modulator incliningly in a predetermined direction with a reference beam irradiated incliningly in an opposite direction to the recording beam so that the beams crosses at a predetermined crossing angle. The recorder includes a beam modulator for converting a Gaussian-beam having a Gaussian-distribution of intensity into a parallel beam having an intensity distribution tending to be uniform and allowing the parallel beam to travel to the spatial modulator as the recording beam. The Gaussian-beam has a center axis decentered from an optical axis of the beam modulator in a decentering direction including a directional component of the predetermined direction in which the recording beam is inclined or an opposite directional component thereto.

Abstract: A hologram recording apparatus includes an objective lens (7) for illuminating a hologram recording medium (B) with a recording beam (S) in a manner such that the recording beam overlaps a reference beam, thereby performing multiple recording of holograms at a portion illuminated with the reference beam and the recording beam (S). The objective lens (7) includes at least one rotationally symmetric lens (7A, 7B), and at least one rotationally symmetric lens (7A) is so arranged that the lens optical axis is inclined with respect to the direction (S1) in which the recording beam (S) travels.

Abstract: The hologram recording/reproducing apparatus is for recording a hologram by emitting a recording beam (S) modulated by a spatial light modulator and a reference beam (R) having a same wavelength as the recording beam onto a hologram recording medium (B) so that the beams overlap each other with polarization direction (p) of the beams being matched to interfere with each other, and for reproducing the hologram by exposing the hologram recording medium storing the hologram to the reference beam to generate diffracted light and receiving the diffracted light by an imaging device. The spatial light modulator is controlled so as to form a data area (H0) corresponding to information to be recorded and a plurality of mark areas (H1) for detecting a position of the data area in the hologram recording medium (B) in recording of the hologram.

Abstract: A hologram recording and reproducing apparatus includes a movable galvanomirror, a mirror controller and a reproduction unit. The galvanomirror guides a reference beam toward a hologram recording medium and changes the incident angle of the reference beam. The mirror controller causes the galvanomirror to move for adjusting the incident angle to a predetermined angle for hologram recording. In reproducing the recorded information, the mirror controller causes the galvanomirror to move, so that the incident angle continuously changes within a predetermined range including the predetermined angle. The reproduction unit receives a detection signal from an optical detector while the incident angle changes continuously. The detection signal corresponds to the intensity of a reflected beam from the hologram recording medium. The reproduction unit reproduces the recorded information, based on the detection signal, when the intensity of the reflected beam is over a predetermined level or reaches the maximum.

Abstract: An optical element for recording/reproducing a hologram condenses a recording beam into a hologram recording medium, while also allowing the passage of a reproduction beam from the hologram recording medium in the reverse direction with respect to the recording beam. The optical element is configured to converge, upon incidence of a parallel beam flux as the recording beam, an on-axis beam and off-axis beams contained in the parallel beam flux onto different image points. A beam condensing spot of the on-axis beam and the off-axis beams is formed, with a predetermined diameter at a predetermined position on an optical axis on a way to the image points. At least one of the on-axis beam and the off-axis beams has a diameter, at the predetermined position on the optical axis, smaller than the predetermined diameter of the beam condensing spot.

Abstract: The invention is a recording and reproducing apparatus for recording data on a recording medium having a holographic recording area and a buffer recording area. The recording and reproducing apparatus has a holographic recording controller which multiplexedly records user data as page data in a holographic form on the holographic recording area, a buffer recording controller which records user data on the buffer recording area, and a recording controller, upon receiving a user data write request, which controls recording of user data in the write request on which one of the holographic recording area and the buffer recording area.

Abstract: A hologram recorder applies a recording beam (S) and a reference beam (R) to the illumination site (p) of a hologram recording medium (B). The interference between the recording beam (S) and the reference beam (R) produces multiple hologram recording at the illumination site (p). The recorder includes a recording-purpose reference beam reflector (10) for reflecting the reference beam (R) to the illumination site (p), and a pivot mechanism for pivoting the reflector (10) about an axis (x) to vary the incident angle (?r) of the reflected reference beam (R) to the recording medium (B). The reflector (10) is disposed to cross a predetermined optical path. The axis (x) of the pivot mechanism is so arranged that the reflected reference beam (R) is directed to the illumination site (p) even when the incident angle (?r) of the beam (R) changes due to the pivoting of the reflector (10).

Abstract: A hologram recording device (A1) includes a laser (1), a beam splitter (3) splitting the laser beam from the laser (1) into recording and reference beams (S), (R), a spatial light modulator (5) modulating the recording beam (S) by record information, a recording opto-system directing the modulated beam (S) to a target site of a hologram recording medium (B), and a reference opto-system directing the reference beam (R) to the target site of the recording medium (B) for interference with the recording beam (S) through difference incident angles. The beam (S)-beam (R) interference enables multiplex hologram recording at the target site. The device (A1) further includes a light amount adjustor (8) that adjusts the amount of the reference beam (R) from the splitter (3) based on the incident angle to the recording medium (B) for keeping the illuminance of the reference beam (R) at the target site at a predetermined level.

Abstract: A hologram recording device records holograms by interference between an recording beam and a reference beam. The device includes an objective lens exhibiting a predetermined aberration. It is supposed that the laser beam applied to the beam splitter has an light intensity of 1, the recording beam and the reference beam emitted from the beam splitter have light intensities of P and 1?P, respectively, the optical magnification for the recording beam traveling from the beam splitter to the objective lens is a, and N pixels are used for modulation of the recording beam in the spatial light modulator. When the recording beam at the predetermined region has an amplitude 1/k times the amplitude of the reference beam, and the amplitude of the recording beam is X times as great as when there is no aberration, the predetermined aberration of the objective lens is determined to satisfy the formula: 0 < X < a ? ( 1 - P ) 0.6 ? P × 1 kN .

Abstract: A hologram recording device illuminates with a recording beam (S) a hologram recording medium (B), and illuminates with a reference beam (R) a region illuminated with the recording beam (p) while variably controlling the incident angle regarding the hologram recording medium (B) whereby holograms are recorded on the illuminated region (p) in multiple by interference of the recording beam (S) and the reference beam (R). The device includes an incident angle variable controller for variably controlling the incident angle of the reference beam (R) in a predetermined range. The hologram recording medium (B) has such characteristics that its recording sensitivity degrades as the incoming light amount increases. The incident angle variable controller changes the incident angle of the reference beam (R) from a larger angle to a smaller angle.

Abstract: A hologram recorder (A) records a hologram in a hologram recording medium (B) by interference of a recording beam (S) irradiated at a predetermined incident angle to the medium (B) via a spatial light modulator (2) incliningly in a predetermined direction with a reference beam (R) irradiated incliningly in an opposite direction to the recording beam (S) so that the beams (S,R) crosses at a predetermined crossing angle. The recorder includes a beam modulator (1) for converting a Gaussian-beam having a Gaussian-distribution of intensity into a parallel beam having an intensity distribution tending to be uniform and allowing the parallel beam to travel to the spatial modulator (2) as the recording beam (S). The Gaussian-beam has a center axis (Gs) decentered from an optical axis (1A) of the beam modulator (1) in a decentering direction including a directional component of the predetermined direction in which the recording beam (S) is inclined or an opposite directional component thereto.

Abstract: A hologram recording device for irradiating a recording beam (S) to a hologram recording medium (B) at a fixed incident angle (?s) and irradiating a reference beam (R) to an illuminated region (p) of the recording beam (S) by variably controlling an incident angle (?r) of the reference beam (R) on the hologram recording medium (B), whereby a hologram is recorded on the illuminated region (p) in multiple, includes at least a variable reflector (10) directing the reference beam (R) to the illuminated region by reflection and being swung around a predetermined axis (x) for changing the incident angle (?r) of the reference beam (R); and a light shield (11) being swung integrally with the variable reflector (10) for partially shielding the reference beam (R) so that a luminous flux diameter thereof becomes narrower as the incident angle (?r) becomes larger.

Abstract: A recording and reproducing apparatus includes a light source to emit a laser beam, an information light beam irradiation unit to irradiate a medium with an information light beam, a reference light beam irradiation unit to irradiate the medium with a reference light beam so as to form a specific speckle pattern on the medium. The reference light beam irradiation unit comprises a diffusion board provided in the way of a light path through which the laser beam is passed and generating the reference light beam, a rotation controller to rotate the diffusion board, and an identification information detector to detect identification information previously formed on a surface of the diffusion board. The diffusion board comprises a plurality of encode storage regions in which different identification information is formed and a plurality of diffusion pattern generation regions specified by the identification information.

Abstract: A hologram recording and reproducing apparatus minimizes reproduction errors by servo control on the tilting of a reference beam relative to a hologram recording medium. The apparatus includes an optical detector for servo control and an optical sensor for reproduction signal conversion. A pixel pattern generator generates, on a wave surface of the recording beam, a discretely distributed recording pixel pattern corresponding to the information to be recorded, and a specifically shaped and localized servo pixel pattern for the servo control. A beam splitter splits the reflected beam from the hologram recording medium into a reproduction beam directed to the optical detector for reproduction signal conversion and a servo beam directed to the optical detector for servo control. A servo controller controls the tilting of the reference beam relative to the hologram recording medium, based on an output signal from the servo control optical detector.

Abstract: A holographic recorder (A1) can vary the optical distance between an object lens (8) and a relay lens (7b) near the object lens (8). This arrangement allows defocus-multiplexing utilizing state variations in the laser beam when the beam reaches a storage medium (B1).