Abstract: A method for recording information in form of a hologram. The method can generate a displacement signal by detecting a displacement of a holographic recording medium. The method can perform an exposure control operation that, if the sampling value of the displacement signal falls within an allowable displacement range, records the information item in the holographic recording medium, and if the sampling value of the displacement signal falls outside the allowable displacement range, blocks or reduces at least one of the information light and the reference light to a light intensity with which the information item is not recorded in the holographic recording medium.

Abstract: According to one embodiment, a displacement detection device includes a light source, objective lens, beam splitter, aperture limiting element, and detection device. The beam splitter may separate reflected light into portions. The reflected light may be reflected by the medium and then transmitted through the objective lens. The aperture limiting element may include an aperture limited so as to block a portion of the reflected light. The detection device may detect displacement of the medium in a direction of the optical axis based on the reflected light having passed through the aperture limiting element.

Abstract: An imaging lens includes: an aperture stop; a first lens having a positive refractive power; a second lens having a negative refractive power which is formed in a concave shape on both sides thereof; a third lens having a positive refractive power which is formed in a meniscus shape in which a concave surface is directed toward the side of an object; and a fourth lens having a negative refractive power in which a convex surface is directed toward the object side, which are sequentially disposed from the object side to the image side, wherein the imaging lens satisfies the following conditional expressions (1), (2), (3), (4) and (5): 0.40<f1/|f2|<0.80??(1) 0.80<|f2|/f3<1.50??(2) 0.90<f/|f4|<2.00??(3) 2.60<|(R2?R3)/f1|<4.00??(4) ?d1??d2>25.

Abstract: An optical information recording/reproducing apparatus includes a spatial light modulator that converts an irradiation beam emitted from a light source to a single information beam that carries information; an optical system that causes the single information beam to be collected on an optical-information recording medium including an information recording layer capable of recording the information as hologram by using interference fringes produced due to interference between the single information beam and a plurality of reference beams, and causes each of the reference beams to be irradiated to the optical-information recording medium from mutually different directions so as to intersect with the single information beam in the information recording layer; and a controller that controls to cause the light source to emit the irradiation beam and performs angular multiplexing recording of the information in the information recording layer while controlling to drive either one of the optical-information recordi

Abstract: The present invention is to provide an imaging lens and an imaging device that achieve optical performance high enough for high-pixel imaging elements, and have the smallest possible sizes and thicknesses. A first lens having positive refractive power, an aperture stop, a second lens having positive or negative refractive power, a third lens having negative refractive power, a fourth lens having positive refractive power, and a fifth lens having negative refractive power are provided in this order from the object side, and the following conditional expressions (1), (2), and (3) are satisfied: (1) 0.80<f1/f<1.40, (2) f1/|f3|<1.50, and (3) ?0.20<f1/f2<0.90, where f represents the focal length of the entire lens system, f1 represents the focal length of the first lens, f2 represents the focal length of the second lens, and f3 represents the focal length of the third lens.

Abstract: The present invention is to provide an imaging lens and an imaging device that achieve optical performance high enough for high-pixel imaging elements, and have the smallest possible sizes and thicknesses. In order from the object side, an aperture stop, a first lens having positive refractive power, a second lens having positive or negative refractive power, a third lens having negative refractive power, a fourth lens having positive refractive power, and a fifth lens having negative refractive power are provided, and the following conditional expressions (1) and (2) are satisfied: (1) 0.3<f1/|f3|<3.0, (2) ?0.3<f1/f2<4.5, where frepresents the focal length of the first lens, f2 represents the focal length of the second lens, and f3 represents the focal length of the third lens.

Abstract: According to one embodiment, an optical pickup configured to record and to reproduce on a layer of a disk, including, a light source configured to emit a laser beam, an objective lens including a variable use magnification and configured to focus the laser beam on the layer, a collimator lens configured to change the magnification of the objective lens by moving along an optical axis direction, and a liquid crystal module configured to generate spherical aberration to cancel a coma aberration which may occur because an object point and an image point of the objective lens at the use magnification do not exist on an optical axis of the objective lens.

Abstract: According to one embodiment, an information recording medium characterized by including, a first servo layer, a second servo layer, and a data layer, the information recording medium further including, a first spiral track and a second spiral track formed between the first servo layer and the second servo layer and spiraling in opposite directions.

Abstract: In one embodiment, a method is disclosed for recoding information in form of a hologram. The method can generate a displacement signal by detecting a displacement of a holographic recording medium. The method can perform an exposure control operation that, if the sampling value of the displacement signal falls within an allowable displacement range, records the information item in the holographic recording medium, and if the sampling value of the displacement signal falls outside the allowable displacement range, blocks or reduces at least one of the information light and the reference light to a light intensity with which the information item is not recorded in the holographic recording medium.

Abstract: An optical element includes an effective diameter area that is centered on an optical axis and transmits an effective light beam, and a flange portion having, on a side surface around the effective diameter area, a slope that is not perpendicular to a direction of the optical axis.

Abstract: According to one embodiment, an information recording and reproducing apparatus including, a focus control module, an objective lens control module, a calculation module, and a tracking control module. If, detection the recording marks line, to focus a laser light of a second wavelength to the recording layer through an objective lens and to operation a recording layer tracking control using a tracking error signal taken out from a second reflected light and a laser light of a first wavelength to a track groove through the objective lens and to operation a guide layer tracking control to control the objective lens using a tracking error signal taken out from a first reflected light.

Abstract: According to one embodiment, a data storage device includes a data recording medium, a light source, and following units. The light application unit splits the laser beam from the light source, and applies the first and second light beams to the data recording medium from different directions. The light detection unit detects reflected light beams from the data recording medium. The light deflection unit deflects the reflected light beams to direct the reflected light beams to the light detection unit. The arithmetic unit calculates positional error information based on the detection signal. The drive unit displaces a position and a posture of the data recording medium based on the positional error information.

Abstract: A focus servo control device includes a first detector, first controller, second detector, and second controller. The first detector detects a first focus error signal. The first controller controls the objective lens based on the first focus error signal, so that a focal point of the first laser agrees with the guide layer. The second detector detects a second focus error signal. The second controller changes a relative distance between the focal point of the second laser and the focal point of the first laser, so that the focal point of the second laser agrees with a target recording/reproducing layer.

Abstract: According to one embodiment, a pickup head includes a plurality of light sources, a first objective lens, second objective lens, a driving unit, a first control unit, a second control unit, light receiving units. The first objective lens focuses a first light beam at a first recording layer. The second objective lens focuses a second light beam at a second recording layer. The driving unit moves the first objective lens and the second objective lens in a first direction and a second direction. The first control unit corrects displacement from target track along the first direction. The second control unit controls a moving direction of a position of the second light spot in the second direction.

Abstract: An imaging lens includes: an aperture stop; a first lens having a positive refractive power; a second lens having a negative refractive power which is formed in a concave shape on both sides thereof; a third lens having a positive refractive power which is formed in a meniscus shape in which a concave surface is directed toward the side of an object; and a fourth lens having a negative refractive power in which a convex surface is directed toward the object side, which are sequentially disposed from the object side to the image side, wherein the imaging lens satisfies the following conditional expressions (1), (2), (3) and (4): 0.40<f1/|f2|<0.80??(1) 0.10<f/f3<0.80??(2) 0.20<f/|f4|<1.00??(3) vd1?vd2>25.

Abstract: An imaging lens includes: an aperture stop; a first lens having a positive refractive power; a second lens having a negative refractive power which is formed in a concave shape on both sides thereof; a third lens having a positive refractive power which is formed in a meniscus shape in which a concave surface is directed toward the side of an object; and a fourth lens having a negative refractive power in which a convex surface is directed toward the object side, which are sequentially disposed from the object side to the image side, wherein the imaging lens satisfies the following conditional expressions (1), (2), (3), (4) and (5): 0.40<f1/|f2|<0.80??(1) 0.80<|f2|/f3<1.50??(2) 0.90<f/|f4|<2.00??(3) 2.60<|(R2?R3)/f1|<4.00??(4) ?d1??d2>25.

Abstract: An information storage device includes an information recording medium, at least a single light source that emits laser light, an illuminating unit that illuminates substantially the same position of the information recording medium with two light rays generated from the laser light, in different directions, a light detecting unit that detects reflection light of the two light rays reflected from the information recording medium and outputs a detection signal, an operation unit that calculates position error information of the information recording medium based on the detection signal; and, a driving device that changes the position of the information recording medium based on the position error information.

Abstract: According to one embodiment, a data reproducing apparatus includes a data recording medium, light source unit, light application unit, photodetector unit and control unit. An address mark string including address marks is formed on the data recording medium. The address marks are spaced from each other by a distance depending on address data. The light application unit is configured to split the light beam into a first branch light beam and a second branch light beam and apply the first and second branch light beams to the address mark string at different angles. The photodetector unit is configured to detect first reflected light beams and second reflected light beams from the address mark string to generate image data. The first and second reflected light beams result from the first and second branch light beams, respectively. The control unit is configured to reproduce address data based on the image data.

Abstract: According to one embodiment, an information reproduction apparatus includes an information acquisition unit, an error detection unit, and a control unit. The information acquisition unit is configured to irradiate a reference beam, convert the reference beam into a luminance signal, and output the luminance signal when reproducing an information recording Medium. The error detection unit is configured to detect at least one selected from a first error and a second error by extracting a feature extraction quantity from the luminance signal. The first error is of an irradiation angle of the reference beam. The second error is of at least one selected from a temperature and a wavelength of the reference beam. The control unit is configured to control at least one selected from the irradiation angle and the at least one selected from the reproduction temperature and the wavelength of the reference beam using the second error.

Abstract: An image pickup lens includes, in order from an object side to an image side, an aperture stop, a first lens element having a positive refractive power, a second lens element having a negative refractive power and a biconcave shape, a third lens element having a positive refractive power and a meniscus shape whose concave surface faces the object side, and a fourth lens element having a negative refractive power. In the image pickup lens, the following conditional expressions are satisfied, 0.20<f/|f2|<0.9 ?d1??d2>25 where f denotes the focal length of the entire lens system, f2 denotes the focal length of the second lens element, ?d1 denotes the Abbe number of the first lens element, and ?d2 denotes the Abbe number of the second lens element.