Abstract: A variable focal length lens includes: a lens portion including a pair of light transmissive members, at least one of which is deformable, and a light transmissive liquid medium sealed between the pair of light transmissive members; and a liquid medium container including a chamber that communicates with the lens portion and is filled with the liquid medium, the liquid medium container causing the shape of the surface of the deformable light transmissive member or members to be changed by changing the volume of the chamber to adjust the amount of liquid medium with which the lens portion is filled.

Abstract: An optical pickup includes: a light source; an objective lens; a beam splitter; a quarter wave plate that transforms the optical beam into a circularly polarized optical beam and also transforms the circularly polarized reflection optical beam into an optical beam whose polarization direction is perpendicular to the optical beam; a light detector; a neutral density filter section placed on a mutual optical path of those beams, reducing the intensity of the optical beam while maintaining the intensity of the reflection optical beam; and a filter drive section that puts the neutral density filter section in the mutual optical path or outside of it, wherein the intensity of the optical beam and the filter drive section are controlled such that the amount of the optical beam emitted to the optical disc is maintained at a predetermined level.

Abstract: An optical pickup for recording or reproducing an information signal in an optical disc includes a light source for emitting a light beam toward the optical disc, an objective lens for focusing the light beam emitted from the light source onto a recording surface of the optical disc, and a photodetector for receiving the light beam reflected by the recording surface of the optical disc and outputting a signal corresponding to an intensity of the received light beam. A spot of the light beam received by the photodetector is asymmetric in both a radial direction and a tangential direction of the optical disc. A lens shift signal for the objective lens is detected by a controller on the basis of the signal output from the photodetector, the controller controlling the objective lens to follow the optical disc.

Abstract: The present invention can simplify the configuration of a polarization adjustment plate. According to the present invention, the crystal axis of the polarization adjustment wavelength plate 32 is so arranged as to be turned up from the X-Y plane being an orthogonal plane with respect to the optical axis 40a, and the wavelength dependence which the crystal material is originally provided with is largely expressed, and further the thickness “ta” with respect to the optical axis 40a is set up such that the phase difference ? to be brought about at the beam center becomes low from 360°+180°=540° being a desired design value to irradiate the optical beam as the P-polarization by a predetermined difference value or 60°.

Abstract: An optical integrated device includes a light source; a light splitting-and-guiding section that splits a reflected light beam into two end light beams, a connection light beam, and a residual light beam, and guides the two end light beams and the connection light beam in directions different from a direction of the residual light beam; and a light receiving section that receives the two end light beams and the connection light beam with photodetection devices divided, in the tangential direction, into at least two regions within a range in which the connection light beam is incident, receives the residual light beam with photodetection devices divided, in the tangential direction, into regions having widths corresponding to portions on which the two end light beams are incident, and outputs a detection signal in accordance with an amount of light received with each of the photodetection devices.

Abstract: An optical pickup includes an optical system in which light from a light source is introduced through an objective lens into an optical recording medium and in which light reflected from the optical recording medium is introduced into a light-receiving unit and an objective lens driving unit for driving the objective lens based on a light output detected at said light-receiving unit. In this optical pickup, a diffraction element is provided between the light source and the objective lens, the diffraction element is provided with at least first and second diffraction areas and the first and second diffraction areas have such grating shapes that ± first-order diffracted lights diffracted are received by the light-receiving unit at the position in which 0-th order light and ± first-order diffracted lights generated from guide grooves of the optical recording medium may not overlap with each other.

Abstract: An optical pickup for recording/reproducing information on/from an optical disc having recording layers, includes a light source; an objective lens for condensing an optical beam emitted from the light source on the recording layer; a photo-detector having a light-receiving section for receiving return light from the optical disc; an optical-path separating unit for separating the optical path of the return light reflected by the optical disc from the optical path of the optical beam emitted from the light source; and a masking member having a masking unit shielding part of a passing-through optical beam, in which the masking unit shields the central region of the optical beam to be incident in the light-receiving section among the optical beams reflected by the other recording layers or surfaces different from the recording layer recording/reproducing information so as not to admit the central region to the light-receiving section.

Abstract: The present invention can simplify the configuration of a polarization adjustment plate. According to the present invention, the crystal axis of the polarization adjustment wavelength plate 32 is so arranged as to be turned up from the X-Y plane being an orthogonal plane with respect to the optical axis 40a, and the wavelength dependence which the crystal material is originally provided with is largely expressed, and further the thickness “ta” with respect to the optical axis 40a is set up such that the phase difference ? to be brought about at the beam center becomes low from 360°+180°=540° being a desired design value to irradiate the optical beam as the P-polarization by a predetermined difference value or 60°.

Abstract: An optical pickup for recording/reproducing information on/from an optical disc having recording layers, includes a light source; an objective lens for condensing an optical beam emitted from the light source on the recording layer; a photo-detector having a light-receiving section for receiving return light from the optical disc; an optical-path separating unit for separating the optical path of the return light reflected by the optical disc from the optical path of the optical beam emitted from the light source; and a masking member having a masking unit shielding part of a passing-through optical beam, in which the masking unit shields the central region of the optical beam to be incident in the light-receiving section among the optical beams reflected by the other recording layers or surfaces different from the recording layer recording/reproducing information so as not to admit the central region to the light-receiving section.

Abstract: An optical pickup includes at least a laser light source emitting a laser beam, a collimator lens system including a plurality of lenses for collimating the light beam emitted from the laser light source and incident thereupon as diffused light, and an objective lens. The laser beam transmitted through the collimator lens system is incident upon the objective lens. The collimator lens system includes a first lens unit held so as to be movable in an optical axis direction of the laser beam and a fixed second lens unit.

Abstract: An optical pickup includes: a light source; an objective lens; a beam splitter; a quarter wave plate that transforms the optical beam into a circularly polarized optical beam and also transforms the circularly polarized reflection optical beam into an optical beam whose polarization direction is perpendicular to the optical beam; a light detector; a neutral density filter section placed on a mutual optical path of those beams, reducing the intensity of the optical beam while maintaining the intensity of the reflection optical beam; and a filter drive section that puts the neutral density filter section in the mutual optical path or outside of it, wherein the intensity of the optical beam and the filter drive section are controlled such that the amount of the optical beam emitted to the optical disc is maintained at a predetermined level.

Abstract: An optical disc device performs tracking control using a light amount difference at two overlapping areas. The optical disc device includes a splitter, objective lens, detection-signal generator, tracking-signal generator, and driver. The splitter splits the light beam from a light source into a main beam and sub-beams. The objective lens converges the split beams and illuminates a signal-recording-layer track. The detection-signal generator receives reflected light beams and generates a detection signal according to the reflected-light-beam light amounts. The tracking-signal generator generates a tracking error signal on the basis of the detection signal. The driver drives the objective lens in a tracking direction on the basis of the tracking error signal. The splitter causes the light amounts of the overlapping areas at sub-reflected-light beams to be less than a light amount of an area other than the overlapping areas.

Abstract: An optical pickup for recording or reproducing an information signal in an optical disc includes a light source for emitting a light beam toward the optical disc, an objective lens for focusing the light beam emitted from the light source onto a recording surface of the optical disc, and a photodetector for receiving the light beam reflected by the recording surface of the optical disc and outputting a signal corresponding to an intensity of the received light beam. A spot of the light beam received by the photodetector is asymmetric in both a radial direction and a tangential direction of the optical disc. A lens shift signal for the objective lens is detected by a controller on the basis of the signal output from the photodetector, the controller controlling the objective lens to follow the optical disc.

Abstract: An optical pickup includes an optical system in which light from a light source is introduced through an objective lens into an optical recording medium and in which light reflected from the optical recording medium is introduced into a light-receiving unit and an objective lens driving unit for driving the objective lens based on a light output detected at said light-receiving unit. In this optical pickup, a diffraction element is provided between the light source and the objective lens, the diffraction element is provided with at least first and second diffraction areas and the first and second diffraction areas have such grating shapes that ±first-order diffracted lights diffracted are received by the light-receiving unit at the position in which 0-th order light and ±first-order diffracted lights generated from guide grooves of the optical recording medium may not overlap with each other.

Abstract: A method for separating light coming from an illuminated multilayer medium having a plurality of reflective surfaces to reach a light receiver through a focusing lens includes the steps of splitting the light traveling toward the light receiver through the focusing lens into at least two portions along the optical axis thereof and separating a light component coming from a particular position of the illuminated medium from each of the split portions of the light by removing a light component focused at a position closer to the focusing lens than the focal position of the light component coming from the particular position between the two focal positions and/or removing a light component focused at a position closer to the light receiver than the focal position of the light component coming from the particular position between the two focal positions.

Abstract: An optical pickup includes at least a laser light source emitting a laser beam, a collimator lens system including a plurality of lenses for collimating the light beam emitted from the laser light source and incident thereupon as diffused light, and an objective lens. The laser beam transmitted through the collimator lens system is incident upon the objective lens. The collimator lens system includes a first lens unit held so as to be movable in an optical axis direction of the laser beam and a fixed second lens unit.

Abstract: An optical pickup includes a laser light source configured to emit laser light, an objective lens configured to focus the laser light emitted from the laser light onto an optical disk, and an image-formation magnification rate varying section for varying an image-formation magnification rate at which the laser light is focused on the optical disk.

Abstract: A phase change optical recording medium which enables optimum direct overwrite even under high speed high density conditions without degrading repetition durability or storage stability of recorded signals. To this end, the phase change optical recording medium has a recording layer formed at least of a phase change material and is recorded and/or reproduced with a laser light beam having a wavelength ranging between 380 nm and 420 nm. A ratio Ac/Aa, where Ac is the absorption rate of said recording layer in a crystalline state and Aa is the absorption rate of said recording layer in an amorphous state, is not less than 0.9, and a crystallization promoting layer promoting the crystallization of the phase change material is contacted with at least one surface of the recording layer.

Abstract: An optical pickup minimizing the modulation caused on the focus error signal by grooves/lands or a train of pits, and implementing a stable focus servo operation. In an optical pickup adapted to obtain focus error information by means of an astigmatism system, the arranging state of an objective lens (5) is set so that a direction (DOB) of an astigmatism generated by the objective lens (5) will be a direction in a predetermined angle range with respect to a direction (DSD) of an astigmatism generated by an astigmatism generating element e.,g (cylindrical lens (7)). The predetermined range is an angle range of ±50° with respect to the direction (DSD) of the astigmatism.

Abstract: Accurate detection of a clock synchronization mark represented by wobbles of a track is realized. A track is wobbled by a synchronization mark signal which has a waveform such that the differential value near the leading portion and the trailing portion of the waveform is a value smaller than that of a rectangular wave, thereby wobbled portions corresponding to synchronization marks are formed. For example, a synchronization mark signal is a signal of a waveform such that both end portions of the waveform are almost linear, in which level variations are moderate, and the center of the waveform has sharp level variations.