Abstract: An optical pickup device according to the present invention comprises: a first mirror for reflecting a first light beam outputted from a first light source and letting a second light beam outputted from a second light source pass therethrough; a first object lens for converging the first light beam reflected by the first mirror on an information recording surface of a recording medium; a second mirror for reflecting the second light beam passing through the first mirror; a second object lens for converging the second light beam reflected by the second mirror on the information recording surface of the recording medium; and an achromatic lens for correcting an axial chromatic aberration of the second object lens generated by wavelength variation of the second light beam, wherein the achromatic lens is provided in an optical path between the first mirror and the second mirror.

Abstract: An optical drive according to the present invention can write information on an optical disc, which includes a substrate on which a number of pre-pits (2) have been formed on its tracks (t1 to t8) and a recording film that is supported on the substrate. The optical drive includes an optical pickup, and a writing control section for controlling the optical pickup so that marks (3a, 3b) are recorded on the tracks (t1 to t8) so as to overlap with some of the pre-pits (2) and for making the optical pickup irradiate the recording film with a writing light beam. The recorded marks (3a, 3b) overlap with at least ten of the pre-pits (2).

Abstract: Has an object of providing an optical pickup capable of realizing tracking control or focus control at a higher level of precision even when relative positions of a light source and a light detector are shifted due to a change in the environmental temperature, long-term deterioration or the like. The optical pickup includes a base member; a light source, fixed to the base member, for emitting a laser beam; an objective lens for collecting the laser beam onto an optical disc; a light detector, fixed to the base member, for detecting the laser beam reflected by the optical disc; fixing means for fixing the light source and/or the light detector to the base member; and a light blocking section for blocking a central portion of the laser beam in a circular shape on an optical path between the collimator lens and the light detector.

Abstract: When recording/reproducing an information recording medium having a plurality of information recording layers, a photodetector receives reflected light from a recording layer which is being recorded/reproduced, as well as reflected light from another recording layer which is not being recorded/reproduced, making it difficult to appropriately detect control signals during a recording/reproducing operation. The present invention employs a polarization hologram element so that the polarization direction of 0th-order diffracted light and that of 1st-order diffracted light are made to be orthogonal to each other before light reflected from an information recording medium is incident upon the detector. Thus, it is possible to reduce the influence of interference with light from the other recording layer and to obtain appropriate control signals, thereby realizing an optical pickup device with desirable recording capability.

Abstract: Light emitted from a radiation light source 1 passes through a diffraction grating 3a and is separated into transmitted light a and +1st/?1st order diffracted lights b, c. These lights are collected through an objective lens 7 on tracks of an optical disc 8 in a partially overlapped state. Light reflected by the tracks passes through the objective lens 7 and is incident upon light diverging means 13a. Subsequently, light corresponding to the transmitted light “a” diverges into two light beams that are respectively incident upon light detection regions A1, A2, light corresponding to the diffracted lights “b” and “c” respectively diverges into two light beams that are respectively incident upon light detection regions B1, B2, and C1, C2. A tracking error signal associated with the tracks of the optical disc 8 is generated by combining signals detected in the light detection regions A1, A2, B1, B2, C1, and C2.

Abstract: When first-order diffracted beams leak into a region, which is for receiving only a zeroth-order diffracted beam from an optical disc, due to positional displacement between an objective lens and a hologram element, an offset compensation signal includes an AC component, the offset compensation signal preferably including a DC component only. Accordingly, there may be caused deterioration in a modulation degree of the tracking error (TE) signal. A partial light shielding element 110 is formed on a hologram surface 112a along boundaries between a light receiving region (121a), which receives a zeroth-order diffracted beam, and light receiving regions (121b, 121c), which receive the zeroth-order diffracted beam and first-order diffracted beams, so as to cover the light receiving region (121a). Further, the partial light shielding element 110 shifts phases of transmitted light beams by ?, whereby the TE signal is offset-compensated, and the modulation degree can be improved.

Abstract: An optical pickup includes a wave plate on an optical path to be followed by every light beam emitted from three light sources (with wavelengths ?1, ?2 and ?3, respectively) both on their way toward an optical disc and back from the disc toward a photodetector. The wave plate has two layers with different retardations and different optic axis directions. The sum of the retardations of the first and second layers is defined to be approximately 5/4?1, 3/4?2 and 1/2?3 to the light beams with the wavelengths ?1, ?2 and ?3.

Abstract: An optical disc drive according to the present invention includes an optical pickup and a writing control section for instructing the optical pickup to record a mark, representing the information to be written, on the optical disc. In recording the mark on the optical disc, the writing control section instructs the optical pickup to irradiate the same area on the optical disc with a light beam a plurality of times so that the mark is recorded in that repeatedly irradiated area.

Abstract: An optical disc drive according to the present invention writes information on an optical disc, which includes a substrate on which a number of pre-pits have been formed on its tracks and a recording film that is supported on the substrate. The optical disc drive includes a writing control section for instructing an optical pickup to record marks on the tracks by irradiating the recording film with a writing light beam. In accordance with information that defines, on the tracks, recordable areas Aa1 through Aa4 where the marks are recordable and pre-pit reading areas Ab1 through Ab4 where no marks are recordable, the writing control section controls the optical pickup so that the marks are recorded on at least some of the recordable areas. On the tracks on which the marks are recorded, each recordable area is shorter than any of the pre-pit reading areas.

Abstract: An optical disc drive according to the present invention can write information on an optical disc, which includes a substrate on which a number of pre-pits 2 have been formed on its tracks and a recording film that is supported on the substrate. The drive includes an optical pickup and a writing control section for controlling the optical pickup so that marks 3 are recorded so as to overlap with some of the pre-pits 2 on the tracks and for making the optical pickup irradiate the recording film with a writing light beam. The writing control section changes the interval of each pair of recorded marks that are adjacent to each other along the radius of the optical disc according to the optical power of the writing light beam. Thus, the optical disc drive of the present invention can record a mark on an optical disc on which pre-pits have already been formed even if the optical disc has a simplified structure.

Abstract: An optical disk apparatus includes: an optical pickup unit for reading out information recorded on an optical disk; a demodulation circuit for demodulating digital data from an output signal of the optical pickup unit; and a controller for performing a servo control based on the output signal of the optical pickup unit. When performing a focus/tracking control in a recess and a protrusion of a guide groove of the optical disk, the controller obtains a focus control gain difference between the recess and the protrusion by comparing focus offsets with respect to variations in amplitudes of signals from the optical disk for the recess and the protrusion, respectively.

Abstract: When recording on and/or reproducing from an information recording medium having a plurality of recording layers is performed, there has been a problem in appropriately detecting a control signal at the time of the recording and/or reproducing, since reflected light from a recording layer, which does not undergo the recording and/or reproducing, enters a photodetector concurrently with reflected light from a recording layer which undergoes the recording and/or reproducing. In the present invention, a polarization hologram is used to diffract light outputted from a light source and to generate a main beam, which is a zeroth-order light beam, and a pair of sub beams, which is a positive first-order light beam and a negative first-order light beam each having a polarization direction perpendicular to a polarization direction of the main beam.

Abstract: A tracking error signal is generated with stability without being easily affected by a distribution fluctuation of light reflected from an optical disc or by a lens shift. An optical disc drive according to the present invention includes: an objective lens 5 with an aperture radius r0 for converging a light beam emitted from a light source 1; a polarizing hologram substrate 2 for dividing the beam reflected from the optical disc 6 into branched light beams; a photodetector substrate 6, on which at least some of the light beams are incident to generate signals representing the intensities of the light beams; and a shielding mask 16 for cutting off the beam partially.

Abstract: An optical disc drive includes: at least one light source; an objective lens configured to focus the light that has been emitted from the at least one light source; a chromatic aberration compensation element, which is arranged on an optical path between the at least one light source and the objective lens in order to compensate for chromatic aberration that has been produced by the objective lens; and an actuator configured to change a position of the objective lens. The actuator changes the position of the objective lens in a tracking direction by a magnitude of an offset, which is determined by a variation in wavelength of the light to be produced when the power of the light emitted from the at least one light source changes.

Abstract: Regarding optical pickup devices usable for performing recording on and reproduction from a plurality of types of optical discs, there is a problem that because of the structure of locating many optical elements in a height direction of an optical system, the height of the optical system is increased and so it is difficult to realize a thin and compact optical pickup device. According to the present invention, a first wave plate is located between a first light source and a first mirror, a second wave plate is located between a second light source and a second mirror, and the first wave plate and the second wave plate cause a desirable phase shift to light beams of the first through third wavelengths. Owing to this, the number of optical elements located in the height direction of the optical system can be decreased, and so the height of the optical system can be reduced.

Abstract: An optical disk apparatus according to the present invention includes: a rotation driving section on which an optical disk is to be mounted and which drives the optical disk so as to be rotated; a light source; an objective lens for converging light from the light source onto an optical disk mounted on the rotation driving section; a photodetector having at least two detection sections for detecting reflected light, from the optical disk, of the light; and an error signal generation section for deriving a difference signal and a sum signal of respective outputs from the two detection sections of the photodetector, adjusting an offset in at least the sum signal among the difference signal and the sum signal, and thereafter dividing the difference signal by the sum signal whose offset has been adjusted to generate a position error signal of the objective lens.

Abstract: An optical pickup includes a wave plate on an optical path to be followed by every light beam emitted from three light sources (with wavelengths ?1, ?2 and ?3, respectively) both on their way toward an optical disc and back from the disc toward a photodetector. The wave plate has two layers with different retardations and different optic axis directions. The sum of the retardations of the first and second layers is defined to be approximately 5/4?1, ¾?2 and ½?3 to the light beams with the wavelengths ?1, ?2 and ?3.

Abstract: There is provided, in an optical disk apparatus which is capable of recording data to or reading data from a plurality of types of optical disks, a wavelength plate and an optical pickup which can reduce deterioration in signal quality even in the presence of a large birefringence of the substrate of an optical disk. A wavelength plate 6 according to the present invention is a wavelength plate to be placed in an optical path through which rays of a plurality of wavelengths travel back and forth, the plurality of wavelengths including a ray having a wavelength ?. The wavelength plate includes a two-dimensional array of a plurality of birefringent regions, the birefringent regions including first regions D1 and second regions D2 having different optic axis directions from each other. The relationship 240°??1?300° is true, where ?1 is a retardation of the wavelength plate 6 for the ray of the wavelength ?.

Abstract: When first-order diffracted beams leak into a region, which is for receiving only a zeroth-order diffracted beam from an optical disc, due to positional displacement between an objective lens and a hologram element, an offset compensation signal includes an AC component, the offset compensation signal preferably including a DC component only. Accordingly, there may be caused deterioration in a modulation degree of the tracking error (TE) signal. A partial light shielding element 110 is formed on a hologram surface 112a along boundaries between a light receiving region (121a), which receives a zeroth-order diffracted beam, and light receiving regions (121b, 121c), which receive the zeroth-order diffracted beam and first-order diffracted beams, so as to cover the light receiving region (121a). Further, the partial light shielding element 110 shifts phases of transmitted light beams by ?, whereby the TE signal is offset-compensated, and the modulation degree can be improved.

Abstract: An optical pickup device according to the present invention comprises: a first mirror for reflecting a first light beam outputted from a first light source and letting a second light beam outputted from a second light source pass therethrough; a first object lens for converging the first light beam reflected by the first mirror on an information recording surface of a recording medium; a second mirror for reflecting the second light beam passing through the first mirror; a second object lens for converging the second light beam reflected by the second mirror on the information recording surface of the recording medium; and an achromatic lens for correcting an axial chromatic aberration of the second object lens generated by wavelength variation of the second light beam, wherein the achromatic lens is provided in an optical path between the first mirror and the second mirror.