Abstract: An objective lens for optical pickup and an optical pickup apparatus having the same are provided. The objective lens for optical pickup includes a light source side lens surface and a disc side lens surface. The light source side lens surface and the disc side lens surface each include an effective region disposed at a central region of the objective lens and a non-effective region disposed outside the effective region. An optical path changing element, disposed in the non-effective region of at least one of the light source side lens surface and the disc side lens surface, changes a path of light incident thereon.

Abstract: An optical pickup apparatus comprising: a laser diode; an objective lens made of a synthetic resin configured to focus laser light emitted from the laser diode to a signal recording layer of an optical disc; and a collimating lens having a diffraction grating and arranged in an optical path between the laser diode and the objective lens, the collimating lens being so moved in an optical axis direction of the laser light as to correct spherical aberration occurring in response to a change in temperature when performing a recording operation for the optical disc, and the collimating lens correcting by the diffraction grating chromatic aberration occurring when switching from the recording operation to a reproducing operation for the optical disc.

Abstract: The present invention relates to an optical pick, an optical drive device, and a light irradiation method capable of suppressing a generated amount of shift ?x of a spot position. The optical pickup irradiates an optical recording medium through a common objective lens which irradiates a first light for use in information recording in or information reproduction from a recording layer and a second light different from the first light, the optical recording medium includes a reference surface having a reflection film in which a position director is formed in a spiral form or the like form, and the recording layer which is provided in a layer position different from the reference surface and in which a mark corresponding to irradiation of light is formed and hence information is recorded.

Abstract: An optical pickup device includes a light source for emitting a light beam, an objective lens for collecting the light beam which is emitted and for irradiating an optical disc with the collected light beam, a diffraction element with a plurality of areas for dividing the light beam which is reflected from the optical disc, a detector with a plurality of detection parts for receiving the light beam which is made to diverge by the diffraction element, and a branching mirror for making the light beam branch into an optical path from the light source to the objective lens and an optical path from the objective lens to the detector. The diffraction element gives an aberration to the light beam diffracted at a specified area.

Abstract: An apparatus for reading from or writing to a near-field optical recording medium capable of detecting tilt and spherical aberration is described. The apparatus comprises a light source for generating a reading light beam, a near-field lens, an aberration compensation element, and a diffractive optical element. The diffractive optical element is switchable between a far-field mode and a near-field mode and is adapted to generate a main light beam and four or more sub-beams from the reading light beam for determining at least a cover layer thickness error signal. For this purpose it has an outer region with a first grating period and an inner region having a diameter smaller than an effective numerical aperture of the near-field lens, which in the near-field mode has a second grating period and which has a switchable inner area having a diameter smaller than a far-field numerical aperture of the near-field lens, which in the far-field mode has the first grating period.

Abstract: An astigmatism element converges laser light in a first direction for generating a first focal line, and converges the laser light in a second direction perpendicular to the first direction for generating a second focal line. A light separating element guides the laser light entered into two first areas and into two second areas to four positions different from each other. The light separating element imparts a light separating function to the laser light entered into the first two areas in directions identical to each other and with magnitudes different from each other, and imparts a light separating function to the laser light entered into the two second areas in directions identical to each other and with magnitudes different from each other.

Abstract: An optical pickup device includes an objective lens portion which converges laser light at a first focal point and a second focal point; an actuator which positions the first focal point or the second focal point on a recording layer in a disc; an astigmatism element which sets a first focal line position and a second focal line position of the laser light reflected on the disc away from each other in a propagating direction of the laser light; a spectral element which disperses four light fluxes obtained by dividing the laser light reflected on the disc in four from each other; and a photodetector having a sensor group which receives the four light fluxes dispersed by the spectral element.

Abstract: An optical pickup apparatus comprising: a diffraction grating configured to diffract laser light from a laser diode so that signals recorded in first and second optical discs are selectively reproduced, thicknesses of protective layers between surfaces and signal recording surfaces of the first and second optical discs being different from each other; a polarization beam splitter configured to divide laser light from the diffraction grating into first and second laser lights whose light amounts are substantially the same; a first objective lens configured to focus the first laser light onto the signal recording surface of the first optical disc; a second objective lens configured to focus the second laser light onto the signal recording surface of the second optical disc; and a photodetector configured to be applied with return lights of the first and second laser lights reflected from the signal recording surfaces of the first and second optical discs.

Abstract: An exemplary optical pickup comprises: a light source with first and second emission points; an optical branching element which branches light emitted from the first emission point into multiple light beams including a first main beam and first sub-beams and which also branches light emitted from the second emission point into multiple light beams including a second main beam and second sub-beams; an optical system which condenses the multiple light beams produced by the optical branching element onto an optical storage medium, thereby making the first and second main beams form a write light beam spot and a read light beam spot, respectively, on a target recording track on the storage medium and making the first and second sub-beams form reference light beam spots and other light beam spots somewhere on the storage medium other than the target recording track.

Abstract: A complex objective lens composed of a hologram and an objective lens, capable of realizing stable and high-precision compatible reproducing/recording of a BD with a base thickness of about 0.1 mm for a blue light beam (wavelength ?1) and a DVD with a base thickness of about 0.6 mm for a red light beam (wavelength ?2). In an inner circumferential portion of the hologram, a grating is formed, which has a cross-sectional shape including as one period a step of heights in the order of 0 time, twice, once, and three times a unit level difference that gives a difference in optical path of about one wavelength with respect to a blue light beam, from an outer peripheral side to an optical axis side. The hologram transmits a blue light beam as 0th-order diffracted light without diffracting it, and disperses a red light beam passing through an inner circumferential portion as +1st-order diffracted light and allows it to be condensed by an objective lens.

Abstract: A disclosed optical element includes three or more sub-wavelength convexo-concave structures having pitches less than a wavelength of an incident light incident to the optical element and having groove depths equal to each other and a periodic structure having the three or more sub-wavelength convexo-concave structures, the pitch of the periodic structure greater than the wavelength of the incident light, in which a predetermined polarization direction of the incident light is diffracted mainly into a specific order.

Abstract: When performing recording/reproduction of information for a given recording layer of an optical disc having three recording layers, influences of reflected light from other recording layers are reduced or removed, thus making it possible to obtain a more stable RF signal or focus error signal. An optical pickup device includes a light source, a collimator lens, an objective lens, a photodetector, and a light shielding member. Among the recording layers of the optical disc, a first layer and a second layer adjoining each other are disposed in the order of the first layer and second layer from near the objective lens.

Abstract: An optical system of an optical pickup device includes an astigmatism element which imparts astigmatism to BD light reflected on BD and CD light reflected on CD, and a spectral element which disperses four light fluxes of BD light and four light fluxes of CD light by diffraction, the four light fluxes of BD light and the four light fluxes of CD light being obtained by dividing the BD light reflected on the BD and the CD light reflected on the CD by a first straight line parallel to a converging direction by the astigmatism element, and a second straight line perpendicular to the first straight line. A photodetector of the optical pickup device is provided with first and second sensor groups for respectively receiving the four light fluxes of BD light and the four light fluxes of CD light dispersed by the spectral element.

Abstract: A liquid crystal element includes: a transparent substrate; and a liquid crystal layer including: a liquid crystal material; and a concavo-convex portion including periodic concaves and convexes, wherein the concavo-convex portion is aligned so that a longitudinal direction of liquid crystal molecules that are positioned on a side of the transparent substrate and on a concavo-convex surface that is an interface of the concavo-convex portion substantially becomes a vertical direction with respect to a concavo-convex surface on the side of the transparent substrate, or a longitudinal direction of liquid crystal molecules that are positioned on a side, in which a medium is disposed and which is opposite to the transparent substrate, and on the concavo-convex surface that is the interface of the concavo-convex portion substantially becomes the vertical direction with respect to a concavo-convex surface on the side, in which the medium is disposed, to form a diffraction grating.

Abstract: An optical head includes a blue-violet laser light source for emitting a blue-violet laser beam, a mirror with a diffraction grating for transmitting and reflecting the blue-violet laser beam at a predetermined ratio, and a front monitor sensor for receiving transmitted light or reflected light from the mirror with a diffraction grating and creating an APC signal for controlling an output of the blue-violet laser light source. The mirror with a diffraction grating includes a first surface which the blue-violet laser beam enters, and a second surface facing the first surface. The first surface and the second surface are mutually parallel. A reflecting coat for transmitting and reflecting the blue-violet laser beam at a predetermined ratio is formed on the first surface, and a diffraction grating is formed on the second surface.

Abstract: A method and an apparatus for reading from a near-field optical recording medium are described. The apparatus includes: an optical system for generating a signal beam and a reference beam; a near-field lens for illuminating the signal beam onto the near-field optical recording medium, for collimating a reflected signal beam, and for reflecting the reference beam; and at least a first detector and a second detector for obtaining a homodyne detection signal from the reflected signal beam and the reflected reference beam.

Abstract: A mounting structure of an optical element, includes: an optical element; an elastic member usable when the optical element is mounted; and a holding unit configured to be mounted with the optical element and the elastic member, the elastic member configured to be pressed into the holding unit, the holding unit configured to be mounted with the optical element by use of the elastic member.

Abstract: There is provided a diffraction grating including a convex portion and a concave portion which are used for lights having different wavelengths ?1, ?2 and ?3 and are alternately disposed on at least one surface of a substrate with a predetermined pitch. An average refractive index of the convex portion is smaller than an average refractive index of the concave portion. A phase difference in the lights having the wavelength ?1 which transmit the convex portion and the concave portion and a phase difference in the lights having the wavelength ?2 which transmit the convex portion and the concave portion are both substantially the integral multiple of 2?, and a phase difference in the lights having the wavelength ?3 which transmit the convex portion and the concave portion is substantially the non-integral multiple of 2?.

Abstract: An optical pickup device is provided with a spectral element which imparts diffraction in such a manner that four light fluxes of the first laser light are separated from each other, when a light flux of the first laser light and a light flux of the second laser light reflected on a recording medium having laminated recording layers and servo layers are divided into four by a first straight line in parallel to a converging direction by an astigmatism element, and a second straight line perpendicular to the first straight line, and that the four light fluxes of the first laser light propagate on an outer side than the light flux of the second laser light; and a photodetector including a first sensor group which receives the first laser light, and a second sensor group which receives the second laser light.

Abstract: An objective lens for an optical information recording/reproducing apparatus, at least one of optical surfaces of the objective lens comprising a diffraction surface having a diffraction structure defined by an optical path difference function, and wherein: the diffraction surface has a first region contributing to converging first and second light beams and having a diffraction structure configured such that diffraction orders at which the diffraction efficiencies are maximized for the first and second light beams are 1st order; the diffraction surface has a second region located outside the first region, and the second region is configured to contribute to converging the first light beam and not to contribute to convergence of the second light beam; and the objective lens satisfies a condition: 35<P2×f2<200 ??(1).

Abstract: According to the present invention, of all beams of light reflected from the optical disc, only light in a peripheral region excluding a push-pull region is used to generate a DPD signal. In this method of signal generation that optimizes internal light-receiving surface interconnections in a photodetector, the lens error signal required for the generation of a tracking error signal in the DPP scheme is amplified at a lower amplification factor. In addition, the light reflected from the multilayered optical disc will be divided into a plurality of regions and the divided beam of light will be focused at different positions on the photodetector. When the beam is focused upon a desired layer, stray light from recording layers other than those to be subjected to information reproduction will not enter the photodetector light-receiving surfaces used for servo signals.

Abstract: A diffractive optical element includes a first optical part and a second optical part bonded to each other with a bonded surface therebetween configured as a diffraction surface. In this diffractive optical element, the diffraction order of diffracted light with the largest quantity of light out of diffracted light for one of a plurality of kinds of laser beams obtained on the diffraction surface is different from the diffraction order for at least another laser beam.

Abstract: An optical pickup apparatus comprising a first laser unit including a first laser light source and a second laser unit including second and third laser light sources, being respectively disposed on a reflection (transmitting) surface side and a transmitting (reflection) surface side of a first beam splitter, laser lights of the first, second, and third wavelengths being guided onto a common optical path through the first beam splitter and guided to the respective sorts of optical recording mediums, each of the laser lights being divided by a diffraction grating disposed on the common optical path into a main beam and sub-beams, a second beam splitter being disposed on the upstream side of the diffraction grating on a return path of each of the laser lights, the laser lights through the second beam splitter being branched from the common optical path and being received by a photodetector.

Abstract: An optical pickup includes: a light source outputting a light beam; an objective lens collecting the light beam on a target recording layer as a target of plural recording layers provided in an optical disc; a lens moving unit moving the objective lens in a tracking direction nearly orthogonal to track grooves helically or coaxially formed in the target recording layer; a collective lens collecting a reflected light beam formed when the light beam is reflected by the optical disc; a diffraction optical element diffracting part of the reflected first-order light beam in predetermined directions as first, second, third and fourth beams; and a photodetector receiving the first and second beams using first and second light receiving areas, and generating light reception signals, and receiving the third and fourth beams using third and fourth light receiving areas, and generates light reception signals.

Abstract: An objective lens a first optical path difference providing structure in which a first basic structure and a second basic structure are overlapped with each other. The first basic structure is a blaze-type structure which emits a Xth-order diffracted light flux, when the first light flux passes through the first basic structure, where the value of X is an odd integer. At least a part of the first basic structure arranged around an optical axis includes a step facing an opposite direction to the optical axis. The second basic structure is a blaze-type structure which emits a Lth-order diffracted light flux, when the first light flux passes through the second basic structure, where the value of L is an even integer. At least a part of the second basic structure arranged around the optical axis includes a step racing the optical axis.

Abstract: A light beam emitted from a laser source is divided into a first light beam and a second light beam. An optical divider is further provided to separate a combined light beam of the first and second light beams into a first light bundle near the optical axis and a second light bundle in the edge portion and to diverge the first and second light bundles so that the first and second light bundles are individually detected by plural detectors. The first light beam is signal light focused on an optical information recording medium by an objective lens and reflected off the medium, and the second light beam is reference light not focused on the optical information recording medium. A focus error signal is then detected for the first light bundle for compensating focus error.

Abstract: A pickup device comprising an irradiation optical system including an objective lens to focus a ray bundle on a track of a recording surface of an optical recording medium to form a light spot, and a detection optical system including a photo detector to receive return light reflected from the light spot via the objective lens and perform photoelectric conversion and controls said objective lens in position according to electrical signals produced through operations on outputs of said photo detector.

Abstract: Provided is an objective lens used in an optical pickup that performs recording and/or reproducing of information signals on three different types of optical discs using different wavelengths. The objective lens is configured to collect light beams with the at least three wavelengths ?1, ?2, and ?3, which satisfy a relationship of ?1<?2<?3, on signal recording surfaces of compatible optical discs corresponding to the respective wavelengths. The objective lens includes: a diffractive portion that has a predetermined diffraction structure formed on an incident side surface. The diffractive portion has a first region that is provided in an innermost peripheral portion so as to diffract the light beams, a second region that is provided outside the first region so as to diffract the light beams, and a third region that is provided outside the second region.

Abstract: An optical pickup apparatus includes at least: a light emitting element capable of emitting at least first wavelength light and second wavelength light; and a diffraction grating configured to split the first wavelength light into at least a first main beam and a first sub-beam and to split the second wavelength light into at least a second main beam and a second sub-beam, a following expression (1) being satisfied: 1.05 < Yp ? ? 1 Yp ? ? 2 < 2.50 ( 1 ) where: Yp1 is an interval between the first main beam and the first sub-beam when a first media corresponding to the first wavelength light is irradiated with the first main beam and the first sub-beam, and Yp2 is an interval between the second main beam and the second sub-beam when a second media corresponding to the second wavelength light is irradiated with the second main beam and the second sub-beam.

Abstract: In an optical pickup device, an optical reflection beam from a multi-layer optical disc is divided into a plurality of areas, divided optical fluxes focus upon different positions on a photodetector, a focusing error signal is detected by using a plurality of divided optical fluxes by a knife edge method, and a tracking error signal is detected by using a plurality of divided optical fluxes. The optical flux divided areas and light receiving parts are disposed in such a manner that in an in-focus state of a target layer, stray light from another layer does not enter servo signal light receiving parts of the photodetector. It is therefore possible to obtain stable servo signals including both the focusing error signal and tracking error signal during recording/reproducing a multi-layer optical disc, without being influenced by stray light from another layer.

Abstract: An optical pickup apparatus according to an embodiment includes a semiconductor laser, an objective lens, a grating, and a light detecting device. The grating is installed between the semiconductor laser and the objective lens to divide the light beam emitted from the semiconductor laser into three beams or more including a main beam and a sub-beam. The light detecting device receives the divided light reflected by the optical recording medium. The grating includes a first diffraction grating and a second diffraction grating. The first diffraction grating has patterns formed for dividing a sub-beam with respect to a first optical recording medium having a first track pitch, and second diffraction grating has patterns formed for dividing the sub-beam divided by the first diffraction grating into sub-beams with respect to a second optical recording medium having a second track pitch.

Abstract: Provided is an optical pickup device which can properly record and/or reproduce information on and/or from three types of discs having different recording densities and is simple in configuration and low cost. An objective lens is also provided. On the optical surface of the objective lens, an optical path difference giving structure is formed. Out of diffracted light generated when a first luminous flux enters the structure, second order diffracted light has the maximum diffraction volume. Out of diffracted light generated when a second luminous flux enters the structure, zero order diffracted light has the maximum diffraction volume. Out of diffracted light generated when a third luminous flux enters the structure, the minus first order diffracted light has the maximum diffraction volume.

Abstract: An optical pick-up apparatus for reproducing information recorded on an optical recording medium or recording information on the optical recording medium is provided. The optical pick-up apparatus includes a light source unit which generates beams; a diffraction element which diffracts the generated beams; and an objective lens which focuses a p order diffracted beam which is used for recording and reproducing information among a plurality of diffracted beams which are diffracted by the diffraction element on any one of a plurality of information layers which are formed on an optical recording medium. A p±1 order diffracted beam which is not used for recording and reproducing information is focused away from the plurality of information recording layers and on the surface of the optical recording medium.

Abstract: An optical disc device is provided with an optical head including a light source, a condensing optical system including an objective lens for receiving a light beam emitted from the light source and forming a microspot on a multilayer optical recording medium, a photodetector for receiving the light beam reflected by the multilayer optical recording medium and outputting an electrical signal corresponding to the amount of light and a coma aberration correcting element for correcting a coma aberration of the condensing optical system, and a processing circuit for controlling the condensing optical system and the coma aberration correcting element.

Abstract: An objective optical system for an optical information recording/reproducing apparatus for recording/reproducing for first, second and third optical discs by selectively using three types of substantially collimated light beams including first, second and third light beams respectively having first, second and third wavelengths, wherein at least one of optical surfaces of the objective optical system comprises a diffraction surface having a diffraction structure, the diffraction surface includes a first region defined by first and second optical path difference functions, a second region defined by at least one type of optical path difference function, and a third region defined by at least one type of optical path difference function, the first region satisfies a condition: ?0.15<f1/fD11<?0.03??(1), where fD11=?1/(2×P112×m11×?), and the diffraction surface satisfies a condition: ?0.05<(?13(h3)??13(h2))/(m13×f1)<?0.005??(2).

Abstract: Provided are a single beam optical pickup device and a disc drive including the optical pickup device. The optical pickup device includes a light controlling device that prevents or limits stray light generated from a medium from being incident on a light sensor. The light controlling device may further include an additional auxiliary light sensor so as to reuse effective light among diffracted light.

Abstract: Of the beams reflected by an optical disk, only peripheral beams excluding the push-pull region are used to generate a DPD signal in order to optimize internal wire connections among the light receiving areas of the optical detector and thereby reduce the amplification factor of the lens error signal, required for generating the tracking error signal of the DPP method. A beam reflected from a multilayered optical disk is divided into some beam diffraction areas. The divided beam diffraction areas and the light receiving areas are so arranged that the divided beams focus at different positions on the optical detector and that, when a beam is focused on a target recording layer of the disk, stray light from other than the target recording layer being reproduced does not enter into the servo signal light receiving area of the optical detector.

Abstract: According to the present invention, a tracking error signal can be obtained with good stability by the three-beam differential push-pull method even if the track guide groove direction of the optical disc changes as viewed from the objective lens. An optical pickup 30 according to the present invention includes: a grating element 110 for splitting light emitted from a light source 121 into multiple light beams including zero-order, ?first-order and +first-order diffracted light beams; an objective lens 118 for condensing the zero-order and ±first-order diffracted light beams, which have come from the grating element 110, onto an optical disc; and a photosensor 101 with multiple photodetectors for receiving respectively the three diffracted light beams reflected from the optical disc.

Abstract: An optical head includes a diffraction element capable of improving the quality of a TE signal by a DPP method even if light amounts of two sub-spots are unbalanced for optical discs having different groove pitches. In a three-beam optical head, a diffraction element is divided in a radial direction of an optical disc into a first area, a second area and a third area, wherein the second area is further divided into a fourth area and a fifth area. The periodic structure of the first area is displaced from that of the fourth area by a ¼ period, the periodic structure of the third area is displaced from that of the first area by a ½ period, and the periodic structure of the fifth area is displaced from that of the third area by a ¼ period and from that of the fourth area by a ½ period.

Abstract: An optical information recording method of recording information three-dimensionally by irradiating a laser light beam onto a medium having a servo information plane on which address information and/or servo information is recorded, is disclosed. The method includes the steps of: dividing a laser light beam from one laser light source into laser light beams, the beam including a first light beam for reading the information, and a second light beam for recording information onto the recording medium; irradiating the first light beam onto the servo information plane to read the information from reflected light of the first light beam to read the information in which optical axes of the first light beam and second light beam are arranged coaxially; and irradiating the second light beam based on the read information to be focused onto a position in a depth direction perpendicular to a horizontal direction of the recording medium.

Abstract: An optical pickup device capable of eliminating interlayer crosstalk which is responsible for fluctuation in control signals and error rate in data signals, thereby ensuring stable action for a multilayered recording disc with a narrow interlayer spacing. The reflected beam coming from the multilayered disc is divided along the central line into two parallel portions by the dividing optical system and then condensed. The reflected beam coming from the active layer, which has been condensed, is reflected by the reflecting plane whose reflecting region is limited and the thus reflected beam is detected by the optical detector. The reflected beam coming from other layers is not reflected by the reflecting plane, so that interlayer crosstalk is reduced.

Abstract: An optical pickup includes a light source, an optical system for irradiating a recording medium including a plurality of recording layers with light from the light source, a diffraction optical element that divides light reflected from the recording medium into a plurality of optical fluxes and diffracts the fluxes, and an optical detector receiving the optical flux diffracted by the diffraction optical element. The optical detector includes a light receiving element detecting a focus error signal, wherein a longitudinal direction of the light receiving element is arranged to coincide with a circumferential direction of the recording medium, or arranged to be inclined to a circumferential or radial direction.

Abstract: An optical-pickup apparatus includes: a laser diode; an objective lens; a diffraction grating; a photodetector including main-beam-, first-sub-beam-, and second-sub-beam-light-receiving portions; a quarter-wave plate having either a second area allowing a reflected-laser beam to pass therethrough without polarization or a third area allowing the reflected beam to pass therethrough at a polarization angle different from that of the first area; and a polarizing member having a separate-light-amount ratio set therefor with respect to the reflected beams passing through the second or third area and an area excluding the second or third area from the first area, such that proportions of the reflected beams passing therethrough toward the photodetector are different, thereby decreasing an irradiation level when the first- and second-sub-beam-light-receiving portions are irradiated, as stray light, with the reflected beam reflected from either one, not subjected to a signal-reading operation, of the first- and secon

Abstract: Provided is an objective lens for selectively focusing each of light beams having three wavelengths ?1, ?2, and ?3 on a signal recording surface of a corresponding optical disc, the wavelengths ?1, ?2, and ?3 satisfying at least a relationship ?1<?2<?3, the objective lens including a diffraction section disposed on an entry-side surface thereof, the diffraction section including a first region disposed in an innermost radius portion, a second region disposed outside the first region, and a third region disposed outside the second region, the first to third regions being formed so that an aperture of the light beams are appropriately limited, the first region including a staircase-like diffractive structure having a certain number of levels configured so that diffracted light of a predetermined order has the highest diffraction efficiency and optical-path-difference phase amounts for the levels of the diffractive structure has a certain relationship.

Abstract: An optical pickup with a simplified structure in which, according to the type of optical disc, diffracted light from three types of laser light can be directed efficiently onto a photodetector and appropriate focus control can be performed based on the signals detected by the photodetector, and a diffractive optical element that can be used in the optical pickup, which has a semiconductor laser 10 that can emit three types of laser light, a diffractive optical element 42 that diffracts the laser light reflected from the optical disc 31, and a single photodetector 43 that detects the diffracted light exiting the diffractive optical element 42.

Abstract: An optical head includes a blue-violet laser light source for emitting a blue-violet laser beam, a mirror with a diffraction grating for transmitting and reflecting the blue-violet laser beam at a predetermined ratio, and a front monitor sensor for receiving transmitted light or reflected light from the mirror with a diffraction grating and creating an APC signal for controlling an output of the blue-violet laser light source. The mirror with a diffraction grating includes a first surface which the blue-violet laser beam enters, and a second surface facing the first surface. The first surface and the second surface are mutually parallel. A reflecting coat for transmitting and reflecting the blue-violet laser beam at a predetermined ratio is formed on the first surface, and a diffraction grating is formed on the second surface.

Abstract: Provided is an optical pickup apparatus using a reduced number of parts. An optical pickup apparatus (26) of the present invention includes: a laser unit (108) for emitting a laser beam complying with the BD standards; a laser unit (106) for emitting a laser beam complying with the DVD standards and a laser beam complying with the CD standards; and a PDIC (10B) for receiving and detecting the laser beams complying with the respective standards. Because the laser beam complying with the DVD standards and the laser beam complying with the BD standards are received by one photo detector provided in the PDIC (10B), the number of parts needed for the optical pickup apparatus (26) can be reduced, and the costs of the apparatus can be decreased.

Abstract: An optical pickup compatible with two wavelengths such as an optical pickup having a two-wavelength, multi-laser source unit to be compatible with both DVDs and CDs prevents, in a simply structured optical system, error signal quality deterioration caused by relative shifting between laser beams and realizes detection of focus and tracking error signals. The optical system is provided with an optical waveguide device and a photodetector. The optical waveguide device includes a holographic diffraction grating having three regions divided by two approximately parallel division lines which extend respectively passing the optical axes of a laser beam for DVD and a laser beam for CD. The photodetector has plural light receiving surfaces each divided into three regions. This allows reliable focus and tracking error signals to be detected during both DVD reproduction and CD reproduction.

Abstract: An optical pickup apparatus changes a propagation direction of luminous fluxes, out of a laser light reflected by a disc, in four luminous flux regions set about a laser optical axis so as to mutually disperse these luminous fluxes. A signal light region in which only a signal light is present appears on a detection surface of a photodetector. A plurality of sensors for a signal light are placed at positions irradiated with the signal light within the region. When an arithmetic process is performed on a detection signal outputted from each sensor, a DC component occurring in a tracking error signal is suppressed.

Abstract: There is provided an optical disk apparatus causing a hologram device to diffract a reflected light beam and causes each of reflected light beams of primary light in a longitudinal direction to generate received light signals by receiving the reflected light beams through receiving regions of a receiving unit before a preformatted signal being generated by a signal processing unit based on the received light signals. Therefore, the preformatted signal that excludes an influence of a stray light pattern by an interlayer stray light beam from a plurality of recording layers can be generated.