Abstract: A holder has walls defining a holding region for holding an optical element, and has a protrusion part overlapping the holding region. The protrusion part is formed at a deformable support part, and can be displaced in a direction away from the holding region by deformation of the support part. When the optical element is fitted into the holding region, the support part deforms and the protrusion part runs on a side surface of the optical element. In this state, the optical element is pressed until a back surface of the optical element abuts a support surface of the holder. The optical element is pressed against the wall and positioned by a return force of the support part.

Abstract: An optical read/write apparatus as an embodiment of the present invention includes: a light-splitting element configured to split a light beam emitted from a light source into multiple light beams including a write beam and a read beam; an optical system configured to converge the write and read beams onto the same track on an optical storage medium; a photodetector including a light receiving element configured to detect the read beam reflected from the optical storage medium and output an electrical signal; and a divider configured to generate a read signal by dividing the signal detected by the light receiving element by a signal that represents a write modulated component and that is obtained by detecting a part of the light beam emitted from the light source.

Abstract: In one embodiment, an optical pickup includes an optical system which forms multiple light beams based on the light emitted from a light source and which converges a write beam and a read beam, thereby forming a main spot and a sub-spot, respectively, on an optical storage medium. This optical system converges the write and read beams onto the optical storage medium so that the main spot moves through the same region on the optical storage medium ahead of the sub-spot. The optical pickup further includes a detector for sensing the write and read beams reflected from the storage medium. The detector includes a first photodiode 10 that receives the reflected light from the main spot 50R on the storage medium and a second photodiode 11 that receives a portion of the reflected light from the sub-spot 51R.

Abstract: New and useful methods and systems for reading optical discs, such as multi-layer Blu-ray discs are disclosed. For example, in an embodiment a device for reading two-layered optical discs includes a laser diode capable of emitting light, a set of optics including a fixed collimator, the set of optics providing a numerical aperture (NA) of substantially less than 0.85, and a detector for detecting laser light focused on a two-layer optical disc to produce a stream of detected bits.

Abstract: Optical pickup device including: semiconductor laser diode emitting optical flux; objective lens converging flux emitted from the diode and radiating flux to an optical disc; diffraction grating branching an optical flux reflected from the disc; and a photodetector receiving flux branched by the grating and has a plurality of light receiving parts, wherein: the grating has areas A, B and C; among diffracted beams diffracted by a track of the optical disc, only a 0-th order diffracted beam becomes incident upon area A, and 0-th and ±1-st order diffracted beams become incident upon area B; the photodetector detects a reproduction signal from optical fluxes diffracted in areas A, B and C; the plurality of light receiving parts which detect the +1-st order diffracted beam or the ?1-st diffracted beam diffracted in area A are aligned in a direction substantially perpendicular or parallel to a track direction of the disc.

Abstract: An objective optical system for an optical information recording/reproducing apparatus, at least one surface of the objective optical system being configured to be a phase shift surface having a phase shift structure, wherein: the phase shift surface has a first area contributing to converging first, second and third light beams onto recording surfaces of first, second and third optical discs, respectively; in the first area, the phase shift surface has at least two types of phase shift structures including a first phase shift structure having first steps and a second phase shift structure having second steps; the phase shift surface has a plurality of combinations of annular zones which satisfy a condition: 0.95<P1/P2<1.05??(1), and the phase shift surface satisfies a following condition: ?3.00<??1/??2<?0.10??(2).

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 lens includes a lens portion which condenses light; a reflecting flat portion which is formed in a periphery of the lens portion and reflects parallel light to be irradiated to the reflecting flat portion in a direction opposite to the irradiation direction; and a flange portion which is adhered to a lens holder by an adhesive. An applied portion of the adhesive which is formed on the flange portion is inclined with respect to the reflecting flat portion.

Abstract: An optical pickup device includes a laser diode for emitting a laser beam, an objective lens for collecting the light beam emitted from the laser diode and irradiating an optical disc with the collected light beam, a diffraction element for making the light beam reflected from the optical disc diverge, and a detector having a plurality of detection parts for receiving the diverging light beams caused by the diffraction element. The diffraction element has first, second, and third divided areas, wherein a 0th-order diffracted light from the first divided area, the second divided area, and the third divided area is detected by at least four divided detection parts; and at least two detection parts for detecting the light beam diffracted at the first divided area into first or higher diffraction order are aligned in a direction generally perpendicular to the track of the optical disc.

Abstract: A light source device configured as a master oscillator power amplifier includes a mode locked laser unit having an external resonator and a semiconductor optical amplifier that amplifies and modulates laser light emitted from the mode locked laser unit. The width in a lateral direction of a waveguide on an incident side of the semiconductor optical amplifier is set so that a horizontal lateral mode of the waveguide on the incident side of the semiconductor optical amplifier becomes multiple modes, and a magnification conversion unit that converts a magnification of incident light from the mode locked laser unit to the semiconductor optical amplifier is disposed so that a basic mode is selectively excited in optical coupling on the incident side of the semiconductor optical amplifier.

Abstract: An optical recording medium includes: N recording layers (where N?4); a number of kinds of layer intervals between the recording layers adjacent to each other being an integer M equal to or less than a minimum integer equal to or more than log2(N); and one or more AB blocks including four recording layers with a first layer interval A, a second layer interval B, and the first layer interval A formed in order in the one or more AB blocks. When the M as the number of kinds of layer intervals is M?3, the optical recording medium has a part of a third layer interval C as a layer interval between a recording layer forming an AB block and a recording layer adjacent to the recording layer, the adjacent recording layer being included in other than the AB block including the recording layer.

Abstract: A recording apparatus includes the following elements. A recording light source emits pulse laser light for recording. A first light source emits first CW laser light. An irradiation optical system irradiates an optical recording medium with the pulse laser light and the first CW laser light via an objective lens in the state in which the optical axis of the first CW laser light is tilted with respect to the optical axis of the pulse laser light. A reception optical system outputs, to a first light receiver, a returned light portion of the first CW laser light which has been reflected by a reflection surface formed on the optical recording medium and which has been input through the objective lens. A focus servo controller performs focus servo control for the objective lens on the basis of a first reception signal obtained by the first light receiver.

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: 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 disc drive according to the present invention includes: a laser light source 2 for emitting a laser beam; a photodetector 10 for detecting a signal that has been supplied from an optical disc 100; and an optical system 200 for irradiating the optical disc 100 with the laser beam and guiding the light reflected from the optical disc 11 to the photodetector 10. The drive further includes a memory 300 for storing information defining a relation between the output value of the photodetector 10 and the output power of the laser light source 2 when the laser light source 2 is emitting the laser beam but the light reflected from the optical disc 100 fails to reach the photodetector 10; and a control section 400 for controlling the output power of the laser light source 2 based on the information stored in the memory 300 and the output of the photodetector 10 when the laser light source 2 is emitting the laser beam but the light reflected from the optical disc fails to reach the photodetector 10.

Abstract: An objective lens for a slim type BD combo disc drive focuses a first light beam onto a first optical disc, a second light beam onto a second optical disc, and a third light beam having a third wavelength onto a third optical disc. The lens may include a first surface through which the first, second, and third light beams emitted from a light source enter the objective lens, and a second surface through which the first, second, and third light beams exit the objective lens and proceed toward the three corresponding optical discs. The first surface may include a diffractive surface which provides focus control in accordance with (i) 0th order light of the first and second light beams which are respectively focused onto the first and second optical discs, and (ii) 1st order diffracted light of the third light beam which is focused onto the third optical disc.

Abstract: Provided are an optical head capable of favorably recording or reproducing information to or from an information recording medium including a plurality of information recording surfaces, an optical disc device including the optical head, an information processing device including the optical disc, and an objective lens. The optical head (40) includes a blue-violet laser light source (1) which emits a blue-violet laser beam, an objective lens (8) which has an orbicular zone-shaped diffractive structure, and which diffracts the blue-violet laser beam and converges the generated diffracted light of n-th order (where n is a natural number) on a predetermined information recording surface of a multi-layer optical disc (60), and a light-receiving element (23) which receives the blue-violet laser beam reflected by the predetermined information recording surface, wherein the diffractive structure adds a positive power component and a spherical aberration component to the n-th order diffracted light.

Abstract: This invention allows super-resolution reproduction with which a better bER value is attainable, when information is recorded by a random pattern including a mark length not longer than a resolution limit, by use of a highly versatile signal decoding method. Information is recorded as marks and spaces coded by RLL(1,7) modulation, which each of the marks and spaces have one of a plurality of lengths, and 2T marks and 2T spaces of the marks and spaces being formed are shorter than 0.12 ?m. An information recording layer (20) includes a reproduction film (21) and a reflective film (22) which are provided in this order from a side from which reproducing light is incident, which reproduction film is made of (i) zinc oxide, (ii) strontium titanate, (iii) titanium oxide, (iv)cerium oxide, or (v) a material including at least one of the (i) through (iv), and which reflective film is made of tantalum or titanium.

Abstract: An optical-pickup apparatus includes: a diffraction grating that a laser beam enters, the diffraction grating being configured to generate a main beam that is 0th-order light and sub-beams that are +1st-order diffracted light and ?1st-order diffracted light; an objective lens to focus the main and sub-beams onto a signal-recording layer; a main-beam light-receiving portion that the main beam reflected by the signal-recording layer is applied to; and sub-beam light-receiving portions that the sub-beams reflected by the signal-recording layer are respectively applied to, each light-receiving area of the sub-beam light-receiving portions being smaller than a light-receiving area of the main-beam light-receiving portion, wherein a focusing-control operation is performed by a differential astigmatic method using the main beam applied to the main-beam light-receiving portion and the sub-beams respectively applied to the sub-beam light-receiving portions.

Abstract: An apparatus includes a light source for producing a beam of light, a coupler for coupling the light into a slider waveguide, a beam expander for expanding the beam of light from the waveguide to produce an expanded beam, a collimator for collimating the expanded beam, and a focusing device for concentrating the collimated beam to a focal point. A method of delivering light to a focal point is also described.

Abstract: An optical pickup, an optical recording/reproducing device, a computer, an optical disk recorder, and a minute spot forming method that can enable light propagation with a high transmittance and can form a minute spot. The optical pickup includes a wavelength plate (202) that converts the polarization state of the light beam emitted from a semiconductor laser (101) and an objective lens optical system (105) that converges the light beam whose polarization state has been converted with a numerical aperture greater than 1. The wavelength plate (202) generates a light beam having a polarization state that differs depending on location. The polarization distribution of the light beam generated by the wavelength plate (202) is axially symmetric with respect to the optical axis of the light beam as an axis of symmetry. A light ray on the light axis is a circularly polarized light. Part of a light ray other than the light ray on the optical axis is an elliptically polarized light with an ellipticity of less than 1.

Abstract: An optical-pickup apparatus includes: a single-wavelength-laser diode to emit a first-laser beam; a two-wavelength-laser diode to emit second- and third-laser beams; an objective lens; a photodetector to be irradiated with first- to third-reflected-light beams of the first- to third-laser beams reflected from the signal-recording layers of first- to third-optical discs; an aberration-correcting plate to guide the second- and third-laser beams toward the lens, and correct astigmatism of the reflected-light beams, and guide the astigmatism-corrected-reflected-light beams toward the photodetector; a semitransparent mirror to guide, toward the lens, the first-laser beam and the second- and third-laser beams having been guided by the aberration-correcting plate, and guide the reflected-light beams toward the aberration-correcting plate; a quarter-wave plate to convert the first- to third-laser beams from linearly-polarized light into circularly-polarized light, and convert the reflected-light beams from circularly

Abstract: The optical element adjustment structure is provided with a rotating side including an optical element to be rotationally adjusted, and a non-rotating side where the rotationally adjusted optical element is securely arranged. The rotating side includes a tapered distal end section, and a contact section provided in an end section on a side opposite the distal end section and adapted to be contacted by an adjustment jig. The non-rotating side includes a recessed section for engaging the distal end section. The adjustment jig contacting the contact section is moved, whereby the rotating side rotates, the distal end section engaged in the recessed section being used as a fulcrum, and the optical element is rotationally adjusted.

Abstract: Provided is an objective lens manufactured well by using a mold and an optical pickup apparatus including the same. The objective lens of the present invention includes a first region that focuses laser beams of a BD, DVD, and CD standards, a second region that focuses the laser beams of the DVD and CD standards, and a third region that focuses the laser beams of the BD and the DVD standards are provided in this order from a center portion of the objective lens. A first annular zone step provided in the first region has a step amount larger than step amounts of annular zone steps provided in other regions.

Abstract: An objective lens element having excellent compatibility with optical discs having different base material thicknesses is provided. The objective lens element has optically functional surfaces on an incident side and an exit side. At least either one of the optically functional surfaces on the incident side and the exit side includes a diffraction portion which satisfies at least either one of the following formulas (1) and (2): ?1×?2<0 (“×” represents multiplication) ??(1), (sin ?2)/?22=?(sin ?1)/?1 ??(2), where ?1 is the diffraction angle of a light beam having a diffraction order providing the maximum diffraction efficiency at the wavelength ?1, and ?2 is the diffraction angle of a light beam having a diffraction order providing the maximum diffraction efficiency at the wavelength ?2.

Abstract: A guide-layer separated optical recording medium includes a guide layer with a guide track formed therein and a plurality of recording layers, these layers being separately deposited from each other. A layer position information region for indicating position information of each of the recording layers, is formed on the guide track within a different range of the guide layer for each of the recording layers. Each of the recording layers includes a preformat region having a predetermined signal written on a record track along the guide track, and the preformat region on each of the recording layers is provided in a region corresponding to the layer position information region. An optical recording medium drive apparatus and a recording layer access method for the guide-layer separated optical recording medium are also provided.

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 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: An optical pickup includes an objective lens, a lens holder which holds the objective lens, a focusing coil attached to the lens holder having the winding axis directed at the optical axis of the objective lens, and a magnet provided opposite the side surface of the lens holder. A protruding portion is attached to the side surface of the lens holder at a side apart from the objective lens with respect to the optical axis direction of the objective lens farther than the focusing coil.

Abstract: An optical disc apparatus in which a bias of a focusing error signal is changed to a value according to a recording power at timing corresponding to a predetermined address position before starting the recording and a defocus of an opposite polarity is preliminarily caused so as to set off a defocus which occurs at the start of the recording.

Abstract: An astigmatism element converges reflected light to generate focal lines, and a light separating element separates light fluxes of the reflected light entered into four first areas from each other. Two of the first areas are disposed in a direction along which a pair of vertically opposite angles defined by first and second straight lines are aligned, and the other two of the first areas are disposed in a direction along which the other pair of vertically opposite angles are aligned. Each of the four first areas is divided into two segment areas by a second area. The reflected light to be entered into the second area is guided to a position on the outside of sensors of a photodetector, and light fluxes of the reflected light to be entered into the paired segment areas are irradiated, on the photodetector, at positions away from each other.

Abstract: Chemically-bonded laminated polymer achromatic polarization devices, such as circular polarizers, are disclosed for use in optical disc (e.g., CD/DVD) pickup heads. Chemically-bonded laminated polymer achromatic polarization devices have the benefit of providing stable retardation and optic axis over an extended wavelength range, thereby ensuring orthogonal polarization in double-pass for two or more laser wavelengths. Moreover, the chemically-bonded laminated polymer achromatic polarization devices can be symmetric in construction, such that there is no specific input and output side. This alleviates the need to produce geometries that prohibit inversion of the part when installed in the system. Manufacturing processes that produce chemically-bonded laminated polymer achromatic polarization devices, with high light efficiency, durability and robust performance in a variety of environmental conditions are disclosed.

Abstract: An optical pickup device, an optical drive using the same, and a method of forming a beam spot are provided. The optical pickup includes a light source system that includes a light source corresponding to at least one of a digital versatile disc (DVD) and a Blu-ray disc (BD). The light source forms a beam spot having an oval shape with a long axis and a short axis on an information recording track of the disc, and the light source is disposed such that the long axis is maintained at an angle ranging from 0° to 30° with respect to a radial direction passing through a rotation center of the disc.

Abstract: Disclosed is an optical recording head which is provided with a surface emitting laser that emits laser light which is efficiently introduced into a waveguide through a grating coupler (diffraction grating). Specifically disclosed is an optical recording head which is provided with a surface emitting laser comprising at least a light source, and a waveguide that is connected thereto through a diffraction grating and irradiates a recording medium with the light from the light source. The light source has a two-dimensional photonic crystal structure in the surface that faces the waveguide. Regions of the two-dimensional photonic crystal structure other than the region facing the diffraction grating are converted, and the region facing the diffraction grating serves as a surface emitting.

Abstract: An optical storage focus servo system may include an optical pickup unit that includes an astigmatic focusing lens, a focusing actuator that controls a position of the lens relative to an optical media, and a plurality of detectors that detect an intensity and shape of a reflected beam from the media. The system may also include a controller that controls the focusing actuator based on the intensity and shape of the reflected beam.

Abstract: A conventional optical pickup apparatus has a problem that due to multiple optical paths provided therein, the number of parts of optical systems becomes larger and a time required for attaching the parts and adjusting an optical axis becomes longer. In optical pickup apparatus 1 of the invention, a major part of optical path 21 of a laser beam emitted from first semiconductor laser device 2 and optical path 20 of a laser beam emitted from second semiconductor laser device 3 are shared. Then, the laser beam reflected from the optical disk 17 (optical feedback) is received by shared PDIC 19 and light-receiving processing is accurately performed on the laser beam as a light detector. With this structure, the number of parts of optical systems disposed in the optical pickup apparatus 1 is reduced, an attachment operation of the parts becomes easier, and a time required for adjusting an optical axis is reduced. Thus, an operational efficiency is greatly improved.

Abstract: An objective lens for an optical pickup device is provided with a light-source-side lens surface by which laser light is converged, and a disc-side lens surface by which the laser light converged by the light-source-side lens surface is converged. The first lens surface and the second lens surface are configured to guide a part of a light collecting portion of the laser light reflected on the second lens surface to a position on an outside of the first lens surface.

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 objective lens for an optical pickup device is provided with a light-source-side lens surface by which laser light is converged, and a disc-side lens surface by which the laser light converged on the light-source-side lens surface is converged. In this arrangement, assuming that a projection area S1 is an area of the light-source-side lens surface when the light-source-side lens surface is viewed from an optical axis direction of the objective lens, and a projection area S2 is an area of the disc-side lens surface lens surface when the disc-side lens surface lens surface is viewed from the optical axis direction of the objective lens, the projection area S1 and the projection area S2 satisfy the following formula: S1/S2?2.0.

Abstract: An optical pickup device has an astigmatism element which imparts astigmatism to reflected light of laser light reflected on a recording layer, and a spectral element into which the reflected light is entered, and which separates the reflected light. The spectral element is divided into four third areas by a first area having a certain width and formed along a straight line in parallel to a first direction, and by a second area having a certain width and formed along a straight line in parallel to a second direction. The spectral element is configured to guide the reflected light passing through the four third areas to respective corresponding sensors on a photodetector while making propagating directions of the reflected light different from each other, and to avoid guiding the reflected light entered into the first area and into the second area to the sensors.

Abstract: An optical pickup device has an astigmatism element which imparts astigmatism to reflected light of laser light reflected on a recording layer, and a spectral element into which the reflected light is entered, and which separates the reflected light. The spectral element is divided into six second areas by a straight line in parallel to a first direction, a straight line in parallel to a second direction, and a first area having a predetermined width and formed along a straight line in parallel to a third direction inclined from the first direction by 45 degrees. The spectral element is configured to guide the reflected light passing through the six second areas to corresponding sensors on a photodetector while making propagating directions of the reflected light different from each other, and to avoid guiding the reflected light entered into the first area to the sensors.

Abstract: An optical pickup device, which can effectively prevent occurrence of trouble in recording and reproducing of information due to the fact that an objective lens for each optical beam is contaminated while not adding unnecessary parts and while reducing a cost, is provided. An optical pickup device (P1) which performs the recording or reproducing of information in or from an optical disc (13) by using an optical beam (B) or (D), comprises: objective lenses (11) and (12) on which cleaning films which are activated by radiation of the optical beam (B) and clean their surfaces are formed in an optical path, and a control unit (15) for setting an optical path of the optical beam (B) in such a way that the optical beam (B) reflected by the optical disc (13) is radiated on the objective lens (12).

Abstract: An optical pickup device, an optical disk drive and method of controlling light performed by the optical pickup device are provided. The optical pickup device includes: a light transmitting system including an object lens for facing a medium having a multi recording layer for storing information, a light source system for providing a plurality of beams used to record information on or reproduce information from the multi recording layer via the light transmitting system, a light-receiving system disposed on a path of a beam reflected from the medium, and a light controller including a light control device for controlling stray light generated in the medium such that the stray light does not reach the light-receiving device.

Abstract: An objective lens relating to the present invention includes 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 facing the optical axis.

Abstract: An optical recording medium and an optical information device that improve the quality of a servo signal and a reproduction signal. In the optical recording medium, when shape-wise thicknesses tr1, tr2, tr3, and tr4 of a cover layer (42), a first intermediate layer (43), a second intermediate layer (44), and a third intermediate layer (45) are respectively converted into thicknesses t1, t2, t3, and t4 of the respective corresponding layers each having a predetermined refractive index “no”, a defocus amount with respect to a layer having a refractive index nr? and a thickness tr? (satisfying: 1???n (where ? is a positive integer and n is an integer of 4 or more)), and a defocus amount with respect to a layer having the refractive index “no” and a thickness t? (satisfying: 1???n (where ? is a positive integer and n is an integer of 4 or more)) are equal to each other.

Abstract: Reference light for interference with signal light from an optical information recording medium is displaced and reflected by a corner cube prism or the like with high accuracy. The signal light and the displaced reference light are made parallel with each other with high accuracy. The signal light and the reference light are each split using a polarization splitter to generate interference light. Thus, regeneration signals are stabilized. Accordingly, an interference-type optical head and optical disc apparatus of higher quality than conventional ones can be provided.

Abstract: A spectral element separates first laser light in such a manner that an area including only signal light as reflected first laser light is formed on a photodetector. The photodetector is provided with a first sensor group which is disposed at an irradiation position of signal light of the separated first laser light, and a second sensor group which receives zero-th order diffraction light of a main beam and two sub beams of second laser light that has been transmitted through the spectral element. The second sensor group includes a four-divided sensor which receives the main beam. The four-divided sensor is disposed in an area surrounded by the first sensor group. Zero-th order diffraction light of the first laser light that has been transmitted through the spectral element is irradiated onto the four-divided sensor.

Abstract: Provided is an objective optical element which can appropriately correct degradation from spherical aberration upon fluctuation of a light source wavelength while maintaining light use efficiency, just by changing the magnification of the objective optical element, and which can record/reproduce information to/from different optical discs. Also provided is an optical pickup device using the objective optical element. When a light flux having two different wavelengths ?11, ?12 (wherein ?11<?12 and ?12??11=5 nm) within a range of wavelength ?1 is introduced to the objective optical element to measure the wavefront aberration, the following third order and fifth order spherical aberrations in unit of ?rms are obtained: SA3(?11), SA5(?11), SA3(?12), SA5(?12). If ?SA3=|SA3(?12)?SA3(?11)|, ?SA5=|SA5(?12)?SA5(?11)|, the following expression is satisfied: 0.18>?SA3>?SA5>0 (1).

Abstract: A near-field light generating device (10) which converts incident light into near-field light, includes: a metallic member (11) made of a metallic material; and a dielectric member (12) made of a dielectric material, the metallic member (11) having a first interface (16) and a second interface (18) that sandwich the dielectric member (12), the first interface (16) and the second interface (18) having flections (P16 and P18), respectively, an inner-interface distance, which is a distance between the first interface (16) and the second interface (18), being minimum at location of the flections (P16 and P18), and a rate of change of the inner-interface distance between the first interface (16) and the second interface (18) being asymmetrical with respect to the flections (P16 and P18). With the arrangement, it is possible to provide a minute near-field light generating device which can be easily fabricated and which can obtain high-intensity near-field light whose temporal change in intensity is small.

Abstract: In a small-sized optical pickup device for enabling to obtain a stable servo-signal, as well as, a focus error signal and a tracking error signal, without receiving ill influences of stray lights from other layers, when recording/reproducing a multi-layer optical disc, a reflection light from the multi-layer optical disc is divided into plural numbers of regions by a diffraction grating. And, it is divided into at least four (4) regions, by a division line in the tangential direction of the optical disc and a division line in the radial direction thereof. Light receiving parts, for detecting either one of grating diffraction lights, i.e.