Abstract: Stable performance of additional recording and erasing and rewriting operations is allowed regardless of a change in inclination of a guide layer separable optical disc. An optical pickup device includes an angle variable reflection mirror (an optical axis angle variable element) which changes directions of optical axes of first and second light beams when the first light beam for recording or reproduction and the second light beam for servo signal detection are emitted from laser diodes and incident upon the optical disc through an objective lens. When additional recording is performed on the optical disc, the optical axis angle of the angle variable reflection mirror is adjusted such that a tracking error signal detected from a record layer with the first light beam is reduced to almost zero while tracking control is being performed on a guide layer with the second light beam.

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: An optical pickup has a first optical system and a second optical system. The optical axis of the first optical system and the optical axis of the second optical system are inclined, for example, 45 degrees with respect to the reference plane, and are parallel to each other. A first objective lens and a second objective lens are arranged substantially side-by-side in a radial direction, and the center position of the second objective lens is slightly displaced from the reference plane in a tangential direction. The first optical system and the second optical system each have a flat-shaped beam splitter; this is used to produce astigmatism for acquiring a focus error signal by the astigmatic method.

Abstract: There is provided an objective lens for information recording/reproducing for three types of optical discs, which includes a first area contributing to converging a third light beam onto a record surface of a third optical disc. The first area includes a phase shift structure having refractive surface zones concentrically formed about a predetermined axis. The phase shift structure includes first and second step groups. The first step group is configured such that an optical path length difference ?OPD1 (nm) given by each step of the first step group to a first light beam satisfies a condition: 2N1+1.10<|?OPD1/?1|<2N1+1.40, where N1 is an integer or zero, and the second step group is configured such that an optical path length difference ?OPD2 (nm) given by each step of the second step group to the first light beam satisfies a condition: 2N2?0.10<|?OPD2/?1|<2N2+0.10, where N2 is an integer.

Abstract: An optical pickup lens for focusing a light beam from a laser light source on an optical information recording medium is a single lens. The optical pickup lens has two surfaces, and a surface R2 opposite to a surface R1 closer to the laser light source has a continuous shape. When the surface R2 has radii h1, h2 and h3 (h1<h2<h3) from an optical axis to a lens periphery, and where sags in the radii h1, h2 and h3 are sag1, sag2 and sag3, and differentials in the sags are ?sag1, ?sag2 and ?sag3, respectively, 0>?sag1>?sag2 and ?sag2<?sag3 are satisfied.

Abstract: An optical pickup includes a lens holder; an objective lens provided on the lens holder and having an effective region for collecting light from a light source and an edge located outer to the effective region; and a lens protector provided on the lens holder. The lens protector protrudes toward an optical disc more than the objective lens. The edge of the objective lens includes a convexed portion protruding toward the optical disc. An apex of the effective region of the objective lens protrudes toward the optical disc more than the convexed portion of the edge. A straight line connecting a part of the edge of the objective lens and a part of the lens protector is closer to the optical disc than the apex of the effective region of the objective lens.

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: An optical pickup lens for focusing a light beam from a laser light source on an optical information recording medium is a single lens. The optical pickup lens has two surfaces, and a surface R2 opposite to a surface R1 closer to the laser light source has a continuous shape. When the surface R2 has radii h1, h2 and h3 (h1<h2<h3) from an optical axis to a lens periphery, and where sags in the radii h1, h2 and h3 are sag1, sag2 and sag3, and differentials in the sags are ?sag1, ?sag2 and ?sag3, respectively, 0>?sag1>?sag2 and ?sag2<?sag3 are satisfied.

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 system includes an objective lens, an imaging module, and a measurement module. The objective lens is configured to receive light emitted by a light source, focus the emitted light onto a target object, and receive light reflected by the target object. The imaging module is configured to receive a first portion of the reflected light. The measurement module is configured to receive a second portion of the reflected light and includes a photo detector and an astigmatic lens configured to direct the second beam onto the photo detector.

Abstract: An optical pickup apparatus includes: a laser diode configured to emit a laser beam; and an objective lens configured to condense the laser beam into a laser spot through which a signal recorded on a signal recording layer of an optical disc is read out by the laser beam, the objective lens having formed thereon a lens surface with a second numerical aperture for acting as a lens, which is larger than a first numerical aperture for forming the laser spot.

Abstract: A disclosed optical pickup includes an aberration correction unit with a phase shifter surface. On the phase shifter surface, rectangular or staircase-like steps are formed in a concentric manner around an optical axial center, in certain regions where a light beam passes through. The steps have different heights in the optical axial direction. A light beam having a wavelength of 405 nm is directly transmitted through the steps so that a phase difference is applied for correcting spherical aberration that occurs on a first optical recording medium. A light beam that passes through an annular region without any steps is focused on a second optical recording medium. A light beam that passes through an outside region is focused by an object lens on the second optical recording medium, and is not focused on the first optical recording medium.

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: An objective lens element having improved diffraction efficiency at least one of used wavelengths is provided. The objective lens element includes one surface including: a first region including an optical axis; and a second region surrounding the first region. A periodic first diffraction structure is formed on the first region, and a periodic second diffraction structure different from the first diffraction structure is formed on the second region. The objective lens element satisfies the following conditions. |A1?B1|<|A2?B2|??(1) |B1|?|B2|??(2) Here, A1 and B1 are diffraction orders at the first region to converge light of a first wavelength and light of a second wavelength on a recording surface, respectively, and A2 and B2 are diffraction orders at the second region to converge the light of the first wavelength and the light of the second wavelength on a recording surface, respectively.

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: A method for driving an optical pickup apparatus which improves the durability of components that drive a movable lens that moves back and forth between an original position and a drive-limit position and achieves stable operability and an extended lifetime of the optical pickup apparatus performs a first step-drive in which a movable lens moves to an original-restoration start position by being driven a specified distance toward a drive-limit position, a second step-drive in which the movable lens thereafter moves to an original position by being driven toward the original position a distance equivalent to the distance from the drive-limit position to the original position, and a third step-drive in which the movable lens thereafter moves to a default position by being driven a specified distance.

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: Proposed is an optical disk device capable of appropriately performing focus control. In an optical disk device, an objective lens is moved in the thickness direction of an optical disk by controlling an actuator and a time interval in which each of the recording layers was detected is measured while moving the objective lens, a first time interval from the first detection of the recording layer to the second detection of the recording layer is compared with a second time interval from the second detection of the recording layer to the third detection of the recording layer, and a focal position of the objective lens is determined based on the comparative result.

Abstract: An optical pickup device includes: a first light source for emitting recording laser light; a second light source for emitting reproducing laser light having a wavelength different from a wavelength of the recording laser light; an objective lens for converging the recording laser light and the reproducing laser light. A quarter wavelength plate is disposed between the first light source and the second light source, and the objective lens. A wavelength-selective polarized beam splitter is disposed between the quarter wavelength plate, and the first light source and the second light source. The reproducing laser light alone out of the recording laser light and the reproducing laser light reflected on recording medium is guided to a photodetector.

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: Provides an objective lens, an optical head and an optical disc apparatus (drive) capable of compensating for various types of aberrations including wavelength changes for a plurality of types of optical discs including high density optical discs, DVDs and CDs with a good wavelength dispersion compensation ability and thus capable of providing good recording or reproduction characteristics. The objective lens according to the present invention includes a first lens and a second lens substantially in close contact with each other such that optical axes thereof match each other, and acts as a convex lens as a whole. Each lens includes a central portion including the optical axis and a peripheral portion located in a periphery of the central portion. The central portion of the first lens acts as a convex lens; and the central portion of the second lens acts as a concave lens. Where the refractive index of the first lens at d line (wavelength: 587.

Abstract: A laminated wave plate includes a first wave plate with a phase difference of ?1=180° with respect to a designed wavelength ?0 and a second wave plate with a phase difference of ?2=180°, in which the first wave plate and the second wave plate are arranged and laminated so that optical axes thereof intersect each other, the laminated wave plate converting an incident linearly-polarized beam into a linearly-polarized beam obtained by rotating a polarization plane of the incident linearly-polarized beam by a predetermined angle ? and outputting the converted linearly-polarized beam. When in-plane bearing angles formed by the polarization plane of the incident linearly-polarized beam and optical axes of the first and second wave plates are represented by ?1 and ?2 and an optical axis adjustment amount is represented by a, the following expressions are satisfied: ?1=?/4+a; and ?2=3?/4?a.

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: The apparatus comprising a pickup for reading data from or writing data to an optical storage medium, wherein the pickup comprises a laser providing a laser beam, an objective lens for focusing the laser beam onto the optical storage medium, a first detector and a beam splitter arranged between the laser and the objective lens for guiding light reflected from the optical storage medium onto the first detector. A selecting means, arranged in front of the beam splitter, with regard to the reflected light from the optical storage medium, is provided for guiding reflected light passing through an outer section of the objective lens onto a second detector. The light guided onto the first detector is utilized for providing a tracking error signal and the light guided onto the second detector is utilized for providing a data signal.

Abstract: An objective lens has a numerical aperture of 0.8 or more and focusing a light beam of a wavelength ? of at least 450 nm or less on an optical information recording medium. In this objective lens, a wavefront-aberration deterioration level TOR, accumulative value of aberration deterioration, satisfies the equation (1): TOR=?{square root over (2.52(DCm32+DCm52)+(TSA32+TSA52))}{square root over (2.52(DCm32+DCm52)+(TSA32+TSA52))}?0.07[?rms]??(1) In the equation (1), TSA3 [?rms/?m] and TSA5 [?rms/?m] refer to a third-order thickness sensitivity level and a fifth-order thickness sensitivity level, which are generated when a thickness error from a predetermined thickness is +1 ?m, respectively. DCm3 and DCm5 refer to a third-order decentering sensitivity level and a fifth-order decentering sensitivity level, which are generated when a decentering error of each of lens surfaces is 1 ?m, respectively.

Abstract: Provided is an optical pickup device capable of ensuring the compatibility among three types of optical discs, i.e., BDs, DVDs, and CDs, with a common objective lens and, in addition, capable of ensuring a sufficient working distance for CDs, and also provided are an optical information recording and reproducing device and an objective lens suitable for the optical information recording and reproducing device. On the objective lens, there is arranged a first optical path difference providing structure formed such that: the direction of step differences of a basic structure wherein the diffraction order of a blue-violet laser light flux become an odd order faces toward the opposite direction of the optical axis; the direction of step differences of a basic structure wherein the diffraction order of the blue-violet laser light flux become an even order faces toward the optical axis; and both the basic structures are overlapped together.

Abstract: A three-dimensional optical memory device comprises an optical disc positioning system, two sources of radiation with wavelengths 21 and 22, a focusing system, an illumination system, focusing system positioning means, a spectrum splitter, an optical sensor, and a control unit. The radiation source with wavelength is an array of laser diodes, which optical axes are parallel and lie in the same plane. The illumination system comprises: a cylindrical lens positioned so that the generatrix of its cylindrical surface is parallel to the plane of the p-n junctions of the laser diodes; a focusing lens; and a stabilizing circuit comprising a beam splitter situated between the focusing lens and the cylindrical lens, a second optical sensor optically coupled to the focusing lens via the beam splitter, and a stabilizer coupled to the focusing lens, wherein the stabilizer and the second optical sensor are electrically connected to the control unit.

Abstract: Provided is an objective lens that enables the suppression of molding defects in a high NA lens, and an optical pickup device. As the objective lens (OBJ) includes a thick-flange section (FT), a thick-flange-section forming section (11c) can be formed on a first-flange-section transfer surface (11b) of a first mold (10) so as to connect to a gate section (GT), as shown in FIG. 2. Thereby, the cross sectional area of the gate section (GT) is increased, which allows optimizing the gate seal time, applying sufficient pressure, and effectively removing air.

Abstract: A compatible near field optical recording/reproducing apparatus includes a solid immersion lens unit including a first lens, which has an aspherical surface in which light incident from the first light source is condensed, and a second lens, which realizes a high numerical aperture via a near field effect by light condensed by the first lens and has an aspherical surface. An effective beam size-controlling device controls an effective size of a light beam transmitted to the solid immersion lens unit such that either near field light or far field light is transmitted to an information storage medium by the solid immersion lens unit and a focal point adjusting optical system adjusts a focal position of light transmitted to the information storage medium according to the type of the information storage medium.

Abstract: Provided is a method for forming a near-field light generating element, which is capable of sufficiently suppressing the unevenness of a waveguide surface and the distortion within the waveguide. The forming method comprises the steps of: forming a first etching stopper layer on a lower waveguide layer; forming a second etching stopper layer; forming, on the second etching stopper layer, a plasmon antenna material layer; performing etching with the second etching stopper layer used as a stopper, to form a first side surface of plasmon antenna; forming a side-surface protecting mask so as to cover the first side surface; and performing etching with the first and second etching stopper layers used as stoppers, to form the second side surface. By providing the first and second etching stopper layer, over-etching can be prevented even when each etching process takes enough etch time, which allows easy management of etching endpoints.

Abstract: A method of manufacturing a synthetic resin lens, comprising: adjusting a degree of change in transmittance of a lens member made of synthetic resin for a blue violet laser beam with accumulated application of the blue violet laser beam, by applying to the lens member an electromagnetic wave shorter in wavelength than the blue violet laser beam.

Abstract: An electromagnetic actuator is provided, including a movable part and a base part. The movable part further includes at least an object lens, an object lens holder, a wire set, a first focus coil set, a second focus coil, a tilt coil set, and a track coil set. The object lens is placed inside object lens holder. One end of the wire set is fixed to object lens holder, and the other end is fixed to the base part so that the wire set is like a suspending wire set for hanging the object lens holder. The base part further includes a focus magnet set, a track magnet set and a tilt and focus shared magnet. The first focus coil set is located to correspond to focus magnet set, and the track coil set is located to correspond to the track magnet set, a second focus coil and a tile coil set in side-by-side layout are located to correspond to the tilt and focus shared magnet.

Abstract: An optical element which can be shared by three wavelengths for BD, DVD, and CD and which is easily manufactured is provided. An objective lens system includes an optical element 1A and a converging lens element 1B. A first surface of the optical element 1A on an incident side is concentrically divided into a region 11 including a rotational symmetry axis, a region 12, and a region 13. On the optical element 1A, a periodic stair-like diffraction structure and a periodic sawtooth-like diffraction structure are provided. A second surface of the optical element 1A is divided into a region 21 including a rotational symmetry axis, a region 22, and a region 23. On the region 21, a sawtooth-like diffraction structure is provided. The converging lens element 1B converges light having passed through the optical element 1A, to form a spot on an information recording surface of an optical disc.

Abstract: An optical element which has optical steps each providing a phase difference to transmitted light and has low light amount loss and a high efficiency is provided. The optical element includes a symmetry axis, a plurality of optically functional surfaces which are ring-shaped regions around the symmetry axis, and a plurality of wall regions connecting the optically functional surfaces to each other. The optically functional surfaces and the wall regions constitute the optical steps. On a cross-section taken by, as a cutting plane, a plane including the symmetry axis, the contour line of each wall region is substantially parallel to a light beam which is incident on the optically functional surface on the outer side and passes near the wall region. The maximum value of the angle between the symmetry axis and the light beam passing near the wall region is equal to or more than 25 degrees.

Abstract: An objective lens element which can obtain appropriate spot performance only by simple position adjustment, and an optical pickup device using the objective lens element are provided. In the objective lens element, an amount of a generated third-order astigmatism of a spot which is formed when symmetry axes of optically functional surfaces are located parallel to the normal line of a base plate and an incident light beam incident such that a central light beam thereof is tilted at 0.5 degree with respect to the normal line of the base plate is converged, is reduced to be less than an amount of a generated spherical aberration of a spot which is formed when the symmetry axes of the optically functional surface are located parallel to the normal line of the base plate and an incident light beam incident parallel to the normal line of the base plate is converged.

Abstract: An optical system for optical pickup includes a magnification conversion optical element moving along an optical axis direction in accordance with each recording surface and an objective lens element converging a light beam incident through the magnification conversion optical element, to form a spot on a corresponding recording surface of the recording surfaces, and satisfies the following formula. 4.0×10?4<Mn/(tn?tc)×f<6.0×10?4??(1) Here tc is the thickness [?m] of the base plate at which a third-order spherical aberration which occurs when a parallel light beam is incident on the objective lens element is the minimum, f is the focal length [mm] of the objective lens element, and Mn is the imaging magnification of the objective lens element when a spot is formed through the base plate having a thickness to [?m].

Abstract: A focus search is performed for an optical disc. A focus drive voltage is output for moving an objective lens in a thickness direction of an optical disc. An average value of focus drive voltages is acquired and recorded while the optical disc is rotating at least one time in an in-focus condition in which a laser beam emitted via the objective lens is in focus to a data layer of the optical disc. A closest-position voltage is set based on the average value, the closest-position voltage being a focus drive voltage at which the objective lens is moved closest to the optical disc in a focus search that is performed after the average value has been recorded. The focus search is performed by moving the objective lens between a specific starting position and a position corresponding to the closest-position voltage.

Abstract: A high-NA and thin objective lens which prevents occurrence of a crack during lens molding and can stably be molded is provided. The present invention is directed to an objective lens having an optical surface having power which is not negative. The objective lens is a single lens and is formed such that a flat portion which is provided at an outer peripheral portion and perpendicular to the optical axis is closer to a disc surface than the position of the top of an exit-side surface of the objective lens and such that the rate of change in sag of the exit-side surface is continuous across the entire region.

Abstract: An object of the invention is to provide an optical element for use in an optical information recording and reproducing device or a like device for recording or reproducing information with respect to an information recording medium using laser light, wherein the optical element is a resin optical element capable of suppressing lowering in transmittance due to deterioration by irradiation of light having a high energy density, and maintaining a high transmittance for a long time. To realize the above object, used is an optical element made of a silicon resin cured material obtained by subjecting a silicon resin composition containing a silsesquioxane compound to a curing treatment.

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: A light source, an objective lens, and an astigmatism generation element producing for light for focus control, and an optical receiver are provided. The astigmatism generation element is interposed between the objective lens and the optical receiver and produces focal points in front of and behind the optical receiver within two mutually orthogonal cross-sectional planes including an optical axis of the reflected light. The astigmatism generation element is a Fresnel mirror that has a plurality of orbicular zones and steps connecting adjacent orbicular zones to each other and that takes the orbicular zones as reflecting mirrors. A depth “d” of the steps is set substantially one-half of a wavelength ?, and a depth d1 of the innermost orbicular zone of the orbicular zones is made larger than the depth d of the steps. The influence of the steps of the Fresnel mirror is minimized, so that a superior servo characteristic can be exhibited.

Abstract: A reproducing apparatus includes: a first laser irradiation section irradiating an optical recording medium having a bulk recording layer and recording marks formed by focusing a laser beam on each predetermined layer position in the recording layer, with a first laser beam through an objective lens; a focus position adjusting section adjusting a focus position of the first laser beam; a beam receiving section receiving a reflected beam of the first laser beam from the marks and generating a light receiving signal; a reproducing section reproducing information recorded with the marks based on the light receiving signal; and a control section performing control to allow the focus position in reproduction of the information to correspond to a position shifted by a certain distance to an upper layer side from a focus position of the laser beam in forming the mark at the layer positions as a reproducing object.

Abstract: There are provided an objective lens for an optical pickup device which can record and/or reproduce information on/from an optical disk with high density with the use of a light flux with a short wavelength while keeping a temperature characteristic to be satisfactory in spite of having a plastic objective lens, and the optical pickup device. The objective lens suppresses generation of a spherical aberration even if a temperature change arises, by sacrificing wavelength characteristics and by enhancing temperature characteristics. Such satisfactory temperature characteristics can be acquired by the ring-shaped structure formed as a turning structure on an optical surface of the objective lens, in which the ring-shaped structure includes ring-shaped zones whose number is 3 or more and 30 or less and the ring-shaped structure is formed such that adjoining ring-shaped zones cause a predetermined optical path difference for an incident light flux.

Abstract: In an optical disk including at least a rewritable phase change material and comprising a recording layer having a reflectivity of more than 15%, an address output value as an address pit signal component occupying in a reproduced signal in a non recording state is prescribed to be 0.18 though 0.27 or a numerical aperture of an address pit signal occupying in a reproduced signal in a non recording state is prescribed to be more than 0.3.

Abstract: An aspheric lens includes at least one aspheric lens surface, and an angle of inclination on the aspheric lens surface is smaller than or equal to 65°. The aspheric lens surface is given by the equation Z ? ( r ) = cr 2 1 + 1 - ( 1 + K ) ? c 2 ? r 2 + Lr 2 + Ar 4 + Br 6 + Cr 8 + Dr 10 + Er 12 + Fr 14 + Gr 16 + Hr 18 + Jr 20 where L?0, c is a curvature, r2=x2+y2, K is a conic integer, and L and A through J are aspheric coefficients.

Abstract: Disclosed is an objective lens that favorably focuses multiple laser beams having different wavelengths on information recording layers of optical discs, and an optical pickup apparatus including the lens. The objective lens of the invention is provided with a first region for focusing laser beams of the BD, DVD and CD standards. The first region is provided with an annular zone step having a height calculated on the basis of a wavelength of the laser beam of the BD standard, and thus causes chromatic aberration of the laser beam of the DVD standard. This chromatic aberration corrects spherical aberration occurring due to a difference in thickness between coating layers of optical discs. In the invention, the curve surface shape of the first region is adjusted so that the BD and DVD standards can share the aberration for reducing the aberration of the laser beam of the DVD standard.

Abstract: Provided is an optical pickup apparatus that stably operates by accurately detecting a fluctuation in a light amount of a laser beam caused by movement of a collimating lens. In an optical pickup apparatus of the present invention, part of a laser beam emitted from a laser device is transmitted through a reflective mirror and detected by a laser beam FMD. An output of the laser device is adjusted based on the output from the FMD. Even when a collimating lens moves during the operation of the apparatus, the change in the light amount of the laser beam caused by the movement is immediately detected by the FMD and the output of the laser device is adjusted. Thus, the light amount of the laser beam radiated on an optical information recording medium is kept constant along a time axis. Accordingly, the optical pickup apparatus can stably perform reading and writing.

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: Provided is a method of, in movement between recording layers of an optical disc, resolving a problem caused by an increase in spherical aberration change as a result of widening of a layer interval at which the movement is made and executing appropriate interlayer movement. An upper limit value is defined for a recording layer interval at which the interlayer movement can be made, and if a layer interval from a moving-source layer to a moving-target layer is equal to or larger than the upper limit value, the interlayer movement and spherical aberration correction are once carried out where a predetermined recording layer for which a layer interval is less than the upper limit value is defined as a temporary shelter layer, and the processing is repeated with this temporary shelter layer defined as a new moving-source recording layer to thereby realize favorable interlayer movement to the target layer.