Abstract: Provided is a recording apparatus including a self-excited oscillation semiconductor laser that has a double quantum well separate confinement heterostructure and includes a saturable absorber section to which a negative bias voltage is applied and a gain section into which a gain current is injected, an optical separation unit, an objective lens, a light reception element, a pulse detection unit, a reference signal generation unit, a phase comparison unit, a recording signal generation unit, and a control unit.

Abstract: A system and method for providing direct read after write functionality in an optical data storage device include an optical head having a first coherent light source modulated at higher power during writing of data to the optical medium and a second coherent light source operating in a continuous wave mode at lower power while the first coherent light source is writing data. Optic components combine light from the first and second light sources and focus light from the first coherent light source to a first spot of a selected track on the optical medium and focus light from the second coherent light source to a second spot on the selected track downstream from the first spot relative to movement direction of the optical medium to read and verify the data directly after writing during the write process rather than in a separate verification process.

Abstract: Provided is a photo detecting element that has a simplified structure and that is easily manufactured and assembled, and an optical pick-up device including the photo detecting element.

Abstract: The invention provides an optical pickup device that ensures complete curing of adhesive when a tilt adjusting holder is glued to an objective lens holder. The optical pickup device comprises: a light source; an objective lens for focusing light emitted from the light source onto an optical storage medium; a tilt adjusting holder to which to secure the objective lens; and an objective lens holder to which to glue the tilt adjusting holder. The objective lens holder includes: adhesive joint sections for securing the tilt adjusting holder to the objective lens holder using an adhesive; a seat section on which the tilt adjusting holder abuts; and adhesive anti-overflow pockets, located between the adhesive joint sections and the seat section, for receiving the adhesive when the adhesive flows from the adhesive joint sections.

Abstract: Provided are an objective lens holder and the like which prevent a wire formed into tracking coils from being loosened. Tracking coils are respectively attached to bobbins provided to sidewalls of an OBL lens holder. In addition, a conducting wire hook portion is formed by projecting a part of a sidewall portion near one of the bobbins, and a conducting wire is hooked round this conducting wire hook portion. Similarly, another conducting wire hook portion is provided to a sidewall portion near another one of the bobbins, and the conducting wire formed into the corresponding tracking coil is hooked round this conducting wire hook portion. This prevents the conducting wire from being loosened.

Abstract: An optical pickup apparatus includes: first and second laser diodes to emit first and second laser beams having first and second wavelengths for reading signals recorded in first and second optical discs, respectively; a first objective lens configured to condense the first laser beam onto the signal recording layer of the first optical disc; a second objective lens arranged, along with the first objective lens, in a radial direction of the first and the second optical discs, the second objective lens configured to condense the second laser beam onto the signal recording layer of the second optical disc; a first optical system configured to guide the first laser beam from the first laser diode to the first objective lens; and a second optical system configured to guide the second laser beam from the second laser diode to the second objective lens independently of the first optical system.

Abstract: In one embodiment, the optical pickup device includes: a light source that emits a light beam; a diffractive element that diffracts the light beam and generates a zero-order and ±first-order diffracted light beams; an objective lens that converges the diffracted light beams onto the same track on the storage medium; and a photodetector that receives the diffracted light beams reflected from the storage medium. If a distance from a light beam spot left by the zero-order diffracted light beam on the track to light beam spots left by the ±first-order diffracted light beams on that track is d [?m], the scanning linear velocity of the storage medium is v [m/s], and a time it takes for a phase-change material of the storage medium that has once been melted by the zero-order diffracted light beam to solidify is T [?s], vT?d is satisfied.

Abstract: The apparatus includes a pickup for reading data from a super-resolution optical disc, the pickup comprising a laser for generating a main beam, a first and a second satellite beam, the two satellite beams each having a radial offset with regard to the main beam, a third satellite beam following the first satellite beam, having the same radial offset as the first satellite beam, and a fourth satellite beam following the second satellite beam, having the same radial offset as the second satellite beam, for providing a crosstalk correction of the HF data signal. The track pitch between adjacent tracks of the optical disc is particularly below the diffraction limit of the pickup, and the light intensity of each of the first and second satellite beams and of the main beam is sufficient to provide a super-resolution effect on the optical disc and the light intensity of each of the third and fourth satellite beams is not sufficient to provide the super-resolution effect.

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: Provided are a small objective lens (OBL) holder in which coils can be easily incorporated, and the like. An OBL holder of the present invention includes: a main surface portion provided with a circular opening portion in which an objective lens is fixed; and four side wall portions integrally extending downward from a peripheral portion of the main surface portion. The side wall portions include: a first side-wall portion extending in a longitudinal direction of the OBL holder; a second side-wall portion opposed to the first side-wall portion; a third side-wall portion extending in a short-side direction of the OBL holder; and a fourth side-wall portion, which are provided on the rear, front, right and left sides in the drawing, respectively. Accommodation regions capable of accommodating focusing coils are arranged on one side and the other side of the objective lens.

Abstract: In one embodiment, an optical pickup device includes a fixed portion 100, a movable portion 11, first and second elastic supporting members 12a and 12b, one and the other ends of which are secured to the fixed portion 100 and the movable portion 11, respectively, and an objective lens 8 secured to the movable portion 11. The objective lens 8 is arranged inside of the area that is defined between two lines that are respectively drawn from one and the other ends of the first elastic supporting member 12a perpendicularly to the first elastic supporting member 12a and outside of the area defined between the first and second elastic supporting members 12a and 12b.

Abstract: An element holding device of the present invention includes: a guide portion engaging with a guide shaft; a lens fixing portion on which to fix a collimator lens; an arm portion; an insertion portion having a hole portion in which to insert a guide shaft; a wire fixing portion made by protruding a side surface of the insertion portion in a ?Y direction; and a wire fixed on the wire fixing portion. A bent portion being a leading end portion of the wire is housed in a slit. Thereby, excess deformation of a contact portion is suppressed.

Abstract: Amplitude and frequency of a high-frequency signal superposed on a reproduction laser beam are changed in accordance with a reproduction spot diameter on the surface of the recording layer upon discrimination of an optical disk in initial adjustment after insertion of the optical disk and change of a layer of a multi-layer optical disk. Further, the high-frequency signal is not superposed on the reproduction laser beam until end of the discrimination and change to a target layer upon discrimination of the optical disk and change of a layer of a multi-layer optical disk.

Abstract: According to one embodiment, an information recording and reproducing apparatus including, a focus control module, an objective lens control module, a calculation module, and a tracking control module. If, detection the recording marks line, to focus a laser light of a second wavelength to the recording layer through an objective lens and to operation a recording layer tracking control using a tracking error signal taken out from a second reflected light and a laser light of a first wavelength to a track groove through the objective lens and to operation a guide layer tracking control to control the objective lens using a tracking error signal taken out from a first reflected light.

Abstract: Aspects of the disclosure provide an apparatus. The apparatus includes a collimator configured to have a plurality of positions, and a controller configured to control the collimator to move to a predetermined position associated with a data layer of an optical storage medium to collimate a light beam. The collimated light beam is then focused onto the data layer of the optical storage medium.

Abstract: Provided is a recording apparatus including a self-excited oscillation semiconductor laser that has a double quantum well separate confinement heterostructure and includes a saturable absorber section to which a negative bias voltage is applied and a gain section into which a gain current is injected, an optical separation unit, an objective lens, a light reception element, a pulse detection unit, a reference signal generation unit, a phase comparison unit, a recording signal generation unit, and a control unit.

Abstract: There are provided an optical head and an optical information device capable of downsizing the optical head, and capable of improving the qualities of a focus error signal, a tracking error signal, and a reproduction signal. A light detector (120) includes a light-receiving unit (121) for receiving a reflected light beam from an optical disc, and a package (125) for covering the light-receiving unit (121). The package (125) has a plurality of light guides (124) formed on a light-receiving surface on the light beam incident side of the light-receiving unit (121), and for guiding a reflected light beam to the light-receiving unit (121), and a light shield (114) for shielding a region except for a plurality of the light guides (124) from light.

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: Provided is an optical pickup device capable of preventing a soldering work from physically damaging any part of a housing of the optical pickup device. In the optical pickup device to be provided, a circuit board fixed to an LD holder and a circuit board covering a housing from below are connected via a solder joint. An inner-side part of an upper-end portion of an external sidewall of the housing located near the connecting position is cut away to form a cut surface. When a soldering iron is used to form the solder joint to connect the two circuit boards, the cut surface prevents the soldering iron from touching the external sidewall and thereby preventing this part of the external sidewall from being damaged by the soldering iron.

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 respective positions different from each other, and guides the laser light entered into a third area to a position different from the four positions. When an intersection of two straight lines extending in parallel to the first direction and the second direction and intersecting with each other is aligned with an optical axis of the laser light, the third area is disposed at the intersection of the two straight lines.

Abstract: An objective lens driving apparatus includes: an objective lens opposing a signal recording surface of an optical disc; a lens holder configured to hold the objective lens; and an actuator configured to displace the lens holder in a focusing direction or a tracking direction of the optical disc, the actuator including a coil attached to the lens holder, a magnet configured to generate a magnetic field effectively acting on the coil, and a yoke having the magnet fixed thereto, the yoke formed by bending a sheet of metal plate into a rectangular shape around an axis in the tracking direction, and the magnet fixed to the yoke with an adhesive.

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 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: In an optical head device which performs recording/reading of data in/from a high-density optical disc using an objective lens with a large NA, a saw-tooth shape diffraction element is used for also performing recording/reading of data in/from a conventional optical disc, such as DVD, CD, or the like. A step difference that produces an optical path length for blue light which is equal to or longer than the wavelength of the blue light and optical path lengths for red and infrared light which are shorter than the wavelengths of the red and infrared light is utilized so as to exert an inverse action on the blue light to those exerted on the red and infrared light. The effect of increasing the working distances for CD and DVD enables multiple compatibility. The optical element is integrally combined with the objective lens to perform a tracking servo following operation.

Abstract: The present invention provides a unit and method for implementing an optical head and optical drive device whose configuration is simple, and which allows the generation of a track error signal in which no offset is caused to occur. The optical drive device includes a light source for emitting light beams, an objective lens for converging the light beams onto an optical disc, an optical-signal generation element for dividing the light beams into at least four regions by using a division line extending in the radial direction of the optical disc, and a division line extending in the track direction of the optical disc, the light beams being reflected by the optical disc, and an optical detector for receiving the light beams divided by the optical-signal generation element, wherein the up and down or right and left areas of the four regions are made different from each other.

Abstract: An optical pick-up is provided. The optical pick-up includes a light source, a first objective lens configured to focus light emitted from the light source on a high-density optical information storage medium, a photo-detector configured to detect a signal by receiving light reflected from the high-density optical information storage medium, an optical-path changer configured to convert a travel path of incident light to allow the light emitted from the light source to proceed toward the high-density optical information storage medium, and to allow the light reflected from the high-density optical information storage medium to proceed toward the photo-detector, and a blocking device disposed in an optical path of signal light reflected from a target reproducing/recording layer of the high-density optical information storage medium, passes through the first objective lens, and proceeds toward the photo-detector.

Abstract: An objective lens driving unit is provided and includes a moving structure having an objective lens and a plurality of driving coils, a permanent magnet and a yoke structure to correspond to the driving coils, a wire holder coupled to the yoke structure and having a plurality of wiring layers buried in a portion of the wire holder, and a plurality of suspension wires to connect the plurality of driving coils to the plurality of wiring layers.

Abstract: Disclosed are an objective lens for optical pickup device and an optical pickup device that are capable of recording/reproducing information for an optical disc having multilayered information recording surfaces with achieving compactness and reduced cost. In the objective lens and the optical pickup device, under the assumption that TMAX (mm) is a maximum transparent substrate thickness among transparent substrate thicknesses of the optical disc, magnification M under the condition that the spherical aberration (?rms) is minimized at transparent substrate thickness T (mm) satisfying the following expression (1), satisfies the following expression (2), and an offense against the sine condition has a positive maximum value in an area between 70 percent and 90 percent of the radius of the effective aperture at the magnification M: TMAX×0.85?T?TMAX×1.1 (1), ?0.003?M?0.003 (2).

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: An optical disc device and a recording method is provided in which information can be additionally recorded on an optical disc, which has a servo layer and recording layers separately formed, by accurately correcting a relative angle between a light beam and the optical disc used in the previous recording without providing an area where recording is not performed while maintaining the stability of tracking servo. The above subject can be solved by studying with high accuracy the relative angle between the optical disc and the optical axis used in the previous recording by applying a radial tilt servo according to a signal from the recording layers with the tracking servo applied by the servo layer. Further, the additional recording can be performed stably by fixing the radial tilt at the previously studied angle when the recording is performed.

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: A focus servo control device includes a first detector, first controller, second detector, and second controller. The first detector detects a first focus error signal. The first controller controls the objective lens based on the first focus error signal, so that a focal point of the first laser agrees with the guide layer. The second detector detects a second focus error signal. The second controller changes a relative distance between the focal point of the second laser and the focal point of the first laser, so that the focal point of the second laser agrees with a target recording/reproducing layer.

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 optical pickup head is provided, which includes a silicon substrate, in which an aperture and an objective lens are disposed on the silicon substrate; and a laser diode (LD), a 135-degree tilted reflector, and a 135-degree tilted holographic reflector are disposed on the silicon substrate. The two 135-degree tilted reflectors and a holographic optical element (HOE) are fabricated on a slant face structure of an optical platform using a semiconductor process, so all the elements are disposed at a straight zone, and then in combination with bonding of the LD and an optical sensor element, an miniaturization objective is achieved and an optical path is shortened.

Abstract: In an optical pickup device for a simple optical system, a light beam emitted from a laser diode is split into first and second light beams by a polarized beam splitter, an optical disc is irradiated with the first light beam to obtain signal light, and the second beam is reflected by a reflection element to obtain reference light. Light beams of the signal light and the reference light are synthesized into one light beam, the synthesized light beam is separated into four light beams by a phase difference forming unit including a grating, a divided wave plate and a polarization grating, and different phase differences are afforded to the signal light and the reference light in each light beam. The four light beams are detected by one detector to generate the reproduction signal.

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: A phase difference layer 12 and a reflection layer 13 are provided. Then, adjustment is performed such that the phase difference layer 12 and the reflection layer 13 impart a predetermined phase difference to light having a particular wavelength bandwidth or plural kinds of light of different wavelengths that enter in an oblique direction relative to the normal direction of the plane of the phase difference layer 12. By virtue of this, the light 16a that goes forward and backward through the phase difference layer 12 and then exits the layer has an ellipticity ? of 0.7 or greater. Thus, in particular, when this wave plate is employed in an optical head device, the function of reflection and the function of a ¼-wave plate are integrated. Thus, stable recording and reproduction of an optical disk are achieved, and size reduction is achieved in the optical head device.

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: In order to achieve further cost reduction while the package size of an optical pickup having two objective lenses and the restriction on the disposition of the two objective lenses are maintained, an optical system for laser light emitted from a red/infrared dual-wavelength laser diode is disposed such that a parallel plate beam splitter is disposed to be inclined with respect to the optical axis of focused light of the laser light reflected by an optical disk and the optical axis of the laser light between a rising mirror and the parallel plate beam splitter is inclined from the signal track direction of the optical disk. The laser light to which astigmatism is given by transmission through the parallel plate beam splitter is caused to be directly incident on a light detector without passing through an astigmatism adjustment optical element.

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: 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: Erroneous data erasure owing to radiation of laser beam with excessive power to the recording layer of the multilayered optical disc upon servo-off while reproducing data of the disc is prevented. When detecting the servo-off based on the amplitude of the tracking error signal or the focus error signal, the laser beam power is reduced to a predetermined minimum value, and the laser beam power value is set again based on the address of the recording medium, which has been obtained later for reproduction. The laser beam power value is changed by applying an offset to the drive current or changing the target value under APC.

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: An optical information recording/reproducing apparatus and an optical information recording/reproducing method that record information using holography, wherein the optical information recording/reproducing apparatus includes a signal generation unit that generates two-dimensional data by a two-dimensional encoding method in which a lower-limit value of a number of continuous ON/OFF pixels in an array in one direction of pixels in a two-dimensional spatial light modulator is K(K?2, K: natural number); and a pickup that records the two-dimensional data, generated by the signal generation unit, on a hologram disc.

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 pickup apparatus includes an objective lens having a numeric aperture and an incident face. An antireflection coating is formed on the incident face. A collimating lens converts laser light from a laser diode into parallel light, and causes the parallel light to be made incident on the incident face through the antireflection coating. The thickness of the antireflection coating causes a transmittance of laser light that enters the objective lens to be: set at a first predetermined transmittance value, when the numeric aperture is between zero and a first predetermined numeric aperture value; set to correlate linearly with the numeric aperture when the numeric aperture is between the first predetermined numeric aperture value and a second predetermined numeric aperture value; and set at a second predetermined transmittance value, when the numeric aperture is between the second predetermined numeric aperture value and a third predetermined numeric aperture value.

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: 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: 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.