Abstract: The light emitted from a semiconductor laser is divided by a diffractive optical element into three light beams which are 0th-order light as the main beam and ±1st-order diffracted lights as the sub-beams, and the track error signals by the main beam and the sub-beams are detected, respectively, by a differential phase detection method. By the effect of the diffractive optical element, the light intensity distributions of the main beam and the sub-beams become different when making incidence on an objective lens. Therefore, when there is radial tilt in a disk, the phases of the track error signals by the main beam and the sub-beams are shifted with each other. Based on the shift in the phases of the track error signals, radial tilt of the disk is detected.

Abstract: A compact and inexpensive optical head that enables stable compatible playback and compatible recording with optical discs of different kinds with the use of a single objective lens is achieved. The order of diffracted light at which the diffraction efficiency by a diffraction element forming the objective lens becomes the maximum is set to the third order for blue light, the second order for red light, and the second order for infrared light in the inner peripheral portion of the diffraction element, and to the sixth order for blue light, the fourth order for red light, and the third order for infrared light to limit the aperture for infrared light in the intermediate peripheral portion. In the outer peripheral portion, the aperture for red light is limited by setting the order to an integer other than multiples of 3 for blue light.

Abstract: There is provided a diffractive element including a first member 2, which includes a first resin 2a and has a predetermined refractive index, and a second member 3, which has the same refractive index as the first member 2 having the predetermined refractive index in one wavelength of light and has a refractive index different from the first member 2 having the predetermined refractive index in the other wavelength of light. The first member 2 and the second member 3 are alternately arranged within an incidence plane of the two wavelengths of light, thereby constituting a diffraction grating. The second member 3 includes a second resin 3a to dissolve an organic matter 5 having optical absorption in a predetermined wavelength range at a molecular level, whereby the refractive index of the second member 3 is formed.

Abstract: An optical pickup which includes first to third light sources each emitting a light beam each having a first to third wavelength; an objective lens condensing each of the light beams emitted from the light sources on a signal recording face of an optical disc; a collimator lens provided between the light sources and the objective lens to convert a divergent angle of each of the light beams emitted from the light sources so as to obtain a parallel light beam; and a diffractive optical element provided between the collimator lens and the objective lens. The diffractive optical element includes first and second diffractive parts which respectively diffract the light beam having the second wavelength and the third wavelength. The second diffractive part has a diffraction structure formed by a plurality of concentric ring zones, having first to fourth optical faces, each having a different height in an optical axis direction.

Abstract: An optical pickup apparatus, comprising: a light source to emit a light flux; a light converging system including an objective lens to converge the light flux emitted from said light source onto an optical information recording medium; a first diffraction element placed within an optical path up to the optical information recording medium; a light flux splitting element that is placed within the optical path from said light source up to the optical information recording medium and that splits an incident light flux emitted by the light source; a monitor element that receives a light flux split by said light flux splitting element and outputs a signal according to a received light amount; a second diffraction element placed between said light flux splitting element and said monitor element; and a control section that controls the drive of said light source according to the signal from said monitor element.

Abstract: An optical head includes a blue color laser beam sources, a red color laser beam sources, a dichroic prism, a collimator lens, a beam splitter, an objective lens, a photo detector element, a detection lens, and a hologram element having a first hologram and a second hologram and the first hologram changes a phase of a +1st order diffraction light of a blue color laser beam so that its condensing point falls on a second photo detecting portion and the second hologram changes a phase of a ?1st order diffraction light of a red color laser beam so that its condensing point falls on a third photo detecting portion.

Abstract: The lens unit for the optical pick-up apparatus has: the objective lens by which the projecting light from the light source is condensed on the information recording surface of the optical information recording medium; the phase control element which is arranged on the light source side to the objective lens, and which controls the phase of the projecting light from the light source; and the supporting member holding the objective lens and the phase control element; and the phase control element is held under the condition that its optical axis is inclined by a predetermined angle to the optical axis of the objective lens, and the intersection at which the optical axis of the phase control element crosses the optical surface having the phase structure is arranged on the optical path passing through the central point which passes the optical axis of the objective lens.

Abstract: The objective optical system of the present invention includes a first diffraction structure that applies diffraction to the light fluxes of wavelength ?1, wavelength ?2 and wavelength ?3 so that the diffracted lights of the L-th order (L: odd number), M-th order (M: integer) and N-th order (N: integer) each will have the maximum diffraction efficiency, and a first optical path difference-generating structure that substantially provides a phase difference to or two of the light fluxes of wavelength ?1, wavelength ?2 and wavelength ?3.

Abstract: A diffraction element for diffracting a particular wavelength of incident optical beam includes: a base section made from a first resin and provided with a predetermined diffraction pattern; and a cover section made from a second resin and covering the diffraction pattern, wherein a rate of change of refraction index of the first resin is substantially the same as a rate of change of refraction index of the second resin in a temperature range between a first temperature and a second temperature.

Abstract: Provided is an optical head device and an optical information recording or reproducing device for performing recording or reproduction to/from a plurality of types of optical recording medium, which can obtain a stable track error signal by a small size and exhibits high efficiency. Light PD and light PC emitted from a double-wavelength light source make incidence to a diffractive optical element in the same polarization directions. Diffraction gratings have a double refractive characteristic and in these areas the polarization directions of the two light beams become orthogonal. The light of 650 nm band is divided into 0th-order light and ±1st-order diffracted light in one of the diffraction grating and transmits through the other diffraction grating. The light of 780 nm band transmits through one of the diffraction grating and is divided into 0th-order light and ±1st-order diffracted light in the other diffraction grating.

Abstract: An apparatus includes a recording medium (100) having substrate (220) and markable coating (230). The apparatus also includes a recording/transmitting device including a light source (150) having at least two separate lasers, a unified apochromatic lens structure (148, 200, 300) having at least two separate lenses functioning as one structure, and a light separating means (201, 301). Lens structure (148, 200, 300) and light separating means (201, 301) enable light (152) to a) pass through lens structure (148, 200, 300) with at least two different wavelengths directed to at least two different spots on medium (100), so as to cause a localized change in chemical and/or physical properties to form at least two optically detectable marks (242) in markable coating (230), or b) pass through lens structure (148, 200, 300) with at least two different wavelengths directed to at least two different spots on medium (100), so as to cause at least one optically detectable mark (242) to reflect light (152).

Abstract: The present invention provides a photodetector capable of generating highly accurate tracking and focusing error signals free of variations in light quantity caused by interference, in an optical pickup with a two-wavelength multilaser. The photodetector comprises first three light receiving areas arranged linearly to receive three light beams respectively resulting from splitting of a light beam emitted from a laser light source of a first wavelength and second three light receiving areas arranged linearly to receive three light beams respectively resulting from splitting of a light beam emitted from a laser light source of a second wavelength longer than the first wavelength. The distance between both-end light receiving areas out of the first three light receiving areas is longer than the distance between both-end light receiving areas out of the second three light receiving areas.

Abstract: An optical pickup including: a light source; a diffractive element; an objective lens; and a photodetector, wherein the diffractive element has first to fourth areas provided with a predetermined periodic structure in each of the areas, the second and third areas have phases of the periodic structures of the second and third areas varied at an angle of about 180 degrees, the first area has a phase of the periodic structure in the first area varied from a phase of the periodic structure in the second area at an angle of about 180 degrees, and the fourth area has a phase of the periodic structure in the fourth area varied from a phase of the periodic structure in the third area at an angle of about 180 degrees. The optical pickup can obtain an excellent tracking error signal and improved amplitude when the objective lens is displaced.

Abstract: An optical device having a sub-wavelength grating formed in a specified region is disclosed that is able to prevent wave front degradation accompanying a phase difference of a polarized light beam passing through the optical device. The optical device includes a circular-belt-like region where the sub-wavelength diffraction grating is formed, and a center portion where the sub-wavelength diffraction grating is not formed. A vertically polarized light beam used for operations on a blue-light optical recording medium A has a phase difference in the sub-wavelength diffraction grating to be an integral multiple of 2? and hence is transmitted through the sub-wavelength diffraction grating. A horizontally polarized light beam used for operations on a blue-light optical recording medium is diffracted by the sub-wavelength diffraction grating.

Abstract: An optical pickup apparatus which conducts reproducing and/or recording information for a first optical information recording medium by using a light flux having a wavelength ?1 (350??1 (nm)?480) and a second optical information recording medium. The optical pickup apparatus comprises an output angle conversion element which is a fixedly arranged single lens which can convert an output angle of the first light flux and the second light flux. The optical detector equipped in the optical pickup apparatus can receive both of the first light flux and the second light flux. And, both optical surfaces of the output angle conversion element are refractive surfaces.

Abstract: A phase correction element comprising a first phase correction layer formed in a region of numerical aperture NA2, and a first phase plate; the first phase correction layer comprising a concavo-convex portion having a rotational symmetry with respect to the optical axis of incident light and having a cross-sectional shape of a saw-tooth-form or a saw-tooth-form whose convex portions are each approximated by a step form; the first phase plate generating a birefringent phase difference of about an odd number times of ?/2 for linearly polarized light of ?1; and the phase correction element that does change a transmitted wavefront of ?1 and changing a transmitted wavefront of the ?2 or transmitted wavefront of both wavelengths of ?2 and ?3 when three types of incident light at ?1=410 nm, ?2=650 nm and ?3=780 nm respectively, are incident.

Abstract: An optical pickup includes an optical system in which light from a light source is introduced through an objective lens into an optical recording medium and in which light reflected from the optical recording medium is introduced into a light-receiving unit and an objective lens driving unit for driving the objective lens based on a light output detected at said light-receiving unit. In this optical pickup, a diffraction element is provided between the light source and the objective lens, the diffraction element is provided with at least first and second diffraction areas and the first and second diffraction areas have such grating shapes that ± first-order diffracted lights diffracted are received by the light-receiving unit at the position in which 0-th order light and ± first-order diffracted lights generated from guide grooves of the optical recording medium may not overlap with each other.

Abstract: A disc device (100) implements information processing with respect to, for example, a zeroth recording layer of an optical disk by an information processing section (510), and outputs a double-layer main voltage value and a double-layer sub voltage value corresponding to the intensities of a zeroth-order light beam and ±first-order light beams which are received by a photodetecting element (350) to an offset calculating section (522) by a voltage value acquiring section (521). The voltage value acquiring section (521) stores voltage values corresponding to the intensities of the zeroth-order light beam and ±first-order light beams which are received by the photodetecting element (350) as a single-layer main voltage value and a single-layer sub voltage value in a memory (400) in a state where a single-layer disc is loaded.

Abstract: An objective optical system is formed of a diffractive optical element with a diffractive surface formed on a virtual plane and an objective lens for focusing three collimated light beams of three different wavelengths at three different numerical apertures onto desired positions of three different recording media with substrates that include different thicknesses, such as an AOD, a DVD, and a CD, that introduce different amounts of spherical aberration in the focused beams. The objective optical system provides compensating spherical aberration to the three light beams by varying the distance between the diffractive optical element and the objective lens with the recording medium being used. The objective optical system focuses second-order diffracted light of one wavelength and first-order diffracted light of the other two wavelengths. An optical pickup device includes the objective optical system, the recording media, and a light source that provides the three light beams.

Abstract: An optical pickup apparatus for information recording and/or reproduction on different optical information recording media with compatibility among these media, the optical surface of a first objective lens and the optical surface of a second objective lens are formed only of a refractive surface. The second objective lens is used in common for the first light flux with a wavelength of ?1 and the second light flux with a wavelength of ?2, but in the case where the protective substrate t2 of the second optical information recording medium and the protective substrate t3 of the third optical information recording medium are the same, it is not necessary to take the difference in thickness of the protective substrate into consideration. Chromatic aberration based on the difference in wavelength between the first light flux and the second light flux can be corrected by displacing the second coupling lens.

Abstract: An optical pickup apparatus for reproducing information from an optical information recording medium or for recording information onto an optical information recording medium, is provided with a first light source for emitting first light flux having a first wavelength; a second light source for emitting second light flux having a second wavelength, the first wavelength being different from the second wavelength; a converging optical system having an optical axis and a diffractive portion, and a photo detector; wherein in case that the first light flux passes through the diffractive portion to generate at least one diffracted ray, an amount of n-th ordered diffracted ray of the first light flux is greater than that of any other ordered diffracted ray of the first light flux, and in case that the second light flux passes through the diffractive portion to generate at least one diffracted ray, an amount of n-th ordered diffracted ray of the second light flux is greater than that of any other ordered diffracted

Abstract: An objective optical element for use in an optical pickup apparatus, includes two or more optical elements having a first surface having a first phase difference providing structure and a second surface having a second phase difference providing structure, wherein each of the first and second phase difference providing structures emit a diffracted light flux corresponding to each of the entering first-third light fluxes, or emit a transmitting light flux which is not applied a diffractive action corresponding to each of the entering first-third light fluxes, and the first-third light fluxes enter into the objective optical element as an almost infinite parallel light flux for information reproducing and/or recording on the first-third optical information recording media respectively.

Abstract: Embodiments of the invention provide fabrication processes for the co-fabrication of microprobe arrays along with one or more space transformers wherein the fabrication processes include the forming and adhering of a plurality of layers to previously formed layers and wherein at least a portion of the plurality of layers are formed from at least one structural material and at least one sacrificial material that is at least in part released from the plurality of layers after formation and wherein the space transformer includes a plurality of interconnect elements that connect one side to the array of probes that has a first spacing to another side that has a second spacing where the second spacing is greater than the first spacing. In some embodiments, the fabrication process includes a plurality of electrodeposition operations.

Abstract: The present invention provides an optical pickup apparatus including a first light source, a second light source, a third light source, and a light-converging optical system including an objective lens. The objective lens includes at least one optical surface with a diffractive structure. The diffractive structure includes a plurality of ring shaped zones. Each of the ring shaped zones is concentrically arranged around an optical axis and includes a step difference extending along the optical axis. In the objective lens, the predetermined conditions according to the offence against a sine condition, an average of step differences of the plurality of ring shaped zones, a focal length, and a magnification, are satisfied.

Abstract: An optical pickup device using a laser beam comprising: a light-emitting element; a collimating lens; an objective lens; and a light-receiving element, wherein the laser beam emitted from the light-emitting element is converged on a recording surface of an optical disc to be disposed through a path related to the collimating lens and the objective lens, and the converged laser beam is entered to the light-receiving element reversely passing through the path after being reflected on the recording surface of the optical disc, the optical pickup device comprising: a front monitor light-receiving element for receiving a part of the laser beam emitted from the light-emitting element and detecting the amount of the laser beam; and an optical guiding member for guiding a part of the laser beam to the front monitor light-receiving element.

Abstract: Provided is an optical pickup device capable of suppressing an increase in the number of parts and complication of an optical system while a diffraction grating is used as an optical axis correcting element. Three kinds of blue, red, and infrared laser light beams are emitted from laser element provided in the same CAN package. A blue light emitting point (wavelength: 405 nm) and an infrared light emitting point (wavelength: 780 nm) are arranged in a layer forming direction of the laser elements such that an interval (d2) between the light emitting points becomes shorter than an interval (d1) between each of the light emitting points and a red light emitting point. An optical axis of the laser light beam emitted from the red light emitting point (wavelength: 650 nm) is aligned with an optical axis of the laser light beam emitted from the blue or infrared light emitting point by using the diffraction grating.

Abstract: An objective lens used for an optical pickup device wherein the optical pickup device includes: light source; and a converging optical system including the objective lens for converging a light beam emitted from the light source to an information recording surface of an optical information recording medium, and the optical pickup device is capable of recording and/or reproducing information by converging the light beam emitted from the light source to the information recording surface of the optical information recording medium with the converging optical system, the objective lens being a plastic single lens and satisfying following formulas when NA is an image-side numerical aperture required for recording and/or reproducing information to the optical information recording medium and f (mm) is a focal length of the objective lens.

Abstract: An optical pickup includes: a first projector for projecting a first light beam of a first wavelength so as to record and reproduce information with respect to an optical disk having a first light transmissive layer; a second projector for projecting a second light beam of a second wavelength longer than the first wavelength so as to record and reproduce information with respect to an optical disk having a second light transmissive layer; an objective lens common to the first and second light beams; and a diffraction optical element made of a lens with a diffraction grating and a refracting face and disposed in an optical path between the first and second projectors and the objective lens. The diffraction optical element is set to satisfy a predetermined equation.

Abstract: An optical pickup device includes a two-wavelength composite light source that can emit laser beams for a CD and for a DVD, a light source that can emit a laser beam for a BD, a hologram element and a photo detector. When spots formed on the photo detector by 0 order light generated by diffraction of the three laser beams in the hologram element are first, second and third spots in the descending order of the wavelength of the laser beams, an attachment angle of the two-wavelength composite light source is adjusted so that positions of the third spot and the second spot match substantially each other while a position of the first spot is shifted from the position of the second spot in the same direction as a diffraction direction of +1st diffracted light.

Abstract: An optical element may include a substrate including a diffractive structure having multiple periods, at least one period of the multiple periods having multiple steps, heights of the multiple steps non-monotonically increasing across the at least one period. The optical element may be used with at least two wavelengths, e.g., three wavelengths, may be on a single surface and may provide an efficiency of at least 50% for all wavelengths.

Abstract: A peak hold circuit is provided that operates stably even if a peak voltage to be held of a motor-drive-current detection voltage is minute. The peak hold circuit includes: a level shift circuit shifting the motor-drive-current detection voltage by a given voltage; a differential amplifier circuit receiving an output voltage of the level shift circuit and a voltage at an output terminal to amplify and output a difference between the voltages; an output transistor receiving at its base an output voltage of the differential amplifier circuit and outputting from its emitter charging current; a capacitor charged with the charging current to hold the voltage at the output terminal; a bias element generating a voltage substantially equal to the given voltage of the level shift circuit; and a resistance element provided between the bias element and the output terminal for controlling discharging current of the capacitor.

Abstract: The invention relates to an optical pickup for an optical recording medium, an electrically controlled diffraction grating suitable for use in such a pickup, and to an apparatus for reading from and/or writing to optical recording media using such an optical pickup or diffraction grating. According to the invention, an optical pickup for optical recording media having two or more data tracks, with a light source for emitting a light beam for reading from and/or writing to an optical recording medium, includes an electrically controlled diffraction grating, which is switchable between at least two states for generating one or more light beams from the light beam emitted by the light source for reading from and/or writing to one or more of the data tracks.

Abstract: A method capable of detecting spherical aberration caused by a storage medium includes generating a plurality of light beams having distinct phases by diffracting light emitted from a light source using a diffractive optical element, measuring optical signals of the plurality of light beams having distinct phases after being reflected by the storage medium, measuring optical signals of the plurality of light beams having distinct phases after being reflected by a reflective mirror, and updating settings of an adjusting device disposed on an optical path between the diffractive optical element and the storage medium in order to compensate for the spherical aberration caused by the storage medium.

Abstract: An optical pickup includes: a first projector for projecting a first light beam of a first wavelength so as to record and reproduce information with respect to an optical disk having a first light transmissive layer; a second projector for projecting a second light beam of a second wavelength longer than the first wavelength so as to record and reproduce information with respect to an optical disk having a second light transmissive layer; an objective lens common to the first and second light beams; and a diffraction optical element made of a lens with a diffraction grating and a refracting face and disposed in an optical path between the first and second projectors and the objective lens. The diffraction optical element is set to satisfy a predetermined equation.

Abstract: A lensless optical servo system (100) has an unfocused light source (102) and patterned photodetectors (104, 106, 108). The unfocused light is reflected by the markings on an LS-120 disk (40) and the reflected light carries the pattern of the markings the considerable distance in its far-field to the photodetectors (104, 106, 108). The convolution of this light pattern and a mating geometric pattern (110, 112, 114) on the photodetectors (104, 106, 108) causes the photodetectors to generate signals representing the position of the track on the disk. According to a presently preferred embodiment, a laser diode (102) and three detectors (104, 106, 108) are formed on the same silicon substrate (101). Sinusoidal metalization (110, 112, 114) is applied to the detectors (104, 106, 108) in the radial direction. The period of the sinusoidal metalization is two times the tracking pitch of the disk radially and tangentially.

Abstract: An optical pickup apparatus and a drive apparatus having the same are provided. Second light-receiving elements or third light-receiving elements for receiving ±first-order diffraction light beams from a polarization hologram are arranged outwardly of a circular region having the optical axis of a zero-order diffraction light beam on a light detector as its center, a radius of which is expressed by (2×t/n)×(f2/f1), where f1 denotes a focal length of an objective lens, f2 denotes a focal length of a coupling lens, t denotes a maximum value of a light transmitting layer thickness, n denotes a refractive index of a light transmitting layer.

Abstract: There is provided an information processing device which is capable of suppressing generation of stray light at the time of recording and reproduction of information, thus enabling quality information recording and reproduction. The information processing device includes: a radiation light source 2; and a converging section for converging rays emitted from the light source toward an information recording medium having a photosensitive layer 11b, wherein the converging section splits the rays into first and second rays 3? and 3 respectively traveling through first and second spaces as divided by a plane at least containing a point optical axis L, and converges the first and second rays 3? and 3 onto first and second points 12? and 12 in the information recording medium 11, the photosensitive layer 11b being interposed between the first and second points 12? and 12.

Abstract: An optical pickup device according to the present invention is constituted so that a laser beam emitted from a light receiving and emitting integral-type element is transmitted or reflected by a beam splitter, transformed to a parallel beam by a collimator lens, introduced into an objective lens, transmitted through the objective lens, and collected on a recording surface of an optical disc and the laser beam thus collected is returned to the light receiving and emitting integral-type element via a reverse path after the laser beam is reflected by the recording surface of the optical disc. The optical pickup device includes a front monitor light receiving element that is arranged between the light receiving and emitting integral-type element and the collimator lens, receives a part of the laser beam emitted from the light receiving and emitting element, and detects a quantity of the received laser beam.

Abstract: An optical head device includes a focusing optical system for focusing a laser beam emitted from a semiconductor laser light source on an optical information medium with an objective lens. A chromatic aberration correction element for correcting chromatic aberration occurring in the objective lens is provided between the semiconductor laser light source and the optical information medium. A light distribution correction element in which the transmittance increases with the distance from the center of the aperture surface of the objective lens is provided so as to correct a reduction of the intensity of the light incident on the aperture surface of the objective lens with the distance from the center of the aperture surface.

Abstract: An optical pickup includes: a first projector for projecting a first light beam of a first wavelength so as to record and reproduce information with respect to an optical disk having a first light transmissive layer; a second projector for projecting a second light beam of a second wavelength longer than the first wavelength so as to record and reproduce information with respect to an optical disk having a second light transmissive layer; an objective lens common to the first and second light beams; and a diffraction optical element made of a lens with a diffraction grating and a refracting face and disposed in an optical path between the first and second projectors and the objective lens. The diffraction optical element is set to satisfy a predetermined equation.

Abstract: An optical pickup apparatus for reproducing information from an optical information recording medium or for recording information onto an optical information recording medium, is provided with a first light source for emitting first light flux having a first wavelength; a second light source for emitting second light flux having a second wavelength, the first wavelength being different from the second wavelength; a converging optical system having an optical axis and a diffractive portion, and a photo detector; wherein in case that the first light flux passes through the diffractive portion to generate at least one diffracted ray, an amount of n-th ordered diffracted ray of the first light flux is greater than that of any other ordered diffracted ray of the first light flux, and in case that the second light flux passes through the diffractive portion to generate at least one diffracted ray, an amount of n-th ordered diffracted ray of the second light flux is greater than that of any other ordered diffracted

Abstract: The present invention relates to a method of reading out information from a multiple layer optical recording medium (10) by an optical readout device (12), the method comprising the steps of: focusing a central light beam (14) and two satellite light beams (16, 18) onto a first recording layer (20) of the optical recording medium, projecting reflection beams (22, 24) of at least part of the satellite light beams on two split detectors (26, 28), thereby creating satellite spots (116, 118), each split detector being associated with one of the satellite light beams, the reflected light interfering with light reflected by a second recording layer (21), and processing the signals from the split detectors for providing a tracking error signal, wherein the influence of a central part (29) of the reflection beams on the tracking error signal is removed and/or modified, thereby reducing a negative influence of this central part on the quality of the tracking error signal.

Abstract: The first and second materials of the diffraction element are selected such that the first material's refraction indexes n1(?1), n1(?2) and n1(?3) for the first, second and third wavelengths ?1, ?2 and ?3 and the second material's refraction indexes n2(?1), n2(?2) and n2(?3) for the first, second and third wavelengths ?1, ?2 and ?3 satisfy one of the conditions (1) or (2).

Abstract: An optical pickup including a two-wavelength multilaser for generating a tracking error signal and a focusing error signal with high accuracy without light quantity variations which otherwise might be caused by the interference. An optical beam of first wavelength is emitted from first laser light source, and an optical beam of second wavelength longer than the first wavelength is emitted from second laser light source. The optical beams of the first and second wavelength are each split into at least one main optical beam and two sub-optical beams by a grating having, in a single plane, a first grating pattern area for splitting the optical beam of the first wavelength and a second grating pattern area for splitting the optical beam of the second wavelength. The area of the first grating pattern area is larger than the area of the second grating pattern area.

Abstract: An objective optical element of an optical pickup apparatus has a magnification m1 satisfying the following formula for a light flux of the wavelength ?1: ? 1/7?m1?? 1/25 and |m1|<|M1, where M1 is an optical system magnification from the first light source to the first optical information recording medium for a light flux of the wavelength ?1. The objective optical element comprises a common region and an exclusive region. The exclusive region includes an exclusive diffractive structure having a function to suppress an increase of spherical aberration due to a raise of atmospheric temperature. A light flux of a wavelength ?2 having passed through the exclusive diffractive structure intersects with the optical axis at a position different from the position of the converged light spot formed on the information recording plane of the second optical information recording medium.

Abstract: In an optical head device responding to optical disc of different track pitches, an effect of both obtaining the tracking error signal by the optimum DPP method using a single diffractive element and suppressing the lowering amount in the amplitude of the tracking error signal in a state the object lens is moved by track following is obtained. In the optical head device, the grating phase of left and right regions of a sub-beam generating diffractive element differ from each other by 180 degrees. A central region of the sub-beam generating diffractive element has a grating pattern different from the left and right regions, and is divided into a plurality of regions to form different gratings different from each other.

Abstract: An optical compensator for use in an optical scanning device for scanning a first optical record carrier (3?) having an information layer (2?) at a first information layer depth d and a second optical record carrier (3?) having an information layer (2?) at a second, different information layer depth d2. The scanning of the first and second optical record carrier is effected using a scanning spot (16) formed on the information layer by a first radiation beam having a first wavelength and a second radiation beam having a second, different wavelength respectively. The optical compensator includes a substantially circular phase structure having an annular zone arranged in the path of the first radiation beam and the second radiation beam.

Abstract: A diffraction element having concave/convex-like diffraction gratings in its two surfaces from which at least two separated light beams can be taken in the same direction without changing largely the propagating direction of diffracted light even if the temperature of the operating environment changes. A diffraction grating having a concave/convex shape in cross-section is formed in the incoming-side surface of the transparent substrate and two diffraction gratings of concave/convex shape in cross-section are formed in the outgoing-side surface wherein the grating pitch of the first one is made equal to the grating pitch of one of the second ones. In addition, a reflection type diffraction element exhibiting a good wavelength dependence of diffraction efficiency without being dependent largely on the direction of polarization of an incoming light is provided.

Abstract: In the present invention, by utilizing the difference between the polarization directions of an optical beam and a reflected optical beam, a neutral density filter part of a variable filter in an optical pickup reduces the light amount of the optical beam and directs the optical beam to the objective lens, and directs the reflected optical beam to a photodetector being a photodetection unit with slight change in the light amount of the reflected optical beam. When reducing a transmitted beam, which is the optical beam transmitted by diffracting the optical beam using a diffraction grating, the irradiation positions of first-order optical beams being diffracted±first-order optical beams on the recording layer of an optical disc are dispersed.

Abstract: According to one embodiment, an optical head device provides a signal processing circuit which sets a control amount to move an objective lens so that a distance between the objective lens and a given recording layer of the an optical disc coincides with a focal position, an optical path length correction mechanism which corrects an influence of an aberration component producing an error in the focal distance, a thickness difference detection circuit which finds an amount of correction to be made by the optical path length, and an aberration correction circuit which generates a correction signal to correct the influence of the aberration component producing the error in the focal distance detected by the thickness difference detection circuit, and supplies the correction signal to the optical path length correction mechanism.