Abstract: An optical system for use in an optical pickup apparatus comprises a first optical surface having a superposition type diffractive structure including a plurality of ring-shaped zones which are formed concentrically around an optical axis, wherein each ring-shaped zone is composed of a plurality of stepped sections stepwise, and a second optical surface having a diffractive structure including a plurality of ring-shaped zones which are formed concentrically around an optical axis, wherein each of the plurality of ring-shaped zones are divided by a stepped section to generate a diffractive light ray of diffractive order whose absolute value is not small than 1 for the light flux.

Abstract: A method of designing an optical element to be used for an optical system in which each of a plurality of light beams having different design wavelengths passes through the optical element is provided. The method includes determining at least two types of optical path difference functions including first and second optical path difference functions in such a manner that proportion, brought by the first optical path difference function, between diffraction orders at which diffraction efficiencies of the plurality of light beams are maximized is different from proportion, brought by the second optical path difference function, between diffraction orders at which diffraction efficiencies of the plurality of light beams are maximized, and obtaining a shape defined by combining the at least two types of optical path difference functions so as to apply the obtained shape to at least one surface of surfaces of the optical element.

Abstract: An objective lens including: a first region to respectively converge first and second light beams onto recording surfaces of first and second optical discs; and a second region located outside of the first region and configured to converge the first light beam onto the recording surface of the first optical disc and not to converge the second light beam onto the recording surface of each of the first and second optical discs, and wherein the first region is divided into a plurality of refractive surface zones concentrically formed about an optical axis and has a first step, a diffraction order at which a diffraction efficiency is maximized for each of the first and second light beams passing through the first step in the first region is a first order, and the objective lens satisfies a condition: 0.80<((Sout?Sd)/Sout)2/?in<1.45??(1).

Abstract: An objective lens includes a diffraction structure for distributing much of a quantity of an incident light beam into two diffracted lights having different diffraction orders from each other, wherein recording or reproduction of information on an optical disk is performed by converging the diffracted light having a longer focal length of the two diffracted lights onto an information recording surface through a protective layer of the optical disk, and a distance from the objective lens to a surface of the protective layer along an optical axis is longer than a distance between focuses of the two diffracted lights along the optical axis when the diffracted light having the longer focal length is converged onto the information recording surface of the optical disk.

Abstract: A disclosed optical pickup for performing at least recording, reproduction, or deletion of information on a first, second, third, and fourth optical recording media having different recording densities includes a first light source configured to emit first light having a first wavelength ?1 corresponding to the first and second optical recording media; a second light source configured to emit second light having a second wavelength ?2 corresponding to the third optical recording medium; a third light source configured to emit third light having a third wavelength ?3 corresponding to the fourth optical recording medium; an objective lens configured to focus the first light, the second light, and the third light on corresponding recording surfaces of the first, second, third, and fourth optical recording media; and an aberration correcting unit between the objective lens and the first, second, and third light sources.

Abstract: An optical-pickup apparatus comprising: a laser-light source including first-and-second-light-emitting points for laser lights with first-and-second wavelengths which points are disposed at positions deviating in a direction optically corresponding to an optical-disc-tracking direction; a diffraction grating including a plurality of periodic structures which are joined to be different in phase from each other in the direction and each of which includes a recess and projection repeated in a direction optically corresponding to an optical-disc-tangential direction, the diffraction grating being configured to generate main-and-sub-luminous fluxes from the laser light; a holder to hold the diffraction grating to be movable in the direction corresponding to the tracking direction; a collimating lens; an objective lens to focus the main-and-sub-luminous fluxes from the collimating lens on the same track of an optical disc; and a photodetector to be applied with reflected lights of the main-and-sub-luminous fluxes f

Abstract: An optical system for use in an optical pickup apparatus comprises a first optical surface having a superposition type diffractive structure including a plurality of ring-shaped zones which are formed concentrically around an optical axis, wherein each ring-shaped zone is composed of a plurality of stepped sections stepwise, and a second optical surface having a diffractive structure including a plurality of ring-shaped zones which are formed concentrically around an optical axis, wherein each of the plurality of ring-shaped zones are divided by a stepped section to generate a diffractive light ray of diffractive order whose absolute value is not small than 1 for the light flux.

Abstract: A microplate for use within an interrogation system and a method of using the microplate are disclosed. The microplate contains within the bottom of each well, an optical waveguide grating based sensor. Approximate to each sensor is a mask having an aperture of predetermined size. The aperture regulates the light that enters and exits the sensor upon successive scans and ensures repeatable readings from the sensor. In an extended embodiment, a method of detection is disclosed that utilizes a launch and receive system while employing the aforementioned microplate.

Abstract: An optical pickup includes: a first emission unit emitting an optical beam with a first wavelength corresponding to a first optical disc; a second emission unit emitting an optical beam with a second wavelength, which is longer than the first wavelength, corresponding to a second optical disc different from the first optical disc; a third emission unit emitting an optical beam with a third wavelength, which is longer than the second wavelength, corresponding to a third optical disc different from the first and second optical discs; a condensing optical device condensing, on a signal recording surface of a corresponding optical disc, the optical beams emitted from the first to third emission units; and a diffraction unit provided in the condensing optical device, which is disposed on the optical path of the optical beams with the first to third wavelengths.

Abstract: Provided is an optical pickup apparatus that can be made compact and is capable of producing stable push-pull signals. The optical pickup apparatus includes a light source, an objective lens, a diffraction element, a light-receiving element, and a control-driving section. The diffraction element receives light reflected from an optical recording medium. The light-receiving element receives light beams diffracted by the diffraction element. The light-receiving element has a plurality of light-receiving regions. The light-receiving region produces an output signal responsive to the quantity of the incident light beam. The control-driving section obtains differences among the output signals from a plurality of the light-receiving regions by calculation to derive a push-pull signal, and drives the objective lens under control on the basis of the push-pull signal.

Abstract: An optical head device compatible to different types of optical discs and capable of guaranteeing a sufficiently wide dynamic range for a low density optical disc, and the like are provided. The optical head device includes a plurality of light sources switchably usable; an objective lens for converging light emitted from one of the plurality of light sources to an information recording layer of an optical disc; and a light detector for receiving the light reflected by the information recording layer and outputting an electric signal based on the amount of the received light. The plurality of light sources include a first light source for emitting light having a first wavelength and a second light source for emitting light having a second wavelength shorter than the first wavelength.

Abstract: In the optical pickup device, while reflection light reflected from the optical multi-layer disc is divided into a plurality of regions so as to produce a plurality of divided optical beams, the divided optical beams are focused onto different positions on a photodetector, and a focus error signal is detected by employing a plurality of the divided optical beams by utilizing the knife edge method, and further, a tracking error signal is detected by employing a plurality of the divided optical beams. Furthermore, the dividing regions of the optical beam and light receiving parts are arranged in such a manner that stray light derived from other layers of the optical disc is not entered to a servo signal-purpose light receiving part of the photodetector when the divided optical beam is focused onto a target layer of the optical disc.

Abstract: To provide an optical head device, which can detect an excellent focus error signal for a dual layer optical recording medium, and optical information recording/reproducing device. Reflected light from a dual layer optical recording medium is diffracted by a diffractive optical element divided into four regions, and is received by a photodetector. Optical spots are equivalent to negative first order diffracted light from the four regions of the diffractive optical element, and are received by four dual-divided light receiving sections, respectively, to be used for detection a focus error signal by a Foucault's method. The four dual-divided light receiving sections are provided with positive component light receiving sections for outputting the received light as a positive component of the focus error signal and negative component light receiving sections for outputting the received light as a negative component of the focus error signal, respectively.

Abstract: A near-field detection optical component operating in transmission. It includes at least one portion (11b) forming at least one grating (11) of diffraction microstructures (11a) succeeding one another over several periods (p), this grating (11) being capable of converting evanescent waves (16), which are established between the component and an object (12) located in the near field, when it reflects or emits radiation having a wavelength, into propagating waves (16?) by a diffraction effect during transmission through the portion (11b) forming the grating (11) of diffraction microstructures (11a). The period (p) of the grating (11) being of the order of magnitude of the wavelength of the radiation.

Abstract: An objective lens includes a first optical path difference providing structure in which a first basic structure and a second basic structure are overlapped together, and a second optical path difference providing structure in which a third basic structure, a fourth basic structure, and a fifth basic structure are overlapped together. The first and third basic structures emit diffracted light fluxes with the same diffraction order having the maximum light amount. The second and fourth basic structures emit diffracted light fluxes with the same diffraction order having the maximum light amount. The fifth basic structure emits 0th-order diffracted light fluxes with the maximum light amount, for the first light flux, emits 0th-order diffracted light fluxes with the maximum light amount, for the second light flux, and emits Gth-order diffracted light fluxes with the maximum light amount, for the third light flux, where G is an integer excluding zero.

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

Abstract: A hologram optical device, a compatible optical pickup including the hologram optical device, and an optical information storage medium system including the compatible optical pickup are provided. The hologram optical device includes: a first hologram area having a hologram that is asymmetric with respect to an optical axis to diffract an incident light in a 0th order diffractive light and a 1st order diffractive light, wherein light spots are formed by focusing the 0th order and 1st order diffractive lights using a lens. Accordingly, a light spot of the 1st order diffractive light is formed at a position separated from an optical axis of the lens when a light spot formed by the 0th order diffractive light is formed on the optical axis of the lens.

Abstract: The present invention relates to an optical element for use in an optical pickup apparatus and an optical pickup apparatus. An optical element is provided for use in an optical pickup apparatus which records or reproduces information by converging a light flux from a light source onto an information recording surface of an optical disc and by receiving a light flux reflected by the information recording surface by a photodetector. The optical element includes: a first area including an optical axis of the optical element; and a second area surrounding the first area and including a diffractive structure in a radial shape. The first area transmits a light flux from the light source, and the second area diffracts a light flux with the predetermined wavelength from the light source.

Abstract: An optical pickup includes a collimator lens having a diverging lens and a converging lens, such that it maintains a constant focal length and has a short optical path length. The collimator lens of the optical pickup device includes a diverging lens located at the side of a light source and a converging lens located at the side of generating parallel light or gentle oscillation light. In addition, the diverging lens and the converging lens of the collimator lens may be integrated, or may also be formed of a hologram optical element. As a result, the optical pickup device can be configured in the form of a slim structure using the collimator lens having a short optical path length.

Abstract: An optical pickup device includes a diffraction grating 12 for separating a light beam emitted from a semiconductor laser element into at least three light beams. The diffraction grating 12 is divided into three regions by a straight line extending in a direction parallel to a tangent line of a track of an optical information recording medium. A second region 12B is divided into a first sub-block 13 and a second sub-block 14 by a straight line extending in a direction parallel to a radius direction of the optical information recording medium. The first sub-block 13 has a phase difference of approximately 180 degrees from the second sub-block 14. The first region 12A has a phase difference of approximately 90 degrees from the first sub-block 13 and has a phase difference of approximately 180 degrees from the third region 12C.

Abstract: An optical-pickup apparatus comprising: a laser-light source; a diffraction grating including first-and-second regions of periodic structures different in phase from each other and a third region whose periodic structure is different in phase from the first-and-second regions; an objective lens focusing main-and-sub-luminous fluxes generated by the diffraction grating on the same optical-disc track; and a photodetector to receive reflected light of the main-and-sub-luminous fluxes from an optical disc and output a detection signal for generating main-and-sub-push-pull signals, a relationship between an incident light width in the objective lens corresponding to the third region and pupil diameters of the objective lens corresponding to first-and-second wavelengths of laser lights being adjusted so that a ratio of minimum value to maximum value of a differential-push-pull-signal is at substantially 50% or more and a ratio of sub-push-pull-signal level to main-push-pull-signal level is at substantially 15% or m

Abstract: The optical element comprises a first diffraction structure for generating three beams by diffracting light from a light source and a second diffraction structure that exhibits structural birefringence for a prescribed polarized light returning to the light source. The first diffraction structure is formed on a first face of a translucent optical base material and the second diffraction structure is formed on a second face of the optical base material. The optical base material, the first diffraction structure and the second diffraction structure are formed of a single material.

Abstract: The present invention provides an optical pickup device and optical recording medium information reproduction device that are capable of reproducing information that is recorded on a plurality of kinds of optical discs having different track pitches. With the present invention, an optical pickup device generates a main beam and sub beams that are made up from pairs of semi sub beams, such that the distance in the radial direction between center positions of a pair of semi sub spots on an optical disc where a pair of semi sub beams are formed is an odd multiple of half the track pitch of the optical disc, and the distance in the radial direction between center positions of semi sub spots that correspond to another pair of sub semi sub beams is an odd multiple of half the track pitch of another optical disc.

Abstract: An optical controller includes a light source for emitting light, an object lens for condensing light emitted from the light source, a light detection unit for receiving light reflected on an optical information recording medium and outputting a signal corresponding to the amount of the light, and a laser control unit for controlling the amount of the light emitted from the light source to the information recording surface on which information is to be recorded or reproduced, based on the recording state of an information recording surface disposed closer to the object lens than an information recording surface on which the information is to be recorded or reproduced.

Abstract: An optical pickup device includes a diffraction grating 12 for separating an emitted light beam into at least three light beams. The diffraction grating 12 is divided into three regions by dividing lines D1 and D2 extending in a first direction parallel to a tangent line of a track of an optical information recording medium. A second region 12B is divided into four sub-blocks by a dividing line D3 extending in the first direction and a dividing line D4 extending in a second direction that crosses the first direction. The sub-blocks located diagonally opposite to each other have a same phase, and the sub-blocks located adjacent to each other have a phase difference of approximately 180 degrees. The first region 12A has a phase difference of approximately 90 degrees from each sub-block of the second region 12B, and the first region 12A has a phase difference of approximately 180 degrees from the third region 12C.

Abstract: The present invention relates to a high data density optical recording medium. The invention further relates to an apparatus for reading from such an optical recording medium. The optical recording medium has marks that are arranged in tracks. The tracks have a cross section with a curved shape and protrude above a surface of the optical recording medium.

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: A unit to remove crosstalk in a multi-layered disk, an optical pickup including the unit, and an optical recording and/or reproducing apparatus including the optical pickup, of which the optical pickup includes: a light source; an optical path changer to change the path of light emitted from the light source; a unit to remove crosstalk; an objective lens to focus incident light on a disk; and a photodetector detecting light reflected by the disk such that the unit to remove crosstalk separates light reflected by a target recording layer of the disk from light reflected by adjacent recording layers so that the light reflected by the target recording layer and the light reflected by the adjacent recording layers do not overlap on the photodetector.

Abstract: A complex objective lens composed of a hologram and an objective lens, capable of realizing stable and high-precision compatible reproducing/recording of a BD with a base thickness of about 0.1 mm for a blue light beam (wavelength ?1) and a DVD with a base thickness of about 0.6 mm for a red light beam (wavelength ?2). In an inner circumferential portion of the hologram, a grating is formed. The hologram transmits a blue light beam as 0th-order diffracted light without diffracting it, and disperses a red light beam passing through an inner circumferential portion as +1st-order diffracted light and allows it to be condensed by an objective lens. Because of this, the focal length of the red light beam becomes longer than that of the blue light beam, whereby a working distance is enlarged.

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

Abstract: An optical system for spatially controlling light polarization, and method for manufacturing the same, includes a light source for generating a light beam of a designated wavelength, a beam shaper for splitting the light beam generated from the light source into a plurality of partial beams, and a polarization controller controlling the polarization states of the partial beams. The polarization controller may be formed on the beam shaper or separate from the beam shaper.

Abstract: A pickup device includes a diffraction grating 12 for separating a light beam emitted from the light source into at least three light beams. The diffraction grating 12 is divided into four regions by straight lines extending in a direction parallel to a tangential direction of tracks of an optical information recording medium. A periodic structure of a second region 12B has a phase difference of approximately 180 degrees from a periodic structure of a third region 12C, and a periodic structure of a first region 12A has a phase difference of approximately 180 degrees from a periodic structure of a fourth region 12D.

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 optical pickup including a light source, a light focus device, a diffraction element, an optical split element, a ¼ wavelength board, a light reception device and a correction element wherein the correction element is divided into multiple areas in a surface vertical to an optical axis, each area of the multiple areas has a sub-wavelength convexo-concave structure having a pitch equal to or shorter than a wavelength of the outgoing light beam and the sub-wavelength convexo-concave structures of the multiple areas adjacent to each other have groove directions perpendicular to each other, and the filling factors of adjacent areas of the multiple areas are determined to substantially equalize effective refractive indices with regard to the polarization direction of the outgoing beam emitted from the light source and impart a phase difference of ? with regard to a polarization direction perpendicular to the polarization direction of the outgoing beam.

Abstract: An optical pickup apparatus comprises first, second and third light sources to emit light fluxes of wavelength ?1, ?2 and ?3 for conducting recording and/or reproducing information for first, second and third optical information recording mediums having respective protective substrates of thickness t1, t2 and t3 and a diffractive optical element located on a common optical path for the first, second and third light sources. A converged-light spot is formed on the first optical information recording medium with m-th order diffracted-light ray of the wavelength ?1, on the second optical information recording medium with n-th order diffracted-light ray of the wavelength ?2, and on the third optical information recording medium with k-th order diffracted-light ray of the wavelength ?3 generated by the diffractive optical element respectively, wherein one of m, n and k is different from one of other two numbers.

Abstract: An optical element (10) includes a spherical aberration correction hologram (14) and a color aberration correction hologram (15). For a first laser light requiring the greatest valid diameter, no affect is given to the wave front in either of the aberration correction holograms. However, for a second laser light requiring the second greatest valid diameter, the valid diameter is narrowed down by the spherical aberration correction hologram (14). For a third laser light requiring the smallest valid diameter, the valid diameter is narrowed down to a predetermined amount by the diffusion light coming and the spherical aberration correction hologram (14) and further the valid diameter is narrowed down by the selective diffraction of the light flux incident in the annular area B of the color aberration correction hologram (15) and its diffusion.

Abstract: A diffractive optical element whose two diffraction gratings diffract three different wavelength light beams is provided. The diffractive optical element includes a first diffraction grating and a second diffraction grating that is located opposite the first one, and is configured in such a way that, among three different wavelength incident light beams, the diffraction efficiency in one light beam diffracted on the first diffraction grating is a predetermined value or less, and the diffraction efficiencies in the other two different incident light beams diffracted on the second diffraction grating are predetermined values or less. This arrangement can achieve a diffractive optical element capable of diffracting the three different wavelength light beams in a simple configuration.

Abstract: An optical head includes a first laser diode configured to generate a laser beam with a wave length of ?1, a second laser diode configured to generate a laser beam with a shorter wave length of ?2 than the wave length ?1, a collimator lens arranged so that the laser beams are incident on it, an aperture filter arranged on an optical axis of the collimator lens, and an object lens 0 arranged on the optical axis so that the laser beams passing through the aperture filter are incident on it, wherein the second laser diode is arranged at a position on the optical axis further away from collimator lens than the first laser diode is away from the collimator lens.

Abstract: An optical system of an optical pick-up is provided. The optical system includes an optical element including at least a phase shift surface among the surfaces thereof, and located closer to a light source than the objective lens. In this configuration, t1?t2 is satisfied, where t1 represents a thickness of a cover layer of a first optical disc for which a first laser beam is employed, and t2 a thickness of a cover layer of a second optical disc for which a second laser beam, having a longer wavelength than the first laser beam, is employed. NA1?NA2 is satisfied, where NA1 represents a numerical aperture for the first optical disc, and NA2 the numerical aperture for the second optical disc. The phase shift surface includes a first region that converges the first laser beam on a recording surface of the first optical disc, and the second laser beam on a recording surface of the second optical disc.

Abstract: An optical pickup apparatus and an optical recording/reproducing system including the same, the optical pickup apparatus includes at least two optical systems for different types of optical recording media, one of objective lenses of the optical systems being offset from a central line of the optical recording medium, wherein the optical system including the offset objective lens having a diffraction grating diffracting light emitted from a light source to form a main beam and sub-beams, wherein the diffraction grating includes first and second diffraction regions having different grating patterns arranged alternately thereon, and a center of each sub-beam is arranged at a boundary of the first and second diffraction regions of the diffraction grating, and a center of the diffraction grating and an optical axis of the light source are adjusted to be coincided with each other, preventing generation of an alternating current in a Push-Pull signal of the sub-beams.

Abstract: The present invention provides an optical pickup device requiring no position adjustment of a diffraction grating at the time of assembling the optical pickup device, and capable of suppressing fluctuations in a differential push-pull signal amplitude and cancelling a push-pull offset. An optical pickup device 200 of an embodiment of the present invention has a diffraction grating 230 of a special shape including predetermined grooves and two kinds of lattice grooves arranged at a pitch determined on the basis of a pitch of grooves formed in the surface of an optical disk 50, numerical aperture, wavelength of a light beam, and effective diameter of the light beam applied on the optical disk 50.

Abstract: An optical head device 100 of the invention performs at least one of recording and reproducing of information for a plurality of types of optical recording mediums 7. A light source 1 emits a plurality of kinds of light having mutually different wavelengths. The positions for emitting the plurality of kinds of light from the light source are mutually deviated. A center C1 of first light 2a is matched with a pattern center C3 of a first diffracting plane 3a. A center C2 of second light 2b is matched with a pattern center C4 of a second diffracting plane 3b. The optical head apparatus 100 provided with the light source in which two or more light emitting elements are mounted in one module can perform stable tracking control.

Abstract: Providing an objective lens with a large numerical aperture (NA), the present invention records or plays conventional optical disks such as CDs and DVDs at high light usage efficiency, using an optical head capable of recording or reproducing high-density optical disks. A diffraction optical element (8) is disposed in a light path of a first light beam of a first wavelength ?1 (400 nm to 415 nm) and a second light beam of a second wavelength ?2 (650 nm to 680 nm). And, the present invention principally emits 5th order diffracted light with respect to the first light beam, and principally emits 3rd order diffracted light with respect to the second light beam, from the diffraction optical element (8). Thus, a high diffraction efficiency of substantially 100% can be obtained with respect to both wavelengths.

Abstract: A pickup device includes a diffraction grating 12 for separating a light beam emitted from the light source into at least three light beams. The diffraction grating 12 is divided into four regions by straight lines extending in a direction parallel to a tangential direction of tracks of an optical information recording medium. A periodic structure of a second region 12B has a phase difference of approximately 180 degrees from a periodic structure of a third region 12C, and a periodic structure of a first region 12A has a phase difference of approximately 180 degrees from a periodic structure of a fourth region 12D.

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

Abstract: 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 pickup device that emits laser light beams having different wavelengths to a recording medium is disclosed. A semiconductor laser includes three laser elements having emitting wavelengths of ?1, ?2, and ?3 (?1<?2<?3), respectively. A plurality of diffraction gratings substantially align optical axes of the laser light beams emitted from the laser elements with one another by diffracting action. The diffraction gratings are separately provided for corresponding laser light beams having wavelengths of ?2 and ?3. Diffracting action for aligning ±n-order diffraction light (n is an integer equal to or greater than 1) of each of the laser light beams having the wavelengths of ?2 and ?3 with an optical axis of a laser light beam having a wavelength of ?1 is provided for the laser light beams having the wavelengths of ?2 and ?3.

Abstract: There is provided an objective lens used for an optical information recording/reproducing device for recording information to and/or reproducing information from two types of optical discs, by selectively using one of two types of substantially collimated light beams including first and second light beams. When wavelengths of the first and second light beams are respectively represented by ?1 (nm) and ?2 (nm), ?1<?2 is satisfied. The objective lens includes a first optical element, and a second optical element made of material different from that of the first optical element. The first and second optical elements are cemented via a cementing surface. Further, the objective lens is configured to satisfy a condition: 0.006 < { ( nR ? ? 2 - nR ? ? 1 ) - ( nB ? ? 2 - nB ? ? 1 ) } × ? [ { ( k ? ? 2 r ? ? 2 3 ) + 8 × A ? ? 42 } × f ? ? 1 3 + 2.29 ] < 0.038 ? .

Abstract: An optical pickup device is equipped with a diffraction element (8) that includes liquid crystal, two transparent electrodes sandwiching the liquid crystal, and a liquid crystal control portion (21) with electrodes connected electrically to the transparent electrode for controlling a voltage to be applied between the two transparent electrodes. The diffraction element (8) is provided with two types of diffraction areas (19) and (20). Each of the diffraction areas (19) and (20) generate predetermined diffracted light only from one of different wavelengths of light beams. The transparent electrodes of the diffraction areas (19) and (20) that are patterned are connected electrically to different electrodes (22c) and (22a), respectively.

Abstract: A pickup device includes a diffraction grating 12 for separating a light beam emitted from the light source into at least three light beams. The diffraction grating 12 is divided into four regions by straight lines extending in a direction parallel to a tangential direction of tracks of an optical information recording medium. A periodic structure of a second region 12B has a phase difference of approximately 180 degrees from a periodic structure of a third region 12C, and a periodic structure of a first region 12A has a phase difference of approximately 180 degrees from a periodic structure of a fourth region 12D.