Abstract: The optical pickup device includes a semiconductor laser for emitting laser light of 650 nm and 780 nm in wavelengths, a semiconductor laser for emitting laser light of 400 nm in wavelength, and an optical sensor which is provided in sequence with a first light receiving surface divided into four areas in a matrix manner, a second light receiving surface divided into four areas in a matrix manner, and a third light receiving surface divided at least into two areas aligned inline. Reflected light of three beams of 400 nm in wavelength and reflected light of three beams in 780 nm in wavelength are received on the first to third light receiving surfaces respectively, and a main beam of reflected light of 650 nm in wavelength is received on the first light receiving surface on one side out of the three light receiving surfaces.

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 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: An optical pickup device radiates laser light to a disc having a plurality of recording layers in a direction of lamination. The optical pickup device includes a laser light source, a collimator lens, and an objective lens. The collimator lens changes a spread angle of the laser light emitted from the laser light source. The objective lens converges the laser light having passed through the collimator lens onto the disc. With the laser light in a parallel state having passed through the collimator lens, if a distance f between the laser light source and the collimator lens and a distance L between the collimator lens and the objective lens are in a relation of f<L, the objective lens brings the laser light into focus with minimum spherical aberration at a designed focal position on an inner side of an intermediate position between the foremost and innermost recording layers.

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: An information recording/reproducing device includes a light source separately projecting laser light for recording or reproducing, an optical system leading the projected laser light to a recording medium, a diffracting element separating laser light into main- and beam sub-beams, an evanescent light generating element irradiating evanescent light in relation to the separated sub-beam to a track where no recording pit is formed, a sub-light receiving element for receiving return light in relation to the sub-beam, a moving element for moving the evanescent light generating element in relation to the sub-beam to a direction to change a gap with the recording surface, and a control element; for controlling the moving element so as to make the gap become a predetermined target value in accordance with a gap error signal containing a signal indicative of a light amount of the return light in relation to the received sub-beam.

Abstract: [Problems] To provide an optical head and an optical information recorder/reproducer in which a high signal/noise ratio can be attained for an RF signal. [Means of Solving Problems] Reflected light beam from a disc (6) is divided into three light beams, a zero order light beam and ±first order diffraction light beams by a diffraction optical element (7a). Each light beam is further divided into four light beams by a diffraction optical element (8) which is divided into four regions by two lines passing the optical axis of incident light and respectively being parallel with the radial direction and the tangential direction of the disc (6) before being received by a photodetector (10a). Zero order light beam from the diffraction optical element (7a) is used for detecting a track error signal and an RF signal by a phase difference method or a push-pull method, and ±first order diffraction light beams from the diffraction optical element (7a) is used for detecting a focus error signal by a Foucault method.

Abstract: An optical pickup device according to the present invention comprises: a first mirror for reflecting a first light beam outputted from a first light source and letting a second light beam outputted from a second light source pass therethrough; a first object lens for converging the first light beam reflected by the first mirror on an information recording surface of a recording medium; a second mirror for reflecting the second light beam passing through the first mirror; a second object lens for converging the second light beam reflected by the second mirror on the information recording surface of the recording medium; and an achromatic lens for correcting an axial chromatic aberration of the second object lens generated by wavelength variation of the second light beam, wherein the achromatic lens is provided in an optical path between the first mirror and the second mirror.

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: An optical pickup apparatus for recording and/or reproducing information for an optical information recording medium, comprising a light converging optical system including a coupling lens and an objective lens, wherein a first diffraction structure is installed on the objective lens, and a second diffraction structure is arranged on the coupling lens, whereby the spherical aberration and chromatic aberration caused by the difference in the thickness of the protective layer are corrected in the light converging optical system as a whole.

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 pickup includes a detector, a plurality of light guiding units, and a switching controller. The detector detects, using a plurality of detection areas, a reflected light beam that is emitted from a predetermined light source and is reflected off an optical recording medium. Each of the light guiding units has a specific light guide pattern and inputs a predetermined part of the reflected light beam to a predetermined detection area in accordance with the light guide pattern. The switching controller switches and selects the light guiding unit that acts on the reflected light beam from among the plurality of light guiding units according to a predetermined switching condition.

Abstract: An objective optical system focuses light from a light source onto at least two different types of optical recording media having different substrate thicknesses in order to record or reproduce information on the optical recording media by using a variable refractive power element and an objective lens. The variable refractive power element may be a liquid crystal element with concentric zones that serves as a transparent plate having no convergence effect when no voltage is applied when selecting an AOD, DVD, or CD and as a converging lens when a voltage is applied when selecting a BD. Alternately, the variable refractive power element may electrically vary the refractive index of a nanoparticle dispersion or at least one liquid of a two-liquid lens element. A diffractive optical element may be used to assist in focusing light to four recording media. An optical pickup device includes the objective optical system.

Abstract: A diffractive part for an optical scanning device is described. The device is for scanning a first information layer by means of a first radiation beam having a first wavelength and a first polarisation, a second information layer by means of a second radiation beam having a second wavelength and a second polarisation, and a third information layer by means of a third radiation beam having a third wavelength and a third polarisation. The first, second and third wavelengths differ from each other. The device includes a radiation source for supplying the first, second and third radiation beams, an objective lens system for converging the radiation beams on the respective information layer, and a diffractive part arranged in the optical path of the radiation beams.

Abstract: An optical pickup including a light source, two light focus devices, a light reception device, a polarization selective light path splitting device, a polarization switching device, a first diffraction element including a periodic structure including two kinds of sub-wavelength convexo-concave structures while the two kinds of sub-wavelength convexo-concave structures alternately arranged at right angles to each other, and the filling factors of the two kinds of sub-wavelength convexo-concave structures are determined to substantially equalize effective refractive indices of the two kinds of sub-wavelength convexo-concave structures with regard to the polarization direction of the outgoing light beam, and the second diffraction element having a structure similar to that of the first diffraction element except that the filling factors are determined to substantially equalize effective refractive indices of the two kinds of sub-wavelength convexo-concave structures with regard to a polarization direction perpen

Abstract: An image pickup apparatus has a construction in which a diffraction element is provided in an observation optical system. Zero-order light that is transmitted straight through the diffraction element and one of the +1st-order diffracted light and the ?1st-order diffracted light that is diffracted by the diffraction element are imaged onto an image pickup surface of an image pickup apparatus. The imaging areas of the zero-order light and one of the +1st-order diffracted light and the ?1st-order diffracted light that is diffracted by the diffraction element do not overlap on the image pickup surface of the image pickup apparatus. With this construction, a small image pickup apparatus that provides a high-resolution spectral image and a color image of an object can be obtained.

Abstract: An optical system is described for scanning optical record carriers of different types. The optical system includes a compensator having a number of optical elements (NPS1, NPS2). The optical elements (NPS1, NPS2) are non-periodic phase structures (NPS) having annular areas separated by steps, forming a non-periodic pattern of optical paths of different lengths. By including these multiple optical elements (NPS 1, NPS2) having NPS surfaces in the lens system of an optical system, it is possible to compensate for the effect of variation of a parameters such as temperature, angle of incidence, polarisation of radiation incident on the system and wavelength of radiation, without causing sensitivity to variation of another such parameter.

Abstract: A light focusing optical system focuses light, for recording to and/or reproducing from a plurality of optical recording media of different kinds, onto the recording media by using a diffraction element and lens. The diffraction element has at least first and second diffractive surfaces. The first diffractive surface diffracts light whose wavelength is 630 nm or more and 670 nm or less to perform aberration correction on an optical recording medium whose cover layer has a thickness of approximately 0.6 mm. The second diffractive surface diffracts light whose wavelength is 400 nm or more and 415 nm or less to perform aberration correction on an optical recording medium whose cover layer has a thickness of approximately 0.1 mm or approximately 0.6 mm.

Abstract: A double-wavelength light source unit capable of stable signal detection, is realized.

Abstract: An objective optical element for use in an optical pickup apparatus first-third light sources emitting first-third light fluxes and a light converging optical system, includes a first optical path difference providing structure for providing an optical path difference which provides a substantial phase change to the third light flux and does not provide a substantial phase change to the first and second light fluxes; and a second optical path difference providing structure for providing an optical path difference to the first light flux, the second light flux and the third light flux, wherein the objective optical element converges the first-third light fluxes through the protective layers with the thicknesses t1-t3 onto an information recording surface of the first-third optical information media respectively.

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: Provided is an optical disk device to output a reproduction signal to reproduce an optical disk, including: a light output circuit to output light having a high frequency superimposed thereon; a first light receiving circuit to receive the light to output a first voltage corresponding to an amount of the light; a second light receiving circuit to output a second voltage corresponding to an amount of reflected light from the optical disk; an arithmetic circuit to output a calculation result based on a difference between the first voltage and the second voltage; and a reproduction signal generating circuit to control one of the first voltage and the second voltage based on the calculation result to generate the reproduction signal to reproduce the optical disk.

Abstract: An optical pickup apparatus comprising: a collimating lens configured to convert laser light emitted from a laser diode, from diffused light into parallel light; an objective lens; and a prism configured to guide the laser light emitted from the collimating lens to the objective lens, the prism including: a first face that the laser light emitted from the collimating lens enters; a second face that reflects the laser light entering the first face; and a third face that reflects the laser light reflected from the second face in a direction of the second face, and emits the laser light reflected again from the second face in a direction of the objective lens.

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 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 aberrations to the three light beams, two of which are incident on the objective optical system as collimated beams and one of which is incident as a diverging beam. 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: Using one optical element on which diffraction gratings for diffracting two laser beams each having a different wavelength are formed at both surfaces, the first laser beam and the second laser beam outputted from two semiconductor lasers are made to converge on an optical disc by use of the same optical system. Directions of the grating grooves of the first diffraction grating and the second diffraction grating are set in a manner so that the direction in which a straight line binding +1st-order, 0th-order and ?1st-order diffracted lights of the first laser beam diffracted by the first diffraction grating intersects tracks on the optical disc belongs to an opposite side to the direction in which a straight line binding +1st-order, 0th-order, and ?1st-order diffracted lights of the second laser beam diffracted by the second diffraction grating intersects the tracks.

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 head is used to irradiate a beam onto an optical recording medium having multiple recording positions in the thickness direction, and to receive a reflection beam reflected from the recording medium. The optical head has a light source, an optical system, and a detector. The optical system transmits the irradiation beam from the light source to the recording positions of the medium, separates optical components based on wavelength, and transmits the components to respective detection positions, where the components are individually detected.

Abstract: A diffracting portion is disposed in an optical path between a light source and an optical disc. The diffracting portion diffracts the reflected light from recording layers of the optical disc toward a light receiving portion. The diffracting portion includes a first diffraction region having a first diffraction efficiency and a second diffraction region having a second diffraction efficiency lower than the first diffraction efficiency. The first diffraction region includes a FES diffracting portion and first to fourth TES diffracting portions. The second diffraction region includes fifth and sixth TES diffracting portions. First-order diffraction lights from the non-light-collecting recording layer enter on the fifth and the sixth TES diffracting portions, and are diffracted toward the light receiving portion by the fifth and the sixth TES diffracting portions.

Abstract: A diffractive optical element (DOE) corrector for use with three different wavelengths includes a first diffractive element on a first surface of a first material, the first diffractive element diffracting a first wavelength of the three wavelengths, while directing a majority of light of second and third wavelengths of the three wavelengths into a zero-th order, and a second diffractive element on a second surface of a second material, the second material being different from the first material, the second surface being different from and in an optical path of the first surface, the second diffractive element diffracting the second wavelength, while directing a majority of light of the first and third wavelengths into a zero-th order.

Abstract: The optical miniaturized module includes a semiconductor laser for irradiating an optical disk with laser light, a diffraction grating for forming a main beam and two sub beams from the laser light, a polarization hologram for dividing reflected light from the optical disk, and a photodetector for detecting the reflected light. The polarization hologram includes a first parting line defined in a direction optically corresponding to a radial direction as the optical disk rotates. A main beam M incident area is divided with a boundary defined by the first parting line. A sub beam A incident area and a sub beam B incident area are each arranged avoiding the first parting line.

Abstract: A diffractive part for an optical scanning device is described. The device is for scanning a first information layer by means of a first radiation beam having a first wavelength and a first polarisation, a second information layer by means of a second radiation beam having a second wavelength and a second polarisation, and a third information layer by means of a third radiation beam having a third wavelength and a third polarisation. The first, second and third wavelengths differ from each other. The device includes a radiation source for supplying the first, second and third radiation beams, an objective lens system for converging the radiation beams on the respective information layer, and a diffractive part arranged in the optical path of the radiation beams.

Abstract: An optical device diffracts incident light with a hologram element 19 and receives the diffracted light with light receiving regions 20A to 29 on a light receiving element 12. The light receiving element 12 separately receives reflected main beams used to read information from an optical disc and reflected sub-beams used for a tracking operation with different ones of the light receiving regions. The light receiving regions to receive the reflected main beams are common irrespective of the wavelengths of the reflected main beams. The light receiving regions to receive the reflected sub-beams are different depending on the wavelengths of the reflected sub-beams. The optical device can record and/or reproduce information signals to and/or from optical discs, which need light sources of different wavelengths, without the influence of unnecessary reflected light from the optical discs or without complicating operation of output signals.

Abstract: In an optical pickup compatible with BD and HD DVD, when DPP method is used as a tracking error signal detection system for both BD and HD DVD, since the guide groove pitch of the optical disc differs between BD and HD DVD, when a diffraction grating for generation of three beams is shared by both, it is difficult to adjust a spot distance on recording layer of optical disc to ½ of the guide groove pitch for both. Assuming that lateral magnification of the BD optical system is M1, lateral magnification of the HD DVD optical system is M2, a spot distance of three beams on BD-R/RE is S1, a spot distance of three beams on HD DVD-R/RW is S2 the guide groove pitch of BD-R/RE is T1 and the guide groove pitch of HD DVD-R/RW is T2, a setting is made to meet Formulas 1 and 2.

Abstract: The present invention provides an optical pickup apparatus to for recording and/or reproducing information on an optical information recording medium including multilayered information recording surfaces. The optical pickup apparatus includes: a light source; an objective lens; a first optical element including a first optical area and a second optical area; a second optical element including a third optical area and a fourth optical area. The optical pickup apparatus further includes a light-converging element for receiving a main light flux from one information recording surface and a secondary light flux from another information recording surface and converging the main light flux at a position between the first optical element and the second optical element. The optical pickup apparatus further includes a polarization splitting optical member for splitting the main light flux and the secondary light flux; and a photodetector for receiving the main light flux.

Abstract: A lens-side grating diffracts, in a direction of an emitter-side grating, two laser beams passed through the lens-side grating from an optical disk side. The emitter-side grating substantially passes the laser beam having a longer wavelength than the other laser beam, and directs it to a desired region of the light receiving element. The emitter-side grating diffracts the laser beam having a shorter wavelength than the other laser beam to direct a +1st diffracted beam of the laser beam thus diffracted to the same light receiving region as a 0th diffracted beam of the other laser beam. Such a structure may be employed that a ?1st diffracted beam of the laser beam of the longer wavelength is directed to the same light receiving region as the 0th diffracted beam (passed beam) of the laser beam of the short wavelength.

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: An object of the present invention is to attain stable tracking servo performance by suppressing an offset caused by a shift of an object lens or a tilt of a disk, despite the one-beam method which does not cause reduction in light quantity of the main beam. A diffraction grating is provided between a hologram and a light receiving section, and a diffraction efficiency of the diffraction grating is varied in a grating longitudinal direction. For example, if an incident light beam on the diffraction grating is shifted in the grating longitudinal direction, the quantity of received light in each light receiving section varies to cause offset. By performing tracking servo so as to cancel the change, it is possible to correct the offset, thereby attaining stable tracking servo performance.

Abstract: In an optical pickup apparatus of the present invention, either a first laser diode emits a laser beam having a first wavelength or a second laser diode emits a laser beam having a second wavelength. An optical system focuses one of the two laser beams onto a recording surface of an optical recording medium. A photodetector unit receives reflection beams, which are reflected from the recording medium, to generate detection signals from the received reflection beams. A holographic unit has a first hologram suited to the first laser diode and a second hologram suited to the second laser diode, the first hologram provided to diffract a reflection beam of the laser beam of the first laser diode to the photodetector unit, and the second hologram provided to diffract a reflection beam of the laser beam of the second laser diode to the photodetector unit.

Abstract: An optical pickup device wherein at least a high density disc such as HD-DVD is compatible with DVD, and securing an amount of light is compatible with correction of chromatic aberration. An a correcting element representing an optical system used for the aforementioned optical pickup device.

Abstract: A simulation device for simulating an operation of a system constituted by a plurality of machines. An operation program is executed by an arithmetic processing unit in a controller of a machine or by an information processing device having a function of analyzing the operation program equivalent to the controller of the machine, to obtain operation command data for the machine. The obtained operation command data of the machine with lapsing time information are received by the simulation device and stored as historical data. Operation programs of all of the machines constituting the system are executed to obtain historical data of operations of the machines, which are united by arranging the data in time series from a start of simultaneous operations of the machines based on the lapsing time information. Images of three-dimensional models of the machines are displayed by animation based on the united historical data.

Abstract: Laser beams respectively emitted from a SHG blue laser unit and a red semiconductor laser unit that have photo detectors respectively are turned into parallel lights by a collimator lens and then coupled by a dielectric multi-layer film mirror so as to be propagated on the same optical axis. The dielectric multi-layer film mirror is configured so as to transmit light with a wavelength of 500 nm or shorter and reflect light with a wavelength of 500 nm or longer for both P wave and S wave. The lights that are transmitted and reflected by the dielectric multi-layer film mirror pass through a polarizing hologram and a phase variable wave plate and are focused on an optical disk by an objective lens. In this manner, a simple configuration can realize a compatibility with many types of optical disks and a stable signal detection even when using a polarizing optical detection system.

Abstract: The invention is directed to the provision of a liquid crystal optical element, for correcting wavefront aberrations (principally, coma aberration and spherical aberration), that can be mounted separately from an objective lens, and an optical apparatus using such a liquid crystal optical element. The liquid crystal optical element according to the invention includes a first transparent substrate, a second transparent substrate, a liquid crystal sealed between the first and second transparent substrates, and an electrode pattern as a region for advancing or delaying the phase of a light beam and thereby correcting wavefront aberration, wherein the region is formed smaller than the field of view of the objective lens so that the region substantially stays within the field of view of the objective lens regardless of the tracking motion of tracking means.

Abstract: An optical pickup device including a dual wavelength light source module for emitting a selected one of two light beams having different wavelengths, a dual grating for splitting, into three beams, the selected light beam emitted from the dual wavelength light source, and a hologram for focusing the three beams of the selected light beam onto a photodetector having typical 8-section patterns such that the three beams of the selected light beam are focused onto the same spots as those of the other light beam, respectively.

Abstract: An optical pickup apparatus includes a light source module which emits a light beam, a beam splitter which reflects or transmits the light beam emitted from the light source module, an objective lens which focuses the light beam passing through the beam splitter onto a disc, and a photodetector which receives and detects the light beam reflected by the disc, wherein the light source module includes a first light source and a second light source that emit first and second light beams having different wavelengths and are formed into a single module. The optical pickup apparatus further includes a first grating which divides the first light beam emitted from the first light source into three beams of the first light beam and transmits the second light beam emitted from the second light source, and a second grating which transmits the first light beam emitted from the first light source and divides the second light beam emitted from the second light source into three beams of the second light beam.

Abstract: A slider system have been developed to aid in the spacing between read/write heads and the storage medium, and a grating antenna amplifier has been developed to improve illumination spot size and polarization characteristics. The grating antenna can be attached to a grayscale slider to obtain a distance between the illumination spot and antenna that lies in the near field region.

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: 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 diffractive optical element (DOE) corrector for use with three different wavelengths includes a first diffractive element on a first surface of a first material, the first diffractive element diffracting a first wavelength of the three wavelengths, while directing a majority of light of second and third wavelengths of the three wavelengths into a zero-th order, and a second diffractive element on a second surface of a second material, the second material being different from the first material, the second surface being different from and in an optical path of the first surface, the second diffractive element diffracting the second wavelength, while directing a majority of light of the first and third wavelengths into a zero-th order.

Abstract: An optical system for an optical head of an optical disc drive is capable of using first and second discs, protective layer of the second disc being thicker than that of the first disc, a data density of the second disc being lower than that of the first disc. A light source selectively emits first and second laser beams having first and second wavelengths, respectively. An objective lens converges the first and second beams on the first and second discs, respectively. The second beam is incident on the objective lens as diverging light, and the first beam is incident on the objective lens as a beam of which degree of divergence is smaller. A diffraction lens structure is formed in the high NA exclusive area, which compensates for aberrations of a portion of the first laser beam, and causes aberrations to a portion of the second laser beam passed therethrough.

Abstract: An optical semiconductor device comprising an emitted beam branching section (61) which branches an emitted light beam from a laser device (51), a reflected light beam branching section (71) which branches a reflected light beam from an information recording medium (3) into light beams different from each other in focused state, servo signal sensing photodetectors (43, 45) which receive the branched reflected light beam in a defocused state, a first diffraction grating provided in the emitted light beam branching section for diffracting the reflected light beam having passed through the reflected light beam flux branching section, and a signal sensing photodetector (47) which receives the reflected light beam diffracted by the first diffraction grating.