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: The present invention provides an optical pickup apparatus including: a first light source; a second light source; and a light-converging optical system including a coupling lens and an objective lens. The coupling lens includes a first diffractive structure. The optical pickup apparatus satisfies a predetermined condition according to the chromatic aberration, focal length, and dispersion of the material.

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: 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 scanning device scans optical record carriers, such as three optical record carriers, where each optical record carrier has an information layer having a depth which is different from the information layer depth of other optical record carriers, where d3<d2<d1, and where d1, d2, d3 are the information layer depths of the first, second, and third optical record carriers, respectively. The scanning device includes a radiation source system for producing three radiation beams of different wavelengths for scanning the three record carriers. The scanning device further includes a diffraction structure for introducing three different wavefront modifications into the three radiation beams, respectively. The diffraction structure is arranged to operate at selected diffraction orders m1, m2, m3, for the three radiation beams, respectively.

Abstract: An optical pickup includes a diffraction grating partitioned into three areas, in which the phase of periodic grating groove structure in an area is successively shifted from that in the adjacent area by 90°. In the generation of a differential push-pull signal, an amplification factor K for sub push-pull signals is varied depending on the type of the optical disk. By such composition of the optical pickup, amplitude deterioration of the tracking error signal accompanying displacement of the object lens is reduced.

Abstract: An optical pickup includes a diffraction grating partitioned into three areas, in which the phase of periodic grating groove structure in an area is successively shifted from that in the adjacent area by 90°. In the generation of a differential push-pull signal, an amplification factor K for sub push-pull signals is varied depending on the type of the optical disk. By such composition of the optical pickup, amplitude deterioration of the tracking error signal accompanying displacement of the object lens is reduced.

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: There is provided an optical pickup apparatus that can obtain a stable servo signal by reducing stray light generated by diffraction in a recording layer other than a recording layer on which light is condensed. A hologram element provided in an optical pickup apparatus for recording information onto a recording medium and/or reproducing information on the recording medium by use of light includes fourth and fifth divisions where at least first-order diffracted light among diffracted light beams obtained by reflection and diffraction on a recording layer other than a light-condensed recording layer on which light is condensed by an objective lens so as not to be directed toward first and second light-receiving elements for detecting focus position information and third to eighth light-receiving elements for detecting track position information.

Abstract: An optical pickup apparatus comprising: a diffraction grating including a first grating for diffracting a first laser light beam, and a second grating for diffracting a second laser light beam which is shorter in wavelength than the first laser light beam, the diffraction grating being disposed in a common optical path for guiding the first laser light beam and the second laser light beam to an optical disc; and a photo detector including in a first light receiving area, a main light receiving unit, a front sub-light receiving unit, and a rear sub-light receiving unit that receive reflected light beams, which are reflected by the optical disc, of a main beam, of a front sub-beam, and of a rear sub-beam, respectively, the first laser light beam being diffracted by the diffraction grating into the main beam, the front sub-beam formed in front of the main beam, and the rear sub-beam formed at the back of the main beam, wherein the first grating is set such that the front sub-light receiving unit and the rear sub

Abstract: An optical pickup (1) includes a light source (6) capable of emitting laser beams of various wavelengths and an objective optical system (2). The objective optical system (2) includes at least two wavefront conversion surfaces (13a) and (16a) and an objective lens (10). The at least two wavefront conversion surfaces (13a) and (16a) convert a wavefront of any laser beam entered therein into a different wavefront in response to the kind of an optical information recording medium (3) corresponding to the laser light. The objective lens (10) focuses the laser beam came out of the wavefront conversion surface (16a) on an optical information recording surface (3R). The optical pickup (1) satisfies the following condition for every wavelength of the corresponding laser beams: |SCMAX|<0.036??(1) wherein SCMAX is the maximum value of an offence against the sine condition of the objective optical system (2).

Abstract: An object of the invention is to provide a splitter, a light emitter, and an optical pickup apparatus which can realize a stable track servo. Because of the structure of an optical system including an objective lens (27) and a hologram pattern (25), even when the hologram pattern (25) is irradiated with a reflected light from one recording layer other than another recording layer in a focused state, first and second TES splitting portions (35, 36) are not irradiated with the reflected light from the one recording layer, but the reflected light is led to an axis vicinity portion (38) only. Accordingly, light reception by first and second TES light receiving portions (45, 46) is prevented, accurate track position information and deviation information can be positively acquired, and troubles such as the objective lens (27) being driven beyond a movable range can be eliminated.

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: A diffraction element for an optical pick-up apparatus is capable of precisely controlling the tracking of the pick-up apparatus. The diffraction element includes a diffraction grating divided into a first, a second, and a third region. The second region is located between the first and third regions. Any one of the first region and the third region is inclined at a predetermined angle ? with respect to the second region.

Abstract: The present invention is related to a chromatic aberration-correcting element which allows the adoption of BDs even when DVD/CD light beams are incident. The chromatic aberration-correcting element has a diffractive structure formed thereon, which can correct chromatic aberration in BD wavelength light beams in addition to adopting DVD/CD wavelength light beams. Also provided is an optical pickup device whose structure is simplified by employing the chromatic aberration-correcting element.

Abstract: An optical pickup apparatus and an optical disc apparatus are adapted to raise the efficiency of utilization of the lasers of the apparatus for accurately detecting tracking errors by raising the intensity ratio of the beam of the 0-th order to the beams of the ±1st orders produced by splitting of the laser beam of the wavelength to be subjected to division by three. The optical pickup apparatus includes a light emitting section for emitting a first laser beam having wavelength ?1 and a second laser beam having wavelength ?2 different from the wavelength ?1.

Abstract: A converging optical element for use in an optical pickup apparatus reproducing and/or recording information on a first optical disc using a first light flux with a wavelength ?1 emitted by a first light source, reproducing and/or recording information on a second optical disc using a second light flux with a wavelength ?2 emitted by a second light source, and reproducing and/or recording information on a third optical disc using a third light flux with a wavelength ?3 emitted by a third light source, the converting optical element includes: a phase structure arranged on at least one surface of the converging optical element, wherein when f3 is a focal length of the converging optical element for the third light flux, the focal length f3 satisfies a predefined condition.

Abstract: A diffraction element for use in an optical pick-up is capable of calculating a TE signal more stably irrespective of any assembly error in optical elements. The diffraction element of the invention is divided into three areas, a first, a second, and a third area. Each area comprises a diffraction grating with a predetermined period, and the second area is provided between the first area and the third area. The diffraction grating of the first area is substantially parallel to the diffraction grating of the third area, and the diffraction grating of the second area is substantially perpendicular to the diffraction gratings of the first and the third area.

Abstract: An optical pickup includes a diffraction grating partitioned into three areas, in which the phase of periodic grating groove structure in an area is successively shifted from that in the adjacent area by 90°. In the generation of a differential push-pull signal, an amplification factor K for sub push-pull signals is varied depending on the type of the optical disk. By such composition of the optical pickup, amplitude deterioration of the tracking error signal accompanying displacement of the object lens is reduced.

Abstract: An optical pickup includes a diffracting element having a plurality of regions for dividing the laser light emitted from the light-emitting element into a main beam and pairs of first, second, third, and fourth sub-beams. When the first to fourth sub-beams form first to fourth sub-spots, respectively, in that order along a radial direction on a recording surface of an arbitrary kind of disc-shaped recording medium which does not have the largest track pitch, n is a natural number, and the track pitch is Pa, the distance Da12 between the first and second sub-spots is approximately (2n12?1)×Pa/2, the distance Da34 between the third and fourth sub-spots is approximately (2n34?1)×Pa/2, the distance Da13 between the first and third sub-spots is approximately (2n13?1)×Pa, and the distance Da24 between the second and fourth sub-spots is approximately (2n24?1)×Pa.

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 objective lens unit, includes: an objective lens for irradiating and converging laser light on an optical disc as an a light information recording medium; and a lens frame for retaining the objective lens, wherein the lens frame is structured so that at least a portion closer to a rotation center of the optical disc is offset to an inner side of the lens frame with regards to a virtual edge section closer to the rotation center of the optical disc, wherein the virtual edge section is in a nodal line of a virtual plane that includes an end face which is closest to the optical disc in the lens frame and the objective lens, and that is perpendicular to an optical axis and a virtual rotation curved surface that is obtained when a virtual straight line passing a portion which is farthest from the optical axis in the lens frame and the objective lens, in parallel with the optical axis, is rotated around the optical axis as a center axis.

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

Abstract: An optical pickup has a semiconductor laser, a diffractive optical element that has first diffraction regions and second diffraction regions and diffracts a beam emitted by the semiconductor laser, an objective lens that focuses the diffracted beam on an optical disc, and a detection unit that detects a tracking error signal using the diffracted beam reflected by the optical disc. When a zero order diffraction beam is focused on the optical disc, a first order diffraction beam is diffracted by the first diffraction regions to be focused at a position between the objective lens and the optical disc, and diffracted by the second diffraction regions to be focused at a position beyond the optical disc. The first order diffraction beam has a beam width that, on the optical disc in a radial direction thereof, is two times or greater a track pitch of the optical disc.

Abstract: An optical pickup device includes a diffraction grating for separating a light beam from a semiconductor laser into at least three light beams. The diffraction grating is partitioned into five areas each having a given periodic structure: a first area; a second area adjacent to the first area in a first direction; a third area adjacent to the first and second areas in a second direction; a fourth area sandwiching the third area with the first area; and a fifth area adjacent to the fourth area in the first direction and sandwiching the third area with the second area. The phase of the periodic structure of each of the first and fifth areas is ahead of that of the third area by substantially 90°. The phase of the periodic structure of each of the second and fourth areas is behind that of the third area by substantially 90°.

Abstract: An optical system utilized in an optical pickup apparatus comprising: an aberration-correcting element made of a plastic material; and a converging lens to converge a light flux emitted from the aberration-correcting element, the converging lens being made of a plastic material, wherein the aberration-correcting element has a first optical surface provided thereon an optical path difference generating structure and has a second optical surface provided thereon a diffractive structure, and the converging lens is a single refractive lens having at least an aspherical surface.

Abstract: An optical information recording/reproducing apparatus includes an optical mechanism that collects an information beam and a reference beam to an optical information recording medium that has a diffraction grating and an information recording layer by using interference fringes produced due to interference between the both beams which are converted from an irradiation beam for recording or reproduction and that guides a servo irradiation beam into the diffraction grating and causes the servo irradiation beam to be transmitted through the diffraction grating, a photodetector that detects a diffracted beam diffracted by the diffraction grating and transmitted therethrough, and an adjusting unit that controls a drive unit to adjust a position or an angle between the optical information recording medium and the optical mechanism based on the intensity of the detected diffracted beam.

Abstract: An optical system has an optical functional surface including a common region used for conducting information recording and/or reproducing for both of a first optical information recording medium and a second optical information recording medium. The common region comprises a refractive surface of an imaginary basic aspherical surface and a optical path difference providing structure in which plural ring-shapes zones are separated around the center of an optical axis and neighboring ring-shaped zones are displaced to each other in a direction of an optical axis so as to cause an optical path difference obtained by multiplying a predetermined wavelength ?s (?1<?s<?2) with almost an integer. The refractive surface of the imaginary basic aspherical surface is structured such that a spherical aberration becomes under on the first information recording medium and a spherical aberration becomes over on the second information recording medium.

Abstract: An optical pickup is disclosed that includes a simplified phase correction element enabling sufficient correction of spherical aberration and realization of compatibility with blue-light, DVD-type and CD-type optical recording media with a two-stage numerical aperture switching operation. The phase correction element includes a phase shifting part and a diffraction part superposed on the phase shifting part. The phase shifting part has stepwise concentric circular regions including more than two stages. The diffraction part includes periodically arranged projecting and depressed portions formed on the phase shifting part. The phase shifting part suppresses spherical aberration related to red light used for a DVD-type optical recording medium when the object lens is optimized relative to blue light used for a blue-light optical recording medium. The diffraction part sets a most appropriate NA to each of the blue-light, DVD-type and the CD-type optical recording media by switching the numerical aperture.

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: An optical pickup has a light source for emitting a plurality of laser beams with different wavelengths; and an objective lens for focusing the laser beams emitted from the light source on recording surfaces of plural types of information recording media. A diffractive lens structure is provided in a light path of the laser beam, the structure including ring zone areas divided by a plurality of phase steps for correcting a wavefront aberration of the laser beam, a diameter of an outermost phase step of the diffractive lens structure is smaller than a second largest effective diameter of effective diameters required for reproduction of the plural types of information recording media.

Abstract: An optical pickup apparatus includes a diffractive optical element, and an objective lens that focuses a light beam of a first wavelength ?1, a light beam of a second wavelength ?2 and a light beam of a third wavelength ?3 on a first recording medium, a second recording medium, and a third recording medium, respectively, the wavelengths ?1, ?2, and ?3 being different from each other.

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: A multi-focal objective lens for use in an optical pickup apparatus for recording and/or reproducing information using a first light flux with a wavelength ?1 on a first and second optical discs, includes a first optical surface including a first diffractive structure. The multi-focal objective lens converges a diffracted light flux with one of the m-th diffraction order and the n-th diffraction order on an information recording surface of the first optical disc for recording and/or reproducing information of the first optical disc, and converges a diffracted light flux with another of the m-th diffraction order and the n-th diffraction order on an information recording surface of the second optical disc for recording and/or reproducing information of the second optical disc.

Abstract: An optical pickup apparatus for reading/reproducing data on an optical recording medium, includes a plurality of laser diodes configured to emit laser light of different wavelengths respectively, a photodetection device configured to detect each laser light, a diffraction type-optical device configured to transmit each laser light from the plurality of laser diodes to the optical recording medium, and to diffract the light reflected from the optical recording medium to the photodetection device, and wherein the diffraction type-optical device includes a plurality of reflecting type-diffraction elements configured to reflect and diffract each laser light of a corresponding wavelength in the laser light from the plurality of light diodes, to the photodetection device so that the photodetection device can detect each laser light of the corresponding wavelength for monitoring each of the laser light, and a suppression setting device configured to set each of the plurality of reflecting type-diffraction elements t

Abstract: An optical pickup apparatus includes first and second light sources; an objective lens; a spherical aberration correcting optical unit; and a chromatic aberration correcting optical element which includes a diffractive surface on at least one optical surface of the chromatic aberration correcting optical element such that a diffractive structure which is constructed by a plurality of ring-shaped zones separated by fine steps is formed on the diffractive surface, wherein the depth of steps along an optical axis is designed so that n2, which is a diffraction order of a diffracted ray having a largest diffraction efficiency among diffracted rays caused when the second light flux enters into the diffractive structure, is a lower order than n1, which is a diffraction order of a diffracted ray having a largest diffraction efficiency among diffracted light rays caused when the second first light flux enters into the diffractive structure.

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: The optical pickup device according to the present invention includes: a light source which emits a first light at a first wavelength, a second light at a second wavelength and a third light at a third wavelength; an optical path combining unit which combines vectors of the first, second and third light emitted by the light source, and matches optical axes of the first light and the third light; a light collection unit which condenses the light from the optical path combining unit into the optical information storage medium; a diffraction element which diffracts reflected light from the optical information storage medium; a first photo detector, a second photo detector and a third photo detector which receives the diffracted light from the first diffraction element; and a prevention unit formed between the first diffraction element and the first photo detector, the second photo detector and the third photo detector, and which prevents irradiation of + first-order diffracted light diffracted by the first diffr

Abstract: An optical pickup device in which light via a beam shaping mirror is input to an objective lens and the light is directed to an optical disc, includes a collimator lens which changes the light input to the beam shaping mirror into infinite system light and the beam shaping mirror includes a diffraction grating which changes the infinite system light into finite system light.

Abstract: An optical pickup includes a hologram element divided into four regions in a direction parallel to a tracking direction of an optical information recording medium and a direction perpendicular thereto. The hologram element allows two pairs of diffracted lights from two paired regions adjacent in parallel with the tracking direction to be made incident into light receiving elements so as to align in the direction perpendicular to the tracking direction.

Abstract: An optical pickup which, when a first light reflected by a recording medium is divided into a central light area and first and second peripheral light areas at both sides of the central light area, divides the first light reflected by the recording medium into at least 6 light areas, and the at least 6 light areas are independently detected from first through sixth light-receiving portions of a photodetector. Hence, the photodetector can detect a tracking error signal whose offset generation due to a shift of an objective lens is insensitive and whose offset generation due to an initial photodetector balance deviation is depressed.

Abstract: An optical pickup includes a light source which emits light, a grating which separates a portion of the light emitted from the light source, a reflecting member which reflects another portion of the light emitted from the light source, a monitoring photodetector disposed on a traveling path of the light reflected from the reflecting member and which measures the reflected light, an optical path changer which changes an optical path of the light separated by the grating, an objective lens light which condenses the light the optical path of which is changed onto a disc, and a signal detecting photodetector which receives the light reflected from the disc.

Abstract: A compatible optical pick-up apparatus, which records to and/or reproduce from both digital versatile disc (DVD)-type optical disks and compact disc (CD)-type optical disks for improving a signal regeneration capacity and a tracking capacity in operation at a high temperature. A polarized hologram of the optical pick-up apparatus is divided into six diffraction regions. The rays of a first light diffracted at the first and second diffraction regions are separately received by divided parts of a first bisected light-receiving portion of a photodetector.

Abstract: An objective lens of an optical pickup apparatus converges a divergent light flux onto an information recording surface. The following conditional formula is satisfied: |?SA1/?U|·|?U|+|?SA2/?T|·|?T|?0.07 ?rms where ? represents a wavelength of a light source, ?SA1/?U represents a change of a spherical aberration for an object-to-image distance change ?U (|?U|?0.5 mm) and ?SA2/?T represents a change of spherical aberration for a temperature change ?T (|?T|?30° C.), the object-to-image distance is a distance between the light source (a light emitting point) and the information recording surface.

Abstract: An optical pickup includes a diffraction grating partitioned into three areas, in which the phase of periodic grating groove structure in an area is successively shifted from that in the adjacent area by 90°. In the generation of a differential push-pull signal, an amplification factor K for sub push-pull signals is varied depending on the type of the optical disk. By such composition of the optical pickup, amplitude deterioration of the tracking error signal accompanying displacement of the object lens is reduced.

Abstract: A compatible optical pickup includes an optical disc, an objective lens, a diffractive device, and a divergent lens. The optical unit emits a short wavelength light beam corresponding to a high density optical disc and a long wavelength light beam corresponding to a low density optical disc. The objective lens forms a light spot on the high density optical disc and the low density optical disc and the diffractive device diffracts the short wavelength light beam to correct chromatism according to a change in a wavelength of the short wavelength light beam. The divergent lens refracts the long wavelength light beam toward the objective lens to increase a working distance with respect to the low density optical disc.

Abstract: A light source unit is disclosed. The light source unit includes a phase type optical element which modulates a phase distribution of laser beams emitted from a light source. The phase type optical element has a phase distribution so that a first ratio of the peak intensity of side lobe laser beams to the peak intensity of main lobe laser beams in a beam intensity profile at a focal position of the laser beam condensing element is greater than a second ratio of the peak intensity of side lobe laser beams to the peak intensity of main lobe laser beams in the beam intensity profile at the focal position of the laser beam condensing element when it is assumed that the phase type optical element is not disposed.

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.