Abstract: Provided is an objective lens including a diffraction portion provided on a laser beam incident plane or output plane. The diffraction portion includes first second, and third diffraction regions, wherein first laser beams corresponding to a first optical disc having a first transmissive layer are condensed on a data recording portion of the first optical disc, second laser beams corresponding to a second optical disc having a second transmissive layer thicker than the first transmissive layer are condensed on a data recording portion of the second optical disc, and third laser beams corresponding to a third optical disc having a third transmissive layer thicker than the second transmissive layer are condensed on a data recording portion of the third optical disc. An evaluation parameter calculated on the basis of an in-plane efficiency distribution function has a value corresponding to a symbol error rate that is less than a predetermined value.

Abstract: Provided is an objective lens including a diffraction portion provided on a laser beam incident plane or output plane. The diffraction portion includes first second, and third diffraction regions, wherein first laser beams corresponding to a first optical disc having a first transmissive layer are condensed on a data recording portion of the first optical disc, second laser beams corresponding to a second optical disc having a second transmissive layer thicker than the first transmissive layer are condensed on a data recording portion of the second optical disc, and third laser beams corresponding to a third optical disc having a third transmissive layer thicker than the second transmissive layer are condensed on a data recording portion of the third optical disc. An evaluation parameter calculated on the basis of an in-plane efficiency distribution function has a value corresponding to a symbol error rate that is less than a predetermined value.

Abstract: An objective lens is made of a resin material and focuses incident rays, which have a wavelength of 410 nm or less and are emitted from a light source, on an optical disc at a numerical aperture of 0.8 or more, wherein when a lens tilt sensitivity is defined as an amount of a 3rd-order coma aberration caused per a lens tilt of 1 degree which is an angle formed between an optical axis of the objective lens and a system optical axis of an optical system including the objective lens at 0° C., the lens tilt sensitivity is 130 m?rms/degree or less.

Abstract: An objective lens has a numerical aperture of 0.8 or more and focusing a light beam of a wavelength ? of at least 450 nm or less on an optical information recording medium. In this objective lens, a wavefront-aberration deterioration level TOR, accumulative value of aberration deterioration, satisfies the equation (1): TOR=?{square root over (2.52(DCm32+DCm52)+(TSA32+TSA52))}{square root over (2.52(DCm32+DCm52)+(TSA32+TSA52))}?0.07[?rms]??(1) In the equation (1), TSA3 [?rms/?m] and TSA5 [?rms/?m] refer to a third-order thickness sensitivity level and a fifth-order thickness sensitivity level, which are generated when a thickness error from a predetermined thickness is +1 ?m, respectively. DCm3 and DCm5 refer to a third-order decentering sensitivity level and a fifth-order decentering sensitivity level, which are generated when a decentering error of each of lens surfaces is 1 ?m, respectively.

Abstract: Provided is an objective lens for which expressions 0.83<(pM/pL)<1.17 and 0.83<(pM/pT)<1.17 or expressions 0.80<(pM/pL)<1.20 and 0.86<(pM/pT)<1.14 are satisfied, where pL is the ratio of fifth-order spherical aberration to third-order spherical aberration, the spherical aberrations being caused by a difference in the thickness of a cover layer of an optical recording medium, pT is the ratio of fifth-order spherical aberration to third-order spherical aberration, the spherical aberrations being caused by a change in the temperature of an environment of the objective lens, and pM is the ratio of fifth-order spherical aberration to third-order spherical aberration, the spherical aberrations being caused by a change in incident magnification.

Abstract: An objective lens is made of a resin material and focuses incident rays, which have a wavelength of 410 nm or less and are emitted from a light source, on an optical disc at a numerical aperture of 0.8 or more, wherein when a lens tilt sensitivity is defined as an amount of a 3rd-order coma aberration caused per a lens tilt of 1 degree which is an angle formed between an optical axis of the objective lens and a system optical axis of an optical system including the objective lens at 0° C., the lens tilt sensitivity is 130 m?rms/degree or less.

Abstract: An objective lens has a numerical aperture of 8.0 or more and focusing a light beam of a wavelength ? of at least 450 nm or less on an optical information recording medium. In this objective lens, a wavefront-aberration deterioration level TOR, accumulative value of aberration deterioration, satisfies the equation (1): TOR=?{square root over (2.52(DCm32+DCm52)+(TSA32+TSA52))}{square root over (2.52(DCm32+DCm52)+(TSA32+TSA52))}?0.07[?rms]??(1) In the equation (1), TSA3 [?rm/?m] and TSA5 [?rm/?m] refer to a third-order thickness sensitivity level and a fifth-order thickness sensitivity level, which are generated when a thickness error from a predetermined thickness is +1 ?m, respectively. DCm3 and DCm5 refer to a third-order decentering sensitivity level and a fifth-order decentering sensitivity level, which are generated when a decentering error of each of lens surfaces is 1 ?m, respectively.

Abstract: An optical pickup device is disclosed. The device includes: a light source that emits a light beam of a predetermined wavelength of about 405 nm; an objective lens being a plastic lens provided with, on at least one surface, diffraction means of a zone diffractive structure suppressing generation of aberration to be caused by a temperature change, and has a numerical aperture of 0.82 or larger for gathering the light beam emitted from the light source with respect to an optical disk; and a collimator lens disposed between the light source and the objective lens, and derives a substantially-collimated light by converting an angle of divergence of the light beam emitted from the light source.

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

Abstract: Provided is an objective lens for which expressions 0.83<(pM/pL)<1.17 and 0.83<(pM/pT)<1.17 or expressions 0.80<(pM/pL)<1.20 and 0.86<(pM/pT)<1.14 are satisfied, where pL is the ratio of fifth-order spherical aberration to third-order spherical aberration, the spherical aberrations being caused by a difference in the thickness of a cover layer of an optical recording medium, pT is the ratio of fifth-order spherical aberration to third-order spherical aberration, the spherical aberrations being caused by a change in the temperature of an environment of the objective lens, and pM is the ratio of fifth-order spherical aberration to third-order spherical aberration, the spherical aberrations being caused by a change in incident magnification.

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

Abstract: An optical pickup device is disclosed. The device includes: a light source that emits a light beam of a predetermined wavelength of about 405 nm; an objective lens being a plastic lens provided with, on at least one surface, diffraction means of a zone diffractive structure suppressing generation of aberration to be caused by a temperature change, and has a numerical aperture of 0.82 or larger for gathering the light beam emitted from the light source with respect to an optical disk; and a collimator lens disposed between the light source and the objective lens, and derives a substantially-collimated light by converting an angle of divergence of the light beam emitted from the light source.

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

Abstract: An optical pickup includes: a light source that emits first, second and third wavelengths of optical beam; and an objective lens unit including a diffraction element whose one surface includes a first diffraction pattern where the first wavelength is diffracted while the second and third wavelengths pass through and whose other surface includes a second diffraction pattern where the second wavelength is diffracted while the first and third wavelengths pass through; and an objective lens that collects the optical beam from the diffraction element, wherein the second and third wavelengths traveling through the objective lens unit are on the optical axis of the objective lens unit while the first wavelength traveling through the objective lens unit have an angle with respect to the optical axis; and the first diffraction pattern is located at a position so as to minimize aberration of the first wavelength of optical beam.

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: A diffraction element includes: an injection-molded transparent first member having two optical surfaces; and a second member firmly attached to one of the optical surfaces of the first member and provided with a first diffraction pattern on a surface, wherein the second member is a first ultraviolet curable resin having a refraction index in a range of ±0.013 with respect to a refraction index of the first member.