Abstract: There is provided an objective lens including a first optical member and a second optical member which are made of materials different from each other and are cemented together at a cementing surface. The cementing surface includes a first phase shift structure having a plurality of refractive surface zones concentrically formed about an optical axis of the objective lens. The first phase shift structure satisfies conditions (1) and (2): 0.85<?2/?1<1.15??(1) 0.10<|(?3??2)/?1|<0.50??(2) where ?1=m(?1)×(?1/(n2(?1)?n1(?1))), ?2=m(?2)×(?2/(n2(?2)?n1(?2))), ?3=m(?3)×(?3/(n2(?3)?n1(?3))), m(?1), m(?2), and m(?3) are diffraction orders at which diffraction efficiencies of the first through third light beams are maximized, respectively, n1 (?1), n1 (?2), and n1 (?3) are refractive indexes of the first optical member, respectively, and n2 (?1), n2 (?2), and n2 (?3) are refractive indexes of the second optical member, respectively.

Abstract: There is provided an optical disc drive for recordation/reproduction for three types of optical discs by selectively using one of three types of light beams. The optical disc drive comprises an objective lens. The objective lens has a step structure which gives an optical path length difference to an incident beam at each step. When the third laser beam passes through the objective lens, the objective lens produces normal diffraction order light converging to a recording surface of the third optical disc and undesired diffraction order light converging to a point deviating from the recording surface of the third optical disc. A distance from a point to which the normal diffraction order light converges to a point to which the undesired diffraction order light converges is larger than or equal to twice a pull-in range of a focus error signal obtained when the third optical disc is used.

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: There is provided an objective optical system for an optical information recording/reproducing device. The objective optical system includes an optical element having an annular zone structure on at least one surface. The annular zone structure includes annular zones configured to have at least one step formed, at a boundary between adjacent ones of the annular zones, to extend in a direction of an optical axis. The at least one step is provided to cause a predetermined optical path length difference between a light beam passing through an outside of the boundary and a light beam passing through an inside of the boundary. The predetermined optical path length difference given to a first light beam by the at least one step is approximately equal to an odd multiple of a first wavelength ?a. Abbe number of material of the optical element satisfies a condition of 15<?d<35.

Abstract: An objective lens for an optical pick-up which is used to record data to and/or to reproduce data from at least three types of optical discs by selectively using one of at least three light beams having different wavelengths is provided. When thicknesses of a first, second and optical discs are represented by t1, t2 and t3, respectively, a relationship t1?t2<t3 is satisfied. When numerical apertures required for the first, second and third optical discs are represented by NA1, NA2 and NA3, respectively, a relationship NA1?NA2>NA3 is satisfied. The first, second and third light beams are incident on the objective lens as substantially collimated light beams, respectively. In this configuration, at least one of surfaces of the objective lens includes a first area for attaining the numerical aperture required for recording data to and/or reproducing data from the third optical disc, and a second area located outside the first area.

Abstract: There is provided an optical pick-up including first to third light sources respectively emitting first to third light beams, a first coupling lens, and an objective lens formed to converge each of the first, second and third light beams onto the first, second and third optical discs, respectively. The objective lens has a step structure including a plurality of concentrically formed refractive surface zones divided by steps, the step structure having a function of giving, at each step, an optical path length difference of approximately 2?1 to the first light beam. The first coupling lens causes the first light beam to be incident on the objective lens as a converging beam. The objective lens is positioned to satisfy a condition: ?0.35<f2×M2?f1×M1<?0.07??(1).

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 objective lens, for an optical information read/write device that performs read/write operations on each of a plurality of optical discs using a corresponding one of three laser beams having first, second, and third wavelengths ?1, ?2, and ?3 (nm) satisfying a relationship ?1<?2<?3, respectively, includes a phase shift structure having a plurality of ring-shaped refractive surface zones into which at least one surface of the objective lens is concentrically divided. The objective lens is made of material with an Abbe number ?d satisfying a condition 40??d?80. The phase shift structure has a step between each couple of the adjacent refractive surface zones that gives an optical path difference to an incident laser beam, so that a condition 2N+1.00<|?OPD/?1|<2N+1.30 is satisfied, where ?OPD represents the optical path difference (nm) that the step gives to the laser beam with the first wavelength, and N represents a non-negative integer.

Abstract: There is provided an objective lens used for three types of optical discs including by selectively using one of three types of light beams. At least one of surfaces of the objective lens is provided with a first region converging the third light beam on a recoding surface of the third optical disc. The first region has a step structure configured to have concentric refractive surface zones and to give an optical path length difference to an incident beam at each step formed between adjacent refractive surface zones. The step structure is configured such that the optical path length difference given by each step is substantially equal to an odd multiple of a wavelength of a first light beam, and a value of differentiation of an optical path difference function defining the step structure crosses zero in a height ranging from 30% to 70% of an effective diameter of the first region.

Abstract: There is provided an objective optical system used for information recording/reproducing for three types of optical discs. The objective optical system includes an objective lens, and a diffraction structure formed on an optical surface. The diffraction structure includes a first area for contributing to converging the third light beam. The first area includes first and second steps defined by first and second optical path difference functions, respectively. The first step is configured such that diffraction orders at which diffraction efficiencies for the first, second and third light beams are maximized are 1st order, 0-th order and 0-th order, respectively. The first step satisfies a condition: ?0.36×102<P12×f1+5.0×103×(n1?n3)<1.80×102 ??(1) The second step is configured such that diffraction orders at which diffraction efficiencies for the first, second and third light beams are maximized are 2nd order, 1st order and 1st order, respectively.

Abstract: There is provided an objective lens for information recording/reproducing for three types of optical discs, which includes a first area contributing to converging a third light beam onto a record surface of a third optical disc. The first area includes a phase shift structure having refractive surface zones concentrically formed about a predetermined axis. The phase shift structure includes first and second step groups. The first step group is configured such that an optical path length difference ?OPD1 (nm) given by each step of the first step group to a first light beam satisfies a condition: 2N1+1.10<|?OPD1/?1|<2N1+1.40, where N1 is an integer or zero, and the second step group is configured such that an optical path length difference ?OPD2 (nm) given by each step of the second step group to the first light beam satisfies a condition: 2N2?0.10<|?OPD2/?1|<2N2+0.10, where N2 is an integer.

Abstract: There is provided an objective optical system including an optical element having a phase shift structure, and a single-element objective lens made of resin, wherein the phase shift structure includes a plurality of refractive surface zones, the phase shift structure includes a first area to contribute to converging at least the third light beam on a record surface of the third optical disc, the first area includes at least two types of steps, each of which is formed at a boundary between adjacent ones of the plurality of refractive surface zones, the at least two types of steps gives optical path length differences different from each other to an incident light beam, the annular zone structure satisfies following conditions: 0.01<(EP21?EP11)/EP11<0.10 0.04<(EP31?EP11)/EP11<0.30 ?100<?(?OPD11/?1)+?(?OPD12/?1)<?10 where EP11=INT((?OPD11/?1)+0.5)×(?1(n1?1)), EP21=INT((?OPD21/?2)+0.5)×(?2(n1?1)), EP31=INT((?OPD31/?3)+0.5)×(?3(n1?1)).

Abstract: There is provided an objective optical system for an optical information recording/reproducing device. The objective optical system includes an optical element having an annular zone structure on at least one surface. The annular zone structure includes annular zones configured to have at least one step formed, at a boundary between adjacent ones of the annular zones, to extend in a direction of an optical axis. The at least one step is provided to cause a predetermined optical path length difference between a light beam passing through an outside of the boundary and a light beam passing through an inside of the boundary. The predetermined optical path length difference given to a first light beam by the at least one step is approximately equal to an odd multiple of a first wavelength ?a. Abbe number of material of the optical element satisfies a condition of 15<?d<35.

Abstract: There is provided an optical pick-up including first to third light sources respectively emitting first to third light beams, a first coupling lens, and an objective lens formed to converge each of the first, second and third light beams onto the first, second and third optical discs, respectively. The objective lens has a step structure including a plurality of concentrically formed refractive surface zones divided by steps, the step structure having a function of giving, at each step, an optical path length difference of approximately 2?1 to the first light beam. The first coupling lens causes the first light beam to be incident on the objective lens as a converging beam. The objective lens is positioned to satisfy a condition: ?0.35<f2×M2?f1×M1<?0.07??(1).

Abstract: An optical pickup device includes a first light source emitting first light with a first wavelength, a second light source emitting second light with a second wavelength, a third light source emitting third light with a third wavelength, an objective lens having a step structure, the objective lens being disposed to satisfy predetermined conditions, at least one first coupling lens making the first light and the second light incident onto the objective lens as converged light, a second coupling lens making the third light incident onto the objective lens as diverging light, and a liquid crystal aberration correcting element.

Abstract: An objective lens used for recording data to and/or reproducing data from a plurality of types of optical discs having different thicknesses of cover layers. The objective lens satisfies a condition 0.02<M2?M1<0.15, where M1 represents a magnification of the objective lens when recording/reproducing for a first optical disc is performed using the first light beam, and M2 represents a magnification of the objective lens when the recording/reproducing for a second optical disc is performed using the second light beam. Further, at least one of lens surfaces of the objective lens is provided with a diffracting structure having a plurality of annular zones configured to correct spherical aberrations for both of the first and second optical discs.

Abstract: There is provided an optical pick-up used for recording data to and/or reproducing data from at least three types of optical discs having at least two different thicknesses of cover layers. The optical pick-up includes light sources and an objective lens. A thickness t1 of a first optical disc, a thickness t2 of a second optical disc, and a thickness t3 of a third optical disc satisfy a relationship t1?t2<t3. A numerical aperture NA1 for the first optical disc, a numerical aperture NA2 for the second optical disc and a numerical aperture NA3 for the third optical disc satisfy a relationship NA1?NA2>NA3. Further, a first light beam for the first optical disc is incident on the objective lens as a converging light beam, and the second and third light beams for the second and third optical discs are incident on the objective lens as diverging light beams, respectively.

Abstract: There is provided an objective lens used for a plurality of types of optical discs having a front surface and a rear surface, each of which includes an inner region and an outer region. The outer region has a surface shape which suppresses a coma caused when a beam used for a first optical disc is incident thereon obliquely with respect to an optical axis of the objective lens. The inner region is configured such that, at a boundary position between the inner region and the outer region, the coma caused when a beam used for a second optical disc is incident on the inner region obliquely at a first angle with respect to the optical axis is less than the coma caused when the beam used for the second optical disc is incident on the outer region obliquely at the first angle with respect to the optical axis. Further, an inclination ?2A of the inner region and an inclination ?2B of the outer region of the rear surface satisfy a condition: ?2.5<?2B??2A<0.0.

Abstract: There is provided an objective lens used for a plurality of types of optical discs having a front surface and a rear surface, each of which includes an inner region and an outer region. The outer region has a surface shape which suppresses a coma caused when a beam used for a first optical disc is incident thereon obliquely with respect to an optical axis of the objective lens. The inner region is configured such that, at a boundary position between the inner region and the outer region, the coma caused when a beam used for a second optical disc is incident on the inner region obliquely at a first angle with respect to the optical axis is less than the coma caused when the beam used for the second optical disc is incident on the outer region obliquely at the first angle with respect to the optical axis. Further, an inclination ?2A of the inner region and an inclination ?2B of the outer region of the rear surface satisfy a condition: ?2.5<?2B??2A<0.0 . . . (1).

Abstract: There is provided an objective optical system which includes a chromatic aberration correction element having a negative power first lens and a positive power second lens, materials of the first and lenses being different from each other, the first and second lenses being cemented together via a cementing surface to correct a longitudinal chromatic aberration, at least one phase shift surface configured to give a predetermined optical path length difference to a first light beam, and an objective lens. Each of the chromatic aberration correction element and the at least one phase shift surface is located along an optical path common to the first and second light beams. The chromatic aberration correction element is located on a light source side with respect to the objective lens.