Abstract: An objective lens for converging light emitted from a light source on an optical recording medium to record and reproduce information consists of a single lens having at least one aspheric surface. The following conditional expressions (1) to (3) are satisfied: N?1.75??(1) 0.5<f/f1<0.6??(2) 0.8<d/(NA·De)<1.0??(3) where N denotes a refractive index, f denotes a focal length (mm), f1 denotes a focal length (mm) of a light source side surface, d denotes a thickness (mm) on an optical axis, NA denotes a numerical aperture on an optical recording medium side, and De denotes an effective aperture (mm) of the light source side surface.

Abstract: An optical pickup includes a light source emitting a light beam, an objective lens condensing the light beam emitted from the light source onto an optical disc, at least one divergent angle conversion lens (collimator lens) disposed between the light source and the objective lens and changing a divergent angle of the incident light beam, a driving unit (collimator lens driving mechanism) configured to drive the divergent angle conversion lens in a direction of an optical axis, an optical detection device (optical detector) detecting a return light beam reflected at the optical disc, and an environmental change detecting unit (temperature sensor) configured to detect change in environmental temperature, wherein the objective lens is made of a refractive element having, on one surface thereof, a diffraction structure in a stepped shape or a blazed sectional shape, which generates diffraction light providing a spot adapted to perform satisfactory recording and/or reproducing, the objective lens satisfying certai

Abstract: Provided are an objective lens with enhanced transmittance and an optical pickup apparatus which can record and/or reproduce information properly for three kinds of discs with different recording densities, even if a single lens is used as the objective lens. When all the expressions (1) to (3) are satisfied, excellent aberration characteristics can be obtained for the three kinds of discs: ?0.02?m1?0.02 (1); 0?(WD1?WD2)?1.57 m2+0.123 or 1.57 m2+0.24?(WD1?WD2)?0.7 (2); and 0?(WD1?WD3)?1.79 m3+0.333 or 1.66 m3+0.508?(WD1?WD3)?0.7 (3).

Abstract: An aspherical planoconvex lens (20), containing a material with a refractive index of at least 3.0, in which the height (h) of the convex region (21) is a maximum of one fifth of the thickness (l) of the lens (20). Also disclosed is a laser assembly incorporating such a lens and a method for the manufacture of such a laser assembly.

Abstract: Methods and apparatus to correct a curved Petzval focusing surface to a plane using a convex lens, a concave lens, and a space arranged between the curved side of the convex lens and the curved side of the concave lens. The method and apparatus may also include a Fresnel lens arranged between the concave lens and a pixel array.

Abstract: Provided are an optical pickup apparatus and an objective lens which can appropriately record and/or reproduce information on three types of discs with different recording densities and improve the light-utilization efficiency using a simple structure. A first optical path difference providing structure is formed on an optical surface of the objective lens. The first optical path difference providing structure is a step structure in which plural ring-shaped step units each including the same number of steps are arranged concentrically about the optical axis as the center. The width w1 in the direction perpendicular to the optical axis of the highest step or the lowest step in at least one step unit in the step structure is approximately half of the average value w2 of two steps at both sides of the highest step or the lowest step in the direction perpendicular to the optical axis.

Abstract: An imaging optical system for a camera and a video telephony camera employing the imaging optical system. The imaging optical system includes a stop and a first lens that are sequentially arranged from an object side. The first lens has a positive refractive power and two convex aspherical surfaces and satisfies LB/f>0.88 and LT/LB<1.71 wherein LT is the distance along the optical axis from the stop to the image plane of the imaging optical system, f is the total focal length of the imaging optical system, and LB is the distance along the optical axis between the surface of the first lens facing the image side and the image plane of the imaging optical system.

Abstract: An optical system having an optical axis OA and comprising: a light source; a reflector; a lens component situated therebetween; and a receiver. The light source and the receiver are separated, situated substantially symmetrically and decentered with respect to the OA. The lens component collimates the light beam from the light source. The reflector intercepts the collimated beam and to reflects it to the receiver through the lens, the collimated beam being at an angle to the optical axis. The lens component is structured to provide on the receiver an image of the light source characterized by (i) 0.05<astigmatism<0.1 waves RMS, when the lens component is not misaligned with respect to the average emission angle of the light source; and (ii) astigmatism<0.05 RMS when the lens component is tilted by of 2 to 5 degrees with respect to the average emission angle of the light source.

Abstract: An optical recording/reproducing apparatus is arranged so that, upon recording or reproducing a recording medium having a plurality of recording layers, the gap of the lens groups at the time of forming a converged light spot on this first recording layer is DIS (1), the gap of the lens groups at the time of forming the converged light spot on the N-th layer (the furthest layer from the surface of the recording medium) is DIS (N) and the neutral point of the spherical-aberration correcting mechanism is set at a position satisfying the following expression: lens group gap dst (3)=((DIS (1)+DIS (N))/2.

Abstract: An optical element includes: an element body including a resin containing a polymer having an alicyclic structure. The optical element is treated by one of heat treatment and wet-heat treatment for 15 hours or longer at a temperature lower by 10° C. to 30° C. than a glass transition temperature of the resin after being formed by injecting the resin in a mold. The optical element body has a length along an optical axis of the optical element in a range of 0.5 to 3 mm, and a length in a perpendicular direction to the optical axis in a range of 3 to 5 mm.

Abstract: An optical pickup lens for focusing a light beam from a laser light source on an optical information recording medium is a single lens. The optical pickup lens has two surfaces, and a surface R2 opposite to a surface R1 closer to the laser light source has a continuous shape. When the surface R2 has radii h1, h2 and h3 (h1<h2<h3) from an optical axis to a lens periphery, and where sags in the radii h1, h2 and h3 are sag1, sag2 and sag3, and differentials in the sags are ?sag1, ?sag2 and ?sag3, respectively, 0>?sag1>?sag2 and ?sag2<?sag3 are satisfied.

Abstract: There is provided a solid immersion lens in a material of refractive index n1, having an effective dioptre (26) separating from a medium of refractive index n2, an optical axis, a virtual object focal point for a convergent optical beam entering the lens via the effective dioptre, this virtual object focal point being conjugate with a real image focal point. The dioptre (26) is defined by the equation ?{square root over (x2+y2)}?n?{square root over ((x?a)2+y2)}=L, x, y are the coordinates of a point (I) of the dioptre (26) in a system (A, x, y) whose origin is the virtual object focal point (A) and whose abscissa axis is the optical axis (Ax), a is the, nonzero, algebraic distance between the virtual object focal point (A) and its conjugate (A?), L is the, nonzero, optical path, separating the virtual object focal point (A) from its conjugate (A?), n is the ratio n1/n2 of the refractive indexes.

Abstract: In order that thickness reduction, weight reduction, and mass productivity improvement should be achieved in an objective lens even in the case where NA is high, an objective lens according to the present invention is a bi-convex single lens having at least one aspheric surface, and satisfies conditions: (1) 3.5<DH-S/DH-H?<4.3; (2) 3.5<DH?-T2/DT1-H<50; (3) 0.9<d/f<1.1 (NA?0.85).

Abstract: A method of producing a lens that includes shifting a first die relative to a second die, and pressing an optical material shaped in a preliminary form between the first die and the second die so as to form a lens having a configuration corresponding to a hollow portion formed by the first die and the second die while shifting the first die relative to the second die. The produced lens includes an effective optical surface configured to converge a light flux. The effective optical surface includes a light entrance side, a light exit side, and an optical axis. The effective optical surface is a convex surface shaped such that when a maximum normal line angle is defined as an angle formed between the optical axis and a normal line at the outermost circumference of the effective optical surface, the maximum normal angle is 60° to 90°.

Abstract: Plural collimator lenses are arranged corresponding to plural laser light sources to collimate light beams emitted from the laser light sources into substantially parallel light beams, respectively. A condenser lens focuses the substantially parallel light beams. A coupling optical element, on which light beams focused by the condenser lens are incident, couples the light beams into a single light beam. The laser light sources are arranged such that a longitudinal direction of an emitting region of each of the laser light sources is coincident with a radial direction of the condenser lens.

Abstract: A composite optical device 1 includes a first optical section 10 having an optical functional surface 11 and a second optical section 20 bonded to the first optical section 10 on the optical functional surface 11. The optical functional surface 11 includes a smooth part 13 and a concave-convex part 12 adjacent to each other, and is constructed so that a position P2, along a normal direction of the smooth part 13, of a concave bottom of the concave-convex part 12 can be closer to the center of the first optical section 10 than a position P1 along the normal direction of an end of the smooth part 13 on a side of the concave-convex part 12 in a boundary vicinity portion NR between the smooth part 13 and the concave-convex part 12.

Abstract: An object lens for an optical disk may include an aspherical lens surface, and an aspherical equation, which may be applied to form the aspherical lens surface may include two 2nd order function terms. Accordingly, a lens, which has a high numerical aperture (NA) and also has a small flexure on a lens surface or aberration, is provided.

Abstract: The present invention provides an optical element including: a substrate; and an antireflection film formed on a surface of the substrate. The antireflection film includes a plurality of lower refractive index layers, and a plurality of higher refractive index layers which are layered alternately. Each of at least two of the plurality of lower refractive index layers comprises a same main component each other and comprises a side component with a different content ratio independently.

Abstract: A lens may operate in the mid-IR spectral region and couple highly divergent beams into highly collimated beams. In combination with a light source having a characteristic output beam, the lens may provide highly stable, miniaturized mid-IR sources that deliver optical beams. An advanced mounting system may provide long term sturdy mechanical coupling and alignment to reduce operator maintenance. In addition, devices may also support electrical and thermal subsystems that are delivered via these mounting systems. A mid-IR singlet lens having a numerical aperture greater than about 0.7 and a focal length less than 10 mm may be combined with a quantum well stack semiconductor based light source such that the emission facet of the semiconductor lies in the focus of the lens less than 2 mm away from the lens surface. Together, these systems may provide a package that is highly portable and robust, and easily integrated with external optical systems.

Abstract: Provides an objective lens, an optical head and an optical disc apparatus (drive) capable of compensating for various types of aberrations including wavelength changes for a plurality of types of optical discs including high density optical discs, DVDs and CDs with a good wavelength dispersion compensation ability and thus capable of providing good recording or reproduction characteristics. The objective lens according to the present invention includes a first lens and a second lens substantially in close contact with each other such that optical axes thereof match each other, and acts as a convex lens as a whole. Each lens includes a central portion including the optical axis and a peripheral portion located in a periphery of the central portion. The central portion of the first lens acts as a convex lens; and the central portion of the second lens acts as a concave lens. Where the refractive index of the first lens at d line (wavelength: 587.

Abstract: An optical system having an optical axis, the optical system comprising: (I) a light source; (II) a reflector; (III) a lens component situated between the light source and the reflector; (IV) a receiver, wherein the light source and the receiver are situated substantially symmetrically and are decentered with respect to the optical axis, and are separated by a distance d from one another; wherein: (a) the lens component is positioned to provide a collimated beam when intercepting light from the light source, and (b) the reflector is situated to intercept the collimated beam and to reflect the collimated beam to the receiver through the lens; and such that the collimated beam is at an angle ?? to the optical axis; and (c) the lens component is structured to provide on the receiver an image of the light source, the image characterized by (i) astigmatism of more than 0.05 waves RMS, and less than 0.

Abstract: In a laser optical device including a beam shaping optical system 3 for shaping a laser beam 2 into a predetermined cross-sectional intensity distribution and converging the light and an image formation optical system 6 for forming an image of a shaped beam 4 shaped and converged through the beam shaping optical system 3, the image formation optical system 6 is made up of an objective lens system 8 having a negative focal length placed ahead of a focal plane 7 of the beam shaping optical system 3 and an imaging lens system 9 placed behind the objective lens system 8.

Abstract: An optical pickup lens for focusing a light beam from a laser light source on an optical information recording medium is a single lens. The optical pickup lens has two surfaces, and a surface R2 opposite to a surface R1 closer to the laser light source has a continuous shape. When the surface R2 has radii h1, h2 and h3 (h1<h2<h3) from an optical axis to a lens periphery, and where sags in the radii h1, h2 and h3 are sag1, sag2 and sag3, and differentials in the sags are ?sag1, ?sag2 and ?sag3, respectively, 0>?sag1>?sag2 and ?sag2<?sag3 are satisfied.

Abstract: A lens assembly includes a first lens and a second lens. The first lens includes a first optically active portion, a first optically inactive portion surrounding the first optically active portion and a first optical axis. The first optically inactive portion includes a first inclined surface relative to the first optical axis. The second lens includes a second optically active portion, a second optically inactive portion and a second optical axis. The second optically inactive portion includes a second inclined surface relative to the second optical axis. The second lens is coupled to the first lens in such a manner that the first inclined surface is in contact with the second inclined surface, and a gap is maintained between the second optically inactive portion of the second lens and the first optically inactive portion of the first lens.

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: When the DVD provided with the DVD substrate 2 having thickness t2 of 0.6 mm is installed in the optical disc apparatus, the light beam 4 having wavelength ?1=655 nm is used as luminous flux of numerical aperture NA=0.63 to be condensed on the information surface 2a on the DVD substrate 2. When the CD provided with the CD substrate 3 having thickness t2 of 1.2 mm is installed in the optical disc apparatus, the light beam 5 having wavelength ?2=790 nm is effectively used as luminous flux of approximate numerical aperture NA=0.45 to be condensed on the information surface 3a on the DVD substrate 3. The wavefront aberration caused by a thickness difference between the DVD substrate 2 and CD substrate 3 is canceled out by the chromatic aberration caused by a wavelength difference between the light beams 4 and 5. Therefore, in spite of the difference in the transparent substrates, the light beams are suitably condensed respectively on the information surface 2a and 3a.

Abstract: An optical pickup lens for focusing a light beam from a laser light source on an optical information recording medium is a single lens. The optical pickup lens has two surfaces, and a surface R2 opposite to a surface R1 closer to the laser light source has a continuous shape. When the surface R2 has radii h1, h2 and h3 (h1<h2<h3) from an optical axis to a lens periphery, and where sags in the radii h1, h2 and h3 are sag1, sag2 and sag3, and differentials in the sags are ?sag1, ?sag2 and ?sag3, respectively, 0>?sag1>?sag2 and ?sag2<?sag3 are satisfied.

Abstract: A composite material and related methods are described, the composite material configured to exhibit at least one of a negative effective permittivity and a negative effective permeability for incident radiation of at least one wavelength. The composite material comprises an arrangement of electromagnetically reactive cells of small dimension relative to the wavelength, each cell having a plurality of quantum dots associated therewith for enhancing a resonant response thereof to the incident radiation at the wavelength.

Abstract: An optical pickup according to the present invention includes a plurality of light sources for emitting a plurality of light beams including first and second light beams of respectively different wavelengths, an objective lens for converging the plurality of light beams, and a grating structure shaped axisymmetrically with respect to the optical axis of the objective lens. Pth-order diffracted light (where p is a non-zero integer) which is formed from the first light beam (e.g. blue) by the grating structure is converged on an information layer of an optical disk (e.g. a BD) corresponding to the first light beam, owing to the converging actions of the objective lens and grating structure. Moreover, qth-order diffracted light (where q is a non-zero integer such that q?p) which is formed from the second light beam (e.g. red or infrared) by the grating structure is converged on an information layer of an optical disk (e.g.

Abstract: An objective lens used for an optical pickup device wherein the optical pickup device includes: light source; and a converging optical system including the objective lens for converging a light beam emitted from the light source to an information recording surface of an optical information recording medium, and the optical pickup device is capable of recording and/or reproducing information by converging the light beam emitted from the light source to the information recording surface of the optical information recording medium with the converging optical system, the objective lens being a plastic single lens and satisfying following formulas when NA is an image-side numerical aperture required for recording and/or reproducing information to the optical information recording medium and f (mm) is a focal length of the objective lens.

Abstract: Laser light is emitted from a laser oscillator, and the laser light is made to enter a beam expander optical system including a concave lens through a correction lens. The laser oscillator, the correction lens and the concave lens are disposed so that, when an emission point of the laser oscillator is a first conjugate point, a point at which an image at the first conjugate point is formed through the correction lens is a second conjugate point, a distance between the correction lens and the second conjugate point is b, a focal length of the concave lens is f, and a distance between the correction lens and the concave lens is X, the X satisfies b?3|f|?X?b+|f|.

Abstract: An objective lens for converging light emitted from a light source onto an optical recording medium to record and reproduce information consists of a single lens that has at least one aspheric surface. The following conditional expressions (1) and (2) are satisfied: ?0.90<R1/R2<?0.45??(1) 0.70<d/f<1.40??(2) where R1 denotes a radius of curvature (mm) of a light source side surface near an optical axis, R2 denotes a radius of curvature (mm) of an optical recording medium side surface near the optical axis, d denotes a thickness (mm) on an optical axis, and f denotes a focal length (mm).

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: Materials and methods for fabricating and using negative index materials are disclosed. A negative index material comprises a three-dimensional volume including a bulk solution and a plurality of unit cells disposed in the bulk solution in a substantially random pattern. Each unit cell comprises a periodic hole array pattern on a substrate or a resonator formed on a first surface of a substrate, and a thin wire pattern formed on a second surface of the substrate. The combination of the unit cells in the bulk solution produces a negative effective permeability and a negative effective permittivity over a frequency band of interest for the three-dimensional volume. The negative index material may be used to focus radiation by directing an incident radiation at the negative index material and generating a focused radiation by a negative refraction of the incident radiation in the negative index material.

Abstract: A laser beam output from a semiconductor laser light source 1 is transmitted through a cover glass 2 in the optical axis Z direction, is incident on a molded lens 4 in a state of divergent rays, is converted into convergent rays by the molded lens 4, and is applied onto a recording face 5 of the optical recording medium. A diaphragm 3 is arranged. An area of each lens surface onto which a luminous flux of the laser beam restricted by the diaphragm 3 is applied corresponds to an effective area. The following expression (1) is satisfied: d1?d0?0.04 mm??(1) where d0 denotes an effective aperture of one of the lens surfaces, and d1 denotes an outer diameter of the one of the lens surfaces.

Abstract: There is provided an optical pickup apparatus which includes a light source that generates light irradiating an optical recording medium; and an objective lens that collects the light irradiated from the light source on a recording surface of the recording medium, which further includes a coupling lens arranged on an optical path between the light source and the objective lens. In the optical pickup apparatus, a surface shape of the coupling lens is formed so that a preset spherical aberration amount is generated in the light irradiated from the light source at a position settled corresponding to a shift amount of the objective lens and where the light irradiated from the light source passes through the coupling lens, when the objective lens shifts.

Abstract: An optical pickup 1 includes a collimator lens 13 for changing the shape of a laser light by moving on the optical axis AX from a base point. An objective lens 15 is set so as to form a spot of which size, when the collimator lens 13 is located at the base point, is minimum at a point apart from the light source side surface of an information recording medium 20 by a distance of Lc defined by an expression (1): Lc=(L0+Ln)/2??(1), wherein Lc is named as a thickness to the designed center; L0 is a distance between the light source side surface of the information recoding medium and an information recording face located nearest to the light source side surface; and Ln is a distance between the light source side surface of the information recording medium and an information recording face located farthest from the light source side surface.

Abstract: An optical lens in which reflection is suppressed is provided by providing the optical lens with: a convex lens surface having, when the angle between a plane in contact with the lens surface and a direction perpendicular to the optical axis is an inclination angle, a maximum inclination angle of not less than 35 degrees and less than 90 degrees; and an antireflective structure provided on the lens surface and including structural elements that have a predetermined shape and are periodically arranged in an array form with a pitch smaller than the shortest wavelength of the incident light.

Abstract: An object lens arranged on a light proceeding path to focus light on a recording medium includes a first surface that is an incident surface on which light is incident, a second surface from which light exits to be focused on the recording medium, and a diffractive optical element disposed on at least one of the first and second surfaces and which has a refractivity of fD/f<5, fD being a focus distance of the diffractive optical element and f being a focal distance of the object lens. The object lens has a numerical aperture of 0.75 or greater.

Abstract: A protection member for preventing the contact of an objective lens with an optical disk is a thin plate member composed of an elastic material softer than a cover layer of the optical disk and has a plurality of convex-shaped parts formed on a surface thereof, which is opposed to the optical disk, so as to surround the objective lens.

Abstract: An objective lens is included in an optical pickup device that records and/or reproduces an information signal onto and/or from an optical recording medium. The objective lens has a numerical aperture of 0.82 or higher, has first and second surfaces that are both aspherical, and focuses a light beam onto the optical recording medium. The first and second surfaces have surface-to-surface eccentricity therebetween that causes an aberration, the aberration being correctable by tilting an optical axis of the objective lens relative to a central axis of the light beam incident on the objective lens. The aberration caused by the surface-to-surface eccentricity includes a third-order coma aberration. When the optical axis is tilted relative to the central axis of the incident light beam so that the third-order coma aberration becomes substantially 0 m? rms, each of astigmatism, spherical aberration, and high-order coma aberration becomes 20 m? rms or less.

Abstract: A compatible optical pickup includes a light source which emits a first light beam having a wavelength for a first recording medium; a twin light source which emits second and third light beams respectively having wavelengths for second and third recording media; a first objective lens which condenses the first light beam to form a light spot for recording and/or reproduction of the first recording medium; a second objective lens which condenses the second and third light beams to form light spots for recording and/or reproduction of the second and third recording media; an actuator which drives the first and second objective lenses; a first photo-detector which receives the first light beam reflected from a recording medium to detect an information signal and/or an error signal; and a second photo-detector which receives the second and third light beams reflected from a recording medium to detect information signals and/or error signals.

Abstract: A combined laser source includes: a plurality of semiconductor lasers which contain emission elements emitting a plurality of laser beams and being separately and hermetically sealed; a plurality of collimator lenses which collimate the plurality of laser beams emitted from the emission elements of the plurality of semiconductor lasers; an optical condensing system which receives, condenses, and optically combines the plurality of laser beams collimated by the plurality of collimator lenses; and one or more deflection members which are arranged between the optical condensing system and one or more of the plurality of collimator lenses, and deflect one or more of the plurality of laser beams collimated by the one or more of the plurality of collimator lenses so that the one or more of the plurality of laser beams propagate parallel to an optical axis of the optical condensing system.

Abstract: An aspherical lens formed of a high-refractivity low-dispersion glass, which is useful for constituting a compact and high-function image-sensing optical unit and which is formed by precision press-molding, the optical glass having a refractive index (nd) of over 1.83 and an Abbe's number (?d) of 40 or more and comprising, by mol %, 20 to 45% of B2O3, 5 to 24% of La2O3 and 22 to 42% of ZnO but containing no Li2O, the aspherical lens having an optical thin film formed on a surface thereof.

Abstract: It is to provide a wide-angle optical system for a solid image pickup device that favorably corrects distortion. The imaging lens is a biconvex lens, the object side face is formed into an aspheric shape in which the negative refracting power becomes stronger the farther the imaging lens is from an optical axis in the radial direction, and a condition expressed by the following expression (1) is to be satisfied; 0.8>|r1/r2|?0.5??(1) where, r1: center radius curvature of the object side face of the imaging lens r2: center radius curvature of the image surface side face of the imaging lens.

Abstract: An imaging optical system capable of moving a meridian image plane further closer to an ideal imaging plane vertical to an optical axis with the number of lenses kept constant. At least one plane of at least one optical element and including at least one optical element is divided into at least one zonal area surrounding an optical axis and a center area including the optical axis.

Abstract: A bi-convex solid immersion lens is disclosed, having a top and bottom convex surfaces. The radius of curvature of the bottom surface is larger than that of the top surface. A conical sloped side-wall connects the top and bottom surface.

Abstract: An optical pickup according to the present invention includes a plurality of light sources for emitting a plurality of light beams including first and second light beams of respectively different wavelengths, an objective lens for converging the plurality of light beams, and a grating structure shaped axisymmetrically with respect to the optical axis of the objective lens. Pth-order diffracted light (where p is a non-zero integer) which is formed from the first light beam (e.g. blue) by the grating structure is converged on an information layer of an optical disk (e.g. a BD) corresponding to the first light beam, owing to the converging actions of the objective lens and grating structure. Moreover, qth-order diffracted light (where q is a non-zero integer such that q?p) which is formed from the second light beam (e.g. red or infrared) by the grating structure is converged on an information layer of an optical disk (e.g.

Abstract: An image pickup lens system includes a lens 1 of a meniscus shape having a first face as a convex concave face, and a diaphragm 2 disposed on an object side of the lens 1. The lens 1 meets the following conditions: Y?/fl equal to or larger than 0.6; Dt/Dc is equal to or smaller than 0.9 and equal to or larger than 0.5; and Ap2/Am2 is equal to or larger than 0.9. Thus, even when an image pickup element is of a reduced size, a desired optical performance can be maintained, and it is possible to produce a lens easily with a back focal length ensured.

Abstract: An objective lens (1) for an optical disk, which focuses a light beam from a light source, is designed so that a third-order coma aberration generated when the objective lens is inclined at a unit angle is larger than a third-order coma aberration generated when the optical disk (2) is inclined at the unit angle, mounted on an actuator for inclining the objective lens according to an inclination amount of the optical disk, and used. With this structure, it is possible to obtain an objective lens for an optical disk that has a large numerical aperture and is easy to manufacture and assemble, and in which the third-order coma aberration generated when the optical disk surface is inclined owing to a warp or the like can be corrected by small inclination of the objective lens, so as to reduce a residual astigmatism, which is generated according to the inclination amount, after the correction.