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.

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: An objective lens for an optical information recording/reproducing device (executing information reading or writing on first through third optical discs having different data densities and different protective layer thicknesses t1-t3 (t1?t2?t3)) by selectively using first through third substantially collimated light beams having first through third wavelengths ?1-?3 (?1<?2<?3) respectively) includes a first optical member and a second optical member which are cemented together at a cementing surface. At least an area of the cementing surface within an incidence height necessary for securing a numerical aperture NA3 (required for the information read/write on the third optical disc) is provided with a diffracting structure including annular zones. The diffracting structure is formed so that diffraction orders m(?1), m(?2) and m(?3) of the first through third light beams maximizing their diffraction efficiency satisfy m(?1)>m(?2)?m(?3)?1.

Abstract: In an optical information recording/reproducing device which executes information reading or writing on multiple types of optical discs having different data densities by selectively using first through third light beams having first through third wavelengths, respectively, at least one side of an optical element is provided with a step structure including a plurality of concentric refracting surfaces and steps between them. The steps include first steps each giving a first optical path length difference specified by a first optical path difference function, second steps each giving a second optical path length difference specified by a second optical path difference function, and special steps each giving an optical path length difference obtained by the sum or difference of/between the first and second optical path length differences. Annular zone widths between adjacent steps are set at 10 times the first wavelength or more.

Abstract: An objective lens on which a beam having parallel light fluxes is incident includes a single element lens and a reflection suppressing coating formed on at least one surface of the single element lens. The reflection suppressing coating is formed such that the reflectivity across a radius of the objective lens exhibits a local maximal value, and the reflection suppressing coating is formed to achieve the following condition: 0.6<h1/hmax<0.95, wherein h1 denotes a distance between an optical axis and a position at which the reflectivity exhibits the local maximal value, and hmax denotes a distance between the optical axis and an outermost position of the effective diameter of the objective lens.

Abstract: There is provided an objective lens for an optical pick-up which is used to record/reproduce data to/from at least three types of optical discs. Thicknesses t1, t2 and t3 of cover layers of first, second third optical discs are t1?0.6 mm, t2?0.6 mm, and t3?1.2 mm. Numerical apertures NA1, NA2 and NA3 for the first, second and third optical discs satisfy a relationship NA1?NA2>NA3. When the first optical disc is used, a substantially collimated light beam is incident on the objective lens. When the second or third optical disc is used, a diverging beam is incident on the objective lens. With regard to magnifications M1, M2 and M3 and focal lengths f1, f2 and f3 of the objective lens for the first, second and third optical discs, the following conditions (1), (2) and (3) are satisfied: ?0.02<f1×M1<0.02??(1) ?0.10<f2×M2<?0.04??(2) ?0.29<f3×M3<?0.19.

Abstract: An objective lens for an optical pickup is configured such that, when a light beam having a wavelength corresponding to the optical disc requiring the higher NA is converged on the optical disc requiring the higher NA at the higher NA, the phase of light flux passed through the peripheral area is substantially the same as that passed through the central area. When a light beam having a wavelength corresponding to the optical disc requiring the lower NA is converged on the optical disc requiring the lower NA at the lower NA, the phase of light flux passed through a first annular region included in the peripheral area is different from that passed through the central area, and the phase of light flux passed through a second annular region, which is outside the first region, is substantially the same as that passed through the central area.

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: 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: 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: A 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 NA 2 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: A complex lens for a tandem scanning optical system converges a plurality of light beams, which are modulated independently and deflected by a deflector, onto a surface to be scanned, and forms a plurality of scanning lines at the same time. The complex lens includes a plurality of stacked lens portions that are molded as a single-piece element. Thus a plurality of lens surfaces of the lens portions at an incident side are formed by a single-piece mirror surface core and a plurality of lens surfaces of the lens portions at an exit side are formed by another single-piece mirror surface core during the molding process.

Abstract: A method of designing an optical element to be used for an optical system in which each of a plurality of light beams having different design wavelengths passes through the optical element is provided. The method includes determining at least two types of optical path difference functions including first and second optical path difference functions in such a manner that proportion, brought by the first optical path difference function, between diffraction orders at which diffraction efficiencies of the plurality of light beams are maximized is different from proportion, brought by the second optical path difference function, between diffraction orders at which diffraction efficiencies of the plurality of light beams are maximized, and obtaining a shape defined by combining the at least two types of optical path difference functions so as to apply the obtained shape to at least one surface of surfaces of the optical element.

Abstract: In a scanning optical system, a partial light blocking member having an annular light blocking part (for blocking off part of the incident laser beam entering the annular area around the central axis of the laser beam) is placed on an optical path between the laser light source and the polygon mirror. The scanning optical system including such a partial light blocking member is installed in a printer. By the effect of the partial light blocking member, the intensity of side lobes (several rings of light accompanying the main beam) is prevented from exceeding a threshold value even when optical surfaces of an imaging optical system of the scanning optical system have certain microscopic undulations, by which black stripes occurring in halftone printing can be eliminated.

Abstract: An objective lens that satisfies conditions: ?0.02<f1×M1<0.02??(1) ?0.02<f2×M2<0.02??(2) ?0.29<f3×M3<?0.19.??(3) At least one of lens surfaces of the objective lens includes a diffracting structure having a first region for converging the third light beam on a data recording layer of the third optical disc. The diffracting structure within the first region is configured such that a diffraction order at which diffraction efficiency of the first light beam is maximized is a sixth order, a diffraction order at which the diffraction efficiency of the second light beam is maximized is a fourth order, and a diffraction order at which the diffraction efficiency of the third light beam is maximized is a third order.

Abstract: An objective lens for recording data to and/or reproducing data from first and second optical discs. The objective lens is provided with at least one surface including a plurality of annular zones divided by steps. The steps has functions of phase shifting a wavefront of light passing through the plurality of annular zones so that a beam spot formed at a converging point of an average wavefront of the wavefront phase shifted by the steps is used for the first and second optical discs. The plurality of annular zones of the at least one surface includes at least one annular zone structure which includes first and second annular zone groups, each of which has at least three steps for phase shifting the wavefront in a first direction, and a first return step which is a step formed at a boundary between the first and second annular zone groups. The first return step phase shifts the wavefront in a second direction opposite to the first direction.

Abstract: A scanning optical system includes first and a second lens elements, at least one of which is a plastic lens element. Each surface of the plastic lens element is an aspherical surface that is configured such that a shape in a main scanning plane is defined as a function of a distance, in the main scanning direction, from a surface reference axis thereof, and that a curvature in an auxiliary scanning plane which is perpendicular to the main scanning plane is defined as another function of a distance, in the main scanning direction, from the surface reference axis. At least one of the two surfaces of the plastic lens element are arranged such that the surface reference axis thereof is decentered from an axis of the beam in the auxiliary scanning direction.

Abstract: There is provided a scanning optical system including a collimator lens being placed on an optical path between a light source and a deflecting system. At least one of a front surface and a rear surface of the collimator lens includes a central area through which part of the laser beam in the vicinity of a central axis of the laser beam passes, at least one first outer area having an effect on the laser beam so that the laser beam after passing through said at least one first outer area is given a first phase difference not including a phase difference of zero, and at least one second outer area having an effect on the laser beam so that the laser beam after passing through said at least one second outer area is given a second phase difference being different from the first phase difference and including a phase difference of zero.

Abstract: There is provided an objective lens used for at least three types of optical discs when thicknesses are respectively represented by t1, t2 and t3, t1 as 0.6 mm, t2 is 0.6 mm and t3 is 1.2 mm. When numerical apertures for the first, second and third optical discs are respectively represented by NA1, NA2 and NA3, a relationship NA1>NA2>NA3 is satisfied. When the first and second optical discs are used, collimated light beams are incident on the objective lens. When the third optical disc is used, a diverging beam is incident on the objective lens. The following conditions are satisfied: ?0.02<f1×M1<0.02 * * * (1), ?0.02<f2×M2<0.02 * * * (2), and ?0.29<f3×M3<?0.19 * * * (3).

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.