Abstract: An imaging optical system includes a positive first lens element having a convex surface on the object side, a negative second lens element having a concave surface on the image side, a third lens element, a positive fourth lens element, a fifth lens element, and a negative sixth lens element provided with at least one aspherical surface that has inflection points other than at an optical axis thereof. The following conditions (1) and (2) are satisfied: 0.86<f/f12<1.20??(1), and ?0.71<(r11?r12)/(r11+r12)<?0.20??(2), wherein f designates the focal length of the imaging optical system, f12 designates the combined focal length of the first and second lens elements, and r11 and r12 designate the radius of curvatures of surfaces on the object side and image side of the first lens element, respectively.

Abstract: A zoom lens system includes a positive first lens group, a negative second lens group, a positive third lens group and a positive fourth lens group, in that order from the object side. Upon zooming from the short to long focal length extremities, each of the first through fourth lens groups move along the optical axis thereof. The following conditions (1) and (2) are satisfied: 1.05<ft/f1<1.75??(1), and 3.7<M3t/M3w<6.3??(2), wherein f1 designates the focal length of the first lens group, ft designates the focal length of the entire zoom lens system at the long focal length extremity, and M3t and M3w designate the lateral magnifications of the third lens group when focusing on an object at infinity at the long and short focal length extremities, respectively.

Abstract: A zoom lens system includes a positive first lens group, a negative second lens group, a positive third lens group and a positive fourth lens group, in that order from the object side. Upon zooming from the short to long focal length extremities, each of the first through fourth lens groups move along the optical axis thereof. The following conditions (1) and (2) are satisfied: 1.05<ft/f1<1.75??(1), and 3.7<M3t/M3w<6.3??(2), wherein f1 designates the focal length of the first lens group, ft designates the focal length of the entire zoom lens system at the long focal length extremity, and M3t and M3w designate the lateral magnifications of the third lens group when focusing on an object at infinity at the long and short focal length extremities, respectively.

Abstract: An imaging optical system includes a positive first lens element having a convex surface on the object side, a negative second lens element having a concave surface on the image side, a third lens element, a positive fourth lens element, and a negative fifth lens element provided with at least one aspherical surface that has inflection points other than at an optical axis thereof. The following conditions (1) and (2) are satisfied: ?0.80<(r11?r12)/(r11+r12)<?0.20??(1), and ?d1>60??(2), wherein r11 and r12 designate the radius of curvatures of surfaces on the object side and image side of the first lens element, respectively, and ?d1 designates the Abbe number with respect to the d-line of the first lens element.

Abstract: An imaging optical system includes a positive first lens element having a convex surface on the object side, a negative second lens element having a concave surface on the image side, a third lens element, a positive fourth lens element, a fifth lens element, and a negative sixth lens element provided with at least one aspherical surface that has inflection points other than at an optical axis thereof. The following conditions (1) and (2) are satisfied: 0.86<f/f12<1.20??(1), and ?0.71<(r11?r12)/(r11+r12)<?0.20??(2), wherein f designates the focal length of the imaging optical system, f12 designates the combined focal length of the first and second lens elements, and r11 and r12 designate the radius of curvatures of surfaces on the object side and image side of the first lens element, respectively.

Abstract: A zoom lens system includes a positive first lens group, a negative second lens group, a positive third lens group, a negative fourth lens group, and a positive fifth lens group. Upon zooming from the short to long focal length extremities, the distance between the first and second lens groups increases, and the distance between the second and third lens groups decreases. The following conditions are satisfied: 0.30<f1/ft<0.43, and 7.0<M2t/M2w<17.0. f1 designates the focal length of the first lens group, ft designates the focal length of the zoom lens system at the long focal length extremity, and M2w and M2t designate the lateral magnifications of the second lens group when focusing on an object at infinity at the short and long focal length extremities, respectively.

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: An objective optical system for information recording/reproducing, at least one of optical surfaces of the objective optical system comprising a diffraction surface including a first region contributing to converging first, second and third beams and including a diffraction structure formed such that use diffraction orders for the first, second and third beams are 1st-orders and a condition 0.03<(?B11??1)/?1<0.40 is satisfied; a second region contributing to converging only the first and second beams and including a diffraction structure formed such that the use diffraction orders are 1st-orders and a condition: ?0.35<(?B12??B11)/?1<0.35 is satisfied; and a third region contributing to converging only the first beam and including a diffraction structure formed such that the use diffraction order for the first beam is an odd order and a condition: ?0.23<m13 ((?B13??1)/?1)<0.23 is satisfied.

Abstract: An objective optical system for information recording/reproducing, at least one of optical surfaces of the objective optical system comprising a diffraction surface including a first region contributing to converging first, second and third beams and including a diffraction structure formed such that use diffraction orders for the first, second and third beams are 1st-orders and a condition 0.03<(?B11??1)/?1<0.40 is satisfied; a second region contributing to converging only the first and second beams and including a diffraction structure formed such that the use diffraction orders are 1st-orders and a condition: ?0.35<(?B12??B11)/?1<0.35 is satisfied; and a third region contributing to converging only the first beam and including a diffraction structure formed such that the use diffraction order for the first beam is an odd order and a condition: ?0.23<m13 ((?B13??1)/?1)<0.23 is satisfied.

Abstract: A zoom lens system includes a positive first lens group, a negative second lens group, a positive third lens group, a negative fourth lens group, and a positive fifth lens group. Upon zooming from the short to long focal length extremities, the distance between the first and second lens groups increases, and the distance between the second and third lens groups decreases. The following conditions are satisfied: 0.30<f1/ft<0.43, and 7.0<M2t/M2w<17.0. f1 designates the focal length of the first lens group, ft designates the focal length of the zoom lens system at the long focal length extremity, and M2w and M2t designate the lateral magnifications of the second lens group when focusing on an object at infinity at the short and long focal length extremities, respectively.

Abstract: An objective optical system for information recording/reproducing, at least one of optical surfaces of the objective optical system comprising a diffraction surface including a first region contributing to converging first, second and third beams and including a diffraction structure formed such that use diffraction orders for the first, second and third beams are 1st-orders and a condition 0.03<(?B11??1)/?1<0.40 is satisfied; a second region contributing to converging only the first and second beams and including a diffraction structure formed such that the use diffraction orders are 1st-orders and a condition: ?0.35<(?B12??B11)/?1<0.35 is satisfied; and a third region contributing to converging only the first beam and including a diffraction structure formed such that the use diffraction order for the first beam is an odd order and a condition: ?0.23<m13×((?B13??1)/?1)<0.23 is satisfied.

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: An objective optical system for an optical information recording/reproducing apparatus for recording/reproducing for first, second and third optical discs by selectively using three types of substantially collimated light beams including first, second and third light beams respectively having first, second and third wavelengths, wherein at least one of optical surfaces of the objective optical system comprises a diffraction surface having a diffraction structure, the diffraction surface includes a first region defined by first and second optical path difference functions, a second region defined by at least one type of optical path difference function, and a third region defined by at least one type of optical path difference function, the first region satisfies a condition: ?0.15<f1/fD11<?0.03??(1), where fD11=?1/(2×P112×m11×?), and the diffraction surface satisfies a condition: ?0.05<(?13(h3)??13(h2))/(m13×f1)<?0.005??(2).

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: 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 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: An objective optical system for information recording/reproducing, at least one of optical surfaces of the objective optical system comprising a diffraction surface including a first region contributing to converging first, second and third beams and including a diffraction structure formed such that use diffraction orders for the first, second and third beams are 1st-orders and a condition 0.03<(?B11??1)/?1<0.40 is satisfied; a second region contributing to converging only the first and second beams and including a diffraction structure formed such that the use diffraction orders are 1st-orders and a condition: ?0.35<(?B12??B11)/?1<0.35 is satisfied; and a third region contributing to converging only the first beam and including a diffraction structure formed such that the use diffraction order for the first beam is an odd order and a condition: ?0.23<m13×((?B13??1)/?1)<0.23 is satisfied.

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 optical system for an optical information recording/reproducing apparatus for recording/reproducing for first, second and third optical discs by selectively using three types of substantially collimated light beams including first, second and third light beams respectively having first, second and third wavelengths, wherein at least one of optical surfaces of the objective optical system comprises a diffraction surface having a diffraction structure, the diffraction surface includes a first region defined by first and second optical path difference functions, a second region defined by at least one type of optical path difference function, and a third region defined by at least one type of optical path difference function, the first region satisfies a condition: ?0.15<f1/fD11<?0.03??(1), where fD11=?1/(2×P112×m11×?), and the diffraction surface satisfies a condition: ?0.05<(?13(h3)??13(h2))/(m13×f1)<?0.005??(2).

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.