Abstract: An optical system has a positive lens group, a negative lens group, and an aperture stop. The negative lens group is disposed at an object side of the aperture stop and has a cemented lens, and in a rectangular coordinate system in which a horizontal axis is Nd and a vertical axis is ?d, when a straight line indicated by Nd=?×?d+? where ?=?0.017 is set, Nd and ?d of at least one lens forming the cemented lens are included in both an area determined by a line when a lower limit value is in a range of expression (1a) and a line when an upper limit value is in a range of the expression (1a), and an area determined by expressions (2a) and (3a): 1.45<?<2.15 (1a); 1.30<Nd<2.20 (2a); and 3<?d<12 (3a); where Nd denotes a refractive index, and ?d denotes an Abbe's number.

Abstract: The invention relates to a zoom lens and an imaging apparatus incorporating the same. More particularly, the invention is concerned with a zoom lens that is downsized for use with imaging apparatus inclusive of video cameras and digital cameras. The zoom lens comprises a positive first group G1, a negative lens group G2, a positive third group G3, a positive fourth group G4 and an aperture stop S. At least the first group G1 and the second group G2 move for zooming from the wide-angle end to the telephoto end. The first group G1, the third group G3 and the aperture stop S are positioned more on the object side in a state of the telephoto end than in a state of the wide-angle end. The spacing sandwiched between the first group G1 and the second group G2 grows wide, the spacing sandwiched between the second group G2 and the third group G3 becomes narrows, and the spacing sandwiched between the third group G3 and the fourth lens group G4 grows wide.

Abstract: In an image forming optical system having a positive lens group, a negative lens group, and an aperture stop, the negative lens group is disposed at an image side of the of the aperture stop, the negative lens group has a cemented lens which is formed by cementing a plurality of lenses, and in a rectangular coordinate system in which, a horizontal axis is let to be Nd and a vertical axis is let to be ?d, when a straight line indicated by Nd=?×?d+? (where, ?=?0.017) is set, Nd and ?d of at least one lens forming the cemented lens are included in both of areas namely, an area which is determined by a line when a lower limit value is in a range of a following conditional expression (1), and a line when an upper limit value is in a range of the following conditional expression (1), and an area determined by following conditional expressions (2) and (3). 1.45<?<2.15??(1) 1.30<Nd<2.20??(2) 3<?d<12??(3) Here, Nd denotes a refractive index, and ?d denotes an Abbe's number.

Abstract: The first lens group comprises a positive lens and a negative lens, and the total number of lenses in the first lens group is 2. The second lens group consists of, in order from the object side, a front unit of negative refracting power and a rear unit of positive refracting power. The third lens group consists of, in order from the object side, a front unit of positive refracting power and a rear unit of negative refracting power. The fourth lens group comprises a positive lens component, and the total number of lens components in the fourth lens group is 1. The front unit of the second lens group comprises a negative lens component, and the total number of lens components in the front unit of the second lens group is 1. The rear unit of the second lens group comprises, in order from the object side to the image side, a negative lens and a positive lens, and the total number of lenses in the rear unit of the second lens group is 2.

Abstract: A zoom lens has a negative object side lens unit (or first lens unit G1), a positive image side lens unit (or third lens unit G3), a positive intermediate lens unit (or second lens unit G2), and an aperture stop. The distance between the object side lens unit and the intermediate lens unit is smaller at the telephoto end than at the wide angle end, the distance between the intermediate lens unit and the image side lens unit is larger at the telephoto end than at the wide angle end, the intermediate lens unit moves in such a way that it is located closer to the object side at the telephoto end than at the wide angle end, the image side lens unit moves in such a way that it is located closer to the image side at the telephoto end than at the wide angle end, the aperture stop moves integrally with the intermediate lens unit. The image side lens unit is composed of two lens component including a front lens component and a positive rear lens component arranged in the mentioned order from the object side.

Abstract: A zoom lens includes, in order from the object side, a negative lens unit, a positive lens unit and a positive lens unit. During zooming from the object side, the second lens unit moves, the distance between the first lens unit and the second lens unit decreases, the distance between the second lens unit and the third lens unit increases. The second lens unit has two lens components including, in order from the object side, a positive front lens component and a rear lens component. The third lens unit is composes of two lens components including, in order from the object side, a front lens component and a positive rear lens component. An aperture stop is disposed closer to the image side than the first lens unit and closer to the object side than the rear lens component in the second lens unit, and the aperture stop moves integrally with the second lens unit along the optical axis direction during zooming from the wide angle end to the telephoto end.

Abstract: An image forming optical system according to the present invention is characterized in that, in an image forming optical system having a positive lens group, a negative lens group, and an aperture stop, the negative lens group is disposed at an object side of the aperture stop, the negative lens group has a cemented lens which is formed by cementing a plurality of lenses, and in a rectangular coordinate system in which, a horizontal axis is let to be Nd and a vertical axis is let to be ?d, when a straight line indicated by Nd=?×?d+? (where, ?=?0.017) is set, Nd and ?d of at least one lens forming the cemented lens are included in both of areas namely, an area which is determined by a line when a lower limit value is in a range of a following conditional expression (1a), and a line when an upper limit value is in a range of the following conditional expression (1a), and an area determined by following conditional expressions (2a) and (3a). 1.45<?<2.15??(1a) 1.30<Nd<2.

Abstract: In an image forming optical system having a positive lens group, a negative lens group, and an aperture stop, the negative lens group is disposed at an image side of the of the aperture stop, the negative lens group has a cemented lens which is formed by cementing a plurality of lenses, and in a rectangular coordinate system in which, a horizontal axis is let to be Nd and a vertical axis is let to be ?d, when a straight line indicated by Nd=?×?d+? (where, ?=?0.017) is set, Nd and ?d of at least one lens forming the cemented lens are included in both of areas namely, an area which is determined by a line when a lower limit value is in a range of a following conditional expression (1), and a line when an upper limit value is in a range of the following conditional expression (1), and an area determined by following conditional expressions (2) and (3). 1.45<??2.15??(1) 1.30<Nd<2.20??(2) 3<?d<12??(3) Here, Nd denotes a refractive index, and ?d denotes an Abbe's number.

Abstract: An image forming optical system according to the present invention is characterized in that, in an image forming optical system having a positive lens group, a negative lens group, and an aperture stop, the positive lens group is disposed at an image-plane side of the aperture stop, the positive lens group has a cemented lens which is formed by cementing a plurality of lenses, in a rectangular coordinate system in which, a horizontal axis is let to be Nd and a vertical axis is let to be ?d, when a straight line indicated by Nd=?×?d+? (where, ?=?0.017) is set, Nd and ?d of at least one lens forming the cemented lens are included in both of areas namely, an area which is determined by a line when a lower limit value is in a range of a following conditional expression (1), and a line when an upper limit value is in a range of the following conditional expression (1), and in an area determined by following conditional expressions (2) and (3) 1.45<??2.15??(1) 1.30<Nd<2.

Abstract: An image forming optical system according to the present invention is characterized in that, in an image forming optical system having a positive lens group, a negative lens group, and an aperture stop, the positive lens group is disposed at an object side of the aperture stop, the positive lens group has a cemented lens which is formed by cementing a plurality of lenses, in a rectangular coordinate system in which a horizontal axis is let to be Nd and a vertical axis is let to be ?d, when a straight line indicated by Nd=?×?d+? (where, ?=?0.017) is set, Nd and ?d of at least one lens forming the cemented lens is included in both of areas namely, an area which is determined by a line when a lower limit value is in a range of a following conditional expression (1a), and a line when an upper limit value is in a range of the following conditional expression (1a), and of an area determined by following conditional expressions (2a) and (3a). 1.45<?<2.15??(1a) 1.30<Nd<2.

Abstract: A zoom lens includes, in order from the object side, a first lens unit with negative power, a second lens unit with positive power, a third lens unit with positive power, and a fourth lens unit. When the magnification of the zoom lens is changed in the range from a wide-angle position to a telephoto position, spacing between the first lens unit and the second lens unit is narrowed and spacing between the second lens unit and the third lens unit is widened. An aperture stop moved integrally with the second lens unit is interposed between the most image-side lens element of the first lens unit and the most image-side lens element of the second lens unit. The first lens unit has, in order from the object side, a negative lens element and a positive lens element and satisfies the following conditions: 0.15<?IMF/?IMR<1.0 ?3.0<?IPF/?IPR<?1.

Abstract: A zoom optical system has, in order from the object side, a first lens unit with negative refracting power, including one biconcave-shaped lens component, a second lens unit with positive refracting power, a third lens unit with negative refracting power, and a fourth lens unit with positive refracting power. When the magnification of the zoom optical system is changed, relative distances between individual lens units are varied and the zoom optical system satisfies the following condition: 0.2?dCD/fw?1.2 where dCD is spacing between the third lens unit and the fourth lens unit on the optical axis in infinite focusing at a wide-angle position and fw is the focal length of the entire system of the zoom optical system at the wide-angle position.

Abstract: A zoom optical system comprises a lens group 1 having one negative lens component and a lens group 2 wherein a distance on the optical axis between the lens group 1 and the lens group 2 is changed for magnification purpose. The negative lens component consists of a cemented lens of positive lens and a negative lens, and when a straight line expressed by ?gFp=?p×?dp+?p (?p=?0.00163) is set up in a rectangular coordinate system in which a horizontal axis is expressed by ?dp and an vertical axis is expressed by ?gFp, ?dp and ?gFp of the positive lens are included in domains specified by the following conditions. 0.6400<?p<0.9000 3<?dp<27 here, ? gFp is a ratio of a partial dispersion (ng?nF)/(nF?nC) of the positive lens LAP; ?dp is Abbe number (nd?1)/(nF?nC) of the positive lens LAP; nd, nC, nF, and ng are refractive indices of d,C,F and g line, respectively.

Abstract: A compound lens on which a plastic lens is formed on a glass lens, having: an annular step part which is formed on the end part of the optical functional surface, on which the plastic lens is formed, on the outer circumference side on the outside of the outermost diameter of the optical functional surface and which is formed for directly mounting on a resin-made lens tube frame; and a caulk-fix part, being formed, in a form of a chamfer, in the outer form part of the glass lens on the optical functional surface on the opposite side of the optical functional surface on which the plastic lens is formed, wherein an influence of a heat on the plastic lens is eliminated when fixing the glass lens onto the resin-made lens tube frame by means of thermal caulking.

Abstract: The invention relates to a zoom lens and an imaging apparatus incorporating the same. More particularly, the invention is concerned with a zoom lens that is downsized for use with imaging apparatus inclusive of video cameras and digital cameras. The zoom lens comprises a positive first group G1, a negative lens group G2, a positive third group G3, a positive fourth group G4 and an aperture stop S. At least the first group G1 and the second group G2 move for zooming from the wide-angle end to the telephoto end. The first group G1, the third group G3 and the aperture stop S are positioned more on the object side in a state of the telephoto end than in a state of the wide-angle end. The spacing sandwiched between the first group G1 and the second group G2 grows wide, the spacing sandwiched between the second group G2 and the third group G3 becomes narrows, and the spacing sandwiched between the third group G3 and the fourth lens group G4 grows wide.

Abstract: A zoom optical system comprises in order from an object side, the first lens group consisting of one cemented lens in which each of the surfaces contacted with air is aspherical, and having negative refracting power as a whole, the second lens group consisting of one positive single lens and one cemented lens, and having positive refracting power as a whole, the third lens group of one negative lens having an aspherical surface, and the fourth lens group consisting of one positive lens having an aspherical surface. When magnification is carried out, each of the lens groups is moved while changing each relative distance among the lens groups.

Abstract: A zoom optical system has, in order from the object side, a first lens unit with negative refracting power, including a single lens component; a second lens unit with positive refracting power, simply moved toward the object side when the magnification of the zoom optical system is changed in the range from a wide-angle position to a telephoto position; a third lens unit with negative refracting power; and a fourth lens unit with positive refracting power. In focusing on an object point separated at least 300 times a focal length at the wide-angle position, when the magnification is changed in the range from the wide-angle position to the telephoto position, the third lens unit and the fourth lens unit are moved together so that a relative spacing between the third lens unit and the fourth lens unit is widened or the fourth lens unit approaches an imaging point.

Abstract: A zoom optical system comprises a lens group 1 having one negative lens component and a lens group 2 wherein a distance on the optical axis between the lens group 1 and the lens group 2 is changed for magnification purpose. The negative lens component consists of a cemented lens of positive lens and a negative lens, and when a straight line expressed by ?gFp=?p×?dp+?p (?p=?0.00163) is set up in a rectangular coordinate system in which a horizontal axis is expressed by ?dp and an vertical axis is expressed by ?gFp, ?dp and ?gFp of the positive lens are included in domains specified by the following conditions. 0.6400<?p<0.9000 3<?dp<27 here, ? gFp is a ratio of a partial dispersion (ng?nF)/(nF?nC) of the positive lens LAP; ?dp is Abbe number (nd?1)/(nF?nC) of the positive lens LAP; nd, nC, nF, and ng are refractive indices of d,C,F and g line, respectively.

Abstract: A zoom optical system comprises in order from an object side, the first lens group consisting of one cemented lens in which each of the surfaces contacted with air is aspherical, and having negative refracting power as a whole, the second lens group consisting of one positive single lens and one cemented lens, and having positive refracting power as a whole, the third lens group of one negative lens having an aspherical surface, and the fourth lens group consisting of one positive lens having an aspherical surface. When magnification is carried out, each of the lens groups is moved while changing each relative distance among the lens groups.

Abstract: A zoom optical system has, in order from the object side, a first lens unit with negative refracting power, including one biconcave-shaped lens component, a second lens unit with positive refracting power, a third lens unit with negative refracting power, and a fourth lens unit with positive refracting power. When the magnification of the zoom optical system is changed, relative distances between individual lens units are varied and the zoom optical system satisfies the following condition: 0.2?dCD/fw?1.2 where dCD is spacing between the third lens unit and the fourth lens unit on the optical axis in infinite focusing at a wide-angle position and fw is the focal length of the entire system of the zoom optical system at the wide-angle position.