An optical system (LS) Includes lenses (L22,L23) satisfying the following conditional expressions,
νdLZ<35.0, and
0.702<θgFLZ+(0.00316×νdLZ),
where νdLZ: Abbe number of the lens with reference to d-line, and θgFLZ: a partial dispersion ratio of the lens, wherein θgFLZ is defined by the following expression,
θgFLZ−(ngLZ−nFLZ)/(nFLZ−nCLZ). wherein a refractive index of the lens with reference to g-line is ngLZ, a refractive index of the lens with reference to F-line is nFLZ, and a refractive index of the lens with reference to C-line is nCLZ.

A zoom optical system includes, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power. The first lens group moves toward an object and air distances between the first to the third lens groups are varied upon zooming from a wide-angle end state to a tele-photo end state. The first lens group comprises a cemented lens consisting of a negative lens and a positive lens in order from the object. The following conditional expressions are satisfied:

4.40<f1/(−f2)<8.00

0.60<f3/fw<3.50

0.60<(−f2)/f3<1.05

30.00°<ωw<80.00°

where f1 denotes a focal length of the first lens group, f2 denotes a focal length of the second lens group, f3 denotes a focal length of the third lens group, fw denotes a focal length of the zoom optical system in the wide-angle end state, and ωw denotes a half angle of view in the wide-angle end state

There is provided a zoom lens including first and second lens groups independently movable in an optical axis direction in an optical system. Before and after switching between two modes different in minimum focusing distance, a lens group to rule focusing changes between the first and second lens groups or a relative position between the first and second lens groups changes.

A zoom lens includes, in order from an object side, a first lens group of which at least a part moves for focusing, a plurality of lens groups which move in zooming, an aperture stop, and a final lens group which does not move for zooming. The final lens group includes a separation element PR for separating an incident light thereon into a transmitted light and a reflected light, a relay unit LR having a positive refractive power on which the transmitted light is incident, and a relay unit LA having a positive refractive power on which the reflected light is incident. An inequality about Fwp/Fw is satisfied, where Fw is a focal length at a wide angle end of the zoom lens via the relay unit LR and FwP is a focal length at the wide angle end of the zoom lens via the relay unit LA.

A zoom lens includes, in order from an object side to an image side, a first lens unit having positive refractive power, a second lens unit having negative refractive power, a third lens unit having positive refractive power, and a fourth lens unit having positive refractive power. During zooming from a wide-angle end to a telephoto end, the first lens unit does not move and at least the second lens unit and the fourth lens unit move. A distance between adjacent lens units varies during zooming. In the zoom lens, a lens configuration of the first lens unit, a lens configuration of the second lens unit, a focal length of each lens unit, a focal length of the zoom lens at a wide-angle end, and a lateral magnification of the second lens unit during focusing on an infinite-distance object at the telephoto end are appropriately set based on predetermined conditions.

A zoom lens system including, in order from an object side to an image side, a first lens unit having a positive refractive power that does not move for zooming, a second lens unit having a negative refractive power that moves during zooming, and a third lens unit having a positive refractive power that moves during zooming. In the zoom lens system, a distance between lens units that are adjacent to each other changes during zooming, the first lens unit includes a first a-lens unit that does not move for focusing, and a first b-lens unit that moves from the image side towards the object side during focusing from an infinite object to a near object, and the first a-lens unit comprises two positive lenses and two negative lenses.

Comprising a first lens group G1 having positive refractive power, disposed at the most object side, and an image side lens group disposed at a side closer to an image than the first lens group G1, upon zooming, at least a distance between the first lens group G1 and the image side lens group being varied, the image side lens group comprising a vibration reduction lens group GVR which is moved so as to have a component in a direction perpendicular to the optical axis and a focusing lens group GF which is moved along the optical axis upon focusing, thereby providing a variable magnification optical system which has a higher optical performance, an optical apparatus and a method for manufacturing a variable magnification optical system.

A zoom lens has, in order from an object: a first lens group having positive refractive power; a second lens group having negative refractive power; a third lens group having positive refractive power; and a fourth lens group having positive refractive power. Zooming is performed by changing an air gap between the lens groups. The fourth lens group includes, in order from the object, a first positive lens component, a second positive lens component having a convex surface facing the object, and a negative lens component. A specified conditional expression is satisfied.

A zoom lens system with a large zoom ratio is disclosed, which operates in a broad spectral range, including visible and infrared spectra. The zoom lens system comprises, in order from the object side to the image side, a positive first lens group, a negative second lens group, a positive third lens group, a positive fourth lens group, and a detection system, wherein zooming from a wide-angle end to a telephoto end is performed by axially moving the second and third lens groups. The system has a relatively long back focal length, and satisfies the following conditions: 0.2<|f2|/(f.sub.W*f.sub.T)½<2, 1<f4/|f2|<8, 0.3<|f2|/f3<1.5, where f.sub.W is the system focal length at the wide-angle end, f.sub.T is the system focal length at the telephoto end, (f.sub.W*f.sub.T).sup.1/2 is the geometric mean of the two focal lengths, and fi is the focal length of the i-th lens group.

A variable magnification optical system includes: in order from an object side, a first lens unit having a positive refractive power; a second lens unit having a negative refractive power; a third lens unit having a positive refractive power; and an image-side lens unit. The image-side lens unit includes a lens belonging to a first region and a lens belonging to a second region. At a time of changing magnification, the second lens unit and the third lens unit move.