An imaging optical system of the present disclosure includes a first lens group having positive power, a second lens group having negative power, a third lens group having the positive power, and a succeeding lens group including one or more lens groups in order from an object side toward an image side. The third lens group includes a lens having the positive power and a lens having the positive power in order from the object side toward the image side, and includes a lens L3R1 having the positive power, a lens L3R2 having the positive power, and a lens L3R3 having the negative power in order from the image side toward the object side. The lens L3R2 and the lens L3R3 are bonded, the lens L3R1 moves to optically correct image blur, and at least a distance between the second lens group and the third lens group changes during zooming from a wide angle end to a telephoto end.

A zoom lens includes, in order from object side: a positive first unit not moving for zooming; a second unit moving during zooming; a positive third unit; a positive fourth unit; and a rear unit including at least one unit, the second unit including one or more lens sub-units and having a negative refractive power as a whole, the fourth unit moving during zooming, the zoom lens including a stop between the second and third units or between the third and fourth units. Lateral magnifications of the second unit at a wide angle end and a telephoto end when beam enters from infinity, focal lengths at the wide angle end and the telephoto end, a focal length of the first unit, and a focal length of the second unit at the wide angle end are appropriately set.

Provided are: a zoom lens including, in order from an object side, a positive first lens group, a negative second lens group, an intermediate group as a whole, a negative lens group, and a rear group, wherein the intermediate group includes, in order from an object side, a first positive lens subgroup including one or two positive lenses, a first negative lens subgroup including only one cemented lens, a second negative lens subgroup including a negative lens with a concave surface facing an object, and a second positive lens subgroup including one or two positive lenses, the cemented lens constituting the first negative lens subgroup has at least one cemented surface with a convex surface facing an object, and a lens, closest to an image, of the second positive lens subgroup is a positive lens; and an imaging apparatus including the zoom lens.

A zoom lens system includes a first lens group; a second lens group; and a subsequent lens group arranged in that order from the object side. The second lens group consists of a second lens group-a, a second lens group-b, and a second lens group-c arranged in that order from the object side. A distance between the first lens group and the second lens group increases and a distance between the second lens group and the subsequent lens group decreases during a change in magnification from a short focal length end to a long focal length end. During a change in focus from infinity to a short distance, the second lens group-b is movable to the image side, and a distance between the second lens group-a and the second lens group-b and a distance between the second lens group-b and the second lens group-c are changeable.

In a zoom lens system, a distance between a first lens group and a second lens group is increased, a distance between the second lens group and a third lens group is reduced, and a distance between the third lens group and a fourth lens group is reduced. The third lens group includes, in order from an object side, a front lens group and a rear lens group separated from each other by a widest air gap on an optical axis in the third lens group. Camera-shake correction is performed by moving whole or part of the front lens group as a camera-shake correction lens group perpendicularly to the optical axis. Conditional formula below is satisfied: 3.0<fis/f3<0.9, where f3 represents a focal length of the third lens group and fis represents a focal length of the camera-shake correction lens group.

A zoom lens including, in order from object side, a positive first lens unit not moving for zooming, a negative second lens unit moving during zooming, at least one other lens unit moving during zooming as at least a third lens unit, and a rearmost lens unit closest to an image side not moving for zooming, and also including an aperture stop at the image side of the second lens unit, average values of Abbe numbers and relative partial dispersions of each of positive lenses and negative lenses forming the second lens unit, anomalous dispersion of a lens having a smallest Abbe number of negative lenses forming the rearmost lens unit, an axial distance between surface vertex positions of lenses closest to the object and image sides of the zoom lens, and a distance between the aperture stop and the negative lens at a wide angle end are appropriately set.

A camera module includes: an optical imaging system including a frontmost lens disposed closest to an object side, a rearmost lens disposed closest to an imaging plane, and at least one middle lens disposed between the frontmost lens and the rearmost lens. An image-side surface of the rearmost lens is concave and an inflection point is formed on the image-side surface of the rearmost lens. 0.2<D/TTL is satisfied, D being a shortest distance between the rearmost lens and the imaging plane, and TTL being a distance from an object-side surface of the frontmost lens to the imaging plane.

A zoom lens has, in order from an object side to an image side, a positive first lens unit, a negative second lens unit, a positive third lens unit, a positive fourth lens unit, and a fifth lens unit. In the zoom lens, the loci of the lens units moving for zooming are set appropriately, and a reflector for bending an optical path is placed at an appropriate position within the fifth lens unit.

An optical system is provided. The optical system includes a first lens group that has a positive refractive power, a second lens group that has a negative refractive power, a third lens group that has a negative refractive power, a fourth lens group that has a positive refractive power, and a fifth lens group that includes one or more lens groups, in sequence from an object, wherein the first lens group and the fifth lens group are fixed and the third lens group moves parallel to an optical axis to perform focusing when adjusting a magnification of the optical system.

A zoom lens includes, in order from object side: a positive first unit not moving for zooming; a second unit moving during zooming; a positive third unit; a positive fourth unit; and a rear unit including at least one unit, the second unit including one or more lens sub-units and having a negative refractive power as a whole, the fourth unit moving during zooming, the zoom lens including a stop between the second and third units or between the third and fourth units. Lateral magnifications of the second unit at a wide angle end and a telephoto end when beam enters from infinity, focal lengths at the wide angle end and the telephoto end, a focal length of the first unit, and a focal length of the second unit at the wide angle end are appropriately set.