A variable magnification optical system comprising, in order from an object side, a first lens group having negative refractive power, a first intermediate lens group having positive refractive power, a second intermediate lens group having negative refractive power and a rear lens group; upon varying a magnification from a wide angle end state to a telephoto end state, a distance between the first lens group and the first intermediate lens group being varied, a distance between the first intermediate lens group and the second intermediate lens group being varied, and a distance between the second intermediate lens group and the rear lens group being varied; the rear lens group comprising at least one focusing lens group which is moved upon carrying out focusing from an infinitely distant object to a closely distant object and at least one lens component at an image side of the most image side focusing lens group in the focusing lens groups; and predetermined conditional expressions being satisfied, thereby the focusing lens group(s) being reduced in weight.

A wide-angle lens assembly includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninth lens and a tenth lens arranged in order from an object side to an image side along an optical axis. The first lens has negative refractive power and includes a convex surface facing the object side and a concave surface facing the image side. The second lens has negative refractive power. The third lens has refractive power and includes a convex surface facing the image side. The fourth lens has positive refractive power and includes a convex surface facing the object side. The fifth lens has refractive power. The sixth lens has refractive power and includes a concave surface facing the object side. The seventh lens has positive refractive power. The eighth lens is a biconvex lens with positive refractive power. The ninth lens has negative refractive power. The tenth lens has refractive power and includes a convex surface facing the image side.

An ocular lens includes from an object side: a first lens group having negative refracting power, and a second lens group having positive refracting power. An object-side focal plane of the second lens group is positioned between the first lens group and the second lens group. The first lens group includes, from the object side: a meniscus first A lens component whose convex surface is directed toward the object side, and a first B lens component having negative refracting power. The second lens group includes, in a position closest to the object side, a meniscus second A lens component whose concave surface is directed toward the object side, and satisfies conditional expressions.

A wide-angle lens assembly comprises sequentially from an object side to an image side along an optical axis a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens, a seventh lens, an eighth lens, and a ninth lens. The first lens is a meniscus lens with refractive power. The second lens is a meniscus lens with refractive power. The third lens has refractive power and includes a concave surface facing the object side. The fourth lens has positive refractive power and includes a convex surface facing the image side. The fifth lens has refractive power. The sixth lens is a biconvex lens with positive refractive power. The seventh lens has refractive power. The eighth lens has positive refractive power. The ninth lens has positive refractive power.

A variable magnification optical system comprising a plurality of lens groups and, upon varying a magnification, distances between respective lens groups in the plurality of lens groups being varied. The plurality of lens groups comprises an object side focusing lens group which is moved upon carrying out focusing and at least one image side focusing lens group disposed in a more image side than the object side focusing lens group and moved with a trajectory differing from that of the object side focusing lens group, upon carrying out focusing. The predetermined conditional expressions are satisfied. Thus, variations in aberrations upon varying magnification from the wide angle end state to the telephoto end state as well as variations in aberrations upon carrying out focusing from an infinite distance object to a close distance object can be suppressed superbly.

A variable magnification optical system includes, in order from an object: a first lens group (G1) having a negative refractive power; a second lens group (G2); a third lens group (G3); a fourth lens group (G4) having a negative refractive power; and a fifth lens group (G5) having a positive refractive power, the system performing varying magnification by changing the distance between the first and second lens groups, the distance between the second and third lens groups, the distance between the third and fourth lens groups, and the distance between the fourth and fifth lens groups, and the fourth lens group including a 42nd lens group (G42) configured to be movable so as to have a component in a direction orthogonal to an optical axis and a 41st lens group (G41) disposed at an object-side of the 42nd lens group.

Provided is a zoom lens, which includes lens units, in which an interval between each pair of adjacent lens units is changed during zooming, the zoom lens including, in order from an object side to an image side: a first lens unit having a negative refractive power; a first lens subunit having a positive refractive power; and a second lens subunit having a negative refractive power. During focusing from infinity to minimum object distance, the first lens subunit is moved toward the object side, and the second lens subunit is moved toward the image side. Further, a movement amount of the first lens subunit during focusing from infinity to minimum object distance at a telephoto end, a movement amount of the second lens subunit during focusing from infinity to minimum object distance at the telephoto end, and a focal length at the telephoto end are appropriately set.

To attain the above-described objective, a zoom lens according to the present invention includes sequentially from an object side, a front group which includes at least three lens groups and has positive refractive power as a whole, and a lens group disposed on an image side of the front group, a magnification is changed by a change of a distance on an optical axis between adjacent lens groups, the lens group includes sequentially from an image side, a lens component, a lens component, and a lens component, the lens group is moved to an object side at a time of changing a magnification from a wide-angle end to a telephoto end, focusing is obtained by movement of a part of lens groups in the front group along an optical axis, and a predetermined condition expression is satisfied.

A high magnification MWIR continuous zoom optical system is described herein that consists of the following components: a front detachable extender group, a fixed group for focusing incoming radiation, three moving groups for zooming and generating an intermediate image and a relay group. The mentioned optical system has the ability to work with MWIR radiation (3-5 m) and generate a thermal image from the gathered radiation. The system also has the ability to zoom continuously in a wide variable focal length range with a high magnification ratio of 20. With the use of a cooled detector, the combined system allows its user to be able to receive high quality thermal images in all FOV configurations.

A variable magnification optical system includes: a first lens group (G1) having a negative refractive power; a second lens group (G2) having a positive refractive power; an intermediate group (Gn) disposed closer to an image side than the second lens group (G2); and a vibration-reduction lens group (VR) disposed closer to the image side than the intermediate group (Gn) and configured to be movable so as to have a component in a direction orthogonal to an optical axis. The system performs varying magnification by changing at least the distance between the first lens group (G1) and the second lens group (G2) and the distance between the second lens group (G2) and the intermediate group (Gn), and the system satisfies Conditional Expression (1).

1.000<f(1Gn)t/ft<100.000(1)