The zoom lens includes a positive first lens group, a negative second lens group, a positive third lens group, a negative fourth lens group, a negative fifth lens group, and a positive sixth lens group in order from an object side. All distances between adjacent lens groups change during zooming. The first lens group consists of a negative lens, a positive lens, and a positive lens in order from the object side. Only the fourth lens group moves to an image side during focusing from a long range to a short range. Conditional Expression is related to lateral magnification of the fourth lens group and a lateral magnification of the sixth lens group is satisfied.

The disclosed optical apparatus includes a first movable member movable in an optical axis direction a holding member holding an optical element and movable with respect to the first movable member in the optical axis direction, a guide member held by the first movable member and guides the holding member in the optical axis direction, a second movable member movable in the optical axis direction independently of the first movable member, and a drive unit configured to drive the holding member in the optical axis direction. The drive unit is held such that displacement of the drive unit with respect to the second movable member in the optical axis direction is restricted by the second movable member.

The zoom lens includes a positive first lens group, a negative second lens group, a positive third lens group, a negative fourth lens group, a negative fifth lens group, and a positive sixth lens group in order from an object side. All distances between adjacent lens groups change during zooming. The first lens group consists of a negative lens, a positive lens, and a positive lens in order from the object side. Only the fourth lens group moves to an image side during focusing from a long range to a short range. Conditional Expression is related to lateral magnification of the fourth lens group and a lateral magnification of the sixth lens group is satisfied.

The zoom lens includes a positive first lens group, a negative second lens group, a positive third lens group, a negative fourth lens group, a negative fifth lens group, and a positive sixth lens group in order from an object side. All distances between adjacent lens groups change during zooming. The first lens group consists of a negative lens, a positive lens, and a positive lens in order from the object side. Only the fourth lens group moves to an image side during focusing from a long range to a short range. Conditional Expression related to a distance from a lens surface of the first lens group closest to the object side to an image plane and a distance from a lens surface of the second lens group closest to the object side to the image plane is satisfied.

The zoom lens according to the present invention consists of, in order from an object side to an image side, a positive first lens unit, a negative second lens unit, and a positive rear unit including at least four lens units. The second lens unit moves toward the object side during zooming from a wide angle end to a telephoto end, and an interval between each pair of adjacent lens units is changed during zooming. The rear unit includes a positive lens unit LP, which is arranged closest to the image side. Focal lengths of the zoom lens at the wide angle end and at the telephoto end, focal lengths of the first lens unit and the second lens unit, and a distance from the lens surface of the lens unit LP on the image side to an image plane at the telephoto end are each set appropriately.

A variable magnification optical system comprising, in order from an object side, a first lens group and a plurality of lens groups; upon varying a magnification, a distance between the first lens group and the plurality of lens groups being varied, and distances between respective lens groups in the plurality of lens groups being varied; the plurality of lens groups comprising 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 the focusing; and the predetermined conditional expressions being satisfied, whereby 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 zoom lens satisfies Conditional Expression (1) as follows:

20<Twt/Twm<1,(1)

Twt is a moving amount of the second lens group during zooming from the short focal-length end to the long focal-length end, a moving amount to the object side being indicated by a positive sign, a moving amount to an image side being indicated by a negative sign, and
Twm is a moving amount of the second lens group during zooming from the short focal-length end to an intermediate focal length, a moving amount to the image side being indicated by a negative sign,
the intermediate focal length being expressed by fm=(fw.Math.ft).sup.1/2, where fw is a focal length of a whole system at the short focal-length end, and ft is a focal length of the whole system at the long focal-length end.

A lens barrel according to the present disclosure includes a booster transformer that is arranged on an inner circumference side of a cam barrel and constitutes a power supply for an actuator. The booster transformer is arranged on a side surface of a barrel. The booster transformer is configured to move in an optical axis direction together with the barrel in accordance with rotation of the cam barrel.

Provided is a zoom lens including, from an object side to an image 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; a fourth lens unit having a negative refractive power; a fifth lens unit having a positive refractive power; a sixth lens unit having a negative refractive power; a seventh lens unit having a positive refractive power; and an eighth lens unit having a negative refractive power, in which an interval between each pair of adjacent lens units is changed for zooming.

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.