A rear attachment lens according to the aspect of the embodiments is configured to vary a focal length of a system by being attached to an image side of a master lens. The rear attachment lens includes a positive lens arranged closest to the image side in which a lens surface on the image side of the positive lens has a shape convex toward the image side. A focal length of the rear attachment lens, a magnification of the rear attachment lens when attached to the master lens, and a distance from the lens surface on the image side of the positive lens to a rear principal point position of the rear attachment lens when attached to the master lens are appropriately set.

The anamorphic objective lens systems (100LS) and methods for forming a set of anamorphic objective lens assemblies (100(i)) having different focal lengths (FLY) and that utilize a front anamorphic section (20) and a set of two or more non-anamorphic sections (50(i)). The non-anamorphic sections are optically matched to the front anamorphic section and their front ends (52) are configured to be easily attached to and detached from the back end (24) of the front anamorphic section to create the anamorphic objective lens assemblies having the different focal lengths. Because the anamorphic objective lens system uses only a single front anamorphic section and multiple non-anamorphic attachments, the cost of having multiple anamorphic objective lens assemblies is substantially reduced as compared to using individual anamorphic objective lenses for each of the desired focal lengths.

A zoom lens includes, in order from an object side to an image side: a focus lens unit configured to be moved for focusing on an optical axis; a zoom lens unit configured to be moved for zooming on the optical axis; and a relay lens unit, in which an interval between each pair of adjacent lens units is changed for zooming, and the zoom lens includes an aperture stop arranged between the zoom lens unit and the relay lens unit or within the relay lens unit, the relay lens unit includes an extender lens unit insertable into and removable from an optical path of the relay lens unit, in which the extender lens unit includes a negative lens Lm which is an m-th lens from the object side in the extender lens unit and having a refractive index and an Abbe number that satisfy predetermined conditions.

A reduction optical system disposed on an image side of a main optical system, a composite focal length of the main optical system and the reduction optical system being shorter than a focal length of the main optical system, includes a first lens element disposed closest to an object side and having a positive refractive power, a second lens element disposed closest to an image side and having a positive refractive power, and a positive lens and a negative lens disposed between the first lens element and the second lens element.

A system for adjusting an optical path length includes: a camera body; an image sensor coupled to the camera body; a first optical device coupled to the camera body; and a second optical device coupled to the camera body. At least one of the first and the second optical devices are movable relative to the camera body. The optical path length between the image sensor and the camera body opening is continuously adjusted by movement of the at least one of the first and the second optical devices relative to the image sensor. As the at least one of the first and the second optical devices move relative to the image sensor, the first optical device is in continuous contact with the second optical device.

A system for adjusting an optical path length includes: a camera body; an image sensor coupled to the camera body; a first optical device coupled to the camera body; and a second optical device coupled to the camera body. At least one of the first and the second optical devices are movable relative to the camera body. The optical path length between the image sensor and the camera body opening is continuously adjusted by movement of the at least one of the first and the second optical devices relative to the image sensor. As the at least one of the first and the second optical devices move relative to the image sensor, the first optical device is in continuous contact with the second optical device.

An attachment optical system includes a first converter optical system attachable to an object side of an imaging optical system, and a second converter optical system attachable to an image side of the imaging optical system. The first converter optical system includes a dome-shaped cover and at least one positive lens. A predetermined condition is satisfied.

An attachment optical system includes a first converter optical system attachable to an object side of an imaging optical system, and a second converter optical system attachable to an image side of the imaging optical system. The first converter optical system includes a dome-shaped cover and at least one positive lens. A predetermined condition is satisfied.

An extender lens changes a focal length of an entire lens system after replacement to a longer focal length side than a focal length of a master lens by replacing a part of the master lens with the extender lens. The extender lens consists of, in order from an object side to an image side, a first lens group, and a negative second lens group. The first lens group is a lens group that has a positive refractive power as a whole and has a shortest focal length among lens groups consisting of one lens component or a plurality of consecutively arranged lens components. The extender lens satisfies a predetermined conditional expression.

A zoom lens includes, in order from an object side to an image side, a first lens unit configured not to move for zooming, a plurality of zooming lens units configured to move in zooming, a front relay lens unit configured not to move for zooming, an extender lens unit insertable into and removable from an optical path for changing a focal length range of the zoom lens, and a rear relay lens unit configured not to move for zooming, and satisfies specific conditional expressions.