A lens system includes a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a positive refractive power, and a fourth lens group having a negative refractive power. The first, second, third, and fourth lens groups are arranged in order from an object side of the lens system. During a change from focusing on a first object to focusing on a second object closer to the lens system than the first object, at least the second lens group and the third lens group move along an optical axis toward the object side. The lens system satisfies 0.7<|f4/f|<2.0, where f represents a focal length of the lens system, and f4 represents a focal length of the fourth lens group.

A zoom optical system consists of a first lens group having negative refractive power, a second lens group having positive refractive power, and a rear lens group which are disposed in order from an object. The rear lens group comprises a last lens group and an F lens group in order from a side closest to an image. Lens groups forming the first lens group, the second lens group, and the rear lens group are configured in such a manner that, upon zooming, the respective lens groups move and a distance between the lens groups adjacent to each other changes. At least a part of the F lens group is configured to move upon focusing. Further, the following conditional expression is satisfied.

−0.220<f1/fE<0.280

where f1: a focal length of the first lens group, and fE: a focal length of the last lens group

A projection lens structure mainly includes a first group of lenses with a negative dioptric value, a second group of lenses with a positive dioptric value, a third group of lenses with a positive dioptric value and a fourth group of lenses with a negative dioptric value. The first group of lenses further includes at least a first lens and a second lens, of which the first lens ha a plastic aspheric lens in a meniscus shape with a focal length between 2580 mm. The second group of lenses further includes at least a third lens. The third group of lenses further includes at least a first doublet with a focal length between 2580 mm. The fourth group of length further includes at least a group of doublets, a fourth lens and a fifth lens.

A zoom lens consists of, in order from an object side, a focusing group, a zoom group, and a subsequent group. The focusing group consists of, in order from the object side, a front focusing group which does not move with respect to the image plane during zooming and focusing, a middle focusing group which consists of one or two positive lens groups each moving during focusing, and a rear focusing group which consists of a negative lens group moving during zooming and focusing. The rear focusing group has a zoom range in which the amount of movement during focusing changes in accordance with the zoom position and the rear focusing group moves to the image side during focusing from the object at infinity to the closest object. Predetermined conditional expressions relating to the amount of movement of the rear focusing group are satisfied.

The present disclosure relates to a technical field of optical lenses, and discloses a zoom lens. The zoom lens, being sequentially from an object side to an image side, includes a first lens having a negative refractive power, a second lens group having a positive refractive power, a fifth lens having a positive refractive power, and a sixth lens having a negative refractive power, when zooming, among the first lens, the second lens group, the fifth lens, and the sixth lens, a spacing in an optical axis direction of adjacent lenses or lens groups changes, the second lens group includes a second lens having a positive refractive power, a third lens having a negative refractive power, and a fourth lens having a negative positive power. During photographing, when an F number (FNO) of a wide-angle end is less than or equal to 2.0, the zoom lens becomes bright.

A zoom lens includes, in order from an object side to an image side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and three or more lens units. A distance between adjacent lens units varies during zooming. A predetermined condition is satisfied.

Aspects of the embodiments include an optical device comprising a housing; and an afocal lens assembly comprising a zoom lens in the housing, the zoom lens supported in the housing to move along a long axis of the housing. The afocal lens assembly can also include an objective lens configured to move synchronously with the zoom lens based on rotation of a zoom+focus adjustment knob coupled to a lens driving mechanism.

The present invention relates to the field of optical lenses and provides a zoom lens consisting of, from an object side to an image side in sequence, a first lens having negative refractive power, a second lens group having positive refractive power, a fifth lens having positive refractive power, and a sixth lens having negative refractive power. During zooming, a distance between adjacent lenses or between lens and adjacent lens group in a direction of an optic axis varies. The second lens group consists of a second lens having positive refractive power, a third lens having negative refractive power, and a fourth lens having negative refractive power, and following conditions are satisfied: f_Tele/f_Wide?1.80; ?1.75?f3/f2??1.35; ?1.75?f4/f2??1.35. The present invention becomes compact when contracted, while during imaging, FNO is bright, and has good optical properties.

A magnification-variable optical system having a small size, a wide angle of view, and high optical performance, an optical apparatus including the magnification-variable optical system, and a method for manufacturing the magnification-variable optical system are provided. A magnification-variable optical system ZL used for an optical apparatus such as a camera 1 includes a first lens group G1 having a negative refractive power and including at least two lenses, and a rear group GR including at least one lens group disposed on an image side of the first lens group G1, and is configured so that a distance between lens groups adjacent to each other changes at magnification change and a condition expressed by predetermined condition expressions is satisfied.

A zoom lens includes, in order from the object side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a third lens unit having a positive refractive power. The first lens unit includes a negative lens and a positive lens. The zoom lens satisfies the following conditional expression (1):
d.sub.13/f.sub.t<0.4(1)
where d.sub.13 is the total sum of the thickness of the lenses included in the first to third lens units of the zoom lens on the optical axis, and f.sub.t is the focal length of the entire zoom lens system at the telephoto end.