A zoom lens includes a front unit having a negative refractive power; and a rear unit having a positive refractive power, which includes an aperture stop. The front unit includes a first negative refractive power lens, a second negative refractive power lens, and a third positive refractive power lens. The first lens is nearest to an object, and has a meniscus shape with a convex surface directed toward the object side, and the second lens is on an image side of the first lens, and has a meniscus shape with a convex surface directed toward the object side. The rear unit includes a first lens unit A and a second lens unit B, wherein when zooming from a wide angle end to a telephoto end, a distance between the front unit and the rear unit narrows, and a distance between the first lens unit A and the second lens unit B changes. The first lens unit A includes a first sub-lens unit having a positive refractive power, the aperture stop, and a second sub-lens unit. The second sub-lens unit includes a focusing lens unit, and when focusing, only the focusing lens unit moves along an optical axis, and when zooming, a distance between the first sub-lens unit and the second sub-lens unit changes.

According to an embodiment, a projection optical system for an image projection device, that includes a plurality of lenses. The projection optical system satisfies conditional expression (1): where fw is a focal length of a lens having the weakest refractive power in the lenses and f is a focal length of the whole projection optical system.

[00001]$\begin{array}{cc}0.01.Math.\frac{f}{f_w}.Math.<0.34& \left(1\right)\end{array}$

Provided is an optical system and an imaging apparatus provided with the optical system. The optical system includes: a first lens having negative refractive power; a second lens having negative refractive power; a third lens having positive refractive power; and a fourth lens having positive refractive power, the first lens, the second lens, the third lens, and the fourth lens being disposed in this order from an object side. The optical system satisfies a predetermined condition relating to the focal length of the optical system and the distance on the optical axis between an exit pupil and an imaging plane in the optical system.

A stereoscopic vision optical system includes a first lens group having a negative refractive power, disposed nearest to an object, a second lens group having a positive refractive power, and a rear-side lens group having a positive refractive power. The rear-side lens group includes a first rear group and a second rear group. The optical axis of the first lens group, an optical axis of the first rear group, and an optical axis of the second rear group is positioned on the same plane. The optical axis of the first lens group is positioned between the optical axis of the first rear group and the optical axis of the second rear group, and the following conditional expression (1) is satisfied:

0.08((L/2)(f1/f2))(1/WD)0.25(1).

An optical lens includes a first lens group with negative refractive power, a second lens group with positive refractive power, and an aperture stop disposed between the first lens group and the second lens group. A total number of lenses in the first lens group is less than three, and a total number of lenses in the second lens group is less than five. The second lens group includes a first lens, a second lens and a third lens arranged in order in a direction away from the aperture stop. Each of the first lens and the second lens is an aspheric lens, and one of the first lens and the second lens has a diffractive optical surface.

Provided is an optical system consisting of, in order from an object side to an image side: a first lens unit having a negative refractive power; an aperture stop; and a second lens unit having a positive refractive power, in which each of the first lens unit and the second lens unit includes a negative lens. A focal length (fG1N) of a negative lens (G1N) arranged closest to the object side in the first lens unit, a focal length (fGLN) of a negative lens (GLN) having a largest negative refractive power in the second lens unit, a focal length (f) of the optical system, a focal length (f1) of the first lens unit, and other factors are appropriately set.

A zoom lens arranged along an optical axis includes a first lens group and a second lens group. The second lens group has at least one aspheric lens. The first lens group moves toward an image side and the second lens group moves away from the image side along the optical axis during zooming. The first lens group is moved for focusing, and the second lens group is moved for zooming.

An imaging optical system consists of a first lens group and a second lens group, in order from a magnification side along an optical axis, an intermediate image is formed between the first lens group and the second lens group on the optical axis, at least one of the first lens group or the second lens group includes a reflector that bends the optical axis, the second lens group includes a movable lens group that moves during zooming, and predetermined conditional expressions are satisfied.

Pop-out lens systems for compact digital cameras, comprising an image sensor and a lens with a field of view FOV>60 deg and having i lens elements L1-Li starting with L1 from an object side toward an image side, each lens element Li having a respective focal length f.sub.i, the lens elements divided into two lens groups G1 and G2 separated by a big gap (BG), the lens having a pop-out total track length TTL<20 mm in a pop-out state and a collapsed total track length c-TTL in a collapsed state, wherein BG>0.25TTL, wherein either G1 can move relative to G2 and to the image sensor for focusing or G1 and G2 can move together relative to the image sensor for focusing, and wherein a ratio c-TTL/TTL<0.7.

A zoom lens consisting of, in order from an object side to an image side, a first lens unit having a negative refractive power, and a rear lens unit having one or more lens units and having a positive refractive power as a whole. Intervals between adjacent lens units change during zooming. The first lens unit has at least three meniscus lenses each having a negative refractive power and a convex shape toward the object side. At least one of the at least three meniscus lenses includes an aspherical surface having a positive aspherical amount. A predetermined condition is satisfied.