An imaging lens consists of a front group and a rear group in order from the object side to the image side. The front group includes, as lenses, in order from the object side to the image side, only a positive meniscus lens having a surface convex toward the object side, a first cemented lens having a negative power as a whole, and a second cemented lens having a positive power as a whole. In the first cemented lens, a positive lens and a negative lens are cemented in order from the object side, with a surface convex toward the object side and a surface concave toward the image side. The rear group includes a negative most image side lens having a surface concave toward the object side at a position closest to the image side.

An optical system includes, in order from an object side to an image side, a front unit having a positive refractive power and including one or more lens units configured to move during focusing, and a negative lens unit having a negative refractive power. The one or more lens units included in the front unit moves to the object side during focusing from infinity to a short distance so as to widen a distance between the front unit and the negative lens unit. The front unit includes a first subunit having a negative refractive power and including a lens disposed on the object side of a first positive lens that is one of positive lenses included in the optical system, which is the closest to an object. A predetermined condition is satisfied.

An optical system includes, in order from an object side to an image side, a front unit having a positive refractive power and including one or more lens units configured to move during focusing, and a negative lens unit having a negative refractive power. The one or more lens units included in the front unit moves to the object side during focusing from infinity to a short distance so as to widen a distance between the front unit and the negative lens unit. The front unit includes a first subunit having a negative refractive power and including a lens disposed on the object side of a first positive lens that is one of positive lenses included in the optical system, which is the closest to an object. A predetermined condition is satisfied.

A lens apparatus includes two optical systems each of which includes, in order from an object side to an image side, a negative first lens unit, a first reflective member, an aperture diaphragm, a second reflective member, and a positive second lens unit. Each optical system satisfies following inequalities:

5.9<DR/f<13.6

0.7<D2/f2<5.2

10.4<DP/f<19.8

DR represents a distance on an optical axis from a reflective surface of the first reflective member to a reflective surface of the second reflective member. f represents a focal length of the optical system. f2 represents a focal length of the second lens unit. D2 represents a distance on the optical axis from the reflective surface of the second reflective member to an image plane. DP represents a distance on the optical axis from the aperture diaphragm to the image plane.

A lens apparatus includes two optical systems each of which includes, in order from an object side to an image side, a negative first lens unit, a first reflective member, an aperture diaphragm, a second reflective member, and a positive second lens unit. Each optical system satisfies following inequalities:

5.9<DR/f<13.6

0.7<D2/f2<5.2

10.4<DP/f<19.8

DR represents a distance on an optical axis from a reflective surface of the first reflective member to a reflective surface of the second reflective member. f represents a focal length of the optical system. f2 represents a focal length of the second lens unit. D2 represents a distance on the optical axis from the reflective surface of the second reflective member to an image plane. DP represents a distance on the optical axis from the aperture diaphragm to the image plane.

Provided an imaging apparatus including a first optical device, a second optical device disposed such that light transmitted through the first optical device is incident on the second optical device, and a third optical device disposed such that light transmitted through the second optical device is incident on the third optical device, wherein at least one of the first optical device, the second optical device, and the third optical device includes a plurality of nanostructures, and heights of at least two nanostructures of the plurality of nanostructures are different from each other.

Provided an imaging apparatus including a first optical device, a second optical device disposed such that light transmitted through the first optical device is incident on the second optical device, and a third optical device disposed such that light transmitted through the second optical device is incident on the third optical device, wherein at least one of the first optical device, the second optical device, and the third optical device includes a plurality of nanostructures, and heights of at least two nanostructures of the plurality of nanostructures are different from each other.

The finder includes, in order from an object side to an eye point side, a negative objective lens group, and a positive eyepiece lens group. The eyepiece lens group consists of, in order from the object side to the eye point side, a negative first lens, a positive second lens, and a negative third lens. During diopter adjustment, only the second lens moves. The finder satisfies a conditional expression determined in advance.

The finder includes, in order from an object side to an eye point side, a negative objective lens group, and a positive eyepiece lens group. The eyepiece lens group consists of, in order from the object side to the eye point side, a negative first lens, a positive second lens, and a negative third lens. During diopter adjustment, only the second lens moves. The finder satisfies a conditional expression determined in advance.

An illumination system includes an excitation light source, a first variable focus lens, a second variable focus lens, and a control unit. The excitation light source is adapted to provide an excitation light beam. The first variable focus lens is disposed on a transmission path of the excitation light beam. The first variable focus lens is located between the excitation light source and the second variable focus lens. The second variable focus lens is adapted to receive the excitation light beam exited from the first variable focus lens. The control unit is electrically connected to the first variable focus lens and the second variable focus lens, and is adapted to synchronously adjust focal lengths of the first variable focus lens and the second variable focus lens. A projection device including the above-mentioned illumination system of the invention is further provided.