An optical system includes a first unit having positive refractive power, a second unit having positive or negative refractive power and configured to move in focusing, and a third unit having negative refractive power in order from an object side to an image side. A distance between adjacent two of the units changes in focusing. When a distance on an optical axis from a lens surface closest to the object side to a lens surface closest to the image side is TL, a distance on the optical axis from a lens surface closest to the object side to a lens surface closest to the image side in the third unit is TL3, a sum of thicknesses, on the optical axis, of lenses in the third unit is SD3, and the largest of the thicknesses of the lenses in the third unit is DM3, the optical system satisfies predetermined conditional inequalities.

A zoom lens consists of, in order from the object side, a first lens group that has a positive refractive power, a middle group that includes a plurality of lens groups in which the spacings between adjacent lens groups change during zooming, and the final lens group. The focusing group that moves during focusing is disposed in the middle group. The zoom lens satisfies predetermined conditional expressions.

A projection lens system projects an image of a reduction side into a magnification side in an image projection device, a back glass being disposed on the reduction side. In the projection lens system, all of one or more negative lenses that satisfy, in a surface on the reduction side or a surface on the magnification side, condition |h/H|<2.0 defined by height h of a most off-axis principal ray and height H of an axial ray passing through a highest pupil position satisfy conditions Tn≥98.5% and Dn/Db≤0.05 defined by transmittance Tn, thickness Dn of the negative lens on an optical axis, and total thickness Db of the back glass.

The invention relates to a telescope optics for a telescopic observational instrument having an objective lens, having a prism erecting system and having an eyepiece lens, wherein an image of an object generated by the objective lens is located between the prism erecting system and the eyepiece lens, and wherein the objective lens, in an order starting from the object side, comprises a first lens group G1 with a positive refractive power, a second lens group G2 with a negative refractive power and a third lens group G3, and wherein the second lens group G2 is adjustable in parallel to an optical axis for focusing, and wherein at least one lens with a negative refractive power of the third lens group G3 is adjustable perpendicularly to the optical axis for changing the position of the image, and wherein the third lens group G3 has a negative refractive power.

A zoom lens system includes a first lens group; a second lens group; and a subsequent lens group arranged in that order from the object side. The second lens group consists of a second lens group-a, a second lens group-b, and a second lens group-c arranged in that order from the object side. A distance between the first lens group and the second lens group increases and a distance between the second lens group and the subsequent lens group decreases during a change in magnification from a short focal length end to a long focal length end. During a change in focus from infinity to a short distance, the second lens group-b is movable to the image side, and a distance between the second lens group-a and the second lens group-b and a distance between the second lens group-b and the second lens group-c are changeable.

The invention relates to a telescope optics for a telescopic observational instrument having an objective lens, having a prism erecting system and having an eyepiece lens, wherein an image of an object generated by the objective lens is located between the prism erecting system and the eyepiece lens, and wherein the objective lens, in an order starting from the object side, comprises a first lens group G1 with a positive refractive power, a second lens group G2 with a negative refractive power and a third lens group G3, and wherein the second lens group G2 is adjustable in parallel to an optical axis for focusing, and wherein at least one lens with a negative refractive power of the third lens group G3 is adjustable perpendicularly to the optical axis for changing the position of the image, and wherein the third lens group G3 has a negative refractive power.

An imaging module (1000), an imaging method, and an electronic device (2000) are provided. The imaging module (1000) includes a zoom lens (100) and a photosensitive element (402). The zoom lens (100) includes a first lens group (10), a second lens group (20), and a third lens group (30). The imaging method include: during switching from a long focus to a short focus, controlling the second lens group (20) and the photosensitive element (402) to move towards an object side; and during switching from the short focus to the long focus, controlling the second lens group (20) and the photosensitive element (402) to move towards an image side.

[Problem to be Solved] There are provided an optical system having good imaging performance, an optical apparatus, and a method for manufacturing the optical system. [Solution] An optical system OL used in an optical apparatus, such as a camera 1, includes a diffractive optical element GD and at least one specific lens Lp, which is a lens made of crystalline glass. The specific lens Lp satisfies the condition expressed by the following expression: θgFp+0.0017×νdp<0.730, where θgFp represents partial dispersion ratio of a medium of the specific lens Lp, and νdp represents the Abbe number of the medium of the specific lens Lp at a d line.

An optical system includes one or more positive lenses and one or more negative lenses. The first positive lens is a positive lens disposed closest to an object among the one or more positive lenses. The first negative lens is a negative lens that is disposed on an image side of the first positive lens and disposed closest to the object among the one or more negative lenses. At least one of an object side surface and an image side surface of the first positive lens is an aspherical surface. At this time, a relationship between a total lens length of the optical system L0, a focal length of the optical system L0, and a distance Dpn on an optical axis from the image side surface of the first positive lens to an object side surface of the first negative lens is defined.

A zoom lens system includes a first lens group; a second lens group; and a subsequent lens group arranged in that order from the object side. The second lens group consists of a second lens group-a, a second lens group-b, and a second lens group-c arranged in that order from the object side. A distance between the first lens group and the second lens group increases and a distance between the second lens group and the subsequent lens group decreases during a change in magnification from a short focal length end to a long focal length end. During a change in focus from infinity to a short distance, the second lens group-b is movable to the image side, and a distance between the second lens group-a and the second lens group-b and a distance between the second lens group-b and the second lens group-c are changeable.