Abstract: The present disclosure relates to zoom lenses and optical devices using the same. A zoom lens may include in order from an object side to an image side: a first lens group, a second lens group, a third lens group, a fourth lens group; and a fifth lens group. The zoom lens may satisfy the following conditions: ?2.28?f2/fw???1.08, and 0.15?TTL/(BFL*fw?)?0.45, wherein f2 denotes a focal length of the second lens group, fw? denotes a focal length of the zoom lens at a wide angle end, TTL denotes a total track length of the zoom lens, and BFL denotes a back focal length of the zoom lens.

Abstract: The present disclosure relates to zoom lenses and optical devices using the same. A zoom lens may include in order from an object side to an image side: a first lens group, a second lens group, a third lens group, a fourth lens group; and a fifth lens group. The zoom lens may satisfy the following conditions: ?2.28?f2/fw???1.08, and 0.15?TTL/(BFL*fw?)?0.45, wherein f2 denotes a focal length of the second lens group, fw? denotes a focal length of the zoom lens at a wide angle end, TTL denotes a total track length of the zoom lens, and BFL denotes a back focal length of the zoom lens.

Abstract: The present disclosure relates to a lens system and an imaging device including the lens system. The lens system may include a first lens group, a second lens group, a third lens group, a fourth lens group, and a fifth lens group in sequence from an object side to an image side along an optical axis of the lens system. At least one of the first lens group, the second lens group, the third lens group, the fourth lens group, and the fifth lens group may be adjustable along the optical axis of the lens system to adjust a focal length of the lens system. The lens system may satisfy a ? f 2 ( f w · f t ) 1 / 2 ? b , c ? f 3 ( f w · f t ) 1 / 2 ? d , e ? f 4 ( f w · f t ) 1 / 2 ? f .

Abstract: The present disclosure relates to zoom lenses and optical devices using the same. A zoom lens may include in order from an object side to an image side: a first lens group; a second lens group; a third lens group; a fourth lens group; and a fifth lens group; wherein the zoom lens satisfies the following conditions: ?1.7?f2/fw???0.3, 0.7?f3/fw??2.1, 1.1?f4/fw??2.5, and TTL/fw??6.5, wherein f2 denotes a focal length of the second lens group, f3 denotes a focal length of the third lens group, f4 denotes a focal length of the fourth lens group, fw? denotes a focal length of the zoom lens, and TTL denotes a total track length of the zoom lens.

Abstract: The present disclosure relates to a lens system and an imaging device including the lens system. The lens system may include a first lens group, a second lens group, a third lens group, a fourth lens group, and a fifth lens group in sequence from an object side to an image side along an optical axis of the lens system. At least one of the first lens group, the second lens group, the third lens group, the fourth lens group, and the fifth lens group may be adjustable along the optical axis of the lens system to adjust a focal length of the lens system. The lens system may satisfy a ? f 2 ( f w · f t ) 1 / 2 ? b , c ? f 3 ( f w · f t ) 1 / 2 ? d , e ? f 4 ( f w · f t ) 1 / 2 ? f .

Abstract: A telephoto lens includes, from an object-side to an image-side: a first lens having a positive refractive power, wherein an object-side surface of the first lens is convex, an image-side surface of the first lens is convex; a second lens having a refractive power; a third lens having a refractive power, wherein the third lens includes plastic material, each of an object-side and an image-side surface of the third lens is aspheric; a fourth lens having a refractive power, wherein an object-side surface of the fourth lens is convex, the fourth lens includes plastic material, and each of the object-side and image-side surfaces of the fourth lens is aspheric; wherein, the telephoto lens satisfies: 0.7<TTL/f<0.95, and |f4/f|?1.2; where TTL is distance from the first lens' object-side surface to an imaging plane; f is effective focal length of the telephoto lens, and f4 is effective focal length of the fourth lens.

Abstract: A telephoto lens includes, from an object-side to an image-side: a first lens having a positive refractive power, wherein an object-side surface of the first lens is convex, an image-side surface of the first lens is convex; a second lens having a refractive power; a third lens having a refractive power, wherein the third lens includes plastic material, each of an object-side and an image-side surface of the third lens is aspheric; a fourth lens having a refractive power, wherein an object-side surface of the fourth lens is convex, the fourth lens includes plastic material, and each of the object-side and image-side surfaces of the fourth lens is aspheric; wherein, the telephoto lens satisfies: 0.7<TTL/f<0.95, and |f4/f|?1.2; where TTL is distance from the first lens' object-side surface to an imaging plane; f is effective focal length of the telephoto lens, and f4 is effective focal length of the fourth lens.