Compact zoom lens
AssigneeAsia Optical Co., Inc.
InventorChen-cheng Liao
Life of this patent
Estimating the term…
Abstract
A compact zoom lens includes, from the object side to the image side, a negative first lens group (1), a positive second lens group (2) and a positive third lens group (3). The first lens group is stationary, and both the second and third lens groups are movable along the optical axis. The compact zoom lens is zoomed by varying the distance between the first and second lens groups, and the focal length is adjusted by varying the distance between the second and third lens groups. The zoom lens is composed of only four single lenses in three groups, of which three (10, 31, 32) are plastic aspheric lenses and one (20) is a glass spherical lens.
Claims18
A zoom lens comprising, from the object side to the image side, a first lens group of negative refractive power, a second lens group of positive refractive power and a third lens group of positive refractive power, the first lens group being stationary and both the second and third lens groups being movable along the optical axis, the distance between the first and second lens groups being variable for effecting focal length change, the third lens group being movable to compensate for image plane shift due to focal length change and thereby maintain the position of the image plane.
A zoom lens comprising, from the object side to the image side, a stationary first lens group of negative refractive power, a movable second lens group of negative refractive power, and a movable third lens group of positive refractive power, the distance between the first and second lens groups being variable for zooming, the distance between the second and third lens groups being variable for focusing, the zoom lens satisfying the following conditions:
- where fbw is the back focal length at the wide-angle end, and TT is the total optical track of the zoom lens;
- where f2 represents the focal length of the second lens group, and f3 represents the focal length of the third lens group;
- and
- where IC represents the radius of an image circle, and TT represents the total optical track of the zoom lens.
Dependencies are inferred from the claim text.