Zoom lens system
AssigneeRicoh Imaging Company, Ltd.
InventorMasakazu SAORI
Life of this patent
Estimating the term…
Abstract
A zoom lens system includes a positive first lens group, a negative second lens group, in that order from the object side, and a positive nth lens group provided closest to the image side. During zooming from the short to long focal length extremities, the first lens group and the nth lens group remain stationary and the second lens group moves. A positive mth lens group is provided between the second and nth lens groups. The following conditions (1) and (2) are satisfied: 1.23<f1/fn<1.50 (1), and 1.20<fn/fm<1.60 (2), wherein f1, fn and fm designate the focal lengths of the first, nth and mth lens groups, respectively, wherein n is a positive integer of 4 or greater, and m is a positive integer of 3 or greater.
Claims18
A zoom lens system comprising a positive first lens group and a negative second lens group, in that order from the object side, and a positive nth lens group provided closest to the image side,
- wherein, during zooming from the short focal length extremity to the long focal length extremity, said first lens group and said nth lens group remain stationary relative to the imaging plane, and said second lens group moves in a direction of an optical axis of said zoom lens system,
- wherein a positive mth lens group is provided between said second lens group and said nth lens group, and
- wherein the following conditions (1) and (2) are satisfied:
- 1.23<f1/fn<1.50 (1), and
- 1.20<fn/fm<1.60 (2), wherein
- f1 designates the focal length of the first lens group,
- fn designates the focal length of the nth lens group, wherein n is a positive integer of 4 or greater, and
- fm designates the focal length of the mth lens group, wherein m is a positive integer of 3 or greater.
A zoom lens system comprising a positive first lens group, a negative second lens group, a positive third lens group, a negative fourth lens group, and a positive fifth lens group, in that order from the object side,
- wherein, during zooming from the short focal length extremity to the long focal length extremity, said first lens group and said fifth lens group remain stationary relative to the imaging plane, and the second through fourth lens groups move in a direction of an optical axis of said zoom lens system, and
- wherein the following condition (12) is satisfied:
- −1.76<f4/f1<−1.49 (12), wherein
- f1 designates the focal length of said first lens group, and f4 designates the focal length of said fourth lens group.
Dependencies are inferred from the claim text.