Zoom lens system
AssigneeRicoh Imaging Company, Ltd.
InventorMasakazu SAORI
Life of this patent
Estimating the term…
Abstract
A zoom lens system includes a negative first lens group, a positive second lens group, a negative third lens group, and a positive fourth lens group. Upon zooming from the short to the long focal length extremities, the distance between the first and second lens groups decreases, the distance between the second and third lens groups increases, and the distance between the third and fourth lens groups decreases. The following conditions (1) and (2) are satisfied: −2.50<f1/f2<−1.57 (1), and f3/f3B<−0.1 (2), wherein f1, f2 and f3 designate the focal lengths of the first, second and third lens groups, respectively, and f3B designates the focal length of a bonding surface in the cemented lens of the third lens group.
Claims22
A zoom lens system comprising a negative first lens group, a positive second lens group, a negative third lens group, and a positive fourth lens group, in that order from the object side,
- wherein upon zooming from the short focal length extremity to the long focal length extremity, the distance between said first lens group and said second lens group decreases, the distance between said second lens group and said third lens group increases, and the distance between said third lens group and said fourth lens group decreases,
- wherein said third lens group includes a cemented lens provided with a positive lens element and a negative lens element, and
- wherein the following conditions (1) and (2) are satisfied:
- −2.50<f1/f2<−1.57 (1),
- and
- f3/f3B<−0.1 (2),
- wherein
- f1 designates the focal length of said first lens group,
- f2 designates the focal length of said second lens group,
- f3 designates the focal length of said third lens group, and
- f3B designates the focal length of a bonding surface in the cemented lens of said third lens group.
A zoom lens system comprising a negative first lens group, a positive second lens group, a negative third lens group, and a positive fourth lens group, in that order from the object side,
- wherein upon zooming from the short focal length extremity to the long focal length extremity, the distance between said first lens group and said second lens group decreases, the distance between said second lens group and said third lens group increases, and the distance between said third lens group and said fourth lens group decreases, and
- wherein the following conditions (1) and (3) are satisfied:
- −2.50<f1/f2<−1.57 (1),
- and
- 0.9<f12t/f4<3.0 (3),
- wherein
- f1 designates the focal length of said first lens group,
- f2 designates the focal length of said second lens group,
- f12t designates the combined focal length of said first lens group and said second lens group at the long focal length extremity, and
- f4 designates the focal length of said fourth lens group.
A zoom lens system comprising a negative first lens group, a positive second lens group, a negative third lens group, and a positive fourth lens group, in that order from the object side,
- wherein upon zooming from the short focal length extremity to the long focal length extremity, the distance between said first lens group and said second lens group decreases, the distance between said second lens group and said third lens group increases, and the distance between said third lens group and said fourth lens group decreases,
- wherein said second lens group includes a positive first sub-lens group, a positive second sub-lens group and a third sub-lens group, in that order from the object side, and
- wherein said third sub-lens group includes a cemented lens, provided with a negative meniscus lens element having a convex surface on the object side and a positive meniscus lens element having a convex surface on the object side, in that order from the object side.
Dependencies are inferred from the claim text.