Zoom lens
AssigneeTamron Co., Ltd.
InventorToshihide HAYASHI
Life of this patent
Estimating the term…
Abstract
A zoom lens includes a first lens group including at least one positive lens and having a positive refractive power as a whole, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power wherein the first to the fourth lens groups are arranged sequentially from a subject. When magnification is varied from a wide angle end to a telephoto end, the second lens group is moved along an optical axis from the subject-side to an image plane. When given conditions are fulfilled, a small zoom lens with less manufacturing costs, high optical performance, and high magnification is realized.
Claims3
A zoom lens comprising:
- a first lens group including at least one positive lens and having a positive refractive power as a whole;
- a second lens group having a negative refractive power;
- a third lens group having a positive refractive power;
- a fourth lens group having a positive refractive power, wherein
- the first to the fourth lens groups are arranged sequentially from a subject-side,
- a magnification power is varied when at least one lens group is moved, and
- conditions:
- 70≦μd≦81;
- 1.5≦OVL/(ft/fw)≦1.8;
- and
- 2.3≦OVL/M2≦2.5
- are fulfilled, where νd is an Abbe number of at least one positive lens included in the first lens group at d line, OVL is an entire length of the zoom lens, ft is a focal length of the zoom lens at a telephoto end, fw is a focal length of the zoom lens at a wide angle end, and M2 is a travel distance of the second lens group when the magnification is varied.
A zoom lens comprising:
- a first lens group including at least one positive lens and having a positive refractive power as a whole;
- a second lens group having a negative refractive power;
- a third lens group having a positive refractive power;
- a fourth lens group having a positive refractive power, wherein
- the first to fourth lens groups are arranged sequentially from a subject-side,
- a magnification power is varied when at least one lens group is moved, and
- conditions:
- 70≦νd≦81;
- 1.5≦OVL/(ft/fw)≦1.8;
- and
- 1.9≦|f2|/fw≦2.4
- are fulfilled, where νd is Abbe number of at least one positive lens included in the first lens group at d line, OVL is an entire length of the zoom lens, ft is a focal length of the zoom lens at a telephoto end, fw is a focal length of the zoom lens at a wide angle end, and f2 is a focal length of the second lens group.
Dependencies are inferred from the claim text.