Zoom Lens
AssigneeTamron Co., Ltd.
InventorNobuyuki Adachi
Life of this patent
Estimating the term…
Abstract
A high-power zoom lens that achieves size and price reduction, and at the same time provides high-quality imaging. This lens includes at least four lens groups arranged along an optical axis, which are moveable along the axis in order to achieve changes in magnification. The first, third, and fourth lens groups have positive refractive powers, and the second group has a negative refractive power. The second lens group includes a negative meniscus lens arranged closest to the object, provided with a convex surface at the object side. A negative lens is arranged next to the negative meniscus lens, and a negative lens provided with a concave surface at the object side is arranged closest to the image. The fourth lens group includes at least two positive lenses and one negative lens.
Claims13
A zoom lens comprising at least a first lens group having a positive refractive power, 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 arranged in this order from an object side to constitute an optical system, and
- all the lens groups constituting the optical system move along an optical axis direction for adjustment of distance between the respective lens groups to achieve a predetermined magnification change,
- wherein the second lens group includes a negative meniscus lens arranged at closest to an object provided with a convex surface at the object side, a negative lens arranged next to the negative meniscus lens and a negative lens arranged at closest to an image provided with a concave surface at the object side,
- the fourth lens group includes at least two positive lenses and one negative lens, and wherein
- the lenses described below arranged in the second lens group and the fourth lens group satisfy following expressions (1) and (2):
- [Expression 1]
- 1.48≦(NV+NL)/2≦1.62 (1)
- 38≦(VV+VL)/2≦62 (2)
- in the expressions (1) and (2);
- NV:
- Refractive index for a d-line of the negative lens in the second lens group arranged next to the negative meniscus lens
- VV:
- Abbe number of the negative lens in the second lens group arranged next to the negative meniscus lens
- NL:
- Refractive index for a d-line of the lens in the fourth lens group arranged at closest to the object
- VL:
- Abbe number of the lens in the fourth lens group arranged at the closest to the object.
Dependencies are inferred from the claim text.