Zoom lens system
First Claim
1. A zoom lens system comprising, in order from an object;
- a first lens group having negative refractive power;
an aperture stop;
a second lens group having positive refractive power; and
a third lens group having positive refractive power;
wherein when the state of lens group positions varies from a wide-angle end state to a telephoto end state;
the first lens group and the second lens group are moved and the third lens group is fixed such that a distance between the first lens group and the second lens group varies; and
a distance between the second lens group and the third lens group increases; and
wherein the second lens group is composed of four lenses or less;
the second lens group includes a diffractive optical surface formed on a lens surface except the most object side lens surface; and
the following conditional expression is satisfied;
0.2<
C/fw<
2.0 where C denotes the effective diameter of the diffractive optical surface, and fw denotes the focal length of the zoom lens system in the wide-angle end state.
0 Assignments
0 Petitions
Accused Products
Abstract
A zoom lens system having an exit pupil far away from the image plane, zoom ratio of about three, and in particular having compactness and high optical performance includes, in order from an object, a first lens group having negative refractive power, an aperture stop, a second lens group having positive refractive power, and a third lens group having positive refractive power. When zooming from a wide-angle end state to a telephoto end state, the first and second lens groups are moved and the third lens group is fixed such that a distance between the first lens group and the second lens group varies, and a distance between the second lens group and the third lens group increases. The second lens group is composed of four lenses or less and includes a diffractive optical surface formed on a lens surface except the most object side lens surface.
19 Citations
8 Claims
-
1. A zoom lens system comprising, in order from an object;
-
a first lens group having negative refractive power;
an aperture stop;
a second lens group having positive refractive power; and
a third lens group having positive refractive power;
wherein when the state of lens group positions varies from a wide-angle end state to a telephoto end state;
the first lens group and the second lens group are moved and the third lens group is fixed such that a distance between the first lens group and the second lens group varies; and
a distance between the second lens group and the third lens group increases; and
wherein the second lens group is composed of four lenses or less;
the second lens group includes a diffractive optical surface formed on a lens surface except the most object side lens surface; and
the following conditional expression is satisfied;
0.2<
C/fw<
2.0where C denotes the effective diameter of the diffractive optical surface, and fw denotes the focal length of the zoom lens system in the wide-angle end state. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
-
Specification