Zoom lens system
AssigneeNikon Corporation
InventorTakayuki Sensui
Life of this patent
Estimating the term…
Abstract
A super-wide zoom lens system having sufficient zoom ratio and a high speed, capable of obtaining high optical performance. The system includes at least, in order from an object, a first lens group G1 having negative refractive power, and a second lens group G2 having positive refractive power. When zooming from a wide-angle end state to a telephoto end state, a distance between the first lens group G1 and the second lens group G2 varies. The first lens group G1 includes at least one negative lens element and a glass material constructing at least one negative lens element (SL1) in the first group G1 satisfies given conditions.
Claims26
A zoom lens system comprising at least, in order from an object:
- a first lens group having negative refractive power;
- a second lens group having positive refractive power;
- a third lens group;
- and
- a fourth lens group,
- when the state of lens group positions varies from a wide-angle end state to a telephoto end state;
- each lens group being moved such that;
- a distance between the first lens group and the second lens group varies;
- the first lens group comprising at least one negative lens element;
- wherein a glass material constructing at least one of the negative lens element among the at least one negative lens element in the first lens group satisfies all of the following three conditional expressions:
- 67.0<ν
- 1.40<N
- 0<N+0.0032×ν−1.734
- where ν denotes Abbe number of the glass material at d-line (λ=587.6 nm), and N denotes refractive index of the glass material at d-line (λ=587.6 nm).
A method for forming an image of an object and varying a total focal length by a lens system that comprises a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group and a fourth lens group, in order from the object, comprising the steps of:
- providing the first lens group that is composed of at least one negative lens element constructed by a glass material to satisfy the following conditional expressions:
- 67.0<ν
- 1.40<N
- 0<N+0.0032×ν−1.734
- where ν denotes Abbe number of the glass material at d-line (λ=587.6 nm), and N denotes refractive index of the glass material at d-line (λ=587.6 nm);
- and
- varying the total focal length by moving the first lens group, the second lens group, the third lens group and the fourth lens group and by varying a distance between the first lens group and the second lens group when the lens system moves from a wide-angle end state to a telephoto end state.
Dependencies are inferred from the claim text.