Zoom lens system
AssigneeNikon Corporation
InventorYasunori Ueno
Life of this patent
Estimating the term…
Abstract
A zoom lens system is composed of three lens groups. Arranged in the order from an eyepoint side are a first lens group G.sub.1 having a positive refracting power, a second lens group G.sub.2 having a positive refracting power and movable along an optical axis during the period of zooming, and a third lens group G.sub.3 having a negative refracting power and movable along the optical axis during the period of zooming. In the second lens group G.sub.2, at least one positive lens includes a lens surface composed of an aspheric surface at least on one of its eyepoint side and object side. Not only a sufficient eye relief is ensured but also various aberrations are corrected throughout the whole zooming range.
Claims14
A zoom lens system having an eyepoint side and an object side comprising:
- a first lens group G.sub.1 having a positive refracting power;
- a second lens group G.sub.2 having a positive refracting power and being movable along an optical axis;
- a third lens group G.sub.3 having a negative refracting power and being movable along said optical axis;
- and
- an objective lens L.sub.0 having a positive refracting power;
- said first to third lens groups G.sub.1 to G.sub.3 and said objective lens L.sub.0 being arranged in said order from said eyepoint side to said object side,
- said second lens group G.sub.2 and said third lens group G.sub.3 being responsive to a zooming operation to move in opposite directions to each other while interposing therebetween an object image formed by said objective lens L.sub.0 between said second and third lens groups G.sub.2 and G.sub.3,
- said second lens group G.sub.2 including a positive lens configuration, and said positive lens configuration having a lens surface made of an aspheric surface.
A zoom lens system having an eyepoint side and an object side comprising:
- a first lens group G.sub.1 having a positive refracting power;
- a second lens group G.sub.2 having a positive refracting power and movable along an optical axis;
- a third lens group G.sub.3 having a negative refracting power and movable along said optical axis;
- and
- an objective lens L.sub.0 having a positive refracting power;
- said first to third lens groups G.sub.1 to G.sub.2 and said objective lens L.sub.0 being arranged in said order from said eyepoint side to said object side,
- said second lens group G.sub.2 and said third lens group G.sub.3 being responsive to a zooming operation to move in opposite directions to each other while interposing therebetween an object image formed by said objective lens L.sub.0 between said second and third lens groups G.sub.2 and G.sub.3,
- said second lens group G.sub.2 including a positive lens configuration,
- said positive lens configuration having a lens surface made of an aspheric surface,
- whereby the following condition is satisfied
- 0<(r.sub.b +r.sub.a)/(r.sub.b -r.sub.a)<0.7
- wherein r.sub.a and r.sub.b respectively represent radii of curvature at apex portions of an eyepoint-side lens surface and object-side lens surface of said positive lens means.
Dependencies are inferred from the claim text.