Zoom lens system

Details Zoom lens system Zoom lens system

1993-10-15

1998-08-11

Epps, Georgia Y.

Optical: systems and elements

Lens

With variable magnification

359686, 359683, G02B 1514

Patent

active

057935335

ABSTRACT:
The improved zoom lens system comprises, in order from the object side, a positive first lens group, a positive second lens group and a negative third lens group, the third lens group having a biaspheric positive lens element on the side the closest to the object that has a convex surface directed towards the image and the third lens group further including at least one negative lens element that has a concave surface directed towards the object, and the system is further characterized in that all lens groups are moved towards the object during a zoom from the wide-angle end to the narrow-angle end, and the following conditions are satisfied: (a) 0<.DELTA.X.sub.3G1 /fs; (b) -0.75<X.sub.3G2 /.DELTA.X.sub.3G1 <0; (c) -1.5<r.sub.3G2 /fs<-0.5; where .DELTA.X.sub.3G1 : the amount of asphericity of the surface on the object side of the positive lens element on the object side of the third lens group; .DELTA.X.sub.3G2 : the amount of asphericity of the surface on the image side of the positive lens element on the object side of the third lens group; r.sub.3G2 : the paraxial radius of curvature of the aspheric surface on the image side of the positive lens element on the object side of the third lens group; and fs: the focal length of the overall system at the wide-angle end.

REFERENCES:
patent: 4773744 (1988-09-01), Yamanashi
patent: 5004329 (1991-04-01), Tsuchida
patent: 5260833 (1993-11-01), Ito et al.
patent: 5278699 (1994-01-01), Ito et al.
patent: 5315439 (1994-05-01), Ito
British Search Report GB 9321381.7.
Meiron, "On the Design of Optical Systems Containing Aspamic Surkalob", J. Of Optical Soc. of Amer., vol.46, No. 4 Apr. 1956, pp. 288-292.

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