Optical: systems and elements – Lens – With variable magnification
Patent
1997-07-24
1999-07-06
Epps, Georgia
Optical: systems and elements
Lens
With variable magnification
359683, 359676, G02B 1514
Patent
active
059204354
ABSTRACT:
A zoom lens comprises, in order from an object side, a first lens group G1 having a negative refracting power, a second lens group G2 having a positive refracting power, a third lens group G3 having a negative refracting power, and a fourth lens group G4 having a positive refracting power. A focal length of the zoom lens is changed from a wide angle end to a telephoto end by changing an air gap between the first lens group G1 and the second lens group G2, increasing an air gap between the second lens group G2 and the third lens group G3, and reducing an air gap between the third lens group G3 and the fourth lens group G4. When a focal length of the first lens group G1 is f1, a focal length of the total lens system at the wide angle end is fw, and an axial air gap between the first lens group G1 and the second lens group G2 in an infinity in-focus state at the wide angle end is D12W, the zoom lens satisfies following conditions: 0.8<.vertline.f1.vertline./fw<1.6, and D12W/fw<0.1. A preferred zoom lens can be constructed to allow focusing continuously from infinity to an object distance which is about double the focal length at the telephoto end in the infinity in-focus state at any focal length from the wide angle end to the telephoto end, by moving said first lens group G1.
REFERENCES:
patent: 4759617 (1988-07-01), Tokumaru et al.
patent: 5132848 (1992-07-01), Nishio et al.
patent: 5276553 (1994-01-01), Tatsuno
Epps Georgia
Nikon Corporation
Schwartz Jordon M.
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