Two-unit zoom lens system having a high zoom ratio

Details Two-unit zoom lens system having a high zoom ratio Two-unit zoom lens system having a high zoom ratio

1994-12-23

1997-09-09

Epps, Georgia Y.

Optical: systems and elements

Lens

With variable magnification

359686, 359708, G02B 1514

Patent

active

056662335

ABSTRACT:
The invention provides a two-unit zoom lens system comprising a front unit G.sub.F of positive refracting power and a rear unit G.sub.R of negative positive power which achieves a zoom ratio as high as about 3 with the use of a reduced number of lenses, and in which the spacing between both units is varied for zooming, said front unit including on the side proximate to the object a first lens component G.sub.F1 comprising a lens of plastic material having weak power, said first lens component including at least one aspheric surface, said rear unit including at least one positive lens and at least one negative lens, and said zoom lens system conforming to 0.2>.vertline.f.sub.W /f.sub.F1 .vertline. and 1.65<N.sub.RN where f.sub.W is the focal length of the overall system at the wide-angle end, f.sub.F1 is the focal length of said first lens component, and N.sub.RN is the refractive index of the negative lens of said rear unit.

REFERENCES:
patent: 4906077 (1990-03-01), Ito
patent: 5309285 (1994-05-01), Ito
patent: 5315440 (1994-05-01), Betensky et al.

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