Two-group zoom lens

Details Two-group zoom lens Two-group zoom lens

1994-06-13

1996-08-13

Epps, Georgia Y.

Optical: systems and elements

Lens

With variable magnification

G02B 1514

Patent

active

055462324

ABSTRACT:
A two-group zoom lens is provided which has a first lens group of negative power and a second lens group of positive power, located in this order from an object to be photographed. The first and second lens groups are moved relative to one another to provide various degrees of magnification. The first lens group includes a first lens of negative power, a second lens of negative power, and a third lens of positive power. The second lens group includes a fourth lens of positive power, a fifth lens of positive power, a sixth lens of negative power, and a seventh lens of positive power. The fifth lens is cemented to the sixth lens. The fifth and sixth lenses satisfy the following conditions: (a) 0.1<n.sub.N -n.sub.P <0.4; (b) -1.3<r.sub.c /f.sub.2 <-0.5; and (c) 0.6<d.sub.1-2 /f.sub.w <1.2; wherein, n.sub.P represents a refractive index of the fifth lens, n.sub.N represents a refractive index of the sixth lens, r.sub.c represents a radius of curvature of the cementing surface of the fifth and sixth lenses, f.sub.2 represents a focal length of the second lens group, d.sub.1-2 represents a distance between the first and second lens groups, and f.sub.w represents a focal length of the entire zoom lens at a wide angle extremity.

REFERENCES:
patent: 4074931 (1978-02-01), Okudaira
patent: 4653876 (1987-03-01), Yamagata
patent: 4792215 (1988-12-01), Sato
patent: 4812022 (1989-03-01), Sato
patent: 4934797 (1990-06-01), Hirakawa
patent: 5076677 (1991-12-01), Sato
patent: 5155629 (1992-10-01), Ito et al.
patent: 5233474 (1993-08-01), Hirakawa
patent: 5270863 (1993-12-01), Uzawa
patent: 5278699 (1994-01-01), Ito et al.

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