Zoom lens

Details Zoom lens Zoom lens

2005-03-15

2005-03-15

Sugarman, Scott J. (Department: 2873)

Optical: systems and elements

Lens

With variable magnification

C359S687000, C359S684000

Reexamination Certificate

active

06867925

ABSTRACT:
A zoom lens to form an image of an object with variable magnification between a shortest focal length and a longest focal length, is provided with a first lens group having a positive refracting power; a second lens group positioned closer to the image than the first lens group and having a negative refracting power; and a third lens group positioned closer to the image than the second lens group and having a positive refracting power. When the magnification is changed from the shortest focal length to the longest focal length, the third lens group is shifted toward the object and the first lens group and the second lens group are shifted in such a manner that a distance between the first lens group and the second lens group is increased and a distance between the second group and the third group is decreased. The third lens group comprises at least a single positive lens and at least a single negative lens. A variable magnification ratio of the zoom lens is four times or more.

REFERENCES:
patent: 4299454 (1981-11-01), Betensky
patent: 4763998 (1988-08-01), Tsuji et al.
patent: 5694253 (1997-12-01), Shibayama
patent: 6028717 (2000-02-01), Kohno et al.
patent: 6118592 (2000-09-01), Kohno et al.
patent: 6191895 (2001-02-01), Arimoto et al.
patent: 6633437 (2003-10-01), Hoshi et al.
patent: 20020097503 (2002-07-01), Kohno et al.

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