Zoom lens systems

Details Zoom lens systems Zoom lens systems

2005-06-21

2005-06-21

Perkey, W. B. (Department: 2851)

Photography

Having variable focal length of camera objective

C348S240300, C359S689000

Reexamination Certificate

active

06909846

ABSTRACT:
A zoom lens system having an exit pupil far away from the image plane, zoom ratio of about three, and in particular having compactness and high optical performance includes, in order from an object, a first lens group having negative refractive power, an aperture stop, a second lens group having positive refractive power, and a third lens group having positive refractive power. When zooming from a wide-angle end state to a telephoto end state, the first and second lens groups are moved and the third lens group is fixed such that a distance between the first lens group and the second lens group varies, and a distance between the second lens group and the third lens group increases. The second lens group is composed of four lenses or less and includes a diffractive optical surface formed on a lens surface except the most object side lens surface.

REFERENCES:
patent: 6081389 (2000-06-01), Takayama et al.
patent: 6542301 (2003-04-01), Fujibayashi
patent: 6618210 (2003-09-01), Noguchi et al.
patent: 6621642 (2003-09-01), Hagimori
patent: 2003/0076591 (2003-04-01), Ohmori et al.
patent: 11-52235 (1999-02-01), None
patent: 11-52237 (1999-02-01), None
patent: 2000-221397 (2000-08-01), None
“Introduction to Diffractive Optical Elements,” Supervised by Optical Design Study Group in the Optical Soiety of Japan, OPTRONICS, 1997 (with English translation).

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