Optical: systems and elements – Lens – With variable magnification
Patent
1995-10-31
1998-09-15
Epps, Georgia Y.
Optical: systems and elements
Lens
With variable magnification
359684, 359708, G02B 1514, G02B 302
Patent
active
058088105
ABSTRACT:
The invention provides a compact zoom lens system for use on still video cameras, which has a zoom ratio of about 3, an F-number of about 2.0 to about 2.8 at the wide-angle end and a field angle as wide as about 60.degree., and comprises a first group G1 having positive refracting power, a second group G2 having negative refracting power and movable along the optical axis for zooming and focusing and a third group G3 having positive refracting power and movable along the optical axis for zooming. The second group is constantly less than 1 in terms of the absolute value of its magnification, and the third group moves such that the relation between its position on the optical axis and the focal length of the overall system is moving toward the object side. The system conforms to Cond. (1) with respect to the ratio of the zoom ratio of the second group upon focused on a nearby object point to the zoom ratio of the second group upon focused on an object point at infinity, Cond. (2) with respect to the air separation on the optical axis between the first and second groups at the wide-angle end upon focused on an object point at infinity, and Cond. (3) with respect to the amounts of movement of the second group at the wide-angle and telephoto ends upon focused from one object point onto another object point.
REFERENCES:
patent: 4906079 (1990-03-01), Mihara et al.
patent: 5168402 (1992-12-01), Mihara
patent: 5260834 (1993-11-01), Shibata et al.
patent: 5268793 (1993-12-01), Saka et al.
patent: 5543970 (1996-08-01), Hata et al.
Epps Georgia Y.
Olympus Optical Co,. Ltd.
Schwartz Jordan M.
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