Optical: systems and elements – Lens – With variable magnification
Patent
1996-05-17
1998-09-15
Epps, Georgia Y.
Optical: systems and elements
Lens
With variable magnification
359689, 359716, 359725, 359740, G02B 1514, G02B 302, G02B 1306, G02B 308
Patent
active
058088083
ABSTRACT:
The invention provides an ultrawide-angle yet large aperture ratio lens system of the symmetrical type which, while taking aim at improving the vignetting factor and the performance of a sagittal image surface, achieves a field angle coverage of up to about 107.degree. and an aperture ratio of about 1:2.8 to 3.5, and which comprises a first group G1 of negative power, a second group G2 of positive power and a third group G3 of negative power. The first group G1 comprises at least one negative meniscus lens convex on an object side, the second group G2 comprises an aperture stop and one set of cemented lens, and the third group G3 comprises at least one negative meniscus lens convex on an image side, with an aspherical surface used in any one of the lens groups. Specific conditions for the refracting power ratio between the first and second groups G1 and G2, the refracting power ratio between the third and second groups G3 and G2, and the axial distance between the first and second groups G1 and G2 are satisfied. Focusing is effected by floating as well.
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Epps Georgia Y.
Lester Evelyn A.
Olympus Optical Co,. Ltd.
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