Optical: systems and elements – Lens – Reverse telephoto
Patent
1996-05-17
1998-09-08
Font, Frank G.
Optical: systems and elements
Lens
Reverse telephoto
359686, 359747, G02B 1514, G02B 1304, G02B 1302
Patent
active
058053590
ABSTRACT:
The invention provides a solution to a problem of allowing a symmetrical wide-angle lens system to have a large aperture ratio, and achieves an optical system which is well improved in terms of sagittal coma and curvature of field, and has a satisfactory vignetting factor as well. The optical system comprises basically a first lens group G1 having a negative refracting power, a second lens group G2 containing an aperture stop and having a positive negative power, and a third lens group having a negative refracting power. The second lens group G2 is divided into front and rear sub-groups G.sub.21 and G.sub.22, each having a positive refracting power, between which the aperture stop is located. The first lens group G1 comprises at least one negative meniscus lens convex on an object side; the front sub-group G.sub.21 of the second lens group comprises at least one set of cemented lens including a positive lens and a negative lens; and the rear sub-group G.sub.22 of the second group comprises at least one set of cemented lens including a positive lens and a negative lens. A third lens group G3 comprises at least one negative meniscus lens convex on an image side. An aspherical surface is used in any one of the lens groups.
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Font Frank G.
Olympus Optical Co,. Ltd.
Stafira Michael P.
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