Zoom lens using a first lens group having a positive focal lengt

Details Zoom lens using a first lens group having a positive focal lengt Zoom lens using a first lens group having a positive focal lengt

1994-04-21

1996-11-19

Nelms, David C.

Optical: systems and elements

Lens

With variable magnification

359676, 359713, G02B 1514

Patent

active

055768911

ABSTRACT:
In a zoom lens in which a variable power is obtained by changing the distance between a first lens group having a positive focal length and a second lens group having a negative focal length, the first lens group includes a first lens embodied by a positive meniscus lens whose convex surface faces the object, a second lens embodied by a biconcave lens, a third lens embodied by a biconvex lens and a fourth lens embodied by a biconvex lens, the lenses being arranged in the stated order when viewed from the object side, the second lens group includes a fifth lens embodied by a positive meniscus lens whose convex surface faces the image, a sixth lens embodied by a negative lens and a seventh lens embodied by a negative meniscus lens whose convex surface faces the image, the lenses being arranged in the stated order when viewed from the object side, and providing, when the first and second lens groups are in an arrangement characterized by the longest focal length, that the focal length of the whole system is f.sub.T, that the focal length of the first lens group is f.sub.1, that the focal length of the second lens group is f.sub.2, and that the distance between the first lens group and the second lens group is d.sub.8 +d.sub.9T, the following conditions are satisfied,

REFERENCES:
patent: 5398135 (1995-03-01), Ohashi

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