Optical: systems and elements – Lens – With variable magnification
Patent
1996-11-13
1998-08-11
Sugarman, Scott J.
Optical: systems and elements
Lens
With variable magnification
359683, G02B 1514
Patent
active
057935319
ABSTRACT:
A zoom lens is provided that is capable of focusing from infinity to an extremely close range, on the order of -0.5 magnification, in all zoom positions with adequate peripheral light amounts and good imaging performance. The zoom lens includes, in the following order, from the object side: a first lens group having a negative refractive power; a second lens group having a positive refractive power; a third lens group having a negative refractive power; and a fourth lens group having a positive refractive power. Zooming from the maximum wide-angle state to the maximum telephoto state is accomplished with the first lens group in a fixed state and the distance between the first lens group and the second lens group decreasing, the distance between the second lens group and the third lens group increasing, and the distance between the third lens group and the fourth lens group decreasing. Focusing from an object at infinity to a close object is accomplished by moving the first lens group toward the object, and satisfying the equations:
REFERENCES:
patent: 3603669 (1971-09-01), Lai et al.
patent: 4054371 (1977-10-01), Yasukuni
patent: 4653873 (1987-03-01), Kawamura
patent: 5132848 (1992-07-01), Nishio et al.
patent: 5631775 (1997-05-01), Shibata
Nikon Corporation
Sugarman Scott J.
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