Three-unit zoom lens

Details Three-unit zoom lens Three-unit zoom lens

1994-10-21

1998-12-15

Sugarman, Scott J.

Optical: systems and elements

Lens

With variable magnification

359684, 359713, 359714, 359715, G02B 1514, G02B 1318

Patent

active

058503129

ABSTRACT:
The invention provides a zoom lens system which, albeit having a zoom ratio exceeding 2, is composed of fewer lenses, is of small and low-cost construction, and shows sufficient performance over a range from infinity to a short object distance. The three-unit zoom lens system comprises, in order from the object side, a first lens unit having very weak refracting power, a second lens unit having positive refracting power, and a third lens unit having negative refracting power with the separation between the respective lens units varied for zooming. The first lens unit includes at least one aspherical surface and each lens within the first lens unit has very weak refracting power. The three-unit lens system satisfies the following conditional formula:

REFERENCES:
patent: 4984877 (1991-01-01), Ito
patent: 5162947 (1992-11-01), Ito
patent: 5257137 (1993-10-01), Suzuki et al.
patent: 5274504 (1993-12-01), Itoh
patent: 5305148 (1994-04-01), Ikamori et al.
patent: 5455714 (1995-10-01), Kohno
patent: 5539582 (1996-07-01), Kohno et al.
patent: 5572365 (1996-11-01), Ito
patent: 5592334 (1997-01-01), Oshikiri et al.

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