Zoom lens system

Details Zoom lens system Zoom lens system

1994-03-25

1997-01-07

Nelms, David C.

Optical: systems and elements

Lens

With variable magnification

359684, 359791, G02B 1514

Patent

active

055923348

ABSTRACT:
A zoom lens system which enables favorable image quality to be obtained even when it is focused on an object at a short distance. The zoom lens system has a 1-st lens unit (G1) of positive power, a 2-nd lens unit (G2) of positive power, and a 3-rd lens unit (G3) of negative power. Zooming from the wide end toward the tele end is effected by increasing the spacing between the 1-st lens unit (G1) and the 2-nd lens unit (G2) while reducing the spacing between the 2-nd lens unit (G2) and the 3-rd lens unit (G3). The 2-nd lens unit (G2) of positive power is composed of a negative sub-lens unit (G2N) and a positive sub-lens unit (G2P), and an aperture stop is disposed between the 1-st lens unit (G1) and the 2-nd lens unit (G2) (as shown by S') or between the negative sub-lens unit (G2N) and the positive sub-lens unit (G2P) (as shown by S). When focusing is to be effected on an object at a short distance at, at least, the wide end, the negative sub-lens unit (G2N) and the positive sub-lens unit (G2P) are simultaneously moved toward the object side in parallel to the optical axis with the spacing therebetween gradually enlarged.

REFERENCES:
patent: 4978204 (1990-12-01), Ito
patent: 5172273 (1992-12-01), Yamanashi
patent: 5175648 (1992-12-01), Mori
patent: 5343329 (1994-08-01), Ito
patent: 5379154 (1995-01-01), Shibayama et al.
patent: 5424870 (1995-06-01), Hashimura et al.

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