Internal focusing telephoto lens

Details Internal focusing telephoto lens Internal focusing telephoto lens

1996-04-17

1998-04-28

Sugarman, Scott J.

Optical: systems and elements

Lens

Telephoto

359748, 359557, G02B 1302, G02B 2764

Patent

active

057453063

ABSTRACT:
The internal focusing telephoto lens of the invention has a focusing group with a small effective diameter and small focusing movement amount and maintains favorable optical performance. The internal focusing telephoto lens of the invention includes, in the following order from the object side; a first lens group that has a positive refractive power, a second lens group that has negative refractive power, and a third lens group that has a positive refractive power. The first and second lens groups form a substantially afocal system and focusing is performed by moving the second lens group along the optical axis. The first lens group includes, in the following order from the object side, a front group that has a positive refractive power and a rear group, which has about the same positive refractive power as the front group, and satisfies specified conditions.

REFERENCES:
patent: 4978205 (1990-12-01), Sato
patent: 5323270 (1994-06-01), Sato
patent: 5438455 (1995-08-01), Nakatsuji et al.
patent: 5490014 (1996-02-01), Suzuki
patent: 5610769 (1997-03-01), Shoji

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