Zoom lens of rear focus type

Details Zoom lens of rear focus type Zoom lens of rear focus type

1996-01-17

1998-01-27

Nelms, David C.

Optical: systems and elements

Lens

With variable magnification

359684, G02B 1514

Patent

active

057127336

ABSTRACT:
A zoom lens of the rear focus type comprising, in order from an object side to an image side, a first lens unit of positive refractive power, a second lens unit of negative refractive power, a third lens unit of positive refractive power and a fourth lens unit of positive refractive power, wherein the second lens unit and the fourth lens unit are moved to effect zooming and the fourth lens unit is moved to effect focusing, wherein the third lens unit includes a positive first lens and a negative second lens of meniscus form convex toward the image side, and the fourth lens unit includes a negative first lens of meniscus form convex toward the object side and a positive second lens, and wherein an aspheric surface is applied to the third lens unit or the fourth lens unit.

REFERENCES:
patent: Re32923 (1989-05-01), Kreitzer
patent: 4256381 (1981-03-01), Kreitzer
patent: 4299454 (1981-11-01), Betensky
patent: 4770510 (1988-09-01), Mukaiya
patent: 4812024 (1989-03-01), Mukaiya
patent: 4846563 (1989-07-01), Mukaiya
patent: 4934796 (1990-06-01), Sugiura et al.
patent: 5050972 (1991-09-01), Mukaiya et al.
patent: 5056900 (1991-10-01), Mukaiya et al.
patent: 5530592 (1996-06-01), Tochigi

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