Zoom lens system

Details Zoom lens system Zoom lens system

1991-12-12

1994-05-24

Ben, Loha

Optical: systems and elements

Lens

With variable magnification

359685, G02B 1514

Patent

active

053154380

ABSTRACT:
A zoom lens system having a field angle of about 44.degree. to 47.degree. at the wide angle end, a zoom ratio of about 2.6 to 3 and an F-number on the order of 2.8, which is reduced in value while making sure of a back focus and which is improved in terms of its capability to form images. The zoom lens system includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power and a fourth lens group consisting of three lens elements and having a positive refractive power as a whole, the second and third lens groups being movable for zooming.

REFERENCES:
patent: 4789226 (1988-12-01), Ogata
patent: 5000551 (1991-03-01), Shibayama
patent: 5032013 (1991-07-01), Shibayama
patent: 5179472 (1993-01-01), Ohno et al.

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