Zoom lens of the inner focusing type

Details Zoom lens of the inner focusing type Zoom lens of the inner focusing type

1997-08-18

1999-10-12

Epps, Georgia

Optical: systems and elements

Lens

With variable magnification

359684, 359687, 359688, G02B 1514

Patent

active

059662468

ABSTRACT:
A zoom lens having four lens groups, the lens groups having refractive power, in order from the object side, of: fixed positive, variable negative, variable positive or negative, and fixed positive. The first lens group from the object side is composed of three lens subgroups, the middle subgroup of which is moved to perform focusing. The second lens group is moved to vary the amount of zoom, and the third lens group moves when the amount of zoom is varied in order to correct for movement of the image plane resulting when the second lens group is moved. Thus, the optical performance of the zoom lens is favorably maintained over the entire image plane. Further, by satisfying certain conditional equations a system that is compact and can focus objects at very near distances is obtained.

REFERENCES:
patent: 4099845 (1978-07-01), Takesi et al.
patent: 5745300 (1998-04-01), Usui et al.
patent: 5757554 (1998-05-01), Fukami

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