Zoom lens

Optical: systems and elements – Lens – With variable magnification

Patent

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Details

359683, 359687, 359688, 359676, G02B 1514

Patent

active

061249823

ABSTRACT:
This specification discloses a zoom lens which has, in succession from the object side, a first lens unit of positive refractive power, a second lens unit of negative refractive power for focal length change, a third lens unit for correcting the changing of an imaging plane resulting from a focal length change, and a fourth lens unit of positive refractive power, and in which an aspherical surface AS1 is provided on at least one lens surface constituting the first lens unit and satisfying 1.65<hw/ht and 1.15<hw/hz, where ht is the maximum incidence height of an on-axis light beam, hw is the incidence height of an off-axis light beam of a maximum angle of view at the wide angle end, and hz is the incidence height of the off-axis light beam of a maximum angle of view at a zoom position at a variable power ratio Z.sup.1/4, and the power disposition and achromatism condition of the first lens unit, a focusing system, etc. are appropriately set.

REFERENCES:
patent: 5737128 (1998-04-01), Usui
patent: 5745300 (1998-04-01), Usui et al.
patent: 5751497 (1998-05-01), Usui et al.

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