Patent ID: 6124982
Filing Date: 2000-09-26
Classification: G02B

Abstract:
A zoom lens having, 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 fixed fourth lens unit of positive refractive power, characterized in that said first lens unit has a front lens sub-unit of negative refractive power fixed during focusing, an intermediate lens sub-unit movable along the optical axis thereof for focusing, and a rear lens sub-unit of positive refractive power fixed during focusing, and when the variable power ratio of said zoom lens is Z and the maximum incidence height of an on-axis light beam in the first lens unit is ht and the maximum incidence height of an off-axis light beam of a maximum angle of view at the wide angle end in the first lens unit is hw and the maximum 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 is hz, at least one lens surface at a position satisfying 1.65<hw/ht and 1.15<hw/hz is made into an aspherical surface AS1.