Patent ID: 6307683
Filing Date: 2001-10-23
Classification: G02B

Abstract:
A zoom lens, primarily intended for use with a television camera, said zoom lens comprising:a zoom lens main-body constructed using at least four lens groups including, in order from the object side:a first lens group of positive refractive power that is fixed relative to the image surface when zooming;a second lens group of negative refractive power that moves axially toward the image surface when zooming from the wide-angle end to the telephoto end in order to change the image magnification;a third lens group which moves first in one axial direction and then in the opposite axial direction during zooming so as compensate for what would otherwise be a shifting of the image position when changing the image magnification;a fourth lens group having a front sub-assembly and a rear sub-assembly, the front sub-assembly and the rear subassembly being spaced from one another and at a fixed axial location during zooming; anda supportive lens attachment which may be removably positioned in the light path of the zoom lens main body within the space between the front sub-assembly and the rear sub-assembly, said supportive lens attachment being formed of two lens groups which have opposite refractive power.