having an additional movable lens or lens group for varying the objective focal length

Full Title

Optical objectives with means for varying the magnification (anamorphotic objectives G02B13/08) > by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective > with interdependent non-linearly related movements between one lens or lens group, and another lens or lens group (G02B15/22 takes precedence) > having an additional movable lens or lens group for varying the objective focal length