Zoom lens barrel

Claim 1

In a zoom lens barrel having on the outside of a fixed ring an operating ring rotatable about the optical axis and rectilinearly movable in the direction of the optical axis, and wherein a focusing lens optical system is driven by the rotation of said operating ring for focusing and a zooming lens optical system is driven by the rectilinear movement of the operating ring for zooming, the improvement comprising, said operating ring having in an inner periphery thereof an operating ring groove extending circumferentially of said operating ring, said fixed ring having at least first, second and third fixed ring grooves formed therein substantially equidistantly about the periphery of said fixed ring and extending at a first predetermined angle with respect to the operating ring groove, a cam ring provided inside said operating ring and having at least first, second and third cam ring grooves formed therein substantially equidistantly about the periphery of said cam ring, the first, second and third cam ring grooves each extending at a second predetermined angle with respect to the first, second and third fixed ring grooves, respectively, and at a third predetermined angle with respect to said operating ring groove, and a lens frame member for holding part of said zooming lens optical system provided inside of said fixed ring and having at least first, second and third projecting members thereon formed substantially equidistantly in the circumferential direction of said lens frame member, the first, second and third projecting members respectively extending through the first, second and third fixed ring grooves and through the first, second and third cam ring grooves and being fitted in said operating ring groove.