Zoom lens barrel assembly for constant magnification

摘要

A zoom lens barrel is constructed such that the axial movement and rotation of a single operation ring relative to a stationary barrel causes zooming and focusing respectively and provides a device for providing constant magnification photography. This is accomplished by a plurality of cam grooves provided on one of the operation ring and the stationary barrel and a guide pin provided on the other of the operation ring and the stationary barrel and releasably engageable with each of the cam grooves. Each of the cam grooves forces the operation ring to rotate upon axial movement of the operation ring through the engagement with the guide pin such that magnification remains constant during focusing. The magnification that remains constant during focusing varies depending on which of the cam grooves the guide pin is engaged with.