Backlash removing mechanism for zoom lens assembly

摘要

A zoom lens assembly has a rotatable cam ring having first helicoid threads and a cam groove, a front lens group held by a front lens group frame having second helicoid threads held in mesh with the first helicoid threads for moving the front lens groups along an axis of the rotatable cam ring, and a rear lens group held by a rear lens group frame having a cam follower engaging in the cam groove for moving the rear lens group along the axis relatively to the front lens group. A pair of diametrically opposite tension springs in the form of coil springs is coupled between the front and rear lens group frames for normally urging them toward each other thereby to remove backlash between the first and second helicoid threads and between the cam follower and the cam groove.