Zoom lens locking system

摘要

A locking system is provided for selectively locking the operating ring of a zoom lens against axial displacement with respect to a zoom lens housing to secure optical elements of the zoom lens in a selected position of magnification adjustment. The locking system comprises a cam sleeve concentrically within the operating ring and constrained for axial movement with the operating ring upon adjustment of image magnification. The cam sleeve includes a generally helical cam groove for receiving a cam pin on the lens housing such that the cam sleeve is forced to rotate with respect to the operating ring when the operating ring is moved axially. A slide switch on the operating ring selectively moves a ratchet into locking engagement with a toothed rack at one end of the cam sleeve to prevent relative rotation of the cam sleeve with respect to the operating ring and thereby lock the operating ring against axial movement.