Patent ID: 6714357
Filing Date: 2004-03-30
Classification: G02B

Abstract:
A lens drive system comprising:a lens frame having at least one lens element; a nut member which is secured to said lens frame, said lens frame and said nut member being movable in an optical axis direction without rotating relative to a base of said lens drive system, the direction of a screw hole of said nut member being parallel with the optical axis; a feed screw shaft having a male thread portion and a non-threaded portion, said male thread portion being engaged with said screw hole of said nut member so that said male thread portion is engaged with a female thread portion formed on an inner peripheral surface of said screw hole, a diameter of said non-threaded portion being smaller than an inner diameter of said screw hole; an engagement portion formed on said nut member, said engagement portion having at least one deformable screw-engaging portion which is engaged with said male thread portion; and a motor for rotating said feed screw shaft; wherein said engagement portion is forced by rotation of said feed screw shaft to move in an axial direction of said feed screw shaft; wherein said screw-engaging portion is disengaged from said male thread portion so that said male thread portion idles with respect to said engagement portion when a force greater than a predetermined value is applied to said engagement portion via said rotation of said feed screw shaft in said axial direction thereof; and wherein, when the linear movement of said lens frame and said nut member is restricted during the rotation of said feed screw shaft to move said nut member and said lens frame in a direction from said male thread portion toward said non-thread portion, said engagement portion of said nut member remains on said male thread portion of said feed screw shaft while said female thread portion of said nut member is disengaged from said male thread portion of said feed screw shaft to move onto said non-thread portion of said feed screw shaft.