Patent ID: 8331046

Claim:
A focusing device for a beam projector, comprising: a casing; a lens holder including at least one lens, the lens holder being movable forward and backward in a direction of an optical axis of the lens within the casing; a movable member at a side of the lens holder that moves parallel to the direction of the optical axis together with the lens holder; a control knob adjacent to the lens holder and rotatably coupled on the casing, a coupling piece extending from a side surface of the movable member; a bore formed in the coupling piece; and a coupling protrusion attached to the control knob and turning about an axis of rotation of the control knob as the control knob is rotated, wherein the movable member is connected to the control knob in such a manner that as the control knob is rotated, the movable member moves parallel to the direction of the optical axis, thereby moving the lens holder forward and backward in the direction of the optical axis, and wherein the coupling protrusion is positioned in the bore in such a manner that as the control knob is rotated, the coupling protrusion is rectilinearly moved within the bore, and pushes against opposite inner walls of the bore, thereby moving the movable member.