Patent ID: 7568849

Claim:
A light quantity adjusting device comprising: a substrate having an optical path aperture; a blade movably placed on the substrate to restrict quantity of light passing through the optical path aperture; and electromagnetic driving means for drivingly opening and closing the blade, the electromagnetic driving means comprising a rotating shaft, an arm integrated with the rotating shaft, and a transmission pin provided on the arm, wherein the blade includes a cam groove formed therein and engaging the transmission pin, the cam groove comprising a continuous groove having a driving area that crosses a pivoting direction of the transmission pin at a predetermined angle to displace the blade and a non-driving area that crosses the pivoting direction of the transmission pin at a substantially right angle to reduce displacement applied to the blade, and the arm has a weight located opposite the transmission pin via the rotating shaft to apply an inertia force to the transmission pin, the inertia force substantially balancing with a force of the transmission pin and acting in a direction opposite to that of force of the transmission pin.