US Patent 7499231 Auto-focus lens module

An auto-focus lens module that uses electromagnetic force as well as spring force as driving force to drive the lens for auto-focusing is formed by a rectangular base, two copper plates, an insulation spacer, four magnets, a lens holder, a lens, a coiled spring, a coil, and a rectangular top cover. The lens holder, the lens and the coil form a lens set that moves synchronously. The coiled spring is between the coil and the lens and is elastically supporting between a circular slot of the lens holder and the top cover while the four magnets are respectively located outside the coil symmetrically and equidistantly, on four corners of the rectangular base so that the structure and volume of the lens module are simplified and minimized. Moreover, the distance between the coil and the magnets is shortened so that the electromagnetic force therebetween is increased. Furthermore, the diameter of the coiled spring is reduced for improving stability of the spring force.