Patent ID: 7285879
Filing Date: 2007-10-23
Classification: G02B,G03B

Abstract:
1. An autofocus actuator, comprising: a holder having a hollow body portion having one end to which a lens is attached; a coil fixedly secured to the holder in such a manner as to surround the hollow body portion of the holder; a pair of leaf springs respectively provided on opposite end sides of the hollow body portion of the holder for supporting the holder displaceably in an optical axis direction of the lens with the holder being positioned in a radial direction; and a yoke having a plurality of permanent magnets provided in a confronting relationship with the coil, the yoke adapted to adjust the position of the lens attached to the holder in the optical axis through the interaction between a magnetic field of the permanent magnets and a magnetic field generated by the coil as the coil is supplied with electric power, wherein the yoke includes an inner cylindrical portion into which the hollow body portion of the holder is inserted and an outer cylindrical portion provided outside of the inner cylindrical portion with a predetermined spacing left therebetween, in which the coil is located, wherein each of the plurality of magnets is formed from a generally flat plate shape permanent magnet, and the outer cylindrical portion of the yoke is formed into a cylindrical shape having a generally square cross section so as to have four inner surfaces which define magnet mounting surfaces on which the flat plate shape permanent magnets are mounted, respectively, wherein the outer cylindrical portion of the yoke has four corner portions each formed into a cave-in portion which is curved inwardly so that positioning surfaces are defined on opposite sides of each of the magnet mounting surfaces, in which the distance between the positioning surfaces of each magnet mounting surface is substantially equal to the width of the flat plate shape permanent magnet.