Patent ID: 7505219

Claim:
A multi-stage lens driving device, comprising: a holder for carrying a lens and the lens being defined with an axial direction; a carriage for receiving the holder in a manner that the holder is moveable relative to the carriage and linearly along the axial direction; an electromagnetic driving mechanism comprising at least one coil and at least one magnet, the coil and the magnet being opposing each other without direct contact, wherein either the coil or the magnet is disposed on the holder, while the other is disposed on the carriage, and wherein interacting force between the coil and the magnet is generated by applying current of predetermined direction on the coil so as to push the holder to move; and a positioning mechanism disposed on the carriage for maintaining the holder at a predefined position even when no current is applied to the coil, wherein said holder has a hollow annular structure with an outer ring surface, the magnet is coupled to the outer ring surface, whereas the coil is coupled to the carriage and corresponds to the location of the magnet, wherein the magnet is produced by polarizing a lodestone such that the upper and lower portions of the lodestone on the same side have opposite polarity, and as such, the upper and lower portions of magnet on the side facing the carriage have opposite polarity, wherein an outer edge contour of said holder is substantially a polygonal structure and an axial through-hole is configured at the center of holder to hold the lens, and said at least one magnet includes several magnets which are spaced in roughly equal distance apart and mounted on the outer ring surface of holder; said carriage has a hollow structure and the polygonal inner edge contour corresponds to the polygonal outer edge contour of holder; the matching of the inner and outer polygonal contours form essentially a guiding mechanism that allows the holder to engage only in linear displacement inside the carriage without turning.