Patent ID: 7458086

Claim:
An actuator used with an optical pickup, the actuator comprising: a base on which a holder is fixed; a lens holder in which a plurality of installation holes are formed such that a plurality of objective lenses, to record and/or reproduce optical discs having different recording densities, are installed at different heights; a support member, which movably supports the lens holder, having one end coupled to the lens holder and the other end coupled to the holder; and a magnetic circuit which drives the lens holder in focusing and tracking directions, the plurality of installation holes include a first installation hole in which a first objective lens for at least one type of low density optical disc is installed, and a second installation hole in which a second objective lens for a high density optical disc is installed, wherein when a working distance of the first objective lens for the low density optical disc installed in the first installation hole is represented as WD 1 , and a working distance of the second objective lens for the high density optical disc installed in the second installation hole is represented as WD 2 , the first and second installation holes are provided such that the first and second objective lenses are installed to satisfy the Equation: WD1≧WD2 separation distance between an optical disc of the second objective lens=WD 2 +α where, α=|WD 1 −WD 2 |×(0.1˜1.0), and the second installation hole is located in a more outer circumference of the optical disc than the first installation hole.