Patent ID: 6895593

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 being provided so that the first and second objective lenses are installed to satisfy the Equation: WD 1 ≧WD 2 separation distance with respect to optical disc of second objective lens=WD 2 +α where, α=| WD 1 − WD 2 |×(0.1˜1.0), and contact between the second objective lens, having a shorter working distance, and the optical disc is prevented when the optical disc is installed and the first objective lens has a longer working distance operates.