Optical scanning device comprising an actuator for a displaceable collimator lens

Abstract

The invention relates to an optical player and an optical scanning device ( ) used therein for scanning an optical information carrier ( ). The scanning device comprises a radiation source ( ), a collimator lens unit ( ) having a first optical axis ( ), an objective lens unit ( ) having a second optical axis ( ), and an actuator ( ) by means of which the collimator lens unit can be displaced in a direction parallel to the first optical axis from a first position (A) to a second position (B), and conversely. Since the collimator lens unit is displaceable, the scanning device can suitably be used to scan information carriers comprising more than one information layer ( ) or to scan information carriers having mutually different substrate ( ) thicknesses. The actuator ( ) comprises a first part ( ) having a permanent magnet ( ) and a first magnetizable part ( ) of a magnetic circuit ( ), and a second part ( ), which is displaceable with respect to the first part and includes an electric coil ( ) and a second magnetizable part ( ) of the magnetic circuit ( ). Around each of said two positions, and in a non-energized condition of the coil, the first part exerts a magnetic force (F ) on the second part, which magnetic force drives the second part into the respective one of said two positions, so that the magnetic force provides stable equilibriums in both said positions. In a special embodiment, the first magnetizable part is U-shaped, the permanent magnet being arranged between the two legs ( ) of the first magnetizable part and having a magnetization direction (M) which extends parallel to the two legs ( ). In a preferred embodiment, the second part is guided with respect to the first part by means of a pair of leaf springs ( ) extending in a plane transverse to the optical axis of the collimator lens unit.