PURPOSE: To lighten the weight of a movable part including an objective lens and to obtain high-rigity constitution by coupling at least two actuators with an optical element through at least two support coupling members and driving the actuators in the track direction, and thus positioning a light beam in a focus direction and the track direction.
CONSTITUTION: The objective lens 8 is positioned vertically by varying the driving extents of upper electrostrictive type actuators 13a and 13b, and lower actuators 14a and 14b. For example, the free end flanks of the upper actuators 13a and 13b are put far away from the objective lens than the free end flanks of the lower actuators 14a and 14b to move the objective lens 8 upward. Further, the actuators 13a and 14a, and 13b and 14b are driven by the same distance to move away from and toward the objective lens respectively, so that the objective lens moves in the track direction by the same distance.
KATOU KIKUJI
UKITA HIROO
