2014 年 80 巻 814 号 p. DR0161
When the recording density of an optical disc increases, allowable tilt angle between the optical disc and the objective lens decreases. An objective lens actuator for an optical disc drive which is a kind of information processing equipments is needed to have little tilting action when it moves the objective lens in the focusing and tracking directions. We developed a new objective lens actuator with two configurations to reduce the rolling moment generated in the focusing coils and in the tracking coils of the actuator. One configuration is an arrangement in which the tracking coils and magnets at one side of the actuator are arranged reverse to those at the other side. In this configuration, magnetic flux density affecting the tracking coils at one side of a holder holding the objective lens increases at one side of the tracking coils, and magnetic flux density affecting the tracking coils at the other side of the holder increases at the other side of the tracking coils. The other configuration has an inner magnet placed inside the focusing coil. In the second configuration, the inner magnets produce magnetic flux density in the tracking direction affecting the focusing coils in addition to magnetic flux density by the magnets. This actuator cancels the deviation of magnetic flux density when it moves the objective lens in the focusing and tracking directions, and therefore the rolling moment is reduced. Experimental results show that the tilt angles of the developed actuator applying electric current to the tracking coils and to the focusing coils are reduced to 20% and 10%, respectively, of the values for a conventional actuator.
