Miniaturized low-power-consumption optical head provided with a state

Abstract

An optical head which includes a movable bobbin having an objective lens and tracking coils for tracking operation, a carriage guided in such a manner to be able to move in the tracking direction and a state transformation mechanism for transforming the state of the bobbin and carriage between a first state, in which the objective lens can move in the tracking direction but the carriage does not move in the tracking direction, and a second state, in which the movable bobbin and the carriage moves in the tracking direction as one body. When effecting a tracking operation, the state transformation mechanism transforms the state of the bobbin and the carriage into the first state, in which the objective lens can move in the tracking direction but the carriage does not move in the tracking direction, and a tracking drive current is then made to flow through the tracking coils to perform the tracking operation. This results in that the objective lens is supported by a system of a single degree of freedom, of which characteristics are determined by the mass of the movable bobbin and the spring constant of the bobbin supporting means. In contrast, when effecting an access operation, the state transformation mechanism transforms the movable bobbin and the carriage into the second state, in which the bobbin and the carriage move in the tracking direction in one united body, and an access drive current is then made to flow through the tracking coils to effect the access operation. Thereby, tracking performance can be increased and a seeking operation can be performed at a high speed. Further, the tracking coil can be used to effect the access drive operation. Thus, there can be less weight of a movable part of the optical head and lower power consumption.