Objective lens driving device and optical disk unit

摘要

In a background-art optical disk drive, it is necessary to improve acceleration generated in an objective lens driving device in order to make an objective lens track a disk rotating at a high speed. This can be achieved either by increasing a thrust force acting on a movable body including the objective lens or by making the movable body lighter in weight. One method for increasing the thrust force is to make permanent magnets larger or use permanent magnets having a large magnetic force. However, this leads to such a problem that the unit becomes larger in size or higher in cost. In order to solve the foregoing problem, an inner yoke is disposed around a beam of light and inside the movable body of the objective lens driving device. Alternatively, an inner yoke having at least two sides substantially parallel with the radial direction of the disk and at least two sides substantially perpendicular thereto is disposed inside the movable body.