| 摘要 |
PURPOSE:To improve the driving sensitivity of an optical system driver by dividing a coil into the outer and inner circumferential parts of an optical system holder in order to improve the heat radiation effect of the coil and also to increase the allowable current value. CONSTITUTION:When a coil which drives an objective lens holder 2 toward its optical axis is laminated in four layers at a flange part of the holder 2, the winding job is divided into the outer and inner parts of the holder 2. In this case, the coil is divided into two layers 8a and 8b of the outer circumference and layers 8c and 8d of the inner circumference respectively. Thus the number of coil layers is set equal to that of a conventional case in all. Under such conditions, the effective length crossing a magnetic field and the number of coil turns are equal to each other5 among those divided coils together with the same drive current as long as the same magnetic circuit is used. Thus the driving power of the holder 2 is kept constant. The coil surface is directly exposed to outside at both layers 8a and 8d owing to the lamination of coils and therefore the heat of the coil is radiated into the air. While the coil surface has a direct contact with the holder 2 at both layers 8b and 8c and therefore the heat of the coil is radiated to the holder 2 itself. |
