| 摘要 |
PURPOSE:To exactly correct a tracking error, by providing a magnetic field generation means consisting of 4 yokes and 4 coils, and supplying a current corresponding to a tracking error signal indicating a relative position shift, to said 4 coils, so that an objective lens is displaced against its optical axis and information track. CONSTITUTION:When a magnetic field A by a magnetic field generation means is a closed loop which passes through the first-fourth yokes 25-1-25-4, and a pair of magnetic members 24, 24', the magnetic field intensity becomes equal on the right and left of the optical axis of an objective lens 21, therefore, not only its adjustment is unnecessary but also it can be manufactured easily. Also, by a current corresponding to a tracking error signal which is supplied to the first-fourth coils 26-1-26-4, magnetic fields C-1-C-4 which are generated in these coil parts are turned toward the reverse directions mutually on the right and left, therefore, a tracking control having high accuracy can be executed without being influenced by a leakage magnetic flux. |
