| 摘要 |
<p>PURPOSE: To perform access to a desired position at a high speed by fixing a frequency generator which generates a frequency by the phase change of a spindle motor, and simultaneously controlling a rotational speed and the change of the rotational speed by the frequency generated from this. CONSTITUTION: When a disk is rotated, a phase frequency FGO by the rotation of a disk 48 is outputted from a frequency generator FG. That is, the rotation of a spindle motor is sensed by a magnetic sensing or the like, and the FGO is outputted. The outputted FGO is outputted as a signal for detecting the angle (phase) and speed of the disk 48. The FG is placed on the same axis as the axis of a P/U 50, and when moving the P/U 50 at a sector 54 of the present position to a target sector 56, a microcomputer which controls an optical system calculates the number of tracks between the above mentioned two sectors, and moves the P/U 50 at a high speed. This computer calculates the change of the rotational speed of the spindle motor generated by the movement of this track and a reference speed at the target spot, and transmits it to a speed system control circuit.</p> |
