| 摘要 |
PURPOSE:To enable accurate measurement of eccentricity by reproducing a signal by a reading magnetic head, separating two signals of different frequency from the reproduced signal by resonance circuits and making the level difference of two signals the amount of deviation from the center of the track. CONSTITUTION:A signal read out by a reproducing head 1 is amplified to a processable level by a gain control amplifier circuit 2, and an unnecessary high frequency noise is removed by a low-pass filter 3. Then respective signals are separated by the first and the second resonance circuits 4, 5 having recording signal frequency f1, f2 as resonance frequency. Further, it is converted to DC level by passing the first and the second envelope detection circuits 6, 7, and eccentricity output is obtained by finiding the difference between the two signals by a differential amplifier circuit 8. For off-track, it is represented as DC value from zero level, and for eccentricity it is represented by AC value, and the amount of eccentricity and the state of eccentricity in one rotation of a magnetic disk are reproduced in real time. |
