| 摘要 |
PURPOSE:To measure disk eccentricity including track strain by counting up an optical pickup tracking error signal when an optical pickup crosses a track from the inner periphery to the outer periphery or counts down it when the pickup crosses a track from the outer periphery to the inner periphery, and regarding the difference between a maximum and a minimum counted value as a value corresponding to the quantity of eccentricity. CONSTITUTION:A counter 24 counts up when a light beam crosses a track in the 1st direction and counts down when in the 2nd direction. The counter 24 counts up and down repeatedly according to the direction of the light beam as mentioned above; and a maximum value holding part 26 holds the maximum value of the counter 24 all the time and a minimum value holding part 27 holds the minimum value of the counter 26 all the time. Then, a subtracting part 28 calculates the difference between the both and outputs the number of tracks between the outermost peripheral position 21 and innermost peripheral position 22. For the purpose, the value of the subtracting part 28 is multiplied by track pitch to calculate the eccentricity of the disk. |
