DISC DEVICE.

摘要

A magnetic or optical disc device which can correctly follow up the eccentricity of an eccentrically chucked disk and which can immediately follow up the eccentricity of the new disk face when there is a changeover of the disc face being accessed has: a disc, having data tracks provided with uniformly spaced clock marks for providing a timing standard; reproduction means, for reproducing data from the disc; clock sampling means, for extracting a first clock signal outputted by the reproduction means; eccentricity magnitude memory means, for storing a signal corresponding to the eccentricity of the data tracks with respect to the axis of rotation of the disc; clock correction means, including voltage control oscillator means, for, according to the signal corresponding to the eccentricity, causing a second clock signal outputted by the voltage control oscillator means to follow the first clock signal by changing the phase of the second clock signal or the frequency of the second clock signal; and eccentricity magnitude measuring means, for measuring the signal corresponding to the eccentricity from the first clock signal and the output signal of the reproduction means and supplying it to the eccentricity magnitude memory means. The eccentricity magnitude measuring means measures the signal corresponding to the eccentricity by some method such as calculating the number of tracks which the reproduction head crosses or using the non-uniformity of spacing observed in a string of clock pulses reproduced from the uniformly spaced clock marks in the disc.