Disk evaluation device

Abstract

The invention has an object to provide a disk evaluation apparatus capable of performing a highly reliable disk evaluation even on a recording disk on which information is recorded in high density. Amplitude-limited read sample value sequence are obtained by limiting read sample value sequence to a predetermined amplitude limit value, the read sample value sequence obtained by sampling a read signal read out from the recording disk as timed to a clock having the same frequency as that of a channel clock. Where a gap between a maximum sample value and a minimum sample value of the amplitude-limited read sample value sequence is equivalent to a predetermined distance of high-frequency wavelength, the maximum sample value and the minimum sample value are increased thereby to obtain high-frequency enhanced read sample value sequence enhanced at the high region thereof. The high-frequency enhanced read sample value sequence are converted to an analog high-frequency enhanced read signal as timed to the clock having the same frequency as that of the channel clock. Only components having frequencies equal to or smaller than a predetermined cutoff frequency are extracted from the high-frequency enhanced read signal so as to obtain an evaluation read signal. The evaluation read signal is binarized based on a predetermined threshold value to obtain a binary signal, which is outputted as a disk evaluation value.