Patent ID: 7075875

Claim:
A disk evaluation apparatus for evaluating a recording disk on which a modulation signal is recorded, the modulation signal obtained by performing a predetermined modulation processing on information data according to a channel clock, the apparatus characterized by including: information reading means for acquiring a read signal by reading out said modulation signal from said recording disk; an A/D converter for obtaining read sample value sequence by sampling said read signal as timed to a clock having the same frequency as that of said channel clock; amplitude limiter means for obtaining amplitude-limited read sample value sequence by limiting the individual sample values of said read sample value sequence to a predetermined amplitude limit value or less; a high-frequency enhancement filter operative to increase a maximum sample value and a minimum sample value when a gap between said maximum sample value and said minimum sample value of said amplitude-limited read sample value sequence is equivalent to a predetermined distance of a high-frequency wavelength, thereby obtaining high-frequency enhanced read sample value sequence enhanced at the high region thereof; a D/A converter for converting said high-frequency enhanced read sample value sequence to an analog high-frequency enhanced read signal as timed to a clock having the same frequency as that of said channel clock; a lowpass filter operative to extract, from said high-frequency enhanced read signal, only components having frequencies equal to or lower than a predetermined cutoff frequency, thereby obtaining an evaluation read signal; and a binarization circuit operative to binarize said evaluation read signal based on a predetermined threshold value thereby obtaining a binary signal, the apparatus considering a jitter of said binary signal as a disk evaluation value.