Patent ID: 7663998

Claim:
An information reproduction device, comprising: a frequency difference detection means for detecting a difference in frequencies between a read clock, obtained by applying phase locked loop (PLL) to a reproduction signal read from a recording medium, and a reference clock; an information processing means for performing signal processing on the reproduction signal and outputs a processing status information indicating whether or not the information processing is performed normally; and a frequency monitoring means for monitoring whether or not the frequency of the read clock is normal based on the frequency difference and the processing status information; the frequency monitoring means includes a state determination means for calculating a cumulative count difference value, said frequency monitoring means makes a transition to an OK status indicating that the frequency of the read clock is normal when the processing status information is indicating a normal status based on the cumulative count difference value being lower than an OK status threshold; said frequency monitoring means makes a transition to a NG status indicating that the frequency of the read clock is abnormal when the processing status information is indicating an abnormal status based on the cumulative count difference value exceeding an NG threshold, and returns to an OK status when the cumulative count difference value is below an OK threshold during the NG status.