Patent ID: 8514682

Claim:
A reproduction signal evaluation method for evaluating quality of a reproduction signal reproduced from an information recording medium based on a binary signal generated from the reproduction signal using a Partial Response Maximum Likelihood (PRML) signal processing system, the reproduction signal evaluation method comprising: a plurality-of-patterns extraction step of extracting, from the binary signal, a plurality of state transition patterns, which have a possibility of causing a bit error; a differential metric computing step of computing a differential metric, which is a difference of a first metric between an ideal signal of a most likely first state transition sequence corresponding to the binary signal and the reproduction signal, and a second metric between an ideal signal of a second most likely second state transition sequence corresponding to the binary signal and the reproduction signal, based on the binary signal respectively, for each state transition pattern extracted in the plurality-of-patterns extraction step; a low range extraction step of extracting, for each state transition pattern, differential metrics which are not greater than a predetermined signal processing threshold, which is set for each of the plurality of state transition patterns; a low range extraction counting step of counting the number of extractions in the low range extraction step as a count value; an error rate computing step of determining, for each state transition pattern, an error rate predicted based on an integrated value of the differential metrics extracted in the low range extraction step and the count value counted in the low range extraction counting step; a standard deviation computing step of determining a standard deviation which corresponds to a sum of the error rate of each state transition pattern; and an evaluation step of evaluating a quality of the reproduction signal using the standard deviation, wherein the plurality-of-patterns extraction step extracts state transition patterns of the binary signal for which a square of a Euclidean distance between the ideal signal of the most likely first state transition sequence and the ideal signal of the second most likely second state transition sequence is not greater than 14.