Patent ID: 8159918
Filing Date: 2012-04-17
Classification: G11B

Abstract:
1. 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 pattern extraction step of extracting, from the binary signal, a specific state transition pattern which has 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 of the state transition pattern extracted in the pattern extraction step; a threshold setting step of computing an average value of all differential metrics computed in the differential metric computing step and setting the computed average value as a signal processing threshold; an extraction step of extracting a differential metric which is not greater than the predetermined signal processing threshold set in the threshold setting step; a mean value computing step of determining a mean value of differential metrics which are not greater than the signal processing threshold and extracted in the extraction step; a standard deviation computing step of determining a standard deviation which corresponds to an error rate predicted from the mean value; and an evaluation step of evaluating a quality of the reproduction signal using the standard deviation.