<P>PROBLEM TO BE SOLVED: To provide an equalizing method that can stably equalize reproduced signals to a target partial response wave even when the reproduction conditions change in the tilting or the beam diameter when performing PRML detection which is effective in high density reproduction. <P>SOLUTION: Equalization is performed by the least squares method using the predetermined number of samples of the binary data obtained by threshold processing in a Viterbi decoder 3. Even without advance knowledge of the data recorded on an optical disk, the signals can be equalized stably and reproduced with a small error rate without involving unstable factors such as diversions due to external disturbances. <P>COPYRIGHT: (C)2005,JPO&NCIPI 
REPRODUCED SIGNAL EQUALIZING METHOD FOR OPTICAL INFORMATION MEDIUM, AND OPTICAL INFORMATION RECORDING/REPRODUCING DEVICE