PURPOSE: To accurately detect asymmetry and to accurately obtain optimum recording power by preventing a reproduced signal level peak value of a testing EFM signal from being erroneously detected due to a damage, etc., on a disk surface.
CONSTITUTION: The testing EFM signal reproduced from the disk is binarized by a slicer 48, and a synchronizing signal of a 11T-11T pattern is detected by a frame synchronizing signal detection circuit. A synchronizing signal detection timing estimation counter 54 estimates the timing when the synchronizing signal is detected next when the synchronizing signal is detected. Further, signal levels of central parts of respective 11T signals of the first half, the second half of the synchronizing signal are subjected to sample-and-hold by sample-and- hold circuits 60, 62. A synchronization decision circuit 56 transfers outputs of the sample.hold circuits 60, 62 to sample.hold circuits 64, 66 when the synchronizing signal is detected at the estimated timing, and averages them by filters 68, 70, and calculates the asymmetry by an asymmetry arithmetic circuit to obtain the optimum recording power by a discrimination circuit 74.
FUJIWARA KAZUNOBU
OSAKABE KATSUICHI
