{TAIL ~ The method} 2, wherein the magnitude and phase angle of both the pseudo tracking servo output signal and {HEAD ~ the tracking servo output signal} are identical 
{ TAIL ~ The method } 2 , wherein the magnitude and phase angle of both the pseudo tracking servo output signal and { HEAD ~ the tracking servo output signal } are identical
TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH