Patent ID: 8169868

Claim:
A method for detecting surface defects in patterned media comprising the steps of: irradiating a laser beam onto a surface of a rotating patterned medium; detecting reflected light from the surface of the patterned medium by an optical receiver, and converting the reflected light to an analog electrical signal; converting the analog electrical signal to a digital signal by an analog/digital converter; distinguishing between a data area and a servo area based on a profile obtained by sampling the digital signal; determining the presence or absence of a defect by a predetermined threshold with respect to the distinguished data area; obtaining a differential waveform by taking a difference between the profile of the distinguished data servo area and a master servo area profile prepared in advance with synchronizing a servo area at the first point after passing the slice for detecting the servo area or at the peak point; and determining the presence or absence of a defect based on a predetermined threshold with respect to the obtained differential waveform.