Patent ID: 7301871

Claim:
A device for detecting a signal on a defect disc, said device comprising: a servo control unit handling related electromechanical devices of said device; a preamplifier receiving data from a lens and generating an RF signal for data process, servo control signals for said servo control unit and various signals for defect detection; a slicer receiving and digitalizing said RF signal so as to generate digitalized RF signal; a phase lock loop (PLL) synchronizing said digitalized RF signal to a system clock and counting the length of said digitalized RF signal; a decoder decoding the length of said digitalized RF signal to a host; a defect detection unit receiving said various signals for detecting different kinds of defects to set corresponding defect flag signals, wherein said defect detection unit includes means for ADefect 1 detection, means for EFMDefect detection, means for RPDefect detection, means for Interruption detection, means for ADefect detection, and means for DSPDefect detection; and a logic combination unit running a suitable logic operation on said defect flag signals for detecting a particular defect; wherein said defect detection unit further receives eight to fourteen modulation (EFM) signals from said slicer and said PLL; wherein said means for EFMDefect detection further includes: comparing data length of each said EFM signal in a data frame with a first predetermined data length, and setting a second corresponding flag signal when more than a first predetermined number of EFM signals have a data length shorter than said first predetermined data length; comparing data length of each said EFM signal in said data frame with a second predetermined data length, and setting said second corresponding flag signal when more than a second predetermined number of EFM signals have a data length longer than said second predetermined data length; comparing data length of each said EFM signal in said data frame with a third predetermined data length, and setting said second corresponding flag signal when more than a third predetermined number of EFM signals have a data length longer than said third predetermined data length; and resetting said second corresponding flag signal after more than a fourth predetermined number of EFM signals have a data length that is between said first and said second predetermined data lengths; and wherein said second predetermined data length is greater than said first predetermined data length, and said third predetermined data length is greater than said second predetermined data length.