Disk drive and detection method using pre-pit detection and push-pull signal generation

A method of detecting pre-pits formed on a disk-shaped storage medium, grooves serving as recording tracks being formed in a wobbling fashion on the disk-shaped storage medium, address information being represented by the pre-pits formed on lands between adjacent grooves, the method comprising the steps of:

• generating a push-pull signal from reflected-light information obtained when the disk-shaped storage medium is illuminated with a laser beam;
• comparing the push-pull signal with a reference signal and outputting a comparison result as a pre-pit detection signal;
• counting the number of pulses included in the output detection signal, for each of predetermined periodic intervals;
• and
• changing the reference signal depending on the count value.

A disk drive comprising:

• an optical head for emitting a laser beam so as to illuminate a disk-shaped storage medium thereby writing or reading data on or from the disk-shaped storage medium, grooves serving as recording tracks being formed in a wobbling fashion on the disk-shaped storage medium, pre-pits being formed on lands between adjacent grooves;
• a push-pull signal generator for generating a push-pull signal from reflected-light information detected by the optical head;
• a pre-pit detector for comparing the push-pull signal with a reference signal and outputting a comparison result as a pre-pit detection signal, said pre-pit detection signal including a pulse having a pulse width;
• a noise remover for detecting a noise pulse on the basis of the pulse width of the pulse included in the detection signal output from the pre-pit detector, removing the noise pulse from the detection signal, and output the detection signal including no noise pulse;
• a counter for counting the number of pulses included in the detection signal output from the pre-pit detector or included in the detection signal output from the noise remover, for each of predetermined periodic intervals;
• a controller for changing the reference signal depending on the count value of the counter;
• and
• an address decoder for acquiring the address information represented by the pre-pits, from the noise-removed detection signal.

A method of detecting pre-pits formed on a disk-shaped storage medium, grooves serving as recording tracks being formed in a wobbling fashion on the disk-shaped storage medium, address information being represented by the pre-pits formed on lands between adjacent grooves, the method comprising the steps of:

• generating a push-pull signal from reflected-light information obtained when the disk-shaped storage medium is illuminated with a laser beam;
• comparing the push-pull signal with a reference signal and outputting a comparison result as a pre-pit detection signal including a pulse having a pulse width;
• detecting a noise pulse on the basis of the pulse width of the pulse included in the output detection signal, removing the detected noise pulse from the detection signal, and outputting the detection signal including no noise pulse;
• counting the number of pulses included in the output detection signal, for each of predetermined periodic intervals;
• and
• changing the reference signal depending on the count value.