Discriminating between protrusion defects and recess defects on a disk recording medium
View Patent ↗An apparatus is disclosed comprising a thermal sensor operable to detect at least one protrusion defect and at least one recess defect on a disk, the thermal sensor operable to generate a sensor signal. An attack time of the sensor signal is measured when the thermal sensor passes over one of the protrusion defect and the recess defect, and the protrusion defect is discriminated from the recess defect based on the attack time.
1. An apparatus comprising:
a thermal sensor operable to detect at least one protrusion defect and at least one recess defect on a disk, the thermal sensor operable to generate a sensor signal; and
control circuitry operable to:
measure an attack time of the sensor signal when the thermal sensor passes over one of the protrusion defect and the recess defect; and
discriminate between the protrusion defect and the recess defect based on the attack time.
2. The apparatus as recited in claim 1 , wherein the control circuitry is further operable to:
measure an amplitude of a pulse of the sensor signal when the thermal sensor passes over one of the protrusion defect and the recess defect; and
discriminate between the protrusion defect and the recess defect based on the attack time and the amplitude of the pulse.
3. The apparatus as recited in claim 2 , wherein the control circuitry is further operable to discriminate between the protrusion defect and the recess defect based on a ratio of the amplitude to the attack time of the pulse.
4. The apparatus as recited in claim 1 , wherein the control circuitry is further operable to:
measure an interval of a pulse of the sensor signal when the thermal sensor passes over one of the protrusion defect and the recess defect; and
discriminate between the protrusion defect and the recess defect based on the attack time and the interval of the pulse.
5. The apparatus as recited in claim 4 , wherein the interval of the pulse is a decay time of the pulse.
6. The apparatus as recited in claim 4 , wherein the control circuitry is further operable to discriminate between the protrusion defect and the recess defect based on a ratio of the interval to the attack time of the pulse.
7. The apparatus as recited in claim 1 , wherein the control circuitry is further operable to:
sample the sensor signal;
accumulate samples of the sensor signal when the sensor signal exceeds a threshold; and
measure the attack time in response to the accumulated samples of the sensor signal.
8. A method of detecting defects on a disk, the method comprising:
generating a sensor signal by detecting at least one protrusion defect and at least one recess defect on a disk;
measuring an attack time of the sensor signal when detecting one of the protrusion defect and the recess defect; and
discriminating between the protrusion defect and the recess defect based on the attack time.
9. The method as recited in claim 8 , further comprising:
measuring an amplitude of a pulse of the sensor signal when detecting one of the protrusion defect and the recess defect; and
discriminating between the protrusion defect and the recess defect based on the attack time and the amplitude of the pulse.
10. The method as recited in claim 9 , further comprising discriminating between the protrusion defect and the recess defect based on a ratio of the amplitude to the attack time of the pulse.
11. The method as recited in claim 8 , further comprising:
measuring an interval of a pulse of the sensor signal when detecting one of the protrusion defect and the recess defect; and
discriminating between the protrusion defect and the recess defect based on the attack time and the interval of the pulse.
12. The method as recited in claim 11 , wherein the interval of the pulse is a decay time of the pulse.
13. The method as recited in claim 11 , further comprising discriminating between the protrusion defect and the recess defect based on a ratio of the interval to the attack time of the pulse.
14. The method as recited in claim 8 , further comprising:
sampling the sensor signal;
accumulating samples of the sensor signal when the sensor signal exceeds a threshold; and
measuring the attack time in response to the accumulated samples of the sensor signal.