Patterned medium inspection method and inspection device

1. A defect inspection method for a perpendicular magnetic recording medium, the perpendicular magnetic recording medium having discrete recording tracks and grooves between recording tracks, comprising:

DC demagnetizing the perpendicular magnetic recording medium;

detecting a reproduced signal from the perpendicular magnetic recording medium after the DC demagnetizing;

removing output fluctuation components caused by the grooves from the reproduced signal using a filter with a prescribed cutoff frequency, and separating a peak output of the reproduced signal; and

comparing the peak output with a prescribed reference signal, and identifying as a defect location a location where the peak output exceeds the reference signal.

2. The defect inspection method of claim 1 , wherein the prescribed cutoff frequency F c satisfies a relation F c ≦(1/T r )/2, T r being a rise time of the reproduced signal for a magnetic head and the perpendicular magnetic recording medium used in the defect inspection.

3. The defect inspection method of claim 1 , wherein the prescribed cutoff frequency F c satisfies a relation F c ≧(1/T 2 )*2, T 2 being a period when a magnetic head traverses the recording tracks due to eccentricity.

4. The defect inspection method of claim 1 , wherein the DC demagnetizing includes one of DC demagnetizing the entire disk surface of the perpendicular magnetic recording medium in a single operation using a permanent magnet or an electromagnet, and DC demagnetizing an inspection track of the perpendicular magnetic recording medium using a magnetic head.

5. The defect inspection method of claim 4 , wherein the prescribed cutoff frequency F c satisfies a relation F c ≦(1/T r )/2, T r being a rise time of the reproduced signal for a magnetic head and the perpendicular magnetic recording medium used in the defect inspection.

6. The defect inspection method of claim 4 , wherein the prescribed cutoff frequency F c satisfies a relation F c ≧(1/T 2 )*2, T 2 being a period when a magnetic head traverses the recording tracks due to eccentricity.

7. The defect inspection method of claim 1 , further comprising:

performing an envelope detection on the reproduced signal; and

detecting a pre-format region in the perpendicular magnetic recording medium using the result of the envelope detection.

8. The defect inspection method of claim 7 , further comprising:

masking the detected pre-format region; and

detecting the defect location in a region outside the masked pre-format region in the perpendicular magnetic recording medium.

9. A defect inspection device for inspecting a perpendicular magnetic recording medium, the perpendicular magnetic recording medium having discrete recording tracks and grooves between recording tracks, comprising:

means for DC demagnetizing the perpendicular magnetic recording medium;

means for detecting a reproduced signal from the perpendicular magnetic recording medium after the DC demagnetizing;

means for removing output fluctuation components caused by the grooves from the reproduced signal using a filter with a prescribed cutoff frequency, and for separating a peak output of the reproduced signal; and

means for comparing the peak output with a prescribed reference signal, and for identifying a location where the peak output exceeds the reference signal as a defect location.

10. The defect inspection device of claim 9 , wherein the prescribed cutoff frequency F c satisfies a relation F c ≦(1/T r )/2, T r being a rise time of the reproduced signal for a magnetic head and the perpendicular magnetic recording medium used in the defect inspection.

11. The defect inspection device of claim 9 , wherein the cutoff frequency F c ≧(1/T 2 )*2, T 2 being a period when a magnetic head traverses the recording tracks due to eccentricity.

12. The defect inspection device of claim 9 , wherein the DC demagnetizing includes one of DC demagnetizing the entire disk surface of the perpendicular magnetic recording medium in a single operation using a permanent magnet or an electromagnet, and DC demagnetizing an inspection track of the perpendicular magnetic recording medium using a magnetic head.

13. The defect inspection device of claim 12 , wherein the prescribed cutoff frequency F c satisfies a relation F c ≦(1/T r )/2, T r being a rise time of the reproduced signal for a magnetic head and the perpendicular magnetic recording medium used in the defect inspection.

14. The defect inspection device of claim 12 , wherein the prescribed cutoff frequency F c satisfies a relation F c ≧(1/T 2 )*2, T 2 being a period when a magnetic head traverses the recording tracks due to eccentricity.

15. The defect inspection device of claim 9 , further comprising:

means for performing an envelope detection on the reproduced signal; and

means for detecting a pre-format region in the perpendicular magnetic recording medium using the result of the envelope detection.

16. The defect inspection device of claim 15 , further comprising:

means for masking the detected pre-format region; and

means for detecting the defect location in a region outside the masked pre-format region in the perpendicular magnetic recording medium.