Patent ID: 8254051

Claim:
A disk drive, comprising: a disk; a head, said head configured to access said disk; a head-slider, said head-slider comprising said head and configured to fly in proximity to a recording surface of said disk; a moving mechanism, said moving mechanism configured to move said head-slider over said disk, and to support said head-slider; and a controller, said controller configured to read out at least one from a plurality of clearance-measurement data strings from said recording surface of said disk using said head, and to calculate a clearance between said head and said disk from clearance-measurement results obtained from a plurality of resolutions with different frequency components; wherein said head is configured to write a plurality of clearance-measurement data strings with differing bit inversion frequencies to said disk; wherein said controller is configured to read out said plurality of clearance-measurement data strings using said head; and wherein said controller is configured to calculate said clearance between said head and said disk from clearance-measurement results obtained from said resolution of said plurality of clearance-measurement data strings.