Method for direct head-disk clearance measurement by slider vibration and fly height calibration

Abstract

A method models and calibrates the fly height of a slider above the disk for disk drives. The calibration scheme uses the Wallace spacing loss equation and laser doppler velocimetry to predict fly height and detect the actual fly height of the slider. The slider is vibrated at selected resonances, such as by capacitive coupling to the disk, and the fly height is gradually reduced. In one version, contact between the slider and disk may be detected using an arm electronics sensor. The amplitude of mean-to-peak, vibration detection is used as an indication of the actual fly height and to calibrate the modeled fly height.

1 . A method of measuring a clearance between a disk and a slider, comprising:
 (a) flying a slider above a magnetic media disk, the slider having a head for reading data from the disk;   (b) maintaining a fly height of the slider relative to the disk;   (c) vibrating the slider such that the slider oscillates relative to the disk and vibrates freely until the slider contacts the disk;   (d) detecting contact between the slider and the disk; and   (e) detecting a mean-to-peak amplitude of the vibration at contact to determine the disk-slider clearance.   
   
   
       2 . A method according to  claim 1 , wherein step (e) comprises a direct measurement with a laser doppler velocimeter (LDV). 
   
   
       3 . A method according to  claim 1 , wherein step (d) comprises detecting contact with an arm electronics sensor mounted on the slider. 
   
   
       4 . A method according to  claim 1 , wherein step (e) comprises converting a detected magnetic signal, using a Wallace Spacing Loss equation, to a nanometer distance with a fly height correction.