Imaging of media lubricant spacing contributions by readback signal analysis

An in situ method for measuring media lubricant spacing contributions in a hard disk drive by analysis of the magnetic readback signal is presented. Amplitude modulation (AM) is mapped over an area of the disk and the image is scaled into equivalent spacing loss using the known transition length and the Wallace spacing loss equation. The first image acquired is used as a reference for all subsequent measurements. Changes in head to media spacing are created by the removal of a localized area of lubricant in the imaged region on the disk. The area is re-imaged and subtracted from the reference in order to measure the resulting changes in head/media spacing. Spacing changes from 0.6 mm to 0.7 mm were measured after either a Freon TF or a trifluoroethanol wash.