Ultra low head-disk spacing measurement using dual beam polarisation interferometry

In this paper, a dual-beam normal incidence polarisation interferometer is proposed to measure the flying height or head-disk spacing. Using this inte rferometer, the head-disk spacing can be measured both in magnetic real dis k condition and in glass disk condition. It has the advantage of both the c urrently popular intensity interferometry method and the oblique incidence polarisation interferometry method. With this polarisation interferometer, not only the flying height can be measured down to contact without losing a ccuracy, but the pitch and roll of the head-slider can also be detected dyn amically. The optical parameters of the bead-slider can also be determined. Design details and experimental study are presented. (C) 2000 Elsevier Sci ence Ltd. All rights reserved.