Normal incidence polarization interferometry flying height testing

In this paper, a dual-beam normal incidence polarization interferometer is presented to measure the flying height or head-disk spacing. It has the adv antages of both the intensity interferometry method and the oblique inciden ce polarization interferometry method. With this polarization interferomete r, not only can the flying height be measured down to contact without losin g accuracy, but also the pitch and roll of the head-slider can be detected dynamically. The optical parameters of the head-slider can also be determin ed. Design details and experimental results are given.