Comparison of optical and capacitive measurements of slider dynamics

A simultaneous slider air bearing thickness measurement is made using capacitive and optical techniques. The first technique measures the capacitance between a conducting disk and a probe attached to the slider, and the other measures the optical path length using interferometry. A quartz disk with a transparent conductive coating is used for this experiment. Measurements are made simultaneously at three corners of the slider from DC to 100 kHz. The DC flying height measurements agree to within 7 nm while the AC fluctuations agree to within the noise level of each technique (0.2 nm).