Flying Height Measurement Based on Phase Comparison Michelson Interferometry Using White Light Illumination

This paper presents measurement of head flying height in hard disk drives using phase comparison Michelson interferometry (PCMI). To suppress interference noise and to further enhance measurement accuracy, low coherent white light was adopted as an illumination source to replace high coherent laser. The captured images and the measured results indicate that the application of white light illumination effectively improves the interference fringe pattern, and the measurement error of extracting the ridgeline can be consequently reduced in comparison with a laser. Sub-10 nm flying height was measured with high accuracy and good repeatability