Three-dimensional measurement of head flying height and attitude using image processing of fringe patterns formed by Michelson laser interferometry

In-situ measurement of head flying height and attitude using image processing of fringe patterns formed by Michelson interferometry is studied. A wide laser beam is applied to illuminated the slider back surface and disk surface simultaneously to create interferometric fringe patterns. Employing the relationship arising between the two fringe patterns, the calculation procedure is formulated to yield the slider's parallel, pitch and roll displacements. Experimental fringe patterns are captured in a single visual field by a high-speed CCD camera. Image processing for a higher signal-to-noise ratio, such as smoothing, filtering, amplification and ridge line extraction is then applied to the image data. Additionally, average processing with respect to multiple fringe lines to produce higher accuracy is successfully applied. Measured values of flying height and pitch and roll displacements are confirmed to be in good accordance with the calculation results, demonstrating excellent applicability of the present method down to the near-contact region.