One of the most critical parameters encountered in the quest for higher recording densities is minimization of the spacing between the transducer in the slider and the disk over which it flies. As air bearing designers attempt to reduce thisspacing to below one (1) microinch, many of the traditional assumptions related to the aerodynamic models used have come into question. To validate permutations to existing models or to verify new and innovative designs, it is necessary to measure sliders in the flying height domain below one (1) microinch with both accuracy and repeatability. Traditional flying height testers have a fundamental physical limitation in their capability to measure small spacings. A new technique based on polarizationinterferometry provides the capability to measure down to contact with excellent repeatability and verifiable accuracy in the sub microinch region. This unique capability is provided by separating the s & p polarization components of the light from adiode laser so as to produce a signal with real amplitude and a high S/N ratio at contact. This paper describes the details of polarization interferometry and presents a series of test results taken on low flying sliders.
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