A spacing sensor for magnetic disk systems

A sensor based on Frustrated Total Reflection (FTR) for measuring spacing between magnetic disks and sliders has been developed. Theoretical evaluation shows that when polarization and incident angle are properly chosen, this sensor should have twice the measurement range and at least three times the resolution of traditional methods of spacing measurement which use interference. The measurement range of the FTR sensor can be optimized for typical disk-slider spacings (<100 nm) easily, by changing the incident angle of the light. To evaluate its operation, the sensor was fabricated on the side of a glass slider by a lithography technique and spacing was measured. Taking the 20 nm offset caused by the beveled edge of the slider into account, measurement error was less than 1 nm for P polarized light and 10 nm for S polarized light. This sensor could potentially measure spacing between real magnetic disks and ceramic sliders,.