Abstract: A preferred embodiment of the present invention comprises two laser sources of different frequency monochromatic light that are time-multiplexed through a beam combiner to produce composite beams that are steered to a gap between a slider and a disk. A reflected light that includes an interference pattern is then directed to an aperture plate that permits a spot of light to be directly detected by a photodiode which reads the intensity. Measurements of the intensity are taken at respective time-points to sample each laser source, and the measured intensities are compared to determine the slider to disk spacing. Since different frequency light will have different intensity for the same spacing, integer ambiguities can be directly resolved.

Abstract: A process for manufacturing mirrors comprising notching the backside of a plate and etching it from one or both sides. The front side is plated and polished to a flat mirror-like-like surface. The plate is made from glass rods that have been fused together in a bundle and then heated and stretched. One of the glass rods, near the center, is being susceptible to etching while the others are not. Therefore, when the glass rod bundle is drawn out, they will neck-down and become very fine. When the center glass rod has been drawn down to, for example, about five mils in diameter, the neck of the bundle is harvested for the above plates, by slicing out wafers at an angle, e.g., 45.degree.. The etchants will attack the center glass rod, but not those that surround it, due to their chemical properties. The result is a very sharply formed aperture hole of any desired diameter.