Abstract: An apparatus and a method for measuring very small separations between a transparent or semi-transparent first body and a second body, wherein one or more light sources produce light that is split into two distinct paths. One path is directed through the first body at two locations, one where it reflects from the interface at the separation to be measured, and another where the second body does not affect the reflection. The second path is directed at a frequency shifter, which shifts the frequency of the light. The two paths are recombined and interfereometric variations of intensity, substantially at the frequency of the shifter, are detected. The difference in phase between the measurement and reference areas with the second body not present is subtracted from the difference in phase between the measurement and reference areas with the second body present. The difference in differences yields the phase change that occurs when the second body is introduced.

Abstract: A slider is mounted to a rotary drive mechanism. The slider is loaded, i.e., moved toward and positioned near a disk surface, by rotary movement of the rotary drive mechanism in a first rotary direction. Similarly, the slider is unloaded, i.e., moved away from the disk surface, by rotary movement of the rotary drive mechanism in a second rotary direction which is the reverse direction of the first rotary direction.

Abstract: Light is focused on an interface between a transparent probe and a surface to be analyzed. The probe is lowered onto the surface using a computer-controlled actuator. Light reflected from the surface of the probe which is closest to the surface and the surface itself recombines, producing interference effects from the spacing between the probe and the surface over a 2-dimensional area. Since the shape of the probe in known beforehand, the profile of the surface can be readily calculated from the 2-dimensional measurement of the spacing between the probe and the surface. This surface profile indicates the roughness of the surface. The surface hardness and other surface properties can be measured by pressing the probe onto the surface. The contact load between the probe and the surface is detected by a load cell. The force with which the probe is being pressed onto the surface is measured using the load cell.

Abstract: The apparatus and method for measuring a small spacing down to contact uses an interferometric fringe intensity calibration to calibrate maximum and minimum intensity of two or more monochromatic or quasi-monochromatic interference patterns caused by a spacing between two articles, one of which is transparent. The intensity calibration is done by measuring maximum and minimum fringe intensity of each color while altering the spacing by at least 1/4 of the wavelength of the light or other electromagnetic radiation being used. The calibration by changing spacing allows the fringe order to be calculated for each wavelength of the radiation being used. This calibration procedure allows the maximum and minimum intensity of the radiation to be known, as well as the fringe order of the interference patterns to be calculated. With the maximum and minimum intensities and the fringe orders known, the spacing is readily calculated from interferometric theory.

Abstract: The apparatus and method for measuring a small spacing down to contact uses an interferometric fringe intensity calibration to calibrate maximum and minimum intensity of two or more monochromatic or quasi-monochromatic interference patterns caused by a spacing between two articles, one of which is transparent. The intensity calibration is done by measuring maximum and minimum fringe intensity of each color while altering the spacing by at least 1/4 of the wavelength of the light or other electromagnetic radiation being used. The calibration by changing spacing allows the fringe order to be calculated for each wavelength of the radiation being used. This calibration procedure allows the maximum and minimum intensity of the radiation to be known, as well as the fringe order of the interference patterns to be calculated. With the maximum and minimum intensities and the fringe orders known, the spacing is readily calculated from interferometric theory.