A New Optical Surface Microprofiling Instrument

An optical surface microprofiling instrument is described in this paper. The instrument is an interferometric device capable of measuring the the microtopography of a precision surface along a single scan line. A 25 millimeter. scan can be accomplished in less than one minute with the present hardware. The vertical resolution of the instrument is on the order of 10 Angstrons. The lateral resolution is diffraction limited and corresponds to a few micrometers. Surface profile data are output in the form of analog voltages that can be readily digitized by a computer for further analysis, if necessary. The microprofiler is a compact unit that requires no elaborate vibration isolation. Since the test is non-contacting in nature it is a non-destructive test. The instrument can potentially generate surface profile data for large samples. Numerous techniques exist for measuring the microtopography of precision surfaces. A brief overview will highlight the characteristics of the commonly used methods. This discussion will set a background against which the performance of the surface microprofiling instrument can be compared. Examples of surface profile data produced by the instrument for a variety of samples will be presented.