Two-dimensional measurements of lubricant spreading on diamond-like-carbonsurface using image processing on fringe patterns formed by Michelson interferometry

A Michelson interferometer based on the Linnik microscope configuration has been constituted and applied to the measurement of lubricant spreading on diamond-like-carbon (DLC) surface. Performing image processing on the fring e patterns formed by the interferometer, the lubricant thickness, as well a s the spreading behavior can be investigated This method provides complete line profiles in two dimensions and permits direct observation of the sprea ding phenomena, in contrast to the conventional point-by-point scanning met hod To improve the measurement accuracy, a fringe following technique and a noise suppression technique, were introduced. The fringe following techniq ue successfully prevented a fringe shift over the visual field and thus sup pressed the pseudo phase shift caused by a fringe shift. The spatially fixe d,noise dare to non-uniform laser beams and flaws in optical components was also efficiently suppressed by the noise compensation method. From the cal culation of multiple beam interference in a stratified medium, it is found that reduction in sensitivity due to additional reflections from underlayer s is effectively prevented if the lubricant is observed through a glass dis k using reflections on the back surfaces of the glass and lubricant, instea d of being observed on a disk using the front surface reflections. Utilizin g this advantage, a novel scheme was employed to give maximum sensitivity, in which lubricant was coated on the back side of a glass disk it,hose fron t surface was coated with non-reflecting film and ic hose back surface was sputtered with the proper thickness of DLC. The enhanced resolution attaine d by the new scheme was experimentally confirmed by observing lubricant on rite back surface of the glass disk and the front surface of a magnetic dis k.