Use of a fiber optic displacement probe as a surface finish sensor

A series of tests is described that correlates the output of a fiber optic-based displacement sensor with the surface finish and material characteristics of a variety of targets. Nickel-plated targets with a range of surface finishes were examined, and the corresponding sensor sensitivities computed. For common machining processes, the sensivitity decreases with increasing surface peak-to-valley roughness. Material effects are examined by preparing a variety of samples made from different materials using the same polishing techniques. In this way, the relative effects of material and surface finish on the probe's sensivity are examined. The results indicate that the fiber optic probe is capable of discriminating between both material and surface finish variations, and shows promise as an in situ diagnostic tool for use in precision fabrication processes.