A FIBER OPTIC SENSOR FOR SURFACE-ROUGHNESS MEASUREMENT

A fiber optical interferometer system is described for non-contact mea surement of surface topography. The system employs a fiber optic guide and lens arrangement that forms an interferometric cavity between the lens front face and the test surface. Changes in the surface topograp hy are manifested as phase changes between the light reflected from th e surface and the front face of the lens. An electronic control and da ta acquisition system converts the phase change into a voltage signal proportional to surface height. The system is calibrated and compared with stylus surface profile measurements performed on a standard set o f machined surface samples. Comparison of the amplitude parameter, R-a , shows differences of between 17 percent and 34 percent across the se t of samples, whereas, two spatial parameters, frequency and peak coun t, consistently compare within 1 percent to 12 percent throughout the R-a range: 0.42 mu m less than or equal to R-a less than or equal to 2 .89 mu m.