Surface profile analysis using a fiber-optic low-coherence interferometer

Several optical measurement principles have proven their potential for high-resolution surface measurements. Among a few others, white-light interferometry has proven its capability for the measurement of technical surfaces, but yet, white-light interferometer systems cannot be miniaturized enough e.g. for the measurement inside small boreholes. In this work, a fiber-optic measurement system is described. Since the measuring principle is based on lowcoherence interferometry (LCI), the system provides non-contact surface measurements with nanometer accuracy. We present a system set-up for surface profile acquisition as well as the application of the system for the determination of roughness and waviness parameters. An outstanding feature of the proposed system is the miniaturized fiber-optic sensing probe, which is built up in all-fiber design. With a probe diameter down to 800 ?m, the system can be used for measurements inside small cavities, e.g. bearings or injection nozzles. Beam shaping is realized with graded-index (GRIN) fibers. Conclusively, the results of evaluation measurements are compared with ISO 5436-1 type A and D measurement standards.