In-situ fibre-based surface profile measurement system using low coherence interferometer

For many high-value manufacturing applications, advanced control systems are required to ensure product quality is maintained; this requires accurate data to be collected from in-situ sensors. Making accurate in-situ measurements is challenging due to the aggressive environments found within manufacturing machines and processes. This paper investigates a method to obtain surface profile measurements in a spectral-domain, common-path, low-coherence system. A fibre based Low Coherence Interferometer was built and was used to experimentally measure surface profiles. The fringes obtained from interferograms were transformed into the Fourier domain to obtain a trackable peak relating to the surface depth. This has been illustrated with ideal step height measurements and referenced specimens as well as more challenging surface roughness measurements, which have produced complex signal processing issues. This work opens up avenues for a metrology based system where both machining and measurement system can coexist on the same plane, in aggressive environments.