Low-coherence and broadband confocal refractometry: Reducing the measurement time

Abstract This paper describes the steps taken to improve measurement speed of a combined low-coherence and confocal refractive index system. The instrument measures thickness transparent plates using fibre-based interferometer with line-scan spectrometer. spectrometer allows on-line dispersion which is necessary derive sample t as well both phase group indices np, ng. measurements were performed on six surfaces consisting three glass windows mounted in lens tube. Experimental results show that time 4.4 s for multi-layered object, has total approximately 10.5 mm, can be achieved whilst maintaining an accuracy better than 0.1% ng, t. represents hundredfold improvement over previously published measurements.