Francis, DanielHallam, Jonathan M.Tatam, Ralph P.2023-09-182023-09-182023-09-04Francis D, Hallam JM, Tatam RP. (2023) Low-coherence and broadband confocal refractometry: Reducing the measurement time, Measurement Science and Technology, Volume 34, Issue 12, December 2023, Article Number 1252040957-0233https://doi.org/10.1088/1361-6501/acf334https://dspace.lib.cranfield.ac.uk/handle/1826/20227This paper describes the steps taken to improve the measurement speed of a combined low-coherence and confocal refractive index measurement system. The instrument measures the refractive index and thickness of transparent plates using a fibre-based low-coherence interferometer with a line-scan spectrometer. The spectrometer allows on-line dispersion measurement which is necessary to derive the sample thickness t as well as both the phase and group refractive indices np, ng. The measurements were performed on a sample with six surfaces consisting of three glass windows mounted in a lens tube. Experimental results show that a measurement time of 4.4 s for the multi-layered object, which has a total thickness of approximately 10.5 mm, can be achieved whilst maintaining an accuracy of better than 0.1% for np, ng, and t. This represents an approximately hundredfold improvement over previously published measurements.enAttribution 4.0 Internationalhttp://creativecommons.org/licenses/by/4.0/confocalrefractometryrefractive index measurementlow-coherence interferometrydispersionpeak detectionArticle1361-6501