Measurement of the refractive index and thickness of transparent plates is demonstrated using combined low-coherence interferometry and confocal scanning. The low-coherence measurement provides a quantity related to the group index and the confocal scan provides a parameter related to the phase index. Calculation of both the phase and group indices also requires a measurement of the confocal parameter at multiple wavelengths. This is achieved using a broadband source and a line-scan spectrometer to interrogate different regions of the spectrum. Measurements are made on a range of transparent optical materials with the mean percentage errors of each measurand being 0.08%, 0.06%, and 0.12% for n_p, n_g, and thickness t respectively.

Date Published: 9 May 2018
PDF: 7 pages
Proc. SPIE 10680, Optical Sensing and Detection V, 106801I (9 May 2018); doi: 10.1117/12.2306391

Published in SPIE Proceedings Vol. 10680:
Optical Sensing and Detection V
Francis Berghmans; Anna G. Mignani, Editor(s)