Wavelength-dependent refractive index measurement of transparent materials via image analysis

Hiroki Nakata; Hanayo Takenaka; Mayuko Koga; Yugo Akabe; Marilou Cadatal-Raduban; Nobuhiko Sarukura; Noriko Chikumoto; Toshihiko Shimizu

doi:10.1063/5.0298021

Wavelength-dependent refractive index measurement of transparent materials via image analysis

Rev Sci Instrum. 2026 Jan 1;97(1):015204. doi: 10.1063/5.0298021.

Authors

Hiroki Nakata¹, Hanayo Takenaka², Mayuko Koga¹, Yugo Akabe³, Marilou Cadatal-Raduban^{3

4}, Nobuhiko Sarukura³, Noriko Chikumoto³, Toshihiko Shimizu³

Affiliations

¹ Graduate School of Engineering, University of Hyogo, Himeji, Hyogo 671-2280, Japan.
² Department of Engineering, University of Hyogo, Himeji, Hyogo 671-2280, Japan.
³ Institute of Laser Engineering, The University of Osaka, Suita, Osaka 565-0871, Japan.
⁴ Unitec Institute of Technology, 139 Carrington Road, Auckland 1025, New Zealand.

PMID: 41528180
DOI: 10.1063/5.0298021

Abstract

A non-destructive image-analysis method for measuring the refractive index and dispersion of transparent materials without surface polishing or complex preparation is introduced. The technique uses a sugar solution of known refractive index as a reference medium. It determines the sample's refractive index by analyzing the disappearance of boundary contrast in charge coupled device camera-captured images. Dispersion is obtained by employing multiple bandpass filters to record measurements at different wavelengths. The method achieves precision in the order of 10-2 and is demonstrated as a proof of concept for evaluating the refractive index of unpolished, irregular, or inhomogeneous materials. It is ideal for the rapid evaluation of fragile, irregular, and complex materials such as glass and crystal optical materials.