Measurement Method of Refractive Index for Optical Lenses Based on Curvature Radius Fitting of Small-Sized Aspheric Surfaces

Abstract

The study of the refractive index of traditional lenses is one of the foundational topics in the field of optics. The refractive index of a lens determines its ability to refract and focus light, making it a key parameter in optical design and applications. For the measurement of the refractive index of blind samples of finished lenses, this paper proposes a measurement method based on the use of a focal length measuring instrument and an aspheric profilometer to measure the surface shape data of the front and back surfaces of the lens. This method combines curve fitting algorithms and curvature radius fitting algorithms, ultimately reconstructing the lens model using Zemax and back-calculating the refractive index of the lens. For the samples employed in this paper, the measurement accuracy of the focal length can achieve 1.06%, the fitting accuracy of the curvature radius can reach 0.138%, and the recovery accuracy of the refractive index can attain 6.303 × 10−4%.