A number of different approaches have been undertaken by the manufacturers to overcome this difficulty. Efforts to accurately measure the phase refractive index a contact lens directly have for the most part been unsuccessful due to a curved shape of the lens and lens material properties. In this paper we describe a different approach of obtaining a group index dispersion curve with high accuracy of 0.003 or better, and discuss practical implications. We have conducted measurements of the group refractive index (GRI) of hydrogel contact lenses at different wavelengths, from 530 to 670 nm, using time-domain low-coherence interferometer (LCI), based on the super-continuum light source (SCLS). The technique is being developed to overcome sources of error in the current measurement technique. |
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Refractive index
Contact lenses
Optical testing
Interferometers
Phase measurement
Water
Prisms