Evaluation of Water Film Thickness on Contact Lens by Improved Reflectometry Technique

We report the evaluation of water film on a contact lens using an improved optical reflectometry technique. A galvanometer scanner is added to an optical reflectometry system for fast measurement beam alignment. Light from a Tungsten Halogen light source travel down a 2x1 fiber coupler, go through the focusing lens and the galvanometer scanner, and light up the water film on the contact lens. The air/water and water/contact lens interfaces reflect the light back to the fiber, where the spectral dependent reflection data is acquired by the fiber coupled spectrometer for analysis. From the reflective spectra, the water film thickness can be calculated using predictor-corrector curve fitting method. In the scanning selection and the curve fitting calculation, a band stop filter is applied to the reflectance spectrum to eliminate data noise.