Local thickness and wave velocity measurement of wavy films with a chromatic confocal imaging method and a fluorescence intensity technique

This work presents two different methods for measuring the thickness of wavy films. The first one is a new non-intrusive technique called “chromatic confocal imaging method” which uses two optical properties—the confocal image and the chromatic aberration of a lens. The accuracy of this technique depends on the optical components, the local gradient of the film thickness and the accuracy of the refractive index used. The second method for simultaneous measurements of film thickness and wave velocity is based on a fluorescence intensity technique. Film thickness and wave velocity measurements of silicone films with different viscosities are presented for Reynolds numbers from 2 to 700 and various inclination angles. The experimental data agree well with the results from published experimental and theoretical studies.