A novel optical method in micro drop deformation measurements

A novel method was developed to determine the deformation of a micro drop on a substrate. The principle of the method is based on the scattering of parallel fringes pattern from the deformed droplet. Because only a very few components are needed together with a conventional laser Doppler anemometry (LDA) transmitting unit, the newly developed method is very easy to be implemented. Within the geometrical optics approach, it is possible to reconstruct the profile of a non-spherical micro drop from the scattered interference fringes. The spatial frequency of the fringes was analyzed using fast Fourier transform (FFT). The validation experiments for this method in the determination of micro drop deformation which is affected by gravity, capillary force and surface tension were performed and the results are agreed well with the theoretical analysis.