The use of digital processing of video images for determining parameters of sessile and pendant droplets

Methods used at different stages of digital processing of video images in studies of surface phenomena are considered. A segmentation method making it possible to detect several objects in an image field with a nonuniform illuminance is proposed; this method is based on dynamic thresholding. Various methods of determining the characteristics of the capillary system under consideration by fitting the parameters of Laplace's equation are discussed. The factors affecting the accuracy of parameter determination for sessile and pendant droplets are analyzed. On the basis of model calculations, the deviations (due to digitization of the interface profile during its digital processing) of the resultant surface tension and contact angle from exact values are estimated. Some experimental applications of the techniques described in the paper are discussed.