Development of high speed image acquisition systems for spray droplet characterization for spray characterization based on single-droplet experiments

Accurate spray and droplet characterization is important for increased understanding of the pesticide spray application process. The goal of this study was to develop two image acquisition systems based on single-droplet experiments using a piezoelectric single-droplet generator and a high-speed imaging technique, which will be used in a later stage of this study to evaluate micro and macro spray characteristics and droplet impact behavior. Experiments with different camera settings, lenses, diffusers, and light sources and the resulting image quality parameters showed the necessity of having a good image acquisition and processing system. The image analysis results contributed to selecting the optimal setup for measuring droplet size and velocity, which consisted of a high-speed camera with 6 μs exposure time, a microscope
lens at a working distance of 430 mm resulting in a field of view of 10.5 mm × 8.4 mm, and a xenon backlight without a diffuser. The high-speed camera with a macro video zoom lens at a working distance of 143 mm with a larger field of view (88 mm × 110 mm) in combination with a halogen spotlight with a diffuser was found to have the best potential for measuring macro spray characteristics, such as the droplet trajectory, spray angle, and spray shape.