On the feasibility of visualizing transient droplet dynamic process with event based imaging

Abstract

Event-based cameras (EBCs) offer the possibility of overcoming the weaknesses of frame-based cameras (FBCs) due to their high dynamic range, low illumination intensity, low costs, and direct edge detection. Accordingly, EBCs are well suited for the investigation of transient processes. EBCs have independently controllable pixels that detect events when the relative change of the detected voltage exceeds (ON-event) or drops (OFF-event) below a set value. In addition, only the detected events together with their spatial and temporal position are stored, leading to a high memory efficiency. Compared to FBCs, the inherent edge detection of EBCs eliminates the need for a threshold based post-processing, while the memory efficiency allows capturing events with different temporal dynamics. In the present study, the feasibility of using EBCs to investigate transient process is assessed. As an evaluation case, droplet impact on a thin film is selected. The experimental setup consists of a side and a bottom perspective. While the bottom perspective utilises a background illumination with an EBC, the side perspective consists of a shadowgraphy setup with a FBC and an EBC for direct comparison. The present study shows that EBCs are suited for visualizing droplet film interaction with a similar or even higher temporal resolution than FBCs. Moreover, the data structure of EBCs offers additional possibilities for data analysis, such as a presentation in the x,y,t-space. With this, the temporal development of the crown, the time of the crown bottom breakdown as well as the trailing edge of the droplet are clearly shown.