Fig. 1From: Table model and portable optical sensors for the monitoring of time-dependent liquid spreading over rough surfacesThe schematics of the optical sensor (a) Table model (TM), (b) portable (PS). L is the focusing lens, BS is the beam splitter, D is the single-cell photodiode detector, and α, the angle of incidence. The insert is the diffractive optical element (DOE) spatial filterBack to article page