Super-resolution particle imaging velocimetry

The spatial resolution of conventional high-image-density particle image velocimetry (PIV) is determined by the size of the interrogation volume, which is typically a fraction of a millimetre. An improved method of PIV analysis is proposed in which the ultimate resolution of PIV is determined by the smaller of the mean spacing between particles and the displacement of the particles between light pulses. Since these distances must be smaller than the interrogation spot size in the high-image-density limit, the new procedure is referred to as super-resolution. The method combines correlation analysis of the group of particles in a spot with sub-interrogation-spot particle tracking. The theory of the procedure is described and evaluated using Monte Carlo simulations. The feasibility of enhancing resolution significantly is demonstrated by re-analysing turbulent flow PIV data reported by Urushihara et al. (1993). The in-plane resolution has been improved from 250 to 100 mu m.