Spatiotemporally controlled illumination strategy for event-based imaging velocimetry

Event cameras offer unique advantages for Particle Image Velocimetry (PIV) due to their high temporal resolution and low data redundancy. However, traditional full-field illumination schemes suffer from event overflow at high particle concentrations, a critical limitation that prevents achieving high spatial resolution to resolve fine flow structures. This Letter proposes a novel, to the best of our knowledge, spatiotemporally controlled illumination strategy to overcome this bottleneck by smoothing the event stream and optimizing bandwidth utilization. Two implementations are introduced: line-wise scanning illumination and block-wise scanning illumination. Experiments using a Digital Micromirror Device demonstrated that while full-field illumination encounters severe event overflow at concentrations above 0.005 particles per pixel (ppp), block-wise illumination effectively postpones the onset of overflow to 0.03 ppp. Remarkably, the line-wise illumination completely suppressed event overflow even at 0.11 ppp, enabling robust flow-field reconstruction and significantly lower measurement errors across high concentrations. This work paves the way toward enhanced spatial resolution in event-based PIV and offers a promising paradigm for other event-camera applications requiring improved data throughput.