EE3P3D: Event-based Estimation of Periodic Phenomena Frequency using 3D Correlation

We present a novel method for measuring the frequency of periodic phenomena, e.g., rotation, flicker and vibration, by an event camera, a device asynchronously reporting brightness changes at independently operating pixels with high temporal resolution. The approach assumes that for a periodic phenomenon, a highly similar set of events is generated within a specific spatio-temporal window at a time difference corresponding to the phenomenon's period. The sets of similar events are detected by 3D spatio-temporal correlation in the event stream space. The proposed method, EE3P3D, is evaluated on a dataset of 12 sequences of periodic phenomena, i.e. flashing light and vibration, and periodic motion, e.g., rotation, ranging from 3.2 Hz to 2 kHz (equivalent to 192 - 120 000 RPM). EE3P3D significantly outperforms published methods on this dataset, achieving a mean relative error of 0.1%.