Authors: Jakub Kolář, Radim Spetlik, Jiri Matas
Abstract: We introduce a novel method for measuring the speed of periodic events by an event camera, a device asynchronously reporting brightness changes at independently operating pixels. The approach assumes that for fast periodic events, in any spatial window where it occurs, a very similar set of events is generated at the time difference corresponding to the frequency of the motion. To estimate the frequency, we compute correlations of spatio-temporal windows in the event space. The period is calculated from the time differences between the peaks of the correlation responses. The method is contactless, eliminating the need for markers, and does not need distinguishable landmarks. We evaluate the proposed method on three instances of periodic events: (i) light flashes, (ii) vibration, and (iii) rotational speed. In all experiments, our method achieves a relative error lower than ±0.04%, which is within the error margin of ground truth measurements.
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