Coded Strobing Photography : Compressive Sensing of High-speed Periodic Events

We show that, via temporal modulation, one can observe a high-speed periodic event well beyond the abiliti es of a low-frame rate camera. By strobing the exposure with unique sequences within the integration time of each frame, we take coded projections of dynamic events. From a sequence of such frames, we reconstruct a high-speed video of the high frequency periodic process. Strobing is used in entertainment, medical imaging and industrial inspection to generate lowe r beat frequencies. But this is limited to scenes with a detect able single dominant frequency and requires high-intensity lighting. In this paper, we address the problem of sub-Nyquist samplin g of periodic signals and show designs to capture and reconstruc t such signals. The key result is that for such signals the Nyquist r ate constraint can be imposed on strobe-rate rather than the sen sorrate. The technique is based on intentional aliasing of the f requency components of the periodic signal while the reconstr uction algorithm exploits recent advances in sparse representati ons and compressive sensing. We exploit the sparsity of periodic si gnals in Fourier domain to develop reconstruction algorithms that are inspired by compressive sensing.