Overcoming the Nyquist limit with intensity modulation spectral analysis

Abstract

Power spectral density measurements of any sampled signal are typically restricted by both acquisition rate and frequency response limitations of instruments. We present a new method called Intensity Modulation Spectral Analysis (IMSA) that circumvents these limitations, extending the effective bandwidth of potentially any measurement device. We demonstrate this for the specific case of video imaging, where oscillating an LED illumination source allows us to quantify fluctuations of an optically-trapped microsphere at frequencies over 10 times higher than the Nyquist limit.