Beyond the frame rate: Measuring high-frequency fluctuations with light intensity modulation

TL;DR

This paper introduces Intensity Modulation Spectral Analysis (IMSA), a novel method that overcomes traditional bandwidth limits in spectral density measurements, enabling high-frequency fluctuation detection beyond standard video frame rate constraints.

Contribution

The paper presents IMSA, a new technique that extends the effective detection bandwidth for spectral analysis, allowing measurement of high-frequency fluctuations in video-based systems.

Findings

IMSA enables detection of fluctuations over 10 times higher than Nyquist frequency.

The method successfully quantifies microsphere fluctuations at high frequencies.

Demonstrated with video-tracking of optically-trapped microspheres.

Abstract

Power spectral density measurements of any sampled signal are typically restricted by both acquisition rate and frequency response limitations of instruments, which can be particularly prohibitive for video-based measurements. We have developed a new method called Intensity Modulation Spectral Analysis (IMSA) that circumvents these limitations, dramatically extending the effective detection bandwidth. We demonstrate this by video-tracking an optically-trapped microsphere while oscillating an LED illumination source. This approach allows us to quantify fluctuations of the microsphere at frequencies over 10 times higher than the Nyquist frequency, mimicking a significantly higher frame rate.