Wide-field Intensity Fluctuation Imaging

The temporal intensity fluctuations contain important information about the light source and light-medium interaction and are typically characterized by the intensity autocorrelation function, g 2 ( τ ). The measurement of g 2 ( τ ) is a central topic in many optical sensing applications, ranging from stellar intensity interferometer in astrophysics, to fluorescence correlation spectroscopy in biomedical sciences and blood flow measurement with dynamic light scattering. Currently, g 2 ( τ ) at a single point is readily accessible through high-frequency sampling of the intensity signal. However, two-dimensional widefield measurement of g 2 ( τ ) is still limited by camera frame rates. We propose and demonstrate a 2-pulse within-exposure modulation approach to break through the camera frame rate limit and obtain the quasi g 2 ( τ ) map in wide field with cameras of only ordinary frame rates. Highlights The quasi intensity autocorrelation function can be measured at almost arbitrary time lags Cameras of ordinary frame rates are sufficient for the measurement Illumination within the camera exposure is modulated by an acoustic optical modulator using two short pulses