Fig. 1.

Parallel interferometric near infrared spectroscopy ( $\pi$ NIRS) can rapidly measure the two-dimensional, time-of-flight-resolved autocorrelation, $G_1({\tau }_s,{\tau }_d)$ by parallel detection of the light remitted from the sample. (a) To this end, the spectral interference of the reference and the light scattered from the moving particles is recorded using the Mach-Zehnder interferometer with the tunable laser. The output of the interferometer is projected on the two-dimensional camera, whose pixels act as the individual detection channels (b). The complex signal on each pixel fluctuates in time as the scatterers move (c). The latter is used to estimate the autocorrelation for each channel independently (d). However, each autocorrelation is noisy, so averaging $G_1({\tau }_s,{\tau }_d)$ over many detection channels improves the SNR, enabling faster estimation of autocorrelation.