Fig. 2.

Computationally simple axial tracking algorithm based on analysis of the interference spectrum. (A) Interference spectrum captured by the spectrometer at different path length mismatches. (B) The normalized autocorrelation, g₁, of the interference spectrum as a function of lag, in units of Δλ, representing the wavelength shift corresponding to one spectrometer pixel. Note that the smaller path difference has a slower decay rate, and the decay rate can be determined from the normalized autocorrelation at a single lag. (C) The workflow of axial motion tracking, based on the background noise-corrected, normalized autocorrelation. Note that this algorithm does not require a Fourier transform.