From Talbot Bands to No Mirror Terms in Fourier Domain OCT, a Quest on the Fundamental Origin of the Sensitivity Decay with Depth

摘要

We show that the decay of sensitivity with depth in Fourier Domain (FD)-OCT can be explained based on the superposition of wavetrain lengths after dispersion (diffraction). The more coherent the dispersed waves are, the slower the decay of sensitivity. An asymmetry in the decay curve with the optical path difference (OPD) can be introduced via an "intrinsic" delay which has the effect of shifting axially the two wavetrains relative to each other, originating from the object and reference beam of an interferometer. In this way, an equivalent Talbot Bands set-up is implemented, characterized by no mirror terms for the "extrinsic" delay introduced in the interferometer. Such configurations require that the two interfering beams use different parts of the diffraction grating in the interrogating spectrometer. Theory of Talbot Bands is presented and then how this knowledge can be transferred to the field of FD-OCT to achieve A-scans mirror terms free in one step. A theoretical rigorous model and a heuristic model are presented to quantify the Talbot bands.