Unconventional optical coherence tomography (Conference Presentation)

We have introduced the Master Slave (MS) interferometry method to address the limitations due to the use of conventional FTs or its derivatives in OCT data processing. The novel MS technology replaces the FT operator with a parallel batch of correlators. An electrical signal proportional to the channeled spectrum at the interferometer output is correlated with P masks producing P signals, a signal for each point out of P in the A-scan. In this way, it is possible to: (i) directly access the information from selected depths in the sample placed in the slave interferometer; (ii) eliminate the process of resampling, required by the FT based conventional technology, with immediate consequences in improving the decay of sensitivity with depth, achieving the expected axial resolution limit and reducing the time to display an en-face OCT image, while slightly lowering the cost of OCT assembly and (iii) tolerate the dispersion left unbalanced in the slave interferometer. The lecture will present several developments based on the MS-OCT technology, such as: (a) an equivalent OCT/SLO (scanning laser ophthalmoscopy), where no extra optical channel for the SLO is needed; (b) coherence revival swept source OCT employing the MS tolerance to dispersion: (c) Gabor filtering, where large number of repetitions with different focus adjustments can be performed more time efficiently than when employing FT based OCT; (d) MS phase processing, which opens novel avenues in phase- and polarization-sensitive modalities; (e) achieving the theoretical axial resolution when using a ultra wide broadband source such as a supercontinuum laser; (f) down-conversion OCT that can deliver an en-face OCT image from a sample in real-time, irrespective of the tuning speed of the swept source where the mask signals are generated in real time (by a physical master interferometer) while sweeping the frequency of the swept source.