High speed full range imaging with harmonic detection swept source optical coherence tomography

Abstract

A complication of Fourier domain optical coherence tomography (OCT) methods, such as spectral domain and swept source OCT, is the complex conjugate ambiguity due to inverse Fourier transform of real-valued data. As a result, the image is symmetric to the zero plane, and only half of the theoretical imaging depth range is used to avoid overlapping mirror images that confuse the image. We have previously demonstrated harmonic detection in a video-rate spectral domain OCT system using a high speed line scan camera. Harmonic detection removes the complex conjugate ambiguity by providing the real and imaginary components of the spectral interferogram. In this work, we show that harmonic detection is easily applied to swept source OCT to remove the complex conjugate ambiguity while maintaining the imaging performance of the original swept source instrument. Harmonic detection swept source OCT allows simultaneous experimental determination of the real and imaginary components of each spectral interferogram without the need to measure consecutive A-scans at differing phase. This harmonic detection swept source optical coherence tomography system exhibits 110 dB sensitivity, up to 55 dB dynamic range, ≥ 50 dB complex conjugate rejection, and operates at the full 16 kHz sweep rate of the swept source laser for real-time video rate imaging.