Spectral-domain optical coherence tomography with dual-balanced detection for auto-correlation artifacts reduction.

We developed a spectral domain optical coherence tomography (SD-OCT) to reduce auto-correlation artifacts (AC) using dual-balanced detection (DBD). AC were composed of the interference signals between different sample tissue depths, and shown up as artifacts in OCT images. This system employed a free-space Michelson interferometer, at the refraction plane of whose beam splitter, the light reflected experienced a π/2 phase shift with respect to the light transmitted. Then two phase-opposed interferometric spectra sharing the same spectrometer optics were obtained simultaneously using two lines of a three-line CCD. This new design was of lower cost compared to the dual spectrometer design reported previously. DBD enabled this SD-OCT to achieve two-fold increase in the interested signal amplitude inherently, and obtain a SNR increase of ~2.9 dB experimentally. To demonstrate the feasibility and performance of this SD-OCT system with DBD, we conducted an imaging experiment using a glass plate to obtain the optimal spectral matching between dual-balanced spectrometer channels. As a result, this SD-OCT achieved AC reduction up to about 9 dB and direct current (DC) term suppression up to about 30 dB by cancelling the identical components between dual-balanced spectrometer channels. The efficacy of AC reduction and DC suppression was validated by imaging the polymer coating of a drug-eluting stent and fresh swine corneal tissue ex vivo. The quality of DBD optimized images was significantly improved with regard to the single-channel images.