Digitally balanced detection scheme in multiple reference optical coherence tomography

Digitally balanced detection (DBD) has been studied in Fourier domain optical coherence tomography systems to improve sensitivity. We report a technical advancement in a multiple reference optical coherence tomography (MR-OCT) system with the implementation of the DBD technique. We used a free-space, polarization-based balanced detection configuration, which is scalable and suitable for miniaturization. The efficiency of common-mode noise rejection is limited in free-space systems due to the non-uniform illumination of the sensors. We show that recording the signals separately and balancing them in the digital domain improves common mode rejection and signal quality. The application of the DBD scheme for MR-OCT achieves an average sensitivity improvement of 5 +/- 0.5 dB over its analogue balanced detection counterpart. We also show that DBD improves the contrast on images of Scotch tapes and mouse eyes.