Phase sensitive Fourier domain optical coherence tomography

Optical Coherence Tomography (OCT) is an imaging technique with high axial resolution in the micro-meter-scale range combined with a high sensitivity allowing for example to probe weakly back-scattering structures beneath the surface of biological tissues up to several millimeters. A major improvement of this conventional technique represents Fourier Domain OCT with a further decrease in image acquisition time and additional sensitivity. The apparatus including appropriate signal processing reconstructs the depth profile from the spectrally resolved light signal generated by a broadband source and an interferometric imaging system. By frequency shifting the light fields with frequency shifting means in the reference and sample arm a phase resolved signal at high speed can be registered. Therefore the reference arm does not rely on arm length changes or delays. The beating signal generated in this way shows high phase stability. The phase of this beating signal is not wavelength dependent, as the frequency shift applied is the same for all wavelengths. Moreover this results in an additional suppression of unwanted auto-correlated distortion as well as an extended depth range.