Extending the depth of focus of fiber-optic optical coherence tomography using a chromatic dual-focus design.

Abstract

We report a dual-focus fiber-optic probe designed to extend depth of focus (DOF) in high-resolution endoscopic optical coherence tomography. We exploited the broad spectral bandwidth of a supercontinuum source and, in the fiber probe, the foci of the 750-1000nm and 1100-1450nm inputs were axially chromatically shifted. The interference signals from the two spectral bands were measured with a Si camera-based spectrometer and an InGaAs camera-based spectrometer, respectively. We verified the feasibility of the design using a phantom composed of microparticles and swine small intestine tissue ex vivo. The results showed that a transverse resolution below 5μm over 300μm could be maintained, and that the extended DOF was 2times larger than that of the single focus probe via the use of dual spectral band inputs and a chromatic focal shift.