High-resolution optical coherence tomography over a large depth range with an axicon lens

TLDR

In optical coherence tomography, axial resolution depends on source coherence length while lateral resolution depends on the sampling lens’s numerical aperture, but conventional optics trade lateral resolution for focusing depth. The study aims to incorporate an axicon lens into the interferometer’s sample arm to overcome this trade‑off. The authors integrated a 160° axicon lens into the sample arm of the interferometer. The axicon lens maintained 10‑µm or better lateral resolution over at least 6 mm of depth and produced a focus with nearly constant intensity across that range, outperforming conventional lenses.

Abstract

In optical coherence tomography, axial and lateral resolutions are determined by the source coherence length and the numerical aperture of the sampling lens, respectively. Whereas axial resolution can be improved by use of a broadband light source, there is a trade-off between lateral resolution and focusing depth when conventional optical elements are used. We report on the incorporation of an axicon lens into the sample arm of an interferometer to overcome this limitation. Using an axicon lens with a top angle of 160°, we maintained 10‐µm or better lateral resolution over a focusing depth of at least 6 mm. In addition to having high lateral resolution, the focusing spot has an intensity that is approximately constant over a greater depth range than when a conventional lens is used.