Axicon lens for high-resolution optical coherence tomography over a long focus depth

In optical coherence tomography (OCT), axial and lateral resolutions are determined by the source coherence length and numerical aperture of the sampling lens, respectively. While axial resolution can be improved using a broadband light source, there is a trade-off between lateral resolution and focus depth when conventional optical elements are used. In this paper, we report on the incorporation of an axicon lens into the sample arm of the interferometer to overcome this limitation. Using an axicon lens with a top angle of 160 degrees, 10 gm or better lateral resolution is maintained over a focus depth of at least 6 mm. In addition to high lateral resolution, the focusing spot intensity is approximately constant over the whole focus depth.