2mm catheter design for endoscopic optical coherence tomography

A biophotonics catheter was conceived with collimation optics, an axicon lens, and custom design imaging optics yielding a 360 degree scan aimed at imaging within concave structures such as arteries and lung lobes. The large depth of focus is necessary to image a long-depth-range sample with constant transverse resolution in optical coherence tomography (OCT). There are two approaches to achieving constant invariant resolution in OCT: Dynamic focusing or Bessel beam formation. This paper focuses on imaging with Bessel beams. The Bessel beams may be created with axicon optics which can be used instead of a conventional focusing lens in the sample arm of the OCT interferometer. In this paper we present the design of a 2mm catheter for optical coherence endoscopy with resolution of about 5 micron across a depth of focus of about 1.6mm. Importantly, we investigated the fabrication of a 800μm diameter axicon lens and the associated lateral resolution obtained over a long depth range in our OCT system, compared to the same OCT system using a conventional lens.