Long Working Distance Fiber Probes for Endoscopic Optical Coherence Tomography Imaging

In endoscopic optical coherence tomography (EOCT), compact optical structure is often required for the fiber probe to access lumen tissues through a tortuous path. However, to achieve this, current endoscopic probes often have short working distance and complex fabrication technique. In this study, we report two fiber probes, which can be applied in long working distance endoscopic imaging. The first one is a ball lens probe, which consists of a beam expansion part composed of coreless optical fibers and a focusing and reflecting part composed of half ball lens. This method is a simple and low-cost probe fabrication technique that utilizes the surface tension of the molten material itself to form the ball lens on the fiber tip and creates reflective surface by sanding. The other one is a 3D micro printing probe, which consists of a coreless optical fiber part for beam expansion and a focusing and reflecting part composed of freeform micro-optics easily created by 3D micro printing technology. The freeform micro-optics created by this method can compensate for the influence of the catheter on light focusing, thereby enhancing imaging quality. We apply these two probes into a customized SD-OCT system to test the imaging on infrared cards, tapes, and various biological tissue samples. Both probes achieve imaging at a working distance of 6mm. In the future, the compact design, cost-effective and long working distance of our fiber probe will enable broader applications in more endoscopic catheter applications.