Abstract
We propose and demonstrate high-index elliptical epoxy-lensed fiber probes designed specifically for endoscopic common-path (CP) swept-source optical coherence tomography (OCT) imaging inside wet tissues. The high-index epoxy lens uses a beam expansion region of a few hundred microns, which is capped with a spherical surface mounted at the end of an optical fiber. The probe is designed to operate inside wet tissues and shows improved performance over a long imaging depth, compared to bare or simple half-ball-lensed fiber probes. It allows optimal CP-OCT imaging in wet tissues by providing a stable reference power level and optimal beam waist for a long imaging depth. We have fabricated an array of these probes and one with a beam expansion region length of 288 μm and with a lens surface radius of 61 μm exhibiting 25-dB signal-to-noise ratio improvement compared to a bare fiber probe at 1.5-mm distance in water. The proposed probe is tested using a phantom sample comprising several layers of tape in water. The OCT images show that the probe is capable of high-resolution imaging over a distance of 1.5 mm.
Highlights
Compact all-fiber optical coherence tomography (OCT) probes allow insertion into small and tight areas of the body, enabling catheter-based endoscopic imaging
It has been shown that common-path (CP) swept-source OCT (SSOCT) allows the use of a disposable probe of an arbitrary length
Lee et al.: Common-path all-fiber optical coherence tomography probe based on high-index
Summary
Compact all-fiber optical coherence tomography (OCT) probes allow insertion into small and tight areas of the body, enabling catheter-based endoscopic imaging. To overcome the strong divergence of bare fiber probes, various lensed probe systems have been proposed and demonstrated These include fused coreless fiber,[9,10] ball lens,[11,12,13,14] GRIN lens,[15] and conical-frustum tip.[16] While most of them work well for standard OCT configurations, they do not work well for CP setups, especially in vitreous media (i.e., water). We designed and fabricated elliptical highrefractive-index epoxy-lensed fiber probes that exhibit long working distances and large depths of focus (DOF) in vitreous media (i.e., water) compared to standard bare or halfball-lensed fiber probes. The endoscopic OCT-distal sensors were tested for OCT B-mode imaging using a phantom target comprising several layers of tape to confirm the improved performance of the proposed lensed fiber probes
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