Abstract
We report on a new swept source polarization sensitive optical coherence tomography scan engine that is based on polarization maintaining (PM) fiber technology. The light source is a Fourier domain mode locked laser with a PM cavity that operates in the 1300 nm wavelength regime. It is equipped with a PM buffer stage that doubles the fundamental sweep frequency of 54.5 kHz. The fiberization allows coupling of the scan engine to different delivery probes. In a first demonstration, we use the system for imaging human skin at an A-scan rate of 109 kHz. The system illuminates the sample with circularly polarized light and measures reflectivity, retardation, optic axis orientation, and Stokes vectors simultaneously. Furthermore, depolarization can be quantified by calculating the degree of polarization uniformity (DOPU). The high scanning speed of the system enables dense sampling in both, the x- and y-direction, which provides the opportunity to use 3D evaluation windows for DOPU calculation. This improves the spatial resolution of DOPU images considerably.
Highlights
Optical coherence tomography (OCT) has been introduced two decades ago [1] as a noninvasive modality for imaging transparent and translucent tissues with resolution of a few μm [2,3]
The light directly backscattered by the stratum corneum (SC) is in a random polarization state, which is clearly observed by the random color distribution of pixels within this layer in the retardation and axis orientation images
This can be observed in the degree of polarization uniformity (DOPU) image (d) which shows very low DOPU values within the SC
Summary
Optical coherence tomography (OCT) has been introduced two decades ago [1] as a noninvasive modality for imaging transparent and translucent tissues with resolution of a few μm [2,3]. Several dermatologic applications of OCT were reported (see, e.g., [6,7,8]) and the effect of wavelength for different purposes of skin imaging was analyzed [9]. Other tissues of interest for OCT imaging are those accessible by endoscopic probes, like the mucosa of the gastro-intestinal tract [10,11] and vessels [12,13]. Several applications of endoscopic OCT have been reported, ranging from Barrett’s esophagus [14] to differentiation of various types of plaques in vessel walls [15]
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