Development and Application of High-speed and Wide-field Functional Swept Source Optical Coherence Tomography

Abstract

Recent advances in optical coherence tomography (OCT) have significantly broadened their utility in biomedical imaging, particularly for the diagnosis and monitoring of vascular-related and microstructural diseases. However, clinical OCT systems remain constrained by limited imaging speed, shallow ranging distance, narrow field of view (FoV), and the lack of robust functional imaging capabilities. These limitations hinder broader in vivo clinical applications of OCT. In this study, we develop a high-speed, long-range, wide-field swept-source OCT (SS OCT) system based on a 600 kHz micro-mlectro-mechanical system vertical-cavity durface emitting laser (MEMS-VCSEL) laser, designed to deliver high-fidelity morphological and functional imaging. To overcome the depth limitation inherent in conventional k-clock acquisition, we develop a multi-channel delay sampling technique that splits the analog OCT signal into N-channel time-delayed electrical paths. This method increases the effective k-space sampling density without altering k-clock triggering, thereby doubling the imaging depth without compromising acquisition speed or resolution. To further enhance imaging performance, we introduce the concept of electrical dispersion, which arises from the nonlinear phase response of electronic components operating under high-speed k-clock triggering. A global k-space compensation algorithm is proposed to mitigate this distortion, and a vector field-based distortion correction technique is implemented to restore spatial fidelity in wide field scans. Together, these methods enable high-quality structural and optical coherence tomography angiography (OCTA) imaging across a lateral FoV of 42 × 42 mm² and an extended axial range of 36 mm. To address challenges in imaging samples with complex surface topography, such as the oral cavity, we propose an adaptive contour tracking and scanning strategy. This approach integrates an electrically tunable lens and motorized optical delay line with real-time surface profiling to maintain focus and SNR across curved surfaces. Experimental validation confirms improved image consistency and flow visualization across large and irregularly contoured regions. Finally, we incorporate a novel fiber-based polarization-sensitive OCT (PS-OCT) system based on the platform. To address the instability of the input state of polarization in single-input fiber configurations, we introduce a real-time Stokes vector feedback mechanism that dynamically stabilizes incident circular polarization at the sample surface. This innovation enables reliable birefringence imaging under wide-field and handheld conditions. Together, these system-level advancements result in an OCT platform capable of high-speed, long-range, wide-field, and functionally enhanced imaging. The proposed system demonstrates significant potential for clinical applications in oral health assessment and other settings requiring comprehensive, real-time evaluation of tissue structure, microvasculature, and optical anisotropy.