Pushing the Limits of Dynamic Full-Field Optical Coherence Microscopy

Abstract

1. Introduction Dynamic Full-Field Optical Coherence Microscopy ( d -FFOCM) has emerged as a powerful label-free tool specifically tailored for live cellular imaging. Unlike conventional OCT, d -FFOCM utilizes temporal fluctuations within the interferometric signal, originating from intrinsic movements of subcellular components, metabolic processes, and other cellular activities. By analyzing these dynamic patterns, d -FFOCM generates enhanced fluorescence-like contrast, revealing cellular morphology and activities that often remain invisible in static OCT images or other label-free methods [1, 2]. This dynamic contrast mechanism effectively suppresses signals from stationary, highly scattering structures (e.g., collagen), thereby highlighting the more active cellular elements. Recent advancements have demonstrated its capacity to resolve cell types and organelles [1-7]. As with any microscopy technique, d -FFOCM can benefit from improvements in spatial resolution and imaging depth, enabling the observation of smaller subcellular structures deeper within tissues. In this work, we utilize objective lenses with NA = 1.25, which yield a measured lateral resolution of 270 nm and an axial resolution of 500 nm [8]. Furthermore, a significant limitation of LEDs, commonly used as light sources in FFOCM, is their large étendue ; although they produce high total power, only a small portion is effectively utilized to illuminate samples, particularly in high-NA systems. To address it, we employ a bright, laser-based white light source capable of delivering sufficient power onto the sample, even with an objective lens of NA=1.25. This setup enabled us to image various fresh, unfixed ex vivo biomedical mouse tissues.