arXiv subjects

Stefan Forschner

Publications and source records attributed to Stefan Forschner.

2 recordsLinked to original sources

arXiv2025

Fiber Endoscopy Using Synthetic Wavelengths for 3D tissue imaging

Fiber-based endoscopes utilizing multi-core fiber (MCF) bundles offer the capability to image deep within the human body, making them well-suited for imaging applications in minimally invasive surgery or diagnosis. However, the optical fields relayed through each fiber core can be significantly affected by phase scrambling from height irregularities at the fiber ends or potential multi-mode cores. Moreover, obtaining high-quality endoscopic images commonly requires the fiber tip to be placed close to the target or relies on the addition of a lens. Additionally, imaging through scattering layers after the fiber tip is commonly not possible. In this work, we address these challenges by integrating Synthetic Wavelength Imaging (SWI) with fiber endoscopy. This novel approach enables the endoscopic acquisition of holographic information from objects obscured by scattering layers. The resulting endoscopic system eliminates the need for lenses and is inherently robust against phase scrambling caused by scattering and fiber bending. Using this technique, we successfully demonstrate the endoscopic imaging of features approximately 750micrometers in size on an object positioned behind a scattering layer. This advancement represents significant potential for enabling spatially resolved three-dimensional imaging of objects concealed beneath tissue using fiber endoscopes, expanding the capabilities of these systems for medical applications.

physics.optics↗

arXiv2024

Synthetic Light-in-Flight

Light-in-flight (LiF) measurements enable the visualization of light paths through arbitrary, volumetric scenes, making light-matter interactions at ultrafast timescales visible. Traditionally, LiF measurements require specialized equipment, such as ultrashort pulse light sources and high-speed electronics, often limited by low spatial resolution. Herein, we introduce a novel computational approach, "Synthetic Light-in-Flight" (SLiF), that overcomes these constraints by relying solely on tunable, continuous wave (CW) lasers and off-the-shelf CMOS cameras. From multiple CW scene measurements at different optical wavelengths, we create multiple "synthetic fields," each at a "synthetic wavelength," which is the beat wave of two respective optical waves. These synthetic fields are robust to speckle and environmental fluctuations, enabling us to combine multiple synthetic fields into a "synthetic light pulse" that sections the volumetric scene at much lower instantaneous peak illumination power than a comparable physical light pulse. We experimentally demonstrate the generation of synthetic pulses with 1 ps-scale width and show that their complex synthetic pulse fields can be freely manipulated in the computer after their acquisition, allowing for spatial and temporal shaping of different sets of pulses from the same set of measurements to maximize the decoded information output for each scene. Finally, we show that the recovered time-of-flight information can be used to characterize physical scene properties, such as depth and refractive indices.

physics.optics↗