Synthetic Light-in-Flight
arXiv:2407.07872
The paper presents Synthetic Light-in-Flight (SLiF), a computational technique that uses tunable continuous‑wave lasers and standard CMOS cameras to synthesize ultrafast light pulses via beat‑frequency synthetic wavelengths, enabling picosecond‑scale time‑of‑flight imaging without specialized ultrafast hardware.
Abstract
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.
13 pages, 8 figures and supplementary material