Compact biomedical time-domain diffuse optical spectroscopy using a commercial LiDAR sensor

Miniaturising time-domain diffuse optical spectroscopy (TD-DOS) is limited by the cost and complexity of photon-timing instrumentation. We demonstrate TD - DOS using a commercial LiDAR module integrating a 940 nm VCSEL, SPAD detector and timing electronics. A light-guide modification establishes a 20 mm source–detector separation. Using photon-count and mean-time measurements, we retrieve absorption and reduced scattering coefficients from MEDPHOT phantoms with repeatability of 1.96% and 1.55%, respectively. Forearm measurements at 4 Hz detect reversible absorption changes during cuff occlusion. These results demonstrate the feasibility of compact, low-cost TD-DOS using mass-produced LiDAR hardware.