Compact Time-Domain Diffuse Optics System Based on CMOS Technologies for Fast Acquisitions of Heartbeat-Induced Absorption Changes

This work introduces a novel compact time-domain diffuse optics (TD-DOs) system based on CMOS integrated circuits for being potentially used in noninvasive tissue characterization and physiological monitoring. The system incorporates a ~800 nm emitting laser diode and a 256-channel single-photon avalanche diode (SPAD) line sensor, offering high-throughput data acquisition. It offers remarkable capabilities for noninvasive investigations of diffusive media for biological and nonbiological applications. To enhance system performance, an alignment method of the TD curves based on cross-correlation maximization is proposed and validated under internationally agreed protocols, such as MEDPHOT and nEUROPt. Finally, fast oscillations in optical properties corresponding to the heartbeat have been detected, showcasing the potential of the system for real-time physiological tracking. The results display the potential of the proposed compact TD-DO system, paving the way for the implementation of wearable instruments capable of noninvasively tracking fast physiological dynamics with high accuracy and robustness.