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21 February 2020A time-resolved near-infrared spectroscopy based on CMOS image sensor
Time-resolved (TR) near-infrared spectroscopy (NIRS) offers non-invasive clinical applications in monitoring the blood oxygenation, where absolute values of oxygenated and deoxygenated hemoglobin, and absorption and scattering coefficient, can be obtained. Various detectors have been utilized to realize a TR-NIRS system, such as PMT, SiPM, and SPAD. This paper proposed a prototype NIRS device implemented using a 128 x 128 lock-in pixel CMOS image sensor (CIS) based on the lateral electric field-charge modulator (LEFM) to achieve high time resolution. Preliminary experiments based on the reflectance of an agar phantom with varying absorption coefficient have been conducted and the ability to detect the changes in the absorption coefficient has been demonstrated. The reflectance of the agar phantom is directly observed by the image sensor, which was operated at a time-window of 900 ps with a sensor detection area of 2.9mm2 . The results suggest that a NIRS device using CIS is feasible, which opens the potential of a miniature wearable time-resolved NIRS device.