Noncontact simultaneous dual wavelength photoplethysmography: A further step toward noncontact pulse oximetry

We present a camera-based device capable of capturing two photoplethysmographic (PPG) signals at two different wavelengths simultaneously, in a remote noncontact manner. The system comprises a complementary metal-oxide semiconductor camera and dual wavelength array of light emitting diodes (760 and $880nm$⁠). By alternately illuminating a region of tissue with each wavelength of light, and detecting the backscattered photons with the camera at a rate of $16frames∕wavelengths$⁠, two multiplexed PPG wave forms are simultaneously captured. This process is the basis of pulse oximetry, and we describe how, with the inclusion of a calibration procedure, this system could be used as a noncontact pulse oximeter to measure arterial oxygen saturation $(SpO2)$ remotely. Results from an experiment on ten subjects, exhibiting normal $SpO2$ readings, that demonstrate the instrument’s ability to capture signals from a range of subjects under realistic lighting and environmental conditions are presented. We compare the signals captured by the noncontact system to a conventional PPG signal captured concurrently from a finger, and show by means of a