Smartphone Pulse Oximetry Using Two-tone Camera-based Photoplethysmography

SpO
2
monitoring is a non-invasive measure of blood oxygen saturation levels, particularly important to monitor respiratory and heart circulatory diseases. Incorporating SpO
2
measurement into smartphones has the potential to improve patient access and cost-effective monitoring of health status. This paper presents a new smartphone camera-based photoplethys-mography technique for peripheral oxygen saturation measurement without external devices. Most existing methods have limitations for medical use due to a lack of accuracy and insufficient validation. Unlike other approaches, the proposed method uses the smartphone frontal camera and two-tone image patterns to control the emitted light spectrum, allowing for calibration and future clinical application. The method was tested on healthy subjects and demonstrated a strong correlation with reference values (r = −0.742). This approach improves camera-based oximetry acquisition and a validation protocol is also proposed for calibration, highlighting its clinical potential.