Effect of dual-wavelength (visible and near-infrared) light sources on non-contact heart rate detection

Abstract

Image sensors can achieve non-contact detection of heart rate to predict the physiological status of the driver in an automotive driver monitoring system. However, the performance of such methods depends on the intensity of the light source. In this study, the effects of visible (VIS) and near-infrared (NIR) light sources on heart rate measurement are investigated. The custom-built setup employs Complementary Metal Oxide Semiconductor (CMOS) image sensors for visible and dual visible and near-infrared spectra, in addition to the controllable light sources with visible and near-infrared wavelengths. As a reference heart rate, a photoplethysmogram signal from an heart rate sensor is employed. Upon image acquisition, heart rate is estimated based on the facial images with varying intensities of visible and near-infrared light sources under dim light conditions (10-50 lx). Compared to the values obtained using the visible light source alone, the signal-to-noise of the extracted signal increases and the root mean square error of the estimated heart rate decreases when the dual visible and near-infrared light is applied. This study demonstrates that the use of dual visible and near-infrared light sources can enhance the performance of non-contact heart rate measurements, which could be applied to monitor the driver's status under dim light conditions.