Guler Saygun, Ozturk Ozberk, Golparvar Ata, Dogan Huseyin, Yapici Murat Kaya
Department of Electronics Engineering, Faculty of Engineering and Natural Sciences, Sabanci University, Tuzla, 34956, Istanbul, Turkey.
Integrated Circuits Laboratory (ICLAB), École Polytechnique Fédérale de Lausanne (EPFL), 2002, Neuchêtel, Switzerland.
Phys Eng Sci Med. 2022 Dec;45(4):1317-1323. doi: 10.1007/s13246-022-01175-7. Epub 2022 Aug 29.
Point-of-care remote photoplethysmography (rPPG) devices that utilize low-cost RGB cameras have drawn considerable attention due to their convenience in contactless and non-invasive vital signs monitoring. In rPPG, sufficient lighting conditions are essential for obtaining accurate diagnostics by observing the complete signal morphology. The effects of illuminance intensity and light source settings play a significant role in rPPG assessment quality, and it was previously observed that different lighting schemes result in different signal quality and morphology. This study presents a quantitative empirical analysis where the quality and morphology of rPPG signals were assessed under different light settings. Participants' faces were exposed to the white LED spotlight, first when the sources were installed directly behind the video camera, and then when the sources were installed in a cross-polarized scheme. Hence, the effect of specular reflectance on rPPG signals could be observed in an increasing projection. The signal qualities were analyzed in each intensity level using a signal-to-noise (SNR) ratio metric. In 3 of 7 participants, placing the video camera on the same level as the light source led to signal quality loss of up to 3 dB for the range 30-60 Lux. In addition, two fundamental morphological features were analyzed, and the derivative-related feature was found to be increasing with illuminance intensity in 6 of 7 participants.
利用低成本RGB摄像头的即时远程光电容积脉搏波描记术（rPPG）设备，因其在非接触式和无创生命体征监测方面的便利性而备受关注。在rPPG中，充足的光照条件对于通过观察完整的信号形态来获得准确诊断至关重要。光照强度和光源设置的影响在rPPG评估质量中起着重要作用，此前观察到不同的光照方案会导致不同的信号质量和形态。本研究进行了定量实证分析，在不同光照设置下评估rPPG信号的质量和形态。参与者的面部暴露在白色LED聚光灯下，首先是光源直接安装在摄像机后方时，然后是光源以交叉偏振方案安装时。因此，可以在不断增加的投影中观察到镜面反射对rPPG信号的影响。使用信噪比（SNR）指标在每个强度水平分析信号质量。在7名参与者中的3名中，将摄像机与光源置于同一水平导致在30 - 60勒克斯范围内信号质量损失高达3分贝。此外，分析了两个基本形态特征，发现7名参与者中有6名与导数相关的特征随光照强度增加。
