Figure 4
From: New insights into the origin of remote PPG signals in visible light and infrared
Videocapillaroscopic examination of the finger nail fold using green wavelengths: (a) Setup schematics; (b)Average PPG signal, with indication for systolic maxima (circles) and minima (squares); and super-resolved images of the upper dermis at the (c) peak instants and (d) valleys, respectively (imaging area, about 1.6 × 2 mm; amplification, ×60). The downsized and normalized differential image between (c,d) is a PPG-image (e) which suggests no relation between capillary density and PPG-signal strength. The figure was created by A. Moço.
