Outline of experimental setup.

Experimental setup for the measurement of finger-photoplethysmograms using a conventional transmition-type configuration and an integrating sphere-type with NIR laser light at two wavelengths. (See text for more detailed explanation.) AC = alternating-current component, DC = direct-current component, ECG = electrocardiogram, FPPG = finger-photoplethysmogram, HPF = high pass filter, LD = laser diode, LPF = low pass filter, PD = photo diode, S/H = sample and hold.