Figure 5: Organic optoelectronic pulse oximetry system.
(a) Red and green OLEDs are placed on subject’s finger and transmitted light is collected with one OPD pixel placed below the finger. (b) Hardware block diagram for the system set-up—a microcontroller acts as the data acquisition and processing unit. OLEDs are triggered and controlled using general-purpose input/output port and DAC pins, and the OPD signal is recorded using the ADC of the microcontroller. A two-stage amplifier between the OPD and ADC removes the d.c. part from the PPG signal and amplifies the pulsating PPG signal. (c,d) Simultaneous oximetry measurements with a commercially available inorganic oximeter probe and the organic oximeter probe, respectively. The PPG signal was obtained using red and infrared light for the commercially available probe (c) and using red and green light for the organic probe (d). Heart rate (HR; magenta line in c,d) was obtained by timing the systolic peaks in the PPG signals. The ratio of the transmitted light at two wavelengths (Ros; blue line in c,d) is converted to arterial blood oxygen saturation (SaO2; yellow line in c,d) using Beer–Lambert’s law in conjunction with an empirical correction.
