Design of photoplethysmography system detecting blood pulse oxygen saturation signal of finger

According to the different ability of hemoglobin and oxyhemoglobin of blood to absorb red and infra-red light,SpO2 was measured by detecting the photoplethysmography signal of red and infra-red light through finger.The measuring system includes the hardware of photoplethysmography probe,microprogrammed control and signal processing block,output unit and its ports,and the software of main program and timer interrupt program.It can detect,process,display and save data automatically.And moreover it can work in real time.So it will realize the capture of subnormal SpO2 signals that appears suddenly and irregularly.