19 September 2014 Oxygen saturation detection aided with the theory of lock-in amplifier
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Abstract
This paper proposes a method to recover the pulse signal with the theory of lock-in amplifier and calculates the oxygen saturation. The pulse signal is obtained based on the method of Photoplethysmography (PPG). We use a LED as the light source and a photoelectric diode as the receiver to get a measured pulse wave. Because the pulse wave obtained by this method is easily disturbed by motion artifact, we use an electrocardiogram (ECG) signal to aid PPG measurement. Firstly, the ECG signal is processed by the Fast Fourier Transform (FFT) and get the heart rate. Secondly, with the value of heart rate, a typical noise free pulse waveform can be constructed. Finally, we use it as a reference input to get a recovered pulse wave by the theory of lock-in amplifier. Thus, the value of oxygen saturation can be calculated accurately through two recovered pulse waveforms of red (660nm) and infrared (940nm) light. Some volunteers were tested. The correlation coefficient between the experimental data and the data provided by a reference instrument is 0.98, proving that this method has high reliability and utility in motion.
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Manjin Liu, Manjin Liu, Mei Hui, Mei Hui, Ming Liu, Ming Liu, Yuejin Zhao, Yuejin Zhao, Liquan Dong, Liquan Dong, Hong Wu, Hong Wu, Xiaohua Liu, Xiaohua Liu, Zhu Zhao, Zhu Zhao, Yun Feng, Yun Feng, Di Chen, Di Chen, Lei Yang, Lei Yang, Jingsheng Zhao, Jingsheng Zhao, } "Oxygen saturation detection aided with the theory of lock-in amplifier", Proc. SPIE 9216, Optics and Photonics for Information Processing VIII, 921605 (19 September 2014); doi: 10.1117/12.2059755; https://doi.org/10.1117/12.2059755
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