近红外光谱技术可实现组织中血氧代谢的实时无损伤在体测量, 在生物医学领域得到了广泛应用。 本文利用红光、红外光双光束对指尖进行了基于反射式原理的血氧饱和度(SPO2)检测。通过改变入射光的强度, 并在距入射光1.5cm处采集其反射信号, 观察光强变化对光学体积描记（PPG）信号的影响。实验表明在入射光强不同时, 光到达生物组织层次不同, 所得信号幅度、信噪比都不同。以此提出改变光强法来检测组织不同层次的血氧饱和度。

Near-infrared spectrum technology,which can fulfill the real time and non-invasive in-vivo measurements of blood oxygen metabolizing,was widely used in biomedical field.In this paper, oxygen saturation of blood was detected on the fingertips using red light,infrared light based on the reflection principle.By changing the intensity of incident light and collecting the reflected signals at 1.5cm from incident light, observed the influence of the changing of light intensity on the collected PPG signals.Experiments showed that when incident light intensity was different, the level of biological organization that the light arrived was different ,the signal amplitude and signal to noise ratio were also different .By this means,blood oxygen saturation of different biological organization can be detected by changing the incident light intensity.