The sensor is an important part of the oximetry. An ideal sensor can improve the quantity of the signal . After the analysis in theory, we get the optimal source-detector space, and design new type of pulse oximetry sensor, which makes the detecting signal have least dependence on changes in scattering properties of the tissue. The sensor in this paper consists of laser diode(LD) coupled with fiber in the center as light source and ring-like silicon electric cells with 660nm center wavelength at ?(0.4-0.8cm) and 940nm center wavelength at ?(0.8-1.2cm). The design has many advantages: (1) powerful photoelectricity signal and high Signal-to-Noise (SNR),(2) influence of unconscious movement reduces; (3) considering the skin tissue as homogenous media is more reasonable. The paper also discusses the light path length distribution, and makes revision to the formulation given by Lambert-Beer law.
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