本論文提出的非侵入式量測高濃度散射介質中葡萄糖濃度的技術，是建立在擴散光子對密度波(diffused photon-pair density wave, DPPDW)的原理和外差干涉(heterodyne interference)的技術上。雙頻雷射所輸出的雙頻率光束為偏極化態正交且互相關聯的光子對，當光束進入高濃度散射介質後，因為遭受多重散射事件而在散射介質中形成滿足擴散方程式(diffusion equation)的擴散光子對密度波。藉由偵測外差干涉訊號，擴散光子對具有空間同調篩選(spatial coherence gating)與偏極化態篩選(polarization gating)兩個特性，因此能選出較弱散射的光子對並且等效地降低散射效應。此外，由於擴散光子對在散射介質中傳播具有共路徑(common path)與同調偵測(coherent detection)的特性，所以能提升外差干涉訊號的振幅與相位之訊雜比(signal-to-noise ratio)。 隨著散射介質中葡萄糖濃度的增加，溶液的折射率升高，溶液中的懸浮微粒和溶液的折射率不匹配(refraction index mismatch)降低，因此溶液的傳播散射係數會減小。藉由偵測外差干涉訊號的振幅和相位可有效地求得高濃度散射介質的傳播散射係數(reduced scattering coefficient)與吸收係數(absorption coefficient)，進而得知溶液中葡萄糖濃度的變化。In this study, we propose a novel noninvasive glucose detection approach based on diffused photon-pair density wave (DPPDW) and heterodyne interference technique. DPPDW is produced by correlated polarized photon-pairs (PPPs) at different temporal frequencies and a pair of parallel linear polarized states in a multiple scattering medium. Since the heterodyne signal is generated by PPPs based on spatial coherence and degree of polarization (DOP) properties simultaneously, therefore, the spatial coherence gating and the polarization gating are able to select the weak scattering PPPs out of multiple scattering photons in a multiple scattering medium. The signal to noise ratio (SNR) of amplitude and phase detection of the heterodyne signal has been improved by the features of coherent detection and common-path propagation of PPPs in a multiple scattering medium. Adding glucose to a multiple scattering medium will raise the refraction index of the medium and will consequently decrease the reduced scattering coefficient of the medium as a whole. The reduced scattering coefficient and the absorption coefficient are calculated by measurement of DPPDW and then correlate with the change of glucose concentration.
