經由共焦雷射掃描顯微鏡系統掃描一個樣本的斷層影像時，入射光經由物鏡聚焦後進入樣本，當樣本本身或樣本與周圍液體之間有折射率不一致（refractive-index mismatch）的情況，不同入射角度的入射光的光程徑（optical path length）均不相同，因此入射光無法完美地會聚至物鏡的焦點，此為由樣本引入的球面像差（specimen-induced spherical aberration），此球面像差會嚴重地降低共焦顯微鏡系統的光學斷層能力。在本研究當中，我們提出一套極化光子對共焦雷射掃描顯微鏡系統，利用雙頻雷射做為共焦雷射掃描顯微鏡的光源以輸出極化光子對。極化光子對具備共路徑（common-path）的特性，並且結合外差干涉技術，此系統可以有效地降低由樣本引入的球面像差。從實驗結果可以驗證此原理的可行性，並且符合理論的預期。Refractive-index mismatch in conventional confocal microscopy produces severe degradation on axial resolution of sectioning image because the spherical aberration is induced by specimen. In this study, we propose a polarized photon-pairs confocal laser scanning microscope (PPCLSM) in which a two-frequency linear polarized photon-pairs (LPPPs) laser beam is produced. The common-path propagation of LPPPs integrated with optical heterodyne technique can reduce the spherical aberration. Therefore, the better axial resolutions of the sectioning image are produced. In the experiment, a verification and comparison between PPCLSM and conventional confocal laser scanning microscope (CCLSM) on the ability of reduction of spherical aberration induced by cover glass and by slide are demonstrated experimentally. Finally, the ability of PPCLSM which can decrease the spherical aberration based on the common-path propagation of LPPPs is discussed.
