共焦顯微術是一種具有高空間解析度和光學切片能力的重要技術。本研究結合雷射掃描共焦顯微鏡與外差干涉技術建構一套可以有效降低散射效應及球面像差（因樣本折射率不匹配所產生）的三維成像系統。 本論文所提出的共路徑外差干涉共焦顯微鏡是以同時產生雙頻率及正交線偏振光的Zeeman He-Ne 雷射作為系統的光源，此兩種不同頻率的偏振光沿著同一方向傳播，就是本文中所稱的共路徑光子對（photon-pair）。在本研究中，我們量測散射光子對在此系統成像面散射角度分佈的情形，實驗結果證實本共焦顯微鏡在高散射介質中的成像過程中具有過濾多次散射光子及提高影像訊雜比（signal-to-noise ratio, SNR）的能力。同時我們也探討了本顯微鏡在散射介質中的縱向解析度，並對一個浸泡在散射介質中的物體進行取像。另外，對於一般共焦顯微鏡以及本論文所提出的共路徑外差干涉共焦顯微鏡因受觀察樣本與浸潤介質的折射率不匹配所引起的球面像差對軸向解析度的影響，我們提出一些分析並實際以實驗量測之。最後，比較由本論文所提出之顯微鏡和一般雷射掃描共焦顯微鏡所量得的結果，我們可以說本共焦顯微鏡確實比一般共焦顯微鏡優越。 我們認為本論文所提出的共焦顯微鏡之所以比一般共焦顯微鏡優越，乃是由於它同時具備空間濾波閘截（spatial-filtering gating）、極化閘截（polarization gating）、空間同調閘截（spatial-coherence gating）以及共路徑的光子對（photon-pair）等特性。因此，在散射介質中它可以把多次散射光子過濾掉，同時篩選出帶有原來影像資訊的直進光子與弱散射光子。並且能有效的收集弱散射光子而提高系統的訊雜比，進而取得物體在散射介質中的影像，同時也可以應付光學厚度（optical thickness）較大的散射介質。除此之外，由於光子對的共路徑特性使得這些光子對透過光學外差干涉方法所產生的訊號，已相互抵銷因樣本折射率不匹配所產生的波前偏差（wave aberration），因此減少了成像系統的球面像差。Confocal microscopy is a powerful technique because of its high resolution and its abilities of optical sectioning. This research incorporates the optical heterodyne technique in laser scanning confocal microscope (LSCM) to build a three-dimensional imaging system which effectively reduces the scattering effect as well as spherical aberration induced by refractive index mismatch. The common path heterodyne confocal microscope proposed in this research employs a Zeeman He-Ne laser, which emits two orthogonal linear polarized waves of two frequencies simultaneously. These two beams of light travel a common path in the whole setup. The heterodyne signals generated by these two beams after they pass through the scattering media of different concentrations have been measured. The experimental results demonstrate that our setup can filter out multiple scattered photons and increase the ability for image sectioning in the scattering medium. We have also investigated the axial resolution of our setup at different concentrations in the scattering medium. The images have been taken for specimens immersed in the scattered medium. Furthermore, we have analyzed the influence of spherical aberration on the resolution induced by refractive index mismatch between specimen and immersion medium. Experiments have been performed to measure these influences quantitatively. Finally, the performance of our proposed microscope and that of the conventional laser scanning confocal microscope is compared. Our experimental results show that our proposed microscope possesses good ability of spatial-filtering gating, polarization gating, spatial-coherence gating. Therefore, our proposed microscope is able to reject the multiple scattered photons and retain the ballistic photons and weak scattering photons which contain the original image information. The effective collection of the weak-scattered photons increases the SNR of the system, and then acquires the image of the specimen in the scattering medium. As a result, the microscope can look in to a medium of larger optical thickness. Furthermore, because of the common-path feature of the photon pairs, they suffer the same kinds of wave aberration induced by refractive index mismatch, and thus they can cancel each other. The proposed microscope therefore has the ability to reduce the spherical aberration induced by refractive index mismatch.
