現今對生物醫學成像的要求日漸益增，因此研究人員試圖開發更好的技術，進行非侵入式的疾病檢測和治療。其中，光學斷層掃描技術係利用生物體組織對特定光的散射及吸收程度不同，來重建影像。本研究是透過組織或病害本身的光學特性，來重建正常組織和病變組織之影像。利用光擴散理論並修正同調光的卷積函數，來計算光在組織中的穿透或反射傳播過程。在Fresnel邊界條件下，針對瞬態輻射變換建立一散射、吸收、發射的三維離散坐標。對Fresnel邊界效應於組織和病害的漫反射進行研究，反射和穿透輻射量值在一有厚度的組織層內，其Fresnel反射率是非常重要的。 雷射光源模擬部分為高斯光束. 模擬步驟如下: 一、高斯光束穿透一薄透鏡。二、傳播至一特定光學系統。三、藉由穿透和反射的相關函數，來模擬光傳播在所假設的組織和病變。模擬中發現，當高斯光束傳播至薄透鏡，其光腰和曲率會改變。從第二個模擬中，當高斯光束進入到光學系統去檢測眼角膜時，可得到光從眼角膜出來的繞射圖案分布 透過組織和病變的穿透/反射光束模擬，發現光打至正常組織和病變組織會產生不同繞射圖案。其圖案在正常組織中分布均勻，但在病變組織中，反射或穿透的繞射圖案較不規則。

Nowadays the need of biomedical imaging is growing so fast, researchers try to develop better technologies to provide noninvasive methods in disease detection and treatment. It follows by development of optical tomography to reconstruct transmitted and scattered light into an object inside a media. This research concentrate on lesion imaging on normal tissues using optical properties of tissues and lesion. We modified diffusion theory into a convolution function of coherence condition of light. Convolution can be applied to calculate the reflectance for arbitrary sources on transmission or reflection process in tissues.
The discrete ordinates method is developed to study transient radiative transfer in three-dimensional scattering, absorbing, and emitting media subject to Fresnel boundary condition. The Fresnel boundary effect with diffuse reflection at the tissues and lesion is investigated. The reflectance and transmittance of radiative flux inside the tissues in the slab medium. The adequate incorporation of Fresnel’s reflection is very important.
A light beam in a Gaussian format is used in the simulation for the reason of the closest waveform of laser. There are some steps of simulation in this research. First, diffraction by thin lens takes place. Second, the simulation of diffraction is caused by certain optical systems. Third, the simulation of light propagation into tissues and lesion is determined by the correlation function of the transmission and reflection of light in the phantom tissues and lesion.
From the simulation, we found that only the beam waist and curvature are altered when a gaussian beam with a certain parameter transmit into thin lens. And for the second simulation, when gaussian beam transmitting into optical system to examine cornea, the distribution of diffraction pattern transmitted out from cornea is found. In the simulation of the transmitted and reflected beams at tissues and lesion, it can be seen there are some different patterns between light transmitted in normal tissues and lesion. In normal tissues, the pattern appears more uniformly. But when there is a lesion inside the tissues, the reflection and/or transmission pattern appears more irregular.

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