Design and Simulation of Phase Fresnel Lens Array and Microlens Array

在積體成像系統中，包含了微透鏡陣列、感光元件，其中微透鏡陣列可說是整個系統的核心所在，扮演著極其重要的角色，微透鏡陣列能夠擷取外界光線的方向資訊，並將其儲存至感光元件中，以利後續影像處理工作，如景深重建及數位對焦。目前微透鏡陣列的製造方法包含壓印、微影技術、蝕刻、熱回流、噴墨技術等等，在此論文中，我們設計了多種微透鏡及相位型菲涅耳波帶片陣列，並由台灣大學機械系之電腦輔助設計實驗室(CAD Lab)利用雙光子聚合技術製造微透鏡陣列，此技術擁有可製作複雜之高分子結構的優點，再者利用雙光子聚合技術製造相位型菲涅耳波帶片可比折射式微透鏡陣列大量節省製程時間，且菲涅耳透鏡具有重量輕、厚度薄且均一等優點；在本論文中，我們討論不同微透鏡陣列參數如孔徑及微透鏡數量對影像品質之影像，並提出以相位型菲涅耳波帶片做為積體成像中微透鏡陣列的概念；我們提出相位型菲涅耳波帶片及折射式微透鏡陣列之量測及模擬結果。我們也量測並討論CAD Lab製作之增加額外圈數的菲涅耳波帶片；另一方面，為了減少製作微透鏡陣列之成本，我們也發展了可產生元素影像之模擬方法，因此在製作透鏡之前可評估影像品質以達到微透鏡設計之最佳化。Integral imaging is composed of a microlens array (MLA) and a photosensor or CCD. MLA is the key element of capturing the 3D information, which is used to encode the angular information into the photosensor. The 3D information can be applied to image processing, such as depth reconstruction and digital refocusing. Recently, MLA is fabricated by several kinds of methods, including roller embossing, gray-scale photolithography, thermal reflow, and ink-jet methods. In this thesis, we design the several MLAs and PFLs and fabricated by CAD Lab in National Taiwan University using Two Photon Polymerization (TPP) technology. TPP technology offers high resolution, hence the fabrication of complicated micro-structure in polymers is achieved. The effects of microlens parameter such as aperture size and microlens number on image quality are discussed. Due to the advantages of light weight and uniform thin lens thickness, the concept of using a phase Fresnel lens (PFL) array as a microlens array is proposed. The fabrication time of a PFL is significantly reduced compared to a refractive microlens array. The measurement and simulation results of MLA and PFL are presented and discussed. The optical performance and simulation results of supplementary zones-surrounded Fresnel zone plate (SZFZP) are also investigated. Furthermore, a simulation method which can be used to produce elemental image is also proposed. Therefore, the fabrication budget is cost down with this simulation method evaluating the optimized design of MLA