[[alternative]]Lens Design of LED Collimator Using Freeform Surface Approach

碩士電機工程學系[[abstract]]本論文主要的目的在討探LED光學準直透鏡之設計方法與模擬分析。因傳統準直透鏡大都為多個球面透鏡組合而成，除了有增加成本與浪費空間的缺點外，其準直效果也不佳。故本論文提出一個以自由曲面的設計方式設計準直透鏡，此透鏡的特色為一體成型，故沒有傳統組合透鏡的缺點，並可達到成本及空間節省的目的。在光學曲面的設計上，除介紹如何運用自由曲面設計外，同時針對四種幾何問題做詳細分析，並計算出各光學曲面上的切線向量。此外本論文提出兩種自由曲面的建構流程－近似法與精確法，用來計算光學曲面上的點座標，並搭配三維模型建構軟體，建構出兩種不同結構之光學準直透鏡－全反射式透鏡與橢球式透鏡。在光學模擬方面，本論文以理想點光源分別驗證兩種透鏡之準直效果，證明兩種透鏡皆符合原先設計之要求。並以LED晶片光源模擬實際情況，將光線經由準直透鏡投射至兩百公尺遠而直徑為三十五公尺之圓盤偵測面上，光源與偵測面之張角大約為 。在此條件下，兩種透鏡結構分別達到81.7%與88%之光學準直效率。此外並同時分析各種不同模擬參數，包括晶片發光面積、透鏡口徑、光源位置等對透鏡之準直效率的影響。最後再利用光學準直效率之折線圖，估算出所設計的準直透鏡之最大投射距離。 關鍵詞：LED、準直透鏡、光學設計、自由曲面[[abstract]]The object of this thesis is to study the lens design approach to construct an LED collimator and to analyze its optical simulation results. Since most traditional collimator lenses are made from couple pieces of spherical lenses, they have several disadvantages such as higher cost, larger body and worse optical efficiency. This thesis proposes an approach based on freeform surfaces to design the collimator lens. Since the feature of this lens is formed integrately without the drawbacks of conventional assembled lenses, therefore, the fabrication cost and the space can be saved effectively. In the design of optical surfaces, besides the introduction of the freeform surface design approach, four geometric construction problems are analyzed in detail, and the tangent vector to each point on freeform surfaces is also calculated. In addition, this thesis also proposes two construction methods of freeform surfaces－the approximate approach and the precise approach to calculate the coordinate for each point on optical surfaces, and two different collimator lens structures, the TIR (Total Internal Reflection) type and the elliptical type, are constructed in corporation with a 3D-construction software. In the optical simulation, this thesis verifies the collimating performance of these two lens structures based on an ideal point light source and that these two lenses can satisfy the requirement of design is also proved. This thesis also simulates a practical situation using an LED light source chip to project its light rays to a target plane with a diameter of 35 meters and 200-m away from the light source, and therefore the extension angle of the target plane at the light source is or so. Under this condition, these two lens structures can achieve a high optical efficiency of 81.7% and 88% relatively. The effect of various simulation parameters, such as the lighting area of LED chip, the diameter of lens, and the position of light source, on the optical efficiency of the collimator lens is also analyzed. Finally, the maximum projecting distance of the proposed collimator lens is estimated using the plot of the optical collimating efficiency. Keywords: LED, collimator lens, optical design, freeform surface