發光二極體於功能性頻譜照明之研究

Abstract

隨著近年發光二極體(Light emitting diode, LED)的快速發展，多種LED頻譜組合的LED系統已充分具有應用潛能，可根據不同操作目的策略性的調制其複合頻譜能量分布。以一般照明為例，對於一目標色溫，LED系統可藉由頻譜調制提升整體效率與演色性，並拓展適用的環境溫度範圍。延伸到智能照明，則可根據使用者對照明色溫變化的需求調整到對應的頻譜，同時維持系統高效能運作。在醫療照明上的應用，需要更著重於頻譜在溫度與電流變化下的可預測性。 然而，一般而言高功率單色光或螢光轉換的LED，其SPD的變化相對於接面溫度與驅動電流為非線性的關係，因而增加了系統頻譜優化的困難度，導致上述的應用目標難以達成。本論文基於目前市面上商用的LED元件，以現有的製程與材料為基礎，針對各終端應用發展一種LED頻譜調制最佳化的解決方案，建立精確頻譜模型與完整的優化設計流程。 本論文提出將一般非完全對稱的LED頻譜分解成雙高斯函數，準確的預測LED頻譜在不同溫度與電流下的行為，並將此模型推展到螢光粉轉換白光LED (phosphor-converted white LED)。 本論文並嘗試以不同角度切入，成功引入透鏡幾何光學系統設計的概念，針對複合LED照明系統SPD提出相對應的完整設計流程: (1) 初始系統, (2) 邊界條件, (3) 優化, (4) 價值函數分析, (5) 判斷, 與 (6) 容忍度分析。最終以此技術分別應用於低功率與高功率LED照明系統，實現色溫可調、適用環境溫度廣泛、演色性佳的高效率照明設計。

With the rapid progress in light-emitting diode techniques, all kinds of lighting purposes can be achieved by strategically manipulating the spectral power distributions of LEDs clusters. For example, in general lighting there is a fundamental tradeoff between the efficiency and color rendering quality, where an optimal boundary (the Pareto Front) will be produced. By optimizing the composite spectrum, the LEDs lighting system can be operated alongside the boundary. When the spectral-controllable technique is utilized to fields of intelligent illumination, the color temperature can be adjusted in accordance with end demands. As to the medical lighting, the spectral distortion will be predictable with respect to variant ambient temperature and drive current. In this dissertation, a novel methodology for spectral manipulation has been proposed, including a well-defined spectral model and six optimization steps. The spectral model employing the double-Gaussian function can closely estimate the practical spectrum that is imperfectly symmetric and depends on the junction temperature. For the optimization, the concept in imaging system design has successfully been adopted to develop a composite spectral process. The proposed algorithm would be applied to the low power and high power cluster, respectively, to achieve the color-turntable systems with high efficiency, high color rendering property as well as wide operation window at ambient temperature.