Review of Optical Designs for Light-Emitting Diode Packaging

In recent years, light-emitting diodes (LEDs) have attracted tremendous attention for their excellent performances of increased luminous efficiency and improved color rendering for the solid-state lighting application, such as street illumination, display backlighting, and automotive lighting. With the ever-growing attention on energy saving, the luminous efficiency becomes the most fundamental evaluation criterion of the LED design. Moreover, most commercial LEDs are with a circular-symmetry-based radiation pattern, which provides a nonuniform illuminance distribution. In other words, LEDs without packaging design cannot directly meet the requirements of general applications. Therefore, the lighting pattern should be taken into consideration as a key factor. In addition, high-quality lighting always provides uniform color distribution. Optical-design-based LED packaging makes it possible to achieve high luminous efficiency, controllable light patterns, and high color uniformity simultaneously. However, optical designs for LED packaging are confronted with various technical challenges. A deep and comprehensive consideration of existing problems enables the advancement of processes and designs in LED packaging. In this paper, we summarize the recent progresses of optical designs to improve lighting performance for LED packaging. This summarization of recent significant progresses provides a comprehensive understanding of the methods for promoting the development of LED packaging and application technologies.