Optical design: Chip and packaging

Light-emitting diode (LED) has been extensively applied to general lighting since the luminous efficacy exceeded 100 lm/W. In addition to high energy efficiency, the advantages of fast response, wide color range, narrow bandwidth, compact size, and environmental benefits extend the application of LED to display, communication, and others (Sun et al. 2004; Zukauskas et al. 2002; Schubert and Kim 2005). In regard to a light source with the use of an LED in lighting application, three properties related to the optical property should be addressed. The first is the optical efficiency, the second is the light pattern distribution, and the third is the color consistency. All these three properties can be determined in the chip level, the packaging level, and also the luminaire level. The chip level and the packaging level take the majority to determine the most properties of an LED luminaire. Among these properties, chip-level optics is especially important in intrinsic energy efficiency of an LED. In contrast, the packaging design is more important in color performance, especially for a phosphor-converted white LED In this chapter, the optics in the chip level and the packaging level for a pcW-LED will be introduced and discussed. We will start from light extraction of an LED die and then light source modeling, phosphor modeling, and packaging design to performing high-quality chromatic uniformity.