10.1117/2.1201307.005002 Multifunctional LED packaging for simple, color-tunable spotlights Ivan Moreno and Nayeli Rodriguez Combining multiple total internal reflections and segmented diffuse reflection enables a spherical lens package to mix and project light from different color LED chips. Light-emitting diodes have become increasingly common in re- cent times, and users are continuously finding new applications for LED light, which provides unique features such as color- tunable illumination. The color of illumination is easily tuned because LED sources may be integrated with small color LED chips, and their color output may be manipulated without inef- ficient filters. The color controllability of LEDs is very attractive in applications such as downlighting, spot lighting, and enter- tainment, architectural, floodlight, and show lighting, where a narrow beam is projected at a distance. It is not surprising that almost every entertainment stage, building, and monument is now brightly lit with colored LED light. However, multicolor-chip LEDs are non-homogeneous color sources. When projection optics are added, undesirable patterns such as spatial and angular inhomogeneities or strong color sep- aration usually appear. Simultaneous light projection and color mixing is challenging because most collimators separate colors, and most color mixers spread the light beam. Recently, we pro- posed and demonstrated novel optics for multicolor LED spot- lights that used a short, straight, highly reflective lightpipe, a thin volume scattering diffuser, and a compact total internal re- flection (TIR) collimating lens. 1 Another newly developed optics system uses minilenses arranged on both the outer and the in- ner surfaces of a hollow dome that covers the LED chips. 2, 3 This dome mixes colored light, which can then be collimated using additional optics. Although these optics mix and project colored light at a distance, they are secondary optical elements that are added to the encapsulating package. 1–3 We have now developed novel multifunctional LED packag- ing to simultaneously mix and project color light within the Figure 1. (a) Side view and (b) front view of the multifunctional en- capsulating lens with red, green, and blue (RGB) LED chips that are surrounded by a diffuse mirror. encapsulating lens for simple, color-tunable spotlights. 4 The LED package fulfills three optical functions: light extraction, beam projection, and color mixing. The multifunctional encapsulating lens is a transparent sphere with a small diffuse mirror (see Figure 1). Colored LED chips are embedded within a spherical lens, and a section of the sphere that surrounds the chips is mirrored with a scattering reflector. 5 LED chips may be embedded in the dielectric sphere or at- tached by an index-matched material. The diffuse mirror may be added by roughening and then reflective-coating a section of the sphere. Of the light emitted by the LED chips, only that emitted in a narrow cone escapes the sphere, 5 and the remain- der is trapped inside it by TIR, almost without loss of energy (see Figure 2). These trapped rays may be scattered in all directions by a diffuse mirror, giving that light another chance to escape, but only in the forward direction. Ideally, repeated TIR will con- tinue until all the light emitted by the LEDs is projected outside of the encapsulating lens. Colored light is mixed by light circling continuously inside the sphere, like mixing a drink in a cocktail Continued on next page