Abstract: An illumination device using an innovative design to provide a uniform, highly concentrated and substantially longitudinal illumination. The device includes, a compound light guide and a light-extracting section with a built-in light-extracting feature. The compound light guide comprises two optically coupled sub-guides. A first sub-guide has a constant cross-section area with a profile optimized for an integral light-concentrating optics, and a second sub-guide has a varying cross-section area for controlling local light flux density inside the light guide and providing assembly means. A light-homogenizing section provided at an input of the light guide improves illumination uniformity at an area close to a light input end of the light guide without displacing a light source from the central normal line of a light-extracting feature.