An optical irradiation device incorporating a cluster of LEDs arranged so that shaped facets of adjacent LEDs come together to increase the packing density of LEDs in the cluster. A light guide collects light emitted by the LEDs. Two or more light guides and LED clusters may be arranged in series to produce a single light beam. A heat pipe is provided to conduct heat away from the LEDs. The heat pipe may be annular and contain an inner storage space for batteries or the like.