Solid state based illumination source utilizing dichroic reflectors

摘要

A light sourceÄ50Ü having emissions in a plurality of spectral bands. The simplest light source according to the present invention is constructed from first and second light sourcesÄ51, 52Ü and a dichroic beam splitterÄ54Ü. The first and second solid state light sources emit light in first and second bands of non or only partially-overlapping wavelengths. The dichroic beam splitterÄ54Ü combines light from the first and second solid state light sourcesÄ51, 52Ü by passing light in the first band while reflecting light in the second band to generate light having a spectral content in the first and second bands. The solid state light sourcesÄ51-53Ü are preferably arrays of LEDs, VCSELs, or edge emitting semiconductor lasers. A light source having improved radiance in the green region of the spectrum can be constructed by utilizing first and second solid state light sources that emit in different bands in the green portion of the spectrum. A white light source can be constructed by utilizing a third solid state light sourceÄ53Ü and a second dichroic beam splitterÄ55Ü and by choosing the emission bands of the light sources such that light leaving the second dichroic beam splitterÄ55Ü is perceived as white by an observer when all three solid state light sources are emitting light. This light sourceÄ50Ü has a radiance that is higher than the radiance of each individual solid state light source.