Patent ID: 7186004

Claim:
An illumination system comprising: an array of one or more light-emitting sources located in a source plane; a first optical sheet, separated from the source array by a first propagation distance; a first illumination plane separated from said first optical sheet by a second propagation distance; a second optical sheet located at said first illumination plane; and a second illumination plane separated from said first illumination plane, so as to provide substantially uniform intensity output profile, within the illuminated area, versus position across said first illumination plane and to provide substantially uniform intensity output profile versus position across said second illumination plane as well as versus angle within the illuminated area of said second illumination plane, wherein the said optical sheets are light homogenizing optical sheets, each comprising a substantially constant thickness sheet made of transparent material with front and back surfaces, each said front and back surface including a microlens array formed thereon, said microlens array each including a plurality of non-hemispherical microlenses each aligned and registered with a non-hemispherical microlens on an opposite said front and back surfaces, said optical sheet having a sufficient thickness so that said microlenses on opposite said front and back surfaces are separated by a distance substantially equal to the focal length of said microlenses.