An illumination assembly that includes a light guide and a plurality of light sources operable to direct light into the light guide is disclosed. The light sources have a center-to-center spacing of at least 15 mm, and a distance between a primary emitting surface of at least one light source of the plurality of light sources and the input surface is no greater than 1 mm. The assembly further includes a structured surface layer positioned between the plurality of light sources and the input surface. The structured surface layer includes a substrate and a plurality of structures on a first surface of the substrate facing the plurality of light sources. The assembly further includes a plurality of extraction features operable to direct light from the light guide through an output surface of the light guide.