An apparatus includes a coverlay layer having a void therein. A backing layer is disposed against a first side of the coverlay layer. A transmission layer is disposed against a second side of the coverlay layer opposite the first side such that a chamber is formed within the void between the transmission layer and the backing layer. The transmission layer includes a first area having a first level of light transmissivity and a second area having a second level of light transmissivity that is greater than the first level of light transmissivity. The transmission layer is oriented so that at least a portion of each of the first area and the second area overlaps the void. A light source is positioned in the chamber between the first area of the transmission layer and the backing layer.