In various embodiments described herein, a display device includes a front illumination device that comprises a light guide disposed forward of an array of display elements, such as an array of interferometric modulators, to distribute light across the array of display elements. The light guide panel may include a turning layer to deliver uniform illumination from a light source to the array of display elements. For many portable display applications, the light guide panel comprises the substrate used in fabricating the display elements. The light guide panel may include additional films as well. The light guide panel, for example, may include a diffuser and/or an optical isolation layer to further enhance the optical imaging characteristics of the display.