A two-dimensional full-frame illumination assembly is formed, in a preferred embodiment, by coupling light into the edges of a document platen which has been modified by applying a white segment pattern to the bottom platen surface. The coupled light is totally internally reflected within the platen body except for the area covered by the segment pattern. Light encountering the segments is reflected upward towards the document support surface to provide the required document illumination. The light reflected by the document passes back through the screen segment pattern and is projected by a conventional lens or a full-frame, two-dimensional, short focal length lens array onto a photosensitive surface such as a photoreceptor belt.