What is your light source?
Light source is self adhesive LED light strip. The strip is mounted around the inside of the frame. There is a half inch space behind the corian. Light strip is mounted facing the center of the frame to avoid hot spots.
An update on my lithophane project. I tried a different light source. The Star Trek inspired work has a LED light panel as the source. The panel removes shadows caused by internal wires and simplifies the wiring process. The panel does raise the cost of materials from about $17 for electronics to $35, but does provide a more uniform light source.