I am currently building an LED matrix, and would ideally like to diffuse the light from the LED into maybe a square or rectangle shape(using some sort of border). What would be the best way to do this? I've tried using tracing paper, normal paper, fabric etc. to try and spread out the light, but it always seems to create the 'circle' which comes from the top point of the LED rather than spreading it out.
Any help would be gratefully appreciated.