I have an old 36-bulb contact printer that is a very low res version of what you say The bulbs are controllable in concentric rings so you can correct for falloff, dodge and burn, etc. Actually it's a feat of clever engineering, a very nice thing. I wouldn't want to think about scaling it to millions of LEDs though! As I mentioned in the other thread, a computer monitor is pretty close to what you want.... and about as close as you will ever get for reasonable money.