So lately I've had trouble illuminating my entire multitouch screen. I have been using a simple IR illuminator I constructed on a breadboard with 16 leds, but that would only light up a circular area in the middle of the screen. I needed something better and more adjustable and here is what I came up with.
I took a small piece of perf board and wired up 24 ir leds, 3 rows of 8 in parallel. I put this perf board in a small radio shack project box. After making two of these, I bent a aluminum bar in a U shape and attached the lights on each side with a nut and bolt so I can adjust them vertically. Finally, I drilled a hole in the bottom of the U and attached it to some floodlamp stands I had laying around. Viola! I made two of the U light assemblies and hooked them both up to the same 12V cpu power supply. They do a nice job of lighting up my entire screen and are easy to adjust. Here's a pic of what one of them look like.
Hopefully this can help somebody out who is struggling with how to build a simple IR illuminator. Oh, and these things were fairly cheap to build, which I find to be very important as my multitouch bill seems to keep growing and growing ;)