I note in your drawing that the acrylic edge is at an angle, rather than at a 90 degree angle to the surface.  What is the use of that angle?  Does it force more of the light to reflect across the surface of the acrylic?  I wonder if that will assist us in getting clear blobs.

Rather than H-channel, we constructed a wood frame with a lip and an inner channel.  The wires run through the channel, and the acrylic sits on the lip.  A decorative frame sits on top and hides the wiring, but can be easily removed if need be.  I ran reflective tape around the vertical face of the lip.  It wasn’t too hard to put together, and works pretty well.

I tried to ascii-sketch a cross section in this posting, but there was proportional font damage to when it was actually rendered as HTML.  However, I can post pictures if anyone would find it useful.

On this forum , some members have found that either angling the IR LED’s or the plexi-glass can increase the “bouncing” of IR therefore increasing the responsiveness. The angle in the drawing is pictorial only. Based on the IR LED beam width, this angle would change for a better result.

To see for yourself try this link:

FTIR Screen Design Applet .........................

I’m trying to throw together a prototype so that I can learn more about the process.  I have polished my acrylic, purchased my LEDs, modified my webcam, and am ready to put all the LEDs together. 

I like the idea of using the H-channel.  But, I’m having trouble finding the aluminum.  What is a good quick solution that I could use to put together a prototype?

Is there a way to order just a small amount of the H-Channel?  Once you install the LED holders and LEDs’ how do you keep space between the LED tips and the acrylic?  Do you just push the led’s right up to the arylic?

I was able to easily find the right aluminum h-channel for my purposes at this site:

http://www.mcmaster.com/

it’s $17 for a 6’ length

Just search for “h channel”