Once we had made a small IR LED array and modified an X-Box Live camera to be an IR Cam, we found that testing for blobs was a pain in our backside. We could get blobs, but not every time… we had too many moving pieces. We figured that it would be easier once we built a frame to hold the LEDs against the acrylic at the right angle and had the screen in a consistent place with respect to the camera. But every time we experienced a problem, we had to wonder: Is it the surface, or the IR array, or the camera. To make a long story short… It just wasn’t a reliable way to test compliant surfaces.
Our next thought was to build an array of visible light LEDs. The thought behind this was that with visible light, we should be able to see the blobs with our eye, and that took both the computer and the camera out of the equation… two fewer moving parts.
The thought of building another LED array was not a pleasant one though. Luckily, Jim had recently been doing experiments in Tele-presence and had a strip of white LEDs left over. Out of pure laziness, we decided to use that instead of building another array from scratch. As a bonus, the strips are a reliable product, so we no longer had to worry about whether we had a bad solder joint (one fewer moving part). We attached the strip to our test screen using scotch tape and we were rewarded with beautiful, and consistent, white blobs… (and that got us thinking why don’t they make these things in IR?)
Anyway, we highly recommend using the white strips for testing and experimenting. They are about $18 a foot, and they are reusable. You can find them at several places around the net, but please buy them from our friend Greg Thorson (since he was nice enough to take a chance on us and produce IR strips for us… which as far as we know had never been made before).
Here you can see a white light test using a sample piece of Rosco and Sulky Solvy as the compliant surface.
