Principle components (Click links for product info):
$35 PS3 Eye Camera (Recommended but any decent webcam will work)
$20 IR bandpass filter
$200 5-meter dimmable IR LED Strip
$1000 Any recent/decent computer (PC/MAC)
$1000 Any projector >2000 lumens (NEC NP410W)
$40 Front surface mirror
$80 Abrasion resistant acrylic sheet (23" x 35" x 0.236")
$130 Rear projection acrylic sheet (23" x 35" x 0.118")
$145 EndLighten acrylic sheet (23" x 35" x 0.394")
Software (Click links for downloads):
$free CCV (Used to turn images into blobs)
$free CL-Eye Platform Driver (For PS3 Eye camera)
$free Multi-Touch Vista (Optional Multi-Touch TUIO driver for Windows integration)
$? Windows 7 (Recommended)
Written by Justin Klaassen, Duke University B.S.E. 2012
Sponsored by the Duke Library
Step 1: What Is a Multi-Touch Surface?
Step 2: How Does It Work?
1) Touch surface (Abrasion resistant acrylic)
2) Diffuser/Projection layer (Rear projection acrylic)
3) EndLighten acrylic
Step 3: Build a Computer
Example components used in our rig:
Intel Core i5-660 Clarkdale 3.33 GHz
ASUS P7H55D-M EVO Micro-ATX Motherboard
A-DATA 4GB (2 x 2GB) PC3 12800 Memory
XFX HD-567X-YNFC Radeon HD 5670
Step 4: Modify the Camera
In order for the PS3 Eye camera to work, the IR filter needs to be removed and an IR bandpass filter needs to be put in its place. The IR bandpass filter ensures that only the IR light with the utilized wavelength makes it into the system. Therefore it is important that the IR bandpass filter's centering wavelength matches that of the IR LEDs present in the IR strip used for illuminating the surface. A video guide created by Peau Productions for modifying the PS3 Eye camera can be found below.
Step 5: Prepare the Acrylic
If it is possible, I recommend laser cutting the EndLighten layer since that will automatically polish the edge to perfection. If a laser cutter is not an option, then automotive sandpaper will do the trick. Start with 600 grit (lower if the saw cut is rough) and sand each edge until they are perfectly smooth. Finish each of the sides with 1000 grit. Finally, polish the edges with a plastic polish (Brasso will work too). Notice, the edges will still appear milky at this point, this is normal for EndLighten acrylic.
You do not need to polish the other two layers, and I actually recommend that they remain rough that way no IR light can shine into them. The rear projection layer should be placed directly on top of the EndLighten layer. This layer will act as a diffuser for the projector, that way the projector does not simply shine directly though the surface at the user. The abrasion resistant layer should be placed on top of the rear projection layer. This layer is important since it protects the other more expensive layers and is the layer that the actual user will be touching.
Step 6: Attach IR Strip
Step 7: Alignment, Alignment, Alignment
First place the projector under the surface, with a slight angle of elevation so it is not projecting onto anything directly in-front / below it. Next setup the front surface mirror so that it reflects the projector onto the acrylic layers above. A front surface mirror is a necessity since an ordinary mirror will distort the image reducing the clarity of the image projected onto acrylic surface. At this point the image will probably look more like a trapezoid, adjust the keystone on the projector until a perfect rectangle is achieved. You also may need to move the projector forwards or backwards, or the acrylic layers up and down in order to achieve the image size you desire.
Lastly, position the camera so it faces directly upwards towards the acrylic layers. The camera should be placed directly in front of the projector under the center of the surface so it can pick up the entire desired area.
Step 8: Calibration and Testing
CCV is an open-source program that processes the IR image picked up by the camera and turns them into blobs (TUIO events). These events can then be used by programs to allow the user to interact. Once CCV is up and running, click on the use camera option to begin receiving input from your PS3 Eye camera. Now experiment by touching the surface and watching to see what blobs are picked up in the Tracked view. Play with the "Image Threshold" and other settings until the desired blobs are achieved.
Once that is complete, complete the "Calibration" mode in order to map pixels on the projected image to points picked up by the camera.
A complete guide to calibrating and testing your surface can be found here.
Step 9: Package It
I will add additional steps with detailed plans of my enclosure once I have finished building it.