Lights. Camera. Action.

Almost there! Now that the crazy semester is over, we’ll hopefully have a little bit more time to work on this. We received our camera from Unibrain and are very pleased with it so far. The documentation for the Unibrain Fire-i Board Camera, though not “clean” per se, is very helpful and gives you the impression that this device was designed for projects like this. Actually, that’s not too far from the truth as these cameras are designed for use in robotics.

We’ve done some small experimentation to determine the best way to filter visible light from the camera. Many blogs suggest that two fully-exposed negatives placed on top of the lens is a cheap man’s filter, but workable. We’ve found that it does increase contrast and makes blobs more recognizable, but still let’s most visible light through. There are other, more expensive solutions. The first is to use an IR pass filter to only let through a range of IR light (say 800-900 nm). Some suggest using an IR band-pass filter which may provide better results—it would allow only a specific wavelength of light which should be the wavelength of IR emitted by your IR LEDs (in our case, for our Osram SFH485 LEDs, we would get a IR band-filter of 880 nm).

Our acrylic is here also! It is 122×61 cm (48×24 in) and is 10 mm thick (we will be cutting it to a 4:3 ratio, approximately 61×46 cm or 24×18 in). We plan on machining the acrylic to place the LEDs directly into the edges, but first must test with different LED configurations to find the optimal number and placement for our setup.

Also, some great news for the open source multi-touch community: Google Summer of Code received over 42 applications for code projects related to the Natural User Interface Group, seven of which were accepted. The GSoC page contains all the accepted projects and descriptions, but we are very excited for one in particular: the Mac OS X OpenTouch Conversion. For now, we plan to pursue Linux as our main platform for development (and will post soon on how to configure the Unibrain Fire-i on Ubuntu), but the OpenTouch port to OS X would allow us to create multi-touch apps that use Core Animation, the native OS X graphics framework.

Lights. Camera. Action.

The first step towards our physical assembly for the FTIR table has been purchased—we have ordered a pack of Osram SFH485 IR LEDs. Creating a FTIR table requires a lot more to be done to the display surface, as opposed to a DI device where most of the extras are separate from the display.

For our display we are going to use a sheet of acrylic that is 24×18 inches (~ 61×46 cm) and placing the lights along the 24 in. sides. At this point, until we do some tests and more research, we are planning to use about 15 LEDs per side.

We ordered a pack of 100 LEDs from Digi-Key which should give us some extras to create another table or experiment later.

Once we have our our camera and acrylic we plan on doing some tests to see the best number of LEDs to use. From some blog posts we hear 1.5 centimeter apart, from others we hear that you should only need about 12 per side. We’ll see what works best when we get the equipment all set up.

Also, make sure to check out Jason Modisette’s great FTIR Screen Design Applet to help understand and visualize total internal reflection of the infrared light within the acrylic sheet.