To track the blobs, I've followed nuigroup.com and I've bought on fnac.com a PS3 Eye camera for 18€ (21€ including shipping). This camera being able to capture 640*480 at 60fps is the perfect low price device you'll want to buy for your Multitouch table.
Be very careful, as there are actually 2 kinds of PS3 Eyes, that you (unfortunately) can't distinguish from, except by taking them appart. As very well exeplained by PeauProduction in that post, one kind has its IR block filter very easy to remove, whilst the other has it almost impossible without breaking the lense.
To clarify a bit, here's the thing :
A PS3 Eye has 4 parts you must have in order to correctly make it track IR light from your fingers :
- The camera (the base)
- A Lense mount
- A lense
- A bandpass filter.
A OEM PS3 camera has the lense mount glued with the lense : if you want to change the lense, you'll have to buy a new mount. But, in the "good" camera, the IR block filter can be removed from the mount. If you chose to do that, you can add the Bandpass filter (or a floppy disk piece) and you'll have a fully fonctionnal IR camera. But if you want to change the lense (i.e. if your table isn't high enough and your camera can't see the whole display), that'd bring you to the second choice : changing the lense mount, and then the lense. If you have the "bad" camera, you'll HAVE to do that anyway.
The lense mount
There are two types of mounts : the m12, which is the best (but arround $20), and a noname. A couple of people including me found perfectly compatible mounts in random webcams. If you find that webcam on eBay (6€), it has a lense mount (which isn't glued !) that you can take appart for your PS3 Eye.
This webcam is worth 6€ on eBay and can be taken appart for the lense mount
Whilst I was waiting for it to be shipped, I've found a Philips webcam (kinda rubbish) that I took appart and - surprise - it also had that lense mount ! I begin to think this is a really common mount...
That webcam also has the compliant lense mount.
The Philips webcam was even better, as you can very easily take away the IR block filter for testing purpose (as you are waiting for the PS3 Eye or some lense to be shipped). As seen on the picture, a simple knife is enough to get rid of it. The IR filter is simple to spot, it has a reddish reflect when you place it under a light.
If you have the "good" PS3 Eye camera, you can also take that filter appart, follow this very well explained process.
The bandpass filter
Once the IR filter taken appart, your camera is able to see IR light. Good start ! Now, the problem is that it will also see visible light... And you will have a massive light pollution : your camera will have some hard time identifying IR blobs from ambiant light.
Thus, you need to have a bandpass filter that will block all light except the IR light. A typical bandpass filter (not that effective though) is a piece of a floppy disk. If you still can find one (good luck!), you'll notice that you can't see through... It blocks visible light, but not IR light : if you press a remote command button in front of it, and look at your modified webcam, you'll see the white IR light through it.
But it isn't that effective, as it will let a big IR spectre go through, and other IR light from your room will still gets you a hard time detecting your blobs.
To solve that issue, you can buy some bandpass filters at Omegabob2 on eBay or at the PeauProduction online store for $24 : a proper bandpass filter will only let specific wavelength go though, and then will considerably reduce the ambiant light. As I bought 780nm lasers, I've bought a 780DF60 bandpass filter for PS3 Eye. 780DF60 means that it will let light at 780nm go through, +/- 60mn, then from 720nm to 840nm (as seen on the following chart).
If you have the "good" PS3 Eye, and want to keep the OEM lense, you don't need this part.
If you have the "bad" one, or want to change the lense (as I do), you'll need to buy one at PeauProduction (arround $20). You'll have to calculate the focal length you need...
I've found on the nuigroup.com forums that that particular fish eye 2.1mm lense worth $6 worked well with PS3 cameras...I've ordered one, and am still waiting for it ! I hope that one is gonna be Ok.
First test with the modified Philips webcam... IR light spotted :D
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