A couple of researches...

It's been more than a year now that I started to look into Multitouch technologies. I was indeed very keen on getting to know more about it, and could'nt wait to start building my own table. Of course, like almost everyone, I wanted it to be able to do everything : blob recognition, object tracking, fiducial tracking... But that was getting more and more complicated.

I joined the nuigroup.com community (the main reference for everything about MT technologies) and spend a lot of dozains of hours (really) reading threads and posts.

As quite a lot of people did, I chose to start with a "simple" technique : the LLP (Laser Light Plane) or the Rear DI (Diffused Illumination). I was almost sure that a too long / difficult way would have me dropping the projet half finished.

But as I wanted my change my coffee table into a multitouch one, it appeared that Rear DI was only compliant with the projection mode (using a projector) and that that implied the table to be quite big, even using a mirror. As I wanted to use a LCD screen, the LLP was then the way to go for my first table!

LLP chart from Seth Sandler

LLP has quite a lot of pros (taken from nuigroup.com) :

• No compliant surface (silicone) needed
• Can use any transparent material like glass (not just acrylic)
• No LED frame required
• An enclosed box is not required
• Simple setup
• Could be slightly cheaper than other technique

But of course it's not perfect, and the cons are quite rubbish :

• Cannot track traditional objects and fiducials 
• Not truly pressure sensitive (since light intensity doesn’t change with pressure).
• Can cause occlusion if only using 1 or 2 lasers where light hitting one finger blocks another finger from receiving light.

And I was ready to start looking for some parts...