Quick update. Been having a play with my camera - taken it apart (a Logitech Orbit one) and removed the IR filter - sandpaper on lens - not the best way but it seems ok - i've took some pictures of the process..

Once done, tried the cheap and cheerful, 3 strips of negative solution to block out all visible light. I actually cut the strips very small and then sandwiched between the sensor and the lens - works pretty well.

Then took a spare piece of acrylic I've got - only small, about 3 x 8 inches and started having a play with this thing they call Front DI.....

Stunned that it actually works! - there's lots of tweaking to do with the software though as it keeps picking up parts of my hand etc. I suspect that the best solution may be to provide additional IR light from a source either infront or the side. Dunno - need to spend time playing with it really I think.

Have made my mind up - DI is definitely the way to go as the setup is far easier to tweak and play around with - and its far less expensive. The camera I've been using for testing looks like it probably isn't up to the job for a real prototype so I think I'll get a second one - the Philips one that people are mentioning on the Nuigroup site seems the best bet.

Hmm - there's always a draw back isn't there.... Seems that "ficidual recognition" doesn't work with this method. Ficidual Recognition is (if I remember right) getting the system to see objects other than your hands and to know what they are.... not sure why this would be the case but hey, I'm new to this.

Oh man this gets better. Seems the Diffused Illumination techique in my last post is really known as Rear DI. Effectively you are creating a beam of IR light and blasting out the box through the opening at the top. Your camera ( in the box ) looks for the light gathering (scattering?) where you are hands are on the acrylic and the software does the rest.

Now things get funky....

Role on the other type of DI - Front DI. This technique uses the natural ambient IR light that exists in the environment. This means that there's no need for any IR lights in the box at all..

So, my "list" of box items is.... a webcam (with filters etc), a backlight for the tft panel... and er.. that's it!. (it can't be this easy surely!)

Front DI is gonna get tested soon....

Heh - looks like things just got even easier - seems that Diffused Illumination is the "new thing" in terms of Mulit-Touch and the best bit is its even easier. All you need is the acrylic sheet, your tft matrix, a camera, a "diffuser", a light (so you can actually see the tft!) and... an IR light source (you can either make this yourself or buy one - "IR Illuminator" on Ebay. Not sure of how exactly this stuff works, but work it does so plans have now changed a little....

Oh the fun to to be had.

I've got some issues at the moment. In a knutshell I know that the acrylic sheet will be on top with the tft matrix underneath it, in terms of assembling this thing. The problem is that in order to see the display, I need to have some form of light illuminating it from behind. This could be a problem as I also need the webcam (currently an "Orbit" Logitech one) located behind the whole lot and pointing at the screen. If I put the light source behind the camera, you see a silouette of the camera behind the tft matrix. If I put the lightsource infront of the camera then there's a danger that the camera won't be able to see the matrix.

Another problem is the size of the thing. I don't want it to be a big chunky affair but rather something that is fairly slim ( I'm not expecting miracles though). From other setups I've seen most people have used a mirror - ie. the projector and camera are pointing at a mirror which is showing the back of the acrylic sheet - in effect halving the distance that you would need to locate them normally in order to get the same dimensions used.

So these two issues combined are presenting me with a problem - how to light the display, have the camera able to see the entire screen area and detect the "blobs", as well as not making the thing look god damn awful in the looks department.

Hmm...

Have found a good place to get some of the electronics that are needed - which is actually very little. Essential the only purchases I need are the IR Led's to go around the acrylic sheet, some resistors for them and some form of power supply for the whole lot. I've seen some people who have used an old computer powersupply so there's various options. What I'm not sure yet is the maths invovled in terms of how many IR Led's I need, and therefore what kind of power requirements / resistors I should be looking at - need to do some swatting up on this I think.

Anyway, the place I'll be buying from looks like it will be www.farnell.com as they seem to have all the necessary bits (actually looks like there's pretty much everything you could ever want on their site!)