Hi People!
Update December 04:
Got this screen working wonderfully with crayon physics played

I’ve been super interested in making one of these.. but didnt have the time. However now that I’ve convinced my bosses that this technology is the way forward, I’ve been given the green light to pursue ftir MT :D

It’s my first time doing a MT screen and second time for camera tracking (first started way back in 2003 using alessandro valli’s retina program for my FYP..)

Anyways, for all of you, here’s the methods and tools I used and followed…
Resources for buildup:
http://feroz007.wordpress.com/2007/08/18/build-your-own-multitouch-display/

Screen:
750*570mm 8mm acrylic
tracing paper ‘Canson calque 100gm extra blanc’ (still experimenting with various papers..)
silicon layered using tinkerman’s method.. http://nuigroup.com/forums/viewthread/2383/

36 IR leds.. dont know the spec, but the standard ones I think.. 6leds with one 120ohm resistor
leds are placed 4cm apart from each other
powered by pc power - 12v

tack-it removable adhesive as sticking agent for the snugging the leds into the holes in railings
used aluminium U shaped railing 10mm - black colour

Detection:
phillips usb webcam spc900nc - $35usd
BENQ shortthrow projector

Software:
Tbeta

Update:
I am currently waiting for my silicon screen to dry up, so we’ll see how it fares on the acrylic later in the day

Thanks for reading and I’ll keep you guys updated!

Aidil
KL, Malaysia

Hi aidil, great to see you here with your mt project going on. Looking forward to see some shots from you

Welcome! Looks like you’re off to a great start!

Welcome Aidil, i guess you re the only one from Malaysia here…

alessandro valli’s retina program for my FYP.

Can you send more infos about that ?

AlexTan:
Great to see you here man!

Cerupcat:
Thanks for the motivation :]

Jimihertz:
Alextan is also frm malaysia :]
Oh, alessandro valli is from here http://www.naturalinteraction.org/
he did ‘retina’ back in 2003… a cool shareware that did motion detection similar to tbeta

right now the screen works. next is to wait for the silicon sheet to completely dry up cos currently it sticks on the acrylic..

here’s a nice screenshot of the mutha

my acrylic is too grubby..must...clean…
mild dish detergent in warm water did the job.

You can get Retina here:

http://www.interactivespaces.net/projects/WisdomWells/Support/Download/Retina_1.0.0.msi

Regards

Thanks Zono.
A question, is there a time limit when using this version of retina?

Updates:

So I’ve gotten the acrylic lined up with IR leds on 2 sides. And now it’s working fine. Also, the silicone coated tracing paper is dry and is indeed a great touch sensitive screen - just that the surface is a bit rough to the touch of the finger..

However, there’s a situation where the light from the projector’s lens is reflected from the acrylic back into the camera, and the camera is picking that up as IR light…

I wonder if this is a one off problem with certain projectors or is this normal?

I’m using the benq short throw projector btw, placed not more than 1 meter away from the acrylic. My camera has 3 layers of photo negatives. For the meantime, what I did to compensate for this is I angled the camera so it is not parallel to the projector’s beam.

Guys, did you have this similar problem in your setup?

Thanks

hi Aidil ;

this problem is known as the “Hot Spot” .
- You can try to avoid this by changing the angle of your cam
- Or by reflecting your VP on a front surface mirror first .

thanks jimihertz

Front surface mirror is used to remove ghosting, not hot spots though jimi. To remove hotspots from a projector, you want a Hot Mirror. A hot mirror lets visible light pass through it and reflects IR light. That’ll solve your problem aidil.

And if you have a Hotspot and you do use a FS mirror then the hotspot will get worse…

thanks cerupcat and taha
Will definitely look into this

Updates on my screen:

I noticed that my blobs were really weak..

I did some thinking and I remembered an earlier attempt that when I angled the IR leds a bit against the sides of the acrylic and saw a change in blob intensity.

So now I angled the led railing at a 45 degree to the sides of the acrylic and got some pretty intense blobs with just a light touch. good.

Next time I must use better angled leds instead of having to do this..

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Next, is to work on the construction of the housing.