How to build a Multi-Touch surface

Multi-touch gestures are the latest and greatest way to interact with your computer.  However, commercial systems are not widely available and are expensive.  Fortunately, you can do it yourself better and for less cost.

Principle components (Click links for product info):
$35 PS3 Eye Camera (Recommended but any decent webcam will work)
$20 IR bandpass filter
$200 5-meter dimmable IR LED Strip
$1000 Any recent/decent computer (PC/MAC)
$1000 Any projector >2000 lumens (NEC NP410W)
$40 Front surface mirror
$80 Abrasion resistant acrylic sheet (23" x 35" x 0.236")
$130 Rear projection acrylic sheet (23" x 35" x 0.118")
$145 EndLighten acrylic sheet (23" x 35" x 0.394")
Total: ~$2500

Software (Click links for downloads):
$free CCV (Used to turn images into blobs)
$free CL-Eye Platform Driver (For PS3 Eye camera)
$free Multi-Touch Vista (Optional Multi-Touch TUIO driver for Windows integration)
$? Windows 7 (Recommended)

Written by Justin Klaassen, Duke University B.S.E. 2012
Sponsored by the Duke Library

Step 1 What is a Multi-Touch surface?

 A Multi-Touch surface is essentially a giant touch screen that can process multiple touches at once.  And in our case, a virtually unlimited amount of touches.  By allowing multiple touches, gestures can be performed on surface.  These gestures are typically simple things like pinching and pulling on an image to zoom in and out.  By supporting gestures like these interfacing with a computer becomes much more intuitive and fun.  In a public place, a Multi-Touch surface can be a real attention grabber.

Comments

[lrubin28]

Cheapest place for Front Surface Mirror is BostonCraftWorks.com. They charge $39 for a real glass FSM sheet, 16 inches x 20 inches. They sell it for high quality kaleidoscopes although people also use it for things like cameras, copy machines etc. They also sell smaller sheets of acrylic front surface mirror - its about 12" x 12" and it only costs about ten bucks - the only issue for optics is that the acrylic is bendable, so it needs something firm underneath, or you should probably just buy the glass version. The glass version also has a very thin layer of a protectant on it so that it can handle very light cleaning. Normally you want to keep FSM in a sealed environment so it doesn't pick up dust.

[lfields1]

I have been looking at the idea of trying to use a mirror to reduce the distance the camera needs to be from the screen. Have you tried this? I can't seem to find anyone that has. I would just do it myself but I am waiting on a computer that can handle multi touch. I have all the components except that.

[maewert]

I'm considering building this and I happen to have a broken rear projection TV that has a good front-surface mirror. I've seen other designs on the net that used mirrors to get a larger distance but have not done so myself. If you can get a front-surface mirror, then it should work.

[jck112]

I have not tried using a mirror, but your best bet is to use a super wide angle lens - such as one of these: http://peauproductions.com/store/index.php?main_page=index&cPath=26_4

[sifihog]

Is it possible to wire separate LEDs instead of buying a LED reel?

[aismail6]

some one please respond? how manny layers of arcylic do i have to use ?

[fredbana]

three see step 5

[thedickmorris]

if you were to do an "Open Air" construction, would there be issues with false readings from the camera from other IR sources? Like say on a stage with lots of different colored moving lights?

I have an idea...

[Fireater989]

It depends on your method, if you use FTIR, not as much. Other methods like DI or DSI, yes

[jcksparr0w]

do i have to buy the entire reel of ir leds? an entire 5 m/16 ft?

[serch]

Also I forgot to ask ..

On the website posted for the endlighten acrylic
I found three options:

ACRYLITE® Exotic Edge
Green 6F22 GT

ACRYLITE® EndLighten T
Colorless 0F11 L

ACRYLITE® EndLighten
Colorless 0M02 XL (cast acrylic)

Which one is better or which one is the one that works? The higher the transmission they have the better?

[serch]

Hello! I know this is project was done about one year ago. However I was wondering if you could help me out. I am trying to make my own table but I have a few questions.

What is the front surface mirror for?
What is the order in which you place the layers?
Did you put the LEDs on all four sides of the EndLighten Acrylic?

From what I understand the Endlighten Acrylic is placed at the bottom. Then the rear projection acrylic, and then the abrasion resistant acrylic. (Also the abrasion resistant acrylic is to protect the other layers from use right? This would be the layer I would touch?). After this I dont know where the surface mirror goes or what is for.

Thank you very much for all your help and this is by far one of the best instructables or instructions for that matter in building a multitouch table.

[septamusdave]

I was just wondering, would this work with a sheet of glass as the surface layer rather than acrylic, using the rear projection acrylic and endlighten acrylic layers as you have detailed here?

[crewlbn]

I am also wondering if it is possible to use glass sheet instead of an acrylic one? It will work as a table so I would like to make it more resistant for scratches by using glass.

[KriĆĄto25]

Can you use plexiglass instead of acrylic sheet?

[harry599]

decent pc's are nowhere near $1000, epesily if you build them yourself...

[Ankoku92]

if youre smart about your shopping, you can make a pc capable of high end processing/gaming or whatever you need for just over a grand, where as if you'd buy one pre-assembled it'd be upwards of three grand.

[jck112]

I don't know if you are saying they are cheaper or more expensive, but $1000 is definitely a good metric for the quality of PC I am describing. Just try it yourself: www.newegg.com

[the_prototype]

I build my PC for ~600/700€...
It's "High-End" and I can play every single game without lags in Full HD Resolution.
Oh and I uild one time a PC for a friend, it was around 550€ and can to play every game in full hd without any lags.

Just sayin'...

[harry599]

if you build them yourself, you are looking at about £450-£800, i recently built a high spc pc with an i7 and 8gb of ddr3 ram for around £600-£700.

[madfx]

Hi,

I made the table, it's all working, im having problems only with win 7 multitouch driver. I installed it, it's ok, but when i unable my mouse the red point are not moving on the screen, it's stuck. I reinstalled the driver several times but im not getting any result.

could someone help me?

[madfx]

I'm having problems to find the led strip infra red. I live in brazil, is there any other way to use the infra red led? could i use like 2 or 3 simple led lamp infra red?

[multi touch]

Was wondering if there is any drawbacks to using a DLP projector, like heat or power consumption. A pros/cons of using either a LED,LCD, or DLP would be nice if anyone has that info.

Excellent info thus far, by the way.

[jck112]

No real cons, you just want to make sure the projector has a high ANSI brightness (>3000 lumens).

[the_prototype]

I'm sure this will work with any good webcam, won't it?
So why don't just use for exemple a Microsoft Lifecam which you can get for 15€?

[the_prototype]

ok i saw the older comment where the answer was yes...
A "HD" wecam it is then (for best accuracy) :)

[jck112]

Higher resolution is better, more frames per second is better. Its usually a tradeoff between those things so we are looking for good resolution (at least 640x480 or similar) and good frames per second (at least 30 - most webcams are only 15).

[the_prototype]

btw I like your design of the "case" :D
It's ot too big but big enough to store the pc in it so it has only the power cable going out :)
This would be a really great way for stores to get the attention of the people passing by.

[DHaworth]

So, I got the PS3 Eye camera and the IR filter from Peau Productions. Peau productions says the filter will rest on the camera sensor, so don't screw the screws tight, just snug.
My question is, won't this shift cause the camera to be out of focus?

[jck112]

The IR filter will refract light coming in, so in the end the image will be in focus.

[BDubs]

NEC NP410W Projector price went down

[soapdude]

Could you suggest a projector? Which one did you use? Thanks.

[arvindmasti]

where can we get those types of acrylic sheets???????

[genbli]

Hi, I am building a multi-touch surface with IR. It must run under Windows 7 for all standerd application. Wich driver I can used for that? How it works? Please help me! Thanks in addvance

[dbasner]

 Hi,

I am building a multi-touch table and it seems like you have somehow figured out one of the problems we are having.  How is it that you are only using one front surface mirror? shouldn't the image be flipped, like if you look at text in a mirror?  Do you have software to flip it when it's sent to the projector so when it hits the surface, it is "normal"?  Sorry for all the questions but this would save my club a whole lot of time and frustration trying to angle two mirrors at just the right angle, as well as math trying to figure out how high etc. the mirrors need to be so we have the right projection length.

[jck112]

 Hey,
Most modern projectors have a menu option that enables you to flip the image.  It is probably located under something like "projector orientation" or "projector mode".  Just cycle through the different orientations and modes until you find one that works.  As for positioning the mirrors, trial and error seems to work best.  The angles are so precise that even if you calculate them it will take a lot of fine tuning to actually get the mirrors in the position you want.

Good luck.

[dbasner]

Thanks for the quick response!

[tonwac01]

can u just use any camera; like a webcam?

[jck112]

 Ya you can.  But you want to make sure you can get at least 640x320 at 30fps, otherwise the accuracy/smoothness of the touches will be less than desirable.

[technoguy94]

Couldn't you just use a Wiimote, since it already tracks up to 4 IR points?