Interactive Multitouch Display

Step 7 Modify webcam

In order to image the infrared light, we need an infrared camera. Fortunately CCDs in cheap consumer cameras are quite sensitive to IR, so sensitive in fact that it is necessary to filter out the ir in order to get good pictures. I got lucky and had an old intel web cam lying aroud in which the ir filter was a cinch to remove. Replace the ir filter with a visible light filter (so the camera doesn't see the projected display). I used the exposed end of a negative. See e.g., this instructable for more details.

Comments

[cool13q]

 could i use a wii mote as the IR cam?

[Azayles]

You could, but it's not technically a camera in the same way a normal webcam or digicam is. It has a CCD array that detects a grid of light just like a regular camera, but it doesn't output video, instead it outputs a serial protocol that tells you the center coordinates of the four brightest blobs of IR light. A microcontroller inside the Wiimote camera does all the DSP of working out the blob centres.
While you could use the camera from a scrapped Wiimote (the camera itself isn't possible to find on it's own, the company that makes it ONLY makes it for Nintendo) you couldn't detect more than four fingers with it.

[cool13q]

 hmm very good point. Well if you really wanted to use a Wii Mote, you could theoretically use 3 (=12 blobs). 

[Azayles]

True, but chances are the other two cameras would all return the same coordinates for the same four blobs, and with no way to cascade the outputs :(

[cool13q]

oh well, looks like the webcam is the best way to do it after all.
-Thanx

[Azayles]

Welcome :-)
Just remember, you won't need a particularly good webcam. Some dirt cheap PC world thing that gives 192 x 128 pixels will work just as well, 'cause the DSP that calculates blob centres will return coordinate values that are more accurate than the webcam resolution anyway.

[Mr. Anguish]

Greetings! I absolutly love your consept... but I was noticing that you were having diffacultys controlling the actual display.... i'm figuring that it's the frame rate of the camera that is giving you the trouble.... am I correct? i'm thinking about investing in some of the parts as my girlfriend wants to get into graphic design and it would be a most usefull tool to have a gigantic touch screen at her disposal, but it would deffinatly need to be more sensitive... any suggestions?

[MarkFW]

 Hi, 

I've been looking at these types of projects to create one of my own. Is there any software/modification of the idea here that would allow me to have a surface the same as this one, that just acts as a keyboard, and as such just projects the keyboard. Its for my new pc desk i will be building, and the idea is to create a square area solely for keyboard input, but allow the computer to use the input just the same way as typing a key on the board.

Any ideas would be great as this is stumping me, consequently stopping my pc station being created.

Cheers 

[zackthebuddha]

If you're running Windows, it's already on there.
Start -> Accessories -> Accessibility -> On Screen Keyboard
(with Vista it's just Accessories -> On Screen Keyboard. not sure what it is in Windows 7, you could just search for it from the start menu)

[crook17]

Would it be possible to use a ir pen (an old pen with a ir LED and a battery inside) instead of using the large amount of LEDs

[Rjessick]

yeah man, take a look at what Johnny Lee has done. Obviously this would defeat the whole "touch" part of the surface though....

[Rjessick]

Johnny Lee vids @ http://www.youtube.com/watch?v=5s5EvhHy7eQ

[Pyshotic Wards]

step 7 helped me out a lot!!! thx for the life (or grade) saving guide! =)

[redex777]

Greetings and thanks for this wonderful project! Just one question/concern: Judging from your video, the "Pictures" application especially, it seems to lose sensitivity as you put your fingers towards the center of the screen. Could this be because the acrylic pane was too large, and the infrared light wasn't able to reach the center as brightly? ...or maybe the light was too diffuse and therefore inaccurate towards the center? ...or maybe im just imagining things, ;-)

[turkey tek]

Hmmm. I didn't notice that effect myself but it could be the case. A problem I did encounter with the middle of the screen is that there is a reflection of the bright lense of the projector off the back of the acrylic which the camera sees. You can get rid of this by subtracting an image of it from your input but if your fingers cross over the bright spot the tracker can get lost.

[Smidge204]

Thanks for the great project! I'm currently working on my own 36"x48" countertop to use as an interactive drafting table (AutoCAD and custom IR-LED pen) I have a question about the webcam - I have a cheap one that was easy to convert and so far works okay for this (I got the stylus sorta-working on my LCD monitor by having the cam on a tripod behind me). Doing the math, though, my camera doesn't have the view angle to see the entire 36"x48" surface without being almost 8 feet away! Did you encounter any issues like this? If not, I'd love to know what brand of webcam you used or if you have any other suggestions. My current "all-else-fails" plan is to buy a $5 "fish-eye" (160 deg) door peephole and deal with the distortion in software. A new camera is a less kludge-y solution so if it's not too expensive I'd rather go that route. Thanks again!