marzo 24, 2009
Foldable Display
Starting from few video founded in youTube on foldable display: http://www.youtube.com/watch?v=nhSR_6-Y5Kg I’m thinking to reproduce this technology in house.
The theory:
The first step il creating a trackable surface and a tracking system:
- For the trackable surface I used a solid surface with 3 infrared LED
- For the tracking system I user an infrared camera web camera with a narrow light spectrum (near to 850nm)
Building the trackable surface
The trackable surface is made by a plane in a tridimensional space. To define the plane I need 3 points. I developed a simple box with 3 IR LED one for each corner (excluded one of coruse) as shown abowe:
I used:
- DVD boxset,
- 3 IR LED (unfortunatly my 3 LEDs have a narrow view angle becuse I used LED from a remote control, I suggest tu use LED with view angle nero or orve 20°)
- one switch
- one 47hom resistor
- few wire
- 4 1.5V AAA battery pack
Building the tacking system
To track the 3 point in ths space I developed a (quite) special camera to capute the IR light, to do this I hacked a normal web cam adding an additional low-pass IR filter.
Normally a web cam is abel to see in the light emission spectrum from high IR to the entire visible spectrum, the web cam has a hi-pass IR filetr in order to reduce the sensibility of the CCD of the camera to the IR light. This filter is not able to filter the entire IR emission, it only reduce partialy the IR sesibility of the CCD.
I applied another IR low-pass filter in order to create a narrow band in the IR specturm:
To build low cost IR optical filter I used a slide color film, impressied with IR light (I used the wii bar as emitter 
). This article can help ont his: http://photocritic.org/create-your-own-ir-filter/
Here the result wile the camera see the trackable surface (with and without the narrow band IR filter)
