Hi!

Today, I tested my MT. My Acrylic is polished by a shop, so its really perfect, you can look very clear though it. The LEDs work too, so thats not the problem. Perhaps the IR-Light goes through the acrylic and at the end there is nothing to reflect. So my Finger doesnt cause anything because there is not enough IR Light!?!?

I really dont know, pls help me.

Perhaps this is important: My Webcam (Trust 2-Mpixel) has an unexposed Photo Film as IR Filter inside. This blocks very much Light, all Windows of Touchlib are normally very dark. Should I use an exposed one!?

Greets

Hi JanGermany,

It’d help if you told us the method you are trying to use. FTIR or DI?

FTIR

the IR bypass filter has to be exposed photo film or it could be the magnetic disk inside floppies or a real IR bypass filter used in photography.  You also need to remove the IR filter inside your webcam if possible. Remember, IR bypass filters block everything except IR while IR filters block IR.  Is your setup in inches or centimeters?

Hi!

My Setup is 60*45cm. For removing the IR Filter inside the Webcam I followed this Instruction: Klick me

I can see IR very good if I point the LEDs to the Webcam, so it detects IR Light! But if they are pointet to the Acrylic, nothing happens.

If you point the LEDs into the webcam it should blind it and turn white.  How many LEDs do you have of what kind?  Are you sure they are all one?  What resistor/cluster size did you use?

EDIT:  I just looked at your diagram.  If indeed you really only used 8 LEDs, that is probably not enough.  You want about one per inch(2.5 cm).

JanGermany - 19 July 2008 02:29 AM

Hi!

My Setup is 60*45cm. For removing the IR Filter inside the Webcam I followed this Instruction: Klick me

I can see IR very good if I point the LEDs to the Webcam, so it detects IR Light! But if they are pointet to the Acrylic, nothing happens.

What is the angle between LEDs and the acrylic edge?
Did you use anything to block the light on top and bottom edges of acrylic (baffle)?
From your diagram it looks like you just places LEDs to the edge of the acrylic without covering them.
You might have sucessfully created the FTIR, but it might be that a lot of IR light leaks throught top and bottom (if you didn’t create a baffle to block this) resulting in your camera not be able to ‘see’ the blobs.

Look at the diagram here:

~Alex

Hi Guys. First of all, thanks for your answers. I changed the IR-Filter in my Camera and now it’s better, not perfect but ok
The unexposed one doesnt work, now I use the magnetic disk inside floppies like estengineer told me. THANKS!
Now I am going to make the real Setup: (Photo is not mine)

But I gonna add something to save the acrylic from scratches. It’s Tesamoll:

Thats not a good Baffle, or!? Perhaps I should add a Layer of Aluminium on Top and Bottom of the Acrylic before Tesamoll, so there is anything to reflect the IR.

Greets