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FTIR or DI, my final multitouch decision…

After spending a large amount of time focusing on Diffused Illumination ( Rear DI), I’ve switched my concentration back to FTIR. I had great results with DI and was happy with the ease of use and setup, but one issue I had was the constant calibration I would have to go through every time I tested. This most likely had to do with an incomplete setup and open box where the IR light, shinning at the acrylic, would easily change as the environment changed. Although with some fixing it is possible to have a great DI setup, I’ve chosen to go with FTIR.

There are a couple main reasons for this decision:

  1. The calibration won’t have to change every time I test or use the device since the light will always be shinning towards the acrylic in the exact same way.
  2. I can always add DI and have an FTIR/DI setup very easily. All DI requires is the addition of IR light under the table.
  3. I also like the idea of being able to use an object as thin as a pen tip, which is not possible with DI alone.

Both FTIR and DI have there places. One is not better than the other. DI can recognize objects, hovering hands, and can be calibrated to the sensitivity you want very easily. FTIR on the other hand is very robust, doesn’t allow for object recognition, but does allow for thinner objects to be recognized (like pens).

I will be positing results of both my FTIR and DI tests so others have a comparable vision of the differences (although they may be very slight).

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  • Moosa Mahsoom

    Dear Seth, Me and my friends tried to make a FTIR setup. We had to apply a lot of pressure to get the blobs and we had a lot of background IR. It was very difficult for us to make the silicon layer and we did not make it properly. Do you have any suggestions. Our camera was a PS3 Eye Camera with a single Visible light filter.

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