Infrared Light Blocking Foil Test for FTIR Multi-Touch Tables

virttableWithAndWithoutIRBlockingFoil
Figure 1: The Virttable’s display with (right) and without (left) the chosen IR blocking foil.

Some time back, I’ve bought some infrared blocking foil for the Virttable from the German foil store Ifoha. Infrared blocking foil is an approach for the blocking of ambient infrared light (e.g. from a light bulb or daylight) ONLY in a FTIR multi-touch setup as it blocks light that comes from above the table. I.e. in DI your hands reflect light that would be blocked by an IR blocking foil.

allIRBlockingFoilsWithoutProjection
Figure 2: The Virttable’s display with all IR blocking foil samples (without projection). Note the identifier labels from Ifoha.

I ordered samples from Ifoha from all IR blocking foils they have in stock. I put all samples on top of the table (figure 2 and 3). Onto the samples I each put a finger and a fiducial. Afterwards I made a screenshot of what the cameras see (figure 4).

allIRBlockingFoilsWithProjection
Figure 3: The Virttable’s display with all IR blocking foil samples (with projection).

For the Virttable I used the foil with the id 1002300, which blocks 83% of the ambient infrared light.

ir_filter_from_below
Figure 4: What the camera sees on the Virttable’s display with all IR blocking foil samples on top.

If you want to know something specific ask in the comments.

UPDATE: The setup of the surface with the blocking foil is as following:

___ Projection Foil (e.g. Gerriets Optitrans) ___
___ IR blocking foil (e.g. Ifoha 1002300) _______
___ Silicone (e.g. SortaClear) __________________
___ Acrylic Glass _______________________________

Posted in Hochschule RheinMain, Multi-Touch Tagged with: blocking, diy, infrared, Multi-Touch
  • Nat

    That’s very interesting, I assume the IR foil goes on top, is that the surface you touch ? If so, how’s the texture like ?

  • hi nat,
    no, the blocking foil goes between silicone and the diffuser/projection foil. on top the blocking foil would be smudged VERY quickly with fingerprints. I’ve updated the post at the end with the foil setup.

    cheers

  • Nat

    Hi Johannes, interesting. I wondering if this could work with the sillicon roll-on method ? Could you roll silicon on the foil ?

  • hi nat,
    i haven’t coped with the roll on method yet. could you post a link to that method in order that i could check if that possibly could work on the foil?

    cheers

  • Nat

    Hi Johannes, here’s the basic method :
    http://nuigroup.com/forums/viewthread/2383/

    My version is a bit more simple :
    The diffuser is a mylar sheet (plastic drafting paper) I lay it down on a table, I put some window-sealant silicon and roll it on the surface with a foam-roller. I apply 2-3 coats and it’s good to go. Since with your method the silicon is between the IR-Foil and diffuser, I assume we would need to roll the silicon on the foil, the question is, will it adhere to it ?

  • well, i haven’t tried the roll-on technique but i doubt that it is as regular as applying the silicone directly onto the acrylic glass. but maybe it does work well.

    if you try out the roll on technique with infrared blocking foil i will be happy to hear some results from you!

  • Nat

    I will definately try it !
    The roll-on technique works very well and has the advantage of being very easy to do !
    I just need to find some in Canada…