LED Light Plane (LED-LP)

How It Works:

Similar to a Laser Light Plane (LLP) setup but using LEDs instead of lasers, infrared LEDs are placed around the perimeter of the touch surface just higher than the touch surface. The IR light shines over the touch surface and creates a plane of IR light (a much "thicker" plane than in an LLP setup). Typically a shroud or bezel is placed above the LEDs reducing the light directly shining away from the touch surface. When an object breaks this plane of light it is reflected to the camera as a bright blob.

How do I make a MultiTouch LED-LP setup?


Tutorial Video:



The layers from top down are:

  • Touch Surface Acrylic or Glass: All that is needed is a strong, durable surface that can take the pressure of user interaction.
  • Diffuser/Projection Layer: The diffuser stops the image produced by the projector.
The source of infrared light for an LED-LP setup comes from infrared LEDs that are placed around at least 2 sides of the acrylic right above the touch surface. Typically the more sides surrounded, the better the setup will be in IR prevalent lighting conditions.

The camera is placed on the opposite site of the touch surface so that is can see the blobs.

Advantages
  • No compliant surface (silicone)
  • Can use any transparent material like glass (not just acrylic)
  • An enclosed box is not required
  • Can be used with LCD setups
    • Disadvantages
  • Setup calls for some type of LED frame (soldering required)
  • False blobs from hovering objects can be a problem if unintentional
  • Cannot track traditional objects and fiducials
  • Can cause occlusion if only 1 or 2 sides have LEDs.

Examples of LED-LP setups:

Peau Productions LCD LED-LP Table