Laser Light Plane (LLP)

How It Works:


An infrared laser fitted with a lense that makes a plane of light is shone just over the touch surface. When an object contacts the touch surface, it breaks the infrared plane and reflects the light to the camera which creates a blob.

How do I make a MultiTouch LLP 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 LLP setup comes from infrared lasers. A minimum of two lasers must be used in order to not have occultation happen.

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)
  • No LED frame required
  • An enclosed box is not required
  • Simple setup
  • Could be slightly cheaper than other techniques
  • Can be used with LCD setups
    • Disadvantages
  • Cannot track traditional objects and fiducials
  • Not truly pressure sensitive (since light intensity doesn't change with pressure).
  • Can cause occlusion if only using 1 or 2 lasers where light hitting one finger blocks another finger from receiving light.

Examples of LLP setups:

AlexP Laser Wall
Informative LLP Link