Diffused Surface Illumination (DSI)

How It Works:

DSI requires a special type of acrylic known as Endlighten, which has microscopic mirror-like particles embedded throughout it. Using exactly the same LED configuration as FTIR, the infrared light fills the Endlighten acrylic. Because of the particles, the infrared light is reflected out of the acrylic, acting like a giant infrared emitter. Then, like a Rear Diffused setup, an object stops the infrared light, reflecting the light back to the camera and creating a blob.

How do I make a MultiTouch DSI setup?


Tutorial Video:



The layers from top down are:

  • Touch Surface Acrylic or Glass: This is not needed but is one of the best things about doing a DSI setup since you can have a smooth, durable touch surface versus the damagable diffuser top layer in a FTIR setup.
  • Diffuser/Projection Layer: The diffuser stops the image produced by the projector.
  • Endlighten Acrylic: The Endlighten acrylic doesnt need to be as thick as the plain acrylic used in a FTIR setup, but it is still recommended for strength and rigididy.
The source of infrared light for an DSI setup comes from infrared LEDs that are placed around at least 2 sides of the acrylic. 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 easily switch back and forth between DI (DSI) and FTIR
  • Can detect objects, hovering, and fiducials
  • Is pressure sensitive
  • No hotspots
  • Even finger/object illumination throughout the surface
    • Disadvantages
  • Endlighten Acrylic costs more than regular acrylic
  • Blobs have lower contrast (harder to pick up by software) than FTIR and LLP

Examples of DSI setups:

Peau Productions Coffee Table

Informative DSI Link