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Multitouch – How To

How To Make a Multitouch Surface

There are several ways to make a multitouch surface. There are capacitive, resistive, acoustic, and other non-traditional techniques. Our focus will be on optical techniques since they are the easiest and most cost effective for the average person to create. The most popular optical techniques are:

  • Frustrated Total Internal Reflection (ie. Perceptive Pixels)
  • Rear Diffused Illumination (ie. Microsoft Surface)
  • Front Diffused Illumination (ie. MTmini, MTbiggie)
  • Diffused Surface Illumination
  • Laser Light Plane
  • LED Light Plane

Optical Multitouch Techniques

Each technique utilizes 3 main components:

  1. Infrared Camera (or other optical sensor)
  2. Infrared light
  3. Visual Feedback (projector or LCD)

setup An infrared camera is pointed at the touch surface and detects when fingers/objects touch the surface. Infrared light is used to distinguish between a visual image on the touch surface and the objects/fingers being tracked. Since most systems have a visual feedback system where an image from a projector or LCD is projected or placed below the touch surface (the MTmini does not), it is important that the camera does not see this image when tracking objects/fingers on the display. In order to separate the objects being tracked from the visual display, a camera can be modified to only see the infrared spectrum of light (by removing the infrared filter and replacing it with a visible light or bandpass filter); this cuts out the visual image from being seen by the camera and allows the camera to only see infrared light that illuminates the objects/fingers on the touch surface. The projector is connected to a computer in order to display the software on the touch surface. The camera is connected to a computer and a tracking application uses the camera image to track and create touch coordinates.

6 Optical Multitouch Techniques

Click the image or title to view a description, diagrams, images, and other resources about a particular technique.



This page is still being developed. Stop by often to see updates and more information for building your own multitouch surface.

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