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)

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.

Software

• Main Finger Tracking Application
  • Software Setup Guide
  • Installation and Configuration
  • Calibration
  • Flash Application Setup

• Mouse Driver – for controlling your mouse cursor
  • Windows Mouse Driver
  • Mac, Linux, Windows Mouse Driver from TUIO.org

• Demos and Applications – Various multitouch applications
  • My Demo Applications
  • MTmini video demo applications – via ccv.nuigroup.com downloads page

Resources

• Multitouch Terminology
• Multitouch Book (free PDF)
• My Personal Multitouch Surface Build
• NUIGroup (the best place for immediate help on hardware and software)

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