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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 thumb1 Multitouch How To 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.

ftir icon2 Multitouch How To Frustrated Total Internal Reflection
rear di icon2 Multitouch How To Rear Diffused Illumination
front di icon thumb11 Multitouch How To Front Diffused Illumination
dsi icon thumb11 Multitouch How To Diffused Surface Illumination
llp icon2 Multitouch How To Laser Light Plane
ledlp icon2 Multitouch How To LED Light Plane

Software

Resources

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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  • http://www.uconalpukat.com/ uconalpukat

    Can you build perceptive pixel like Jeff Han did?

    • http://sethsandler.com/blog Seth Sandler

      Yes, his first technique is the FTIR one.

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  • Fiorenzano

    obrigado.
    não sou um expert no ramo de informatica por isso gostaria se possivel que usassem uma linguagem menos tecnica pois tem alguns itens que não sei nem o que significa, só quero saber o que devo comprar´para construir uma tela touch para usar o virtual dj e na mais que isso.
    agradeço e muito se puderem me ajudar.

  • Iaoaioaia

    seth i need a tutorial how to make infrared webcam :(

  • denins

    hi im a noob in this i downloaded all the software, after calibration how do i make ccv control the mouse option i have windows 7

    • http://sethsandler.com/blog Seth Sandler

      You’ll need one of the ‘mouse drivers’ listed above. If you need more help, I recommend going to http://nuigroup.com/forums.

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  • http://twitter.com/Neymar_7711 Stephan Burger

    Hi
    I was just wondering if I can do the llp method and instead of using a projector can I use a lcd screen and if it is possible can you please show me how and YES I have gone to http://nuigroup.com/forums and I can’t find it. So thank you in advance
    Steven

    • http://sethsandler.com/blog Seth Sandler

      You can, but you’d need to take apart the LCD. On nuigroup search for ‘LCD’. There’s many different posts about people using LCDs and in conjunction with LLP. I believe there’s posts with pictures where people have taken apart their LCDs.

    • http://twitter.com/Neymar_7711 Stephan Burger

      Thank you very much…..BTW What method would you recommend that will give the best blobs so that the project can give the most accurate touch point

  • http://www.facebook.com/princejerry06 Rishabha Garg

    sir, i need help with camera plz tell me which one i should buy.

  • ishwar

    can normal logitech pc webcam is used to implement FDI pls reply i m eagerly waiting to do it but i m unsuccessful with my MTsetup

  • Ralph Tyndall

    Does the MTBIggie need extra infrared lighting from the sides??

    • http://sethsandler.com/blog Seth Sandler

      No, not if it’s using ambient IR light in the room.

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