From Open Circuits
There are several different technologies that can be used to build a multi-touch display.
[FIXME: sort this by the specific technology]
 bidirectional LEDs
A few multi-touch displays are built from LEDs, using each LED both as a display pixel and also as a light sensor.
- Dietz, P.H.; Yerazunis, W.S.; Leigh, D.L. 2003. "Very Low-Cost Sensing and Communication Using Bidirectional LEDs". http://www.merl.com/publications/TR2003-035/
Multi-Touch Sensing through LED Matrix Displays http://mrl.nyu.edu/~jhan/ledtouch/
- Howard Myers 2006 "Stealth-mode LED controls itself" http://www.edn.com/article/CA6335303.html
"Single microcontroller pin senses ambient light, controls illumination LED circuit senses light and controls its own brightness." by Loren Passmore 2006 http://www.edn.com/article/CA6382648.html
"Red LEDs function as light sensors" by Geoff Nicholls 2008 http://www.edn.com/article/CA6541376.html
"LED senses and displays ambient-light intensity" by Dhananjay V Gadre and Sheetal Vashist 2006 http://www.edn.com/article/CA6387024.html
- "Detecting light with an LED". http://electronics.stackexchange.com/questions/902/detecting-light-with-an-led
 capacitive touch sensors
 unsorted links
"World's Largest Touchscreen Hacked Together with Ordinary Hardware": "It can handle over 100 simultaneous touch points ... hacked together with a bunch of PCs, video cameras, projectors and cheap infrared illuminators at the University of Groningen, in the Netherlands."
Wired: "Boards Get Brains, Chalk Vanishes" <q> "It is a must-have technology," said Shawn Mishler, director of communications technology at Columbia's privately run elementary school. "My dream school would have 7-foot-diagonal, in-wall units in every classroom. ... Interactive whiteboards are made by about a dozen manufacturers, including Numonics, PolyVision and Promethean.
"My speculation is over the next three to five years you'll see an interactive whiteboard in every single classroom," said Nancy Knowlton, president of Smart Technologies, maker of the popular Smart Board interactive whiteboard, which claims a 60-percent market share. </q>
Art? "Distance Touch Generator" <q> Lyta ... consists of two kinetically-charged surfaces, placed 100 metres from each other, and linked telematically so that deformations induced by touching each one are transmitted to the other interactively: when the structure is touched on one site, the touch will be visible and touchable on another.
This networked sculpture haptically connects people at distant locations. It is based on a novel biomimetic haptic displacement transmission network developed in collaboration with Merlin Systems, a robotics firm based in Plymouth, UK. </q>
Ubergizmo: "Digital Lightbox For Hospitals" <q> the huge multi-touch display as seen on Minority Report? That is now reality thanks to BrainLAB AG, of Germany who recently installed its maiden Digital Lightbox radiology system in a Munich hospital. ... Image scrolling can be performed with one finger; zooming in and out of images with two. </q>
NY Times: "No Privacy" briefly mentions that <q> ... Danny Hillis of Applied Minds ... a novel tabletop digital map, about the size of a large flat panel television. The system has a touch-sensitive screen, making it possible to handle high-resolution digital imagery as easily as sliding a paper map across a table.
The system is controlled by a series of hand gestures. For example, to zoom on a region, a user touches both hands to the screen and slides them apart. </q>
Art? "Tabletop that can display, input data for meetings" <q> Hitachi has developed a touch-panel display that doubles as a tabletop. ... A projector built into the table shows images on the transparent acrylic top plate while an infrared camera embedded within recognizes the shape and movement of the shadow created by a hand. A simple gesture such as drawing a circle on the screen can be programmed to zoom into the section encircled by the hand movement. The display could be a useful tool for collaboration, allowing multiple users to input data during meetings.
Hitachi is working with Namco to develop a table that will be used to develop strategies for network gaming. That table should be ready in early 2005 and cost roughly $20,000. </q>
<q> Networked Performance: "Networked Nightlights" John Schimmel's Fireflies are networked nightlights ... For example, if you tap the jar in your bedroom you will pulse the colored fireflies associated with that jar. The neighboring jars in your home will receive and pulse your taps, record them and then play them back. The neighboring jars can respond with their own tapping and broadcast themselves to the nightlights in the home. </q>
Art? "The Message Table" <q> Shawn Bonkowski (with Dana Gordon) made a desk merged with an answering machine. The Message Table receives, plays and stores phone messages. ... When a message is left, a box representing that message slowly rises from the desk. The higher it rises, the longer the message. So when you return home, you know how many messages are waiting for you. To hear one, open the box's lid. Pushing that box back down into the desk deletes the message. ... According to Shawn, one can perfectly use the Message Table as a working desk. </q>
"The IntelliMat is a wireless computer embedded in a very thin mat made of a lightweight thermoplastic alloy with four LCD screens, creating a 30-inch diagonal display with full multi-media capability. IntelliMat is 1.5cm thick and designed to be used on the floor" http://www.gizmag.com/go/4868/ via http://www.byz.org/~rbanks/movableType/webLog/trends/archives/003733.html
"TouchKit: the open source, multi-touch screen developer's kit" uses an infrared camera -- Gizmag: TouchKit
Gizmag: "LucidTouch -- the see-through mobile device" <q> Touch is a compelling input modality for interactive devices, but fingers get in the way on the small screen of a mobile device ... LucidTouch ... addresses this limitation by allowing the user to control the application by touching the back of ... device.
The key to making the LucidTouch usable is pseudo-transparency: by overlaying an image of the user’s hands onto the screen, Microsoft has created the illusion of the mobile device itself being semitransparent. This pseudo-transparency allows users to accurately acquire targets while not occluding the screen with their fingers and hand.
LucidTouch also supports multi-touch input, allowing users to operate the device simultaneously with all 10 fingers. </q>
"The Contact Board" http://www.we-make-money-not-art.com/archives/2005/09/contact-board-i.php via http://www.byz.org/~rbanks/movableType/webLog/trends/archives/003409.html <q> The Contact Board ... The board comes with a series of magnets. Each one is embedded with an RFID tag and stores a [phone] number. </q>
"The Onomy Tilty Table is a table with an image that moves when the table is tilted. This enables the viewer to look at a very large document or picture ... ... Museum visitors quickly discovered the wonderful sensation of flying you get when you lay on the table with the image sweeping across you, so the tables were designed to take a lot of punishment and still perform. ... The latest innovation in Tilty Tables is the "Twisty Table" ... Like our classic Tilty Table, tilting the table top allows the visitor to scroll around an image. The new twist feature enables the visitor to zoom in to see much more detail, or to zoom out and get a sense of the whole." http://www.onomy.com/blue/tilty.html
A list of interactive tables that may support collaboration http://liftlab.com/think/nova/2005/01/10/space-and-place-a-list-fo-interactive-tables/
MERL DiamondTouch http://www.engadget.com/2006/03/27/mitsubishi-randd-rocks-warcraft-iii-with-new-diamondtouch-table/ http://veryspatial.com/?p=2389 <q> Multi-user interactive tables DiamondTouch embeds a giant multi-user tablet into a table. "The MERL DiamondTouch is basically a ginormous touchscreen, embedded in a table, that supports multiple simultaneous inputs, so different users can be manipulating objects on the screen at the same time. This DiamondTouch is totally wasted on research and corporate meetings -- all it needs is some cup holders and we’d ditch our coffee table in a second." </q> via http://www.byz.org/~rbanks/movableType/webLog/trends/archives/003324.html
"CUBIT is an open source multi-touch system" Wikipedia: CUBIT
"Add multitouch gesture support to a TouchPad-equipped laptop: Enable 'Three-Finger Swipe,' and open- and close-pinch gestures using synclient and synthetic X events" by Nathan Harrington (email@example.com), Programmer, IBM 03 Jun 2008 http://www.ibm.com/developerworks/library/os-touchpad/index.html via Multitouch touch-pad support for Linux laptops http://www.hackszine.com/blog/archive/2008/08/multitouch_touchpad_support_fo.html
"What is this with premade stuff?" http://cuznersoft.com/wordpress/?p=79 mentions yet another way to implement multitouch: <q> My second semester, one person in the class made something that absolutely astounded me in its simplicity and how obvious it was to construct. He basically made a multitouch enabled touch screen using an LCD with the backing taken off, a bunch of infrared LEDs shining into a glass plate, and a camera with a remote control bezel over the lens. He hooked up the webcam to the computer and used open source software to interface it to his computer as a multitouch human interface device (HID). He said it cost him about $200 mainly because of the monitor he bought and cannibalized. I was impressed. I was so surprised I hadn’t thought of doing something like that. It’s things like that with premade stuff that I find awesome. I had never before seen a monitor like this and from what he said it was the cheapest yet from a quick look around on the web. </q>
"a little test applet to shows the touch points as reported by the MacBook multitouch pad." http://www.steike.com/code/multitouch-demo/
sparsh-ui A Multitouch API for any multitouch hardware / software system http://code.google.com/p/sparsh-ui/
PyMT is a python module for developing multi-touch enabled media rich applications. pymt is a multi touch UI toolkit for pyglet. Pyglet is a cross-platform windowing and multimedia library for Python. http://code.google.com/p/pymt/
pyTUIO: A Python library that understands the TUIO protocol http://code.google.com/p/pytuio/ the TUIO protocol, "which was specially designed for transmitting the state of tangible objects and multi-touch control on a table surface."
"H-P Testing a Touchless "Wall of Touch"" January 19, 2010 by Lauren Goode Reporter, The Wall Street Journal http://voices.allthingsd.com/20100119/h-p-testing-a-touchless-wall-of-touch/