Posted on January 25, 2010 by Jeff Paries — 2 Comments
Waggener Edstrom gives employees the opportunity to create something we call an Experience Influence Project, or EIP. This project is a self-paced, self-designed learning opportunity, and can be done as an individual or group effort. The real goal is to bring some learning to the agency in a way that expands our understanding of influence.
We had an idea floated several months ago that I decided to follow up on for my EIP — building a multi-touch table from scratch. Touch computing has really taken off and doesn’t seem like it will be going away anytime soon; most cell phones support single- or multi-touch, Windows 7 supports multi-touch on tablet PCs, Apple has a tablet PC coming soon according to long-standing rumors, and there are high-end multi-touch systems like the Microsoft Surface table. The goal of my EIP project is to build a multi-touch table along the lines of the Surface computer on a limited budget (the cost of a Surface is north of $10,000).
I started out by gathering a small group of co-workers to help me complete the main build of the system. Once the project is completed, we’ll go into a more broad, open development pattern that involves more people with an interest in the project or environment. The current group consists of me (Lead Experience Developer), Scott McAuliffe (Digital Experience Designer) and Allen Newton (Experience Developer).
In building the table, the first thing we did was a ton of research. There are several methods that can be employed to create a multi-touch environment:
- Frustrated Total Internal Reflection (FTIR). For this method infrared (IR) light is cast into an acrylic pane. The IR light becomes trapped inside the pane by internal reflection. When the surface of the acrylic is touched, the light is “frustrated” and scattered downwards out of the acrylic. By placing an inexpensive IR camera beneath the acrylic, the touch points can be detected and processed. To improve the touch sensitivity and feel, a “compliant surface” (usually a vellum sheet coated on one side with silicone) is placed on top of the acrylic pane.
- Rear Diffused Illumination. Using this method, IR light is shined at a glass, plexiglass or acrylic screen from below at a diffuser that is placed on top of or below the touch surface. Objects touching the surface reflect more light than the diffuser, and an IR camera is once again used to detect the extra light. A “Front Diffused Illumination” setup casts IR light at the screen from above the touch surface rather than behind.
- Laser Light Plane (LLP). To implement this method, a plane of laser light is cast just above the touch surface (acrylic, glass, plexiglass, etc.). The laser light plane is about 1mm thick (about 10 times the thickness of an average human hair). When a finger intersects the laser light plane, the scattered light is cast through the touch surface and registers as an IR blob to a camera beneath the touch surface.
- Diffused Surface Illumination (DSI). This technique is similar to FTIR described above, but uses a special acrylic that contains particles that reflect and spread the IR light cast into the acrylic to the surface.
We’ve elected to go with the FTIR setup as it seems to be one of the easier and faster methods to employ, and is not terribly expensive. There are some downsides, which we will explore later as development advances, but that’s part of the learning experience.
For now, I’d only ask that you sit back and enjoy the knowledge we are able to share. I will be posting updates on this blog as we make progress. Also, if you’re at Waggener Edstrom and would like to check in on our progress or see it when it gets to an interesting point, feel free to swing by one of our cubes (we’re all on the fourth floor of the Portland office).
Thanks to the efforts of the Natural User Interface group at NUI Group for the wealth of information they share on touch computing (and where the descriptions of the above types of multi-touch systems came from).