Re: FTIR Interface project

Solo Projects (Ideas, Shares)

FTIR Interface project

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FarMcKon 06-22-2007, 9:39 AM
Hey Makers,
I just moved to town, so I figured I'd share my new project here.  I've just started working on a Frustrated Total Internal Reflaction (FTIR)  Interface. I've ordered most of the parts over the last week or so, and I'm starting on the build soon.

General Overview:
FTIR displays are a type of multitouch display that use a touch-sensitive membrane.  They consist of a projection and an input system.

1. Projection System
   Simply a projector, generally setup for back projected to a diffusion screen, with a membrane (more info below on that) in front of it.
   
2. The Input System
   The input is via a is camera system that can register multiple touch points. This can be done several ways for different systems, but FTIR displays do this by bouncing some UV light inside of a membrane (Z.b. pelxiglas) which has an index of refraction high enough the light does not escape (the Total Internal Reflection part). Now, when pressure is put on the membrane, compression changes the properties of the membrane, and it's index of refraction at the pressure point changes, and UV light escapes.  The UV is picked up by the camera (filtered for a specific UV wavelength) and converted into an set of points, and passed to the PC where it's used as an input system.

My project:
First I'm building a simple FTIR based on a demo unit I saw in Rohcester. It's simple, a proof of concept, and mostly to get the software chain working and some bugs nailed down. It will use simple plexiglass (not best, but easiest to get) for it's membrane, and will be a 'stand in front of a monitor' unit.  If/when that goes well, I'm planning to build a full projection system to install someplace (Geoff at P'unk Ave hs offered to convert a window if it works well) as a art/hacking project.

Status:
I'm just starting today.  I'm 100% for making this build a group project with any folks want to work on it. Let me know if you are interested.  I'll be posting on my personal website, IndustrialSomething.org. The FITR section of my weblog will can be reached here. If people here want it,  I'd be willing to mirror my posts here, or make some kind of note when I updated.

This looks like a great town, and in the last 2 weeks I've heard a dozen people tell me "you've moved to Philly at the right time, things are just starting to take off". I look forward to meeting folks in person.

- Far  (Jon McKamey)

Re: FTIR Interface project

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FarMcKon 07-03-2007, 2:44 PM
An update:

I build a 8x10 demo FTIR interface as a test, and (in a rush) submitted it to Instructables in the last day before the deadline.  The 8x10 demo works well, including some example code for vvvv, I'll drag it to the next Make meeting to show around.

It's easy to build, and (outside of the webcam) should only cost about $20 to make an 8x10 to 10x24 (ish) touch display without projector. My next build *will* include a projector for intuitive GUI interface, but for now the demo interface is up and running.

Re: FTIR Interface project

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bbustard 09-04-2007, 7:39 PM
Hi FarMcKon,
I am also making a multi touch display. I went with rear DI and it's coming along nicely.  I don't know if you already brought it to a meeting but  I'd love to see your setup if you could drag it to the next one.  I assume you've seen the nuigroup website.  http://nuigroup.com  if you haven't then you must check it out.  Here is my setup.  http://nuigroup.com/forums/viewthread/561/     If you have any thoughts or ideas on it I would appreciate the input.

Ben

Re: FTIR Interface project

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FarMcKon 09-06-2007, 5:02 PM
Sweet.
My setup is pretty simple. I can bring the test panel over for the next Make:Philly, but I don't have a laptop setup yet, so I can't bring a working techdemo.  I haven't finished a full build yet, I'm still saving my pennies to get a DPL projector.