How I built ORION mt

The ORION mt table has been one of the smoothest/responsive DI (Diffused Illumination) tables that I have built. Below is a video of the ORION mt in it's prototype state.

You can view the original post on the NuiGroup forum here

Please see the Showcase post on Nui Group forums here:



Here is a short explanation on how it was built.

Rear Diffused Illumination: DI - The Theory:

Infrared light is shined at the screen from below the touch surface from. A diffuser is placed on the bottom of the touch surface. When an object touches the surface it reflects more light than the diffuser or objects in the background. The extra light is sensed by an Infrared camera. Below are pictures illustrating the effect of DI and also a screenshot an image captured by the camera.





The above images and text have been extracted from the NUI Group wiki

The Box:
Made out of 12mm craft wood (MDF), the box is 710mm(w) x 775mm(l) x 655mm(h). I left a section on the top of the box so that I could mount a small mirror to increase projection throw.



The Projector:
For the projection I'm using a SHARP DLP projector Model: PGM15S


Table Specs:
My PC is an AMD Athlon 64X2 Dual Core 3600+ with 2GHz RAM, Nvidia GeForce 7600gt Graphics Card. Sharp PG-M15S projector, Frosted Glass as diffuser/projection/surface.

The resolution that I am using is 1024x768 (DVI to DVI).

WebCam Specs:


The camera is an Xbox Vision 360 (AUD$50) (I’m using 320x240 res @ 60fps)
This camera was fairly easy to modify the IR filter.

Also our friends Jose & Vasco (jmccd) from NUI Group have summarized our posts on the forum and made a pdf guide which you can download here

See the original NuiGroup post here

IR Illuminators:


In the ORION mt there are 3 illiminators. I’ve drawn up a crappy picture in MS Paint to show the layout of the illuminators. (1x 140 IR Leds, 1x 80 IR Leds and a smaller 45 Led illuminator too!)

Illuminator number 1 is the 140 IR led I got from a mate. Number 2 is the 80 IR Led I made up, and Number 3 is the 45 Led one.
The purple border represents the physical screen projection size in relation to the illuminators and the box.

The need for more IR light was due to the fact that during the day or close to a IR light source (overhead lights or the sun) the IR that I was generating was not enough to receive clear blobs.

WebCam & Projector Placement:
Here are some pictures to illustrate the camera, mirror and projector placements in the ORIONmt. I originally had a camera angle issue where i wanted to place the camera in the middle of the floor facing upwards, however I could not capture the entire screen. To overcome this, I ended up moving the camera to reflect of the 2nd mirror. That way I can capture the entire screen (with overscan)

See below:



I have also added a beamer/mirror placement applet that may help with design of your own multi-touch display.

Please see below:

Beamer/Mirror Placement Guide Applet




IR Illuminators - detail
The 140IR LED Illuminator was originally bought by my mate from ebay, and I found one similar on ebay (after typing in the search bar of ebay "140 IR Led"), so here are some specs on it.



- Built-in sensor (which I taped over)

- Illuminating range: Detecting range is 80m, viewing range is 60m (outdoor)

- Definition Consumed power: 18W

- Wave length : 850nM

- Structure: All weather aluminum and reinforced glass

- Power: DC 12V 1000mA

Because of the narrow beam of this IR illuminator, I was getting a large hotspot on the glass. To get around this, I have angled the 140 IR Illuminator so that the light is emitted and reflected off the side wall of the box. (please see above pics)

Also, the placement of the illuminators can be seen in the picture below...



Glass Specs
The sheet of glass is 4mm thick, 71cmx56cm frosted (sandblasted) on one side for the diffuser/projection surface. It was bought from a glass manufacturer, cut to size while I waited and cost about AUD$40-50.

I will add photos soon...

More soon....