Smoke & Mirrors

First images of my table, almost finished. The LED circuit is connected to the power with a 12 V transformer, and works like a charm.

I was doing some quick tests to check if it generates blobs and, indeed, when I put my fingers on the panel they are generated, without any sort of pressure. They are a little faint,, but the tests where made with my phone camera, that filters a great part of the IR.

I still couldn’t try with the PS Eye without filter, but judging by the images I took with it the last time I think it will catch blobs nicely.

Now I only have to obtain a projector so I would do some real tests, but if I couldn’t obtain it soon I probably will use an standard monitor and a mirror.

Taking advantage of my recent acquisition of a Playstation 3 (I should write about it in a near future since I have high expectations regarding its Power Cell), I bought also the PS Eye camera, since the specifications are perfect for multitouch, and most importantly, it is really affordable (considering that a camera with similar characteristics having good performance for MT is around 300€ and not easy to find).

Sony PS3 Eye:

• 4 input audio channels: 16 bits/per channel, 48kHz, SNR 90db
• FOV: 56º o 75º
• 60 fps 640x480 or 120 fps 320×240
• Uncompressed video, JPEG compression

60 fps is just what we need for smooth blob tracking, but we can get up to those 120 if we want extra smoothness, at the cost of lower resolution and higher cpu requirements).

The problem with this camera is to make it work on a PC. I was about to start …

Today I was building the LED frame that will light the acrylic panel. As I wrote before, for the prototype I’m building I’m using two 90cm L-shaped aluminium profiles (the panel is 76cm, but I bought 90cm to use them as a support over the sawhorses). I will put 25 infrared LEDs on them.

I haven’t done any test yet, but I already have some concerns. The profiles are raw aluminium, and probably I should use polished aluminium to help with reflecting the light leaks back to the acrylic. In any case, this is only a prototype, the final version shoul duse polished frames U-shaped to seal the entire panel perimeter.

Separation between each LED is 3cm aprox., and I will mount them so one side frame will cover the low iluminated point on the other side. To explain it better, where we have a “hole” between …

After a long wait, at last I have received my materials to start working on the project and make the firs tests with the FTIR phenomenon.

I bought 100 LEDs (100, but I only need 50 for this). I have chosen Oshram SFH485, because are optimal for an FTIR configuration: It’s wavelength is 880nm, and their emission angle 40º. Wavelengths avobe that are harder to filter for our purpose, and the angle is optimal for my plexiglass thickness.

In the other hand, the acrylic (I had to wait a lot to obtain it). It’s thickness is 8mm and it’s measurese 76×54 cm. I could use a thinner one, but it’s so big, so I prefer this thickness to avoid bending when applying pressure over it. LED’s are 5mm, so a 5 – 6mm acrylic should be enough.

I got a couple of 90cm L-Shaped aluminium profiles …

Since I watched Jeff Han’s video and his multi touch interface a year ago, I was totally charmed with that technology and I was researching a lot about it. It actually is not a new technology, and is relatively simple.

There is a great community around the multi touch displays, and geeks all over the world are building their own devices of this kind, researching and improving them. The prototypes that you can find in that community don’t have anything to envy to commercial ones.

I’m a fulltime geek, and I’m the first to melt with this wonder so I was researching and doing my homewroks to start building my own device. I’m interested on it, because as a coder, I’ll have a new world where to experiment with new software paradigms.

When I first started this project, the first thing I needed was …

This article was originally published NetSearch Ezine number #1 , in 1999.

The code this presentation does not work intentionally (the code is altered so it can not be executed), and only would affect Word 7.0

The objective of the article was to demonstrate a vulnerability in the software.