Hello, I’m desperately in need of help. I would consider myself a beginner in multi touch technology. I have already done some basic multi-touch projects such as Johnny Chung Lee’s Wiimote Multi Touch Whiteboard and cerupcat’s MTmini Multi Touch Pad. However, I wanted to try something a bit more advanced. My idea is to make an upright monitor like multi-touch computer such as the HP TouchSmart. I have already taken a brief glance at the DI (Diffused Illumination) method and was awed. Is the method that simple, I’ve heard that the DI method was made for a table multi touch surface, but I was wondering whether you could just flip the schematic to make it upright. Also could someone elaborate on the DI method, this is the method I am intending to use but I need a lot of information for my planning process.

My table uses DI and is flat, but as far as I know there’s no reason it wouldn’t work in an upright position. I also chose to go with DI because it seemed simple, and I guess it is, but there are certain issues with the approach, such as;

It can be difficult to get even coverage of IR on whole of screen, resulting in hotspots/deadspots.

The set up is susceptible to ambient IR, meaning it’s not likely to work in daylight.

Infrared illuminators can be pricey, unless bought from China, in which case they are liable to explode and/or catch fire (I exaggerate, but we had at least 3 power supplies fail in a week).

But it worked great after ironing out these problems. Just a heads up for you!

Have fun!

Thank you, you clarified many of the points I was confused about. What is the best lighting pattern to use, so that roughly 100% of the LCD is illuminated? Also is there a solution to the ambient IR problem? And lastly; what is an IR illuminator?

Well the angle you use for your illuminators really is going to vary depending on the size and shape of your box. We covered our walls with tin foil and pointed the illuminators straight at the walls. The idea was that the IR would bounce all aroundthe box before hitting the screen, therefore being roughly evenly distributed.

Infra red illuminators come in many shapes and sizes, here is en example from ebay

http://cgi.ebay.co.uk/140LED-Infrared-illuminator-for-CCTV-Camera-System-ec66_W0QQitemZ200241954008QQcmdZViewItem?hash=item200241954008&_trksid=p3286.m14.l1318

The only solution to the IR problem that we found worked was to stay the hell away from it!