Flush Touch Screen, version 5

The version 3 Touch Screen’s geometry was greatly determined by the thickness of UV coated polycarbonate sheet I had found at HomeDepot that seemed to do the best job of aiding the FTIR effect as well as providing smooth finger glide across the screen. Since the sheet was .095″ thick and the LEDs are .2″ in diameter LED guide had to have a substantial bevel in order to align the LED and the screen.

I have since found thicker UV coated plastic after a short web search and determined after a couple of quick prototypes using existing simple LED guides that the thicker sheet did in fact exhibit satisfactory FTIR qualities. It seemed right to design a flush touch table LED guide that would allow us to inset a touch screen in an existing table, mount the projector and camera underneath and begin in-house touch table experiments.

Here is the AutoCAD side view of the LED guide:


Since this is just a (quick and dirty) proof of concept prototype, I only machined enough of an LED guide to hold 18 LEDs or about 5.1″ worth of LED, (twice, one for each side)…


A closer view of the flush edge LED guide:


The side view, seen if screen extends to edge of table…


All this assuming that we might end up with a table that looks something like this:


Anyway, I will bring both the beveled and flush prototypes in to evaluate…

Inside the LED Guide

Just to make whats happening with the LED guide a little clearer, here’s the underside of the guide with the LED PCB board in the background. Note that the LEDs have to turn the corner in this version.


Here the LED PCB has been put in place (with some difficulty, ’cause there’s not much room in there)


Finally, a shot looking from the side the touch screen and video screen see. I discovered after this version 4 proto was made that the holes need to be deeper in order to mitigate the strong side illumination lobes from the LEDs. (Sadly I didn’t get a picture of the version 5 deep holes until the whole thing was taped together)..



Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: