Flush Touch Screen, Version 7

At our last meeting we determined that big plastic touch screen frame bezels were out, that inserting the touch screen directly into the melamine-MDF table surface was the way to go. In further comparison testing of the different screen material options, I found that the thinner the touch screen material the better the FTIR effect. I now have a design that shows the glowing finger with the minimum of pressure across the entire surface, as well as eliminate all “bezelness”. I also had the good fortune to find a supplier of the same “Cherry Veneer” melamine surface used on the conference tables.

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The challenge was to get the maximum amount of light into the edge of the touch screen. The approach I took with version 5, with the 1/4″ touch screen, was to put the LED on axis with the center of the screen. But in the case of this .107″ screen, there simply is not the room to do this. The LED must be at an angle to the axis of the screen, but the angle must be as shallow as possible to keep the light inside the screen, rather than spilling out onto the projection surface.

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In this version we expose the LED as much as possible and cover the channel with reflecting mylar tape to direct the light into the screen edge.

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here’s edge view from below the screen

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and finally a little video of what the IR camera sees. The small dots are where the finger is lightly touching the screen, bigger dots show more pressure.

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