Stupid Question 112: How do touch screens work? Are there different types of touch screens?

[To celebrate my first year of programming I will ask a ‘stupid’ questions daily on my blog for a year, to make sure I learn at least 365 new things during my second year as a developer]

I love touch centric apps, I love programming them, and I love using them. I’ve been waiting for the computer of my dreams with a touch screen to come to market, and while searching, waiting and dreaming I started wondering a bit about touch screens. I always assumed that touch screens worked by electrical conduction, but my parents own a few nightclubs and the new touch screen seem to work by applying pressure. Some touch screens are made of glass, and some- like those at the nightclub, seem to use a sort of plastic. So how do touch screens work, and the real question- are there different types?

How do touch screens work? Are there different types of touch screens?

On the day before Christmas I decide to find out.

There are indeed different types of touch screens, and they work differently- all with their pro’s and con’s. Here are the types I found, this is just a small summary- I would probably rather want a touch screen expert to explain each of them in detail as I’m just a mere programmer trying to understand how these things work to adjust my code therefore.

Resistive
Thin layered electrically-resistive layers, the touch screen works by applying pressure, which connects the layers and creates a connection and the point of pressure can be located. This is the one at my parent’s nightclub. It is rather resistive to dirt and such.

Surface acoustic waves
Basically sound waves are send across the surface, touch will absorb the waves where the screen is touched, and the point can be located.

Capacitive
A touch by something that conducts electricity, such as a human, will interrupt this electrostatic field. Most smartphones work this way. The technology for filtering and finding the touch spots differ a lot. I’ll get back to this in another question.

Infrared grid
Infrared light beams in the screen record interruption of the light

Infrared acrylic projection
Works in a similar way to the infrared grid, only that an acrylic sheet is used as a ‘projection screen’

Optical imaging
Image sensors are placed around the edges, as well as back lights. Touch is detected as a shadow.

Acoustic pulse recognition
Works by detecting unregistered sounds waves

Stupid Question 112: How do touch screens work? Are there different types of touch screens?

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