TouchIT Technologies

Different Types of Technology used on Interactive Flat Panels

Avoid Overlays and Non-Integrated units

To the inexperienced, a TV and a touch overlay would seem to present a school with an inexpensive option for an Interactive Flat Panel, but this really doesn’t work.

An overlay is a second piece of technology that lays on the screen of a regular TV or monitor to create a touch screen. The problem with this technology is that while it may be cheaper than a fully integrated unit – by integrated we mean that the touch component as well as the screen are all in one – the experience that you get as a user is not good.

First, there is a problem with accuracy due to something called a large parallax. A parallax refers to the amount of space there is between your finger or pen pointing at the screen and where the cursor is displayed on the screen. With the larger parallax you get when using an overlay, this causes problems when you try to do things that require great accuracy – manipulating an Excel sheet for example. It’s hard to have accuracy with an overlay.

Think of how many times on NBC’s Monday Night Football [1] you see the presenters touching the same player two or three times to try and move him around. This is because of the large parallax on their screen.

Second, the overlays never seem to actually fit the screen properly. This causes problems as the screen and overlay get out of sync. You need to recalibrate often to regain the accuracy – rather like with the Interactive Whiteboards you are looking to replace!


Infra-Red and Surface Light Wave Technology are two of the most common touch technologies found on Interactive Flat Panels today.


The way they work is by casting an invisible grid across the surface of the panel. When you touch the screen, you break the infra-red line of sight across the X and the Y axis creating a coordinate. The computer converts this coordinate into a mouse position. This is how you control the computer from the screen.

Infra-Red is also good for multi-touch input as it accurately tracks the multiple mouse positions. The technology is incredibly fast and accurate and it is not humanly possible to move your finger quicker than the technology can track. This technology is not pressure sensitive so you don’t need to press hard on the surface.

PCAP (Projected Capacitive)

PCAP or Projected Capacitive technology is a totally flat “iPad[2] like” surface. This is very much the future of the Interactive Flat Panel as the technology is very responsive and the flat surface provides a fantastic user experience when using the touch screen. The problem is that the technology is really just now being used for larger screens so is very expensive. You are looking at somewhere between one and half to twice the cost of the same sized infra-red touch unit. This will put PCAP out of range of most education budgets at this time.


There are a number of other technologies out there. Five and Seven wire resistive technology as well as Surface Acoustic Waves (SAW). These technologies are really not suited to the large screen and are much more accustomed for smaller monitors of 24” or below.

They are also not great for touch-based annotation (with a finger or pen) and are more commonly found on Point of Sale (POS) machines where you are simply registering clicks on an unchanging screen – such as you would find at the checkout of a grocery store or in a restaurant.

[2]iPad is a Registered Trademark of Apple Inc


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