General Idea of Touch Screen

Do you know what a touch screens is? It is a human machine interface (HMI). HMI, as its name indicates, is an interface or device that allows communication between machine and its user.

Can you give me examples of HMI?

There are various types of HMI around us. Push button is one of the simplest types of HMI. You see them on a TV remote control, on telephone set, in an elevator, and many other locations. Mouse and keyboard are more advanced types of HMI than push buttons. These types of HMI are used to interact with electronic devices with images. When a user operates a personal computer, he moves image of the cursor in the screen with mouse, and input images of characters with keyboard. A touch screen is also this type of HMI that uses images for communications between a user and electronic device. Unlike mouse and keyboard, touch screen allows a user to interact with electronic device by directly touching images displayed on the screen.

OK, I think I grasped the idea of HMI and touch screen. I have a smartphone that I operate with my fingers. As I touch its display, the images on the display change. It is a touch screen, isn't it?

Yes, exactly. But, touch screen itself is just a transparent switch that detects touched locations. How the device reacts to your touches is controlled by software. Various input devices can be made with combination use of touch screen, display and software.

What kind of input devices can be made with touch screen? Can you give me an example?

OK. For instance, a touch screen can work as a simple push button. Image of a button switch can be displayed on screen, and the device will be programmed to be on and off upon a touch on the image. If number of the button images increase, a touch screen can be used like a keyboard. Since a touch screen can detect coordinate points, it can also function as a mouse (although it does not distinguish between right and left clicks like a mouse).

I see, a touch screen can perform the same functions as other types of HMI like push button, mouse and keyboard. But, then do we need a touch screen if it performs just the same functions as other HMI? Is there any advantage to choose a touch screen over other HMI?

I will not be saying that a touch screen is better than other HMI in every aspect, but it surely has many advantageous aspects that no other HMI can replace it. The advantages and drawbacks of touch screen will be introduced here.

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