What Is a Digitizer?

The term digitization has long been used in the general sense to describe any conversion of analog information such as text, image or sound into a digital format for storage, transmission and computer processing. In this sense, a digitizer is any device that performs digitization, such as an image scanner. However, the introduction of the computer tablet and smart phone has led to a more specialized use of the term digitizer to describe devices that work in conjunction with touch screens.

One of the biggest issues with finger-based touch technology used by many tablet computers and smart phones is the difficulty many users have in executing complex tasks using touch. A digitizer that improves touch accuracy is embedded in the screens of some tablets and smart phones. Others use a digitizer device such as a stylus to allow users to specify locations on the display more precisely. There are three common types of touch-screen digitizers: passive, active and dual.

An example of a passive digitizer is a plastic stylus that you use on a touch screen for increased accuracy. This type of stylus, also known as a capacitive stylus, is detected by the touch screen as if it were a finger press. No communication takes place between stylus and the touch screen.

An active digitizer in the screen of a tablet or smart phone can detect when a special type of pen is near the screen or touches it. This is accomplished by a sensor grid that's integrated with the display and a digital pen (no battery required) that bounces a signal back to the display so its location can be calculated. The digitizer pen may have buttons, similar to the buttons on a mouse, providing additional input and control.

There are advantages to active digitizers over passive, including the masking out of accidental touches by fingers or the palm of the hand while the pen is in use. Because these digitizers are sensitive to pressure, a firmer press can be represented with a thicker or bolder stroke. They are the preferred digitizers for touch-screen handwriting.

A dual digitizer provides features of both active and capacitive digitizers, allowing a user to employ either fingers or a digitizer pen for different types of interaction. Fingers can be used with the GUI (graphical user interface), while the digitizer pen can be used for detailed drawing or writing. This provides the accuracy of an active digitizer with the ease-of-use of capacitive touch screen, allowing users to switch seamlessly between the two modes of operation.