Definition of Graphics Tablets

A tablet is useful for computer graphics applications.

A graphics tablet is a computer input device that lets you trace or sketch images as if you were drawing with a pen and paper. You write on a special tablet using a tablet cursor, sending signals to your computer. This can be a stylus or a puck. Graphics tablets allow you to draw and trace more naturally.

Principles

A graphics tablet works using an X-Y matrix: a grid of vertical and horizontal coordinates.
When you draw or trace lines on the tablet, a series of co-is generated -- either as a continuous stream or as points at the beginning and end of each line. Typically you can use a tablet in one of two main modes: "digitizer mode," where the movements of your cursor correspond to points on the screen; and "mouse mode," where the computer generates the position of the pointer on the screen relative to the starting position of the cursor on the pad.

Tablet Cursor

The device you use to "draw" on the tablet is called the cursor. Typically, this will either be a stylus or a puck. You hold and use the stylus much like a pen. A puck may look like a mouse or may be a large, complex device with several buttons. Either can be used for drawing, but a puck is superior for tracing. Professional graphics pucks often include a clear window called a reticule or a magnifying lens known as a loupe, which allow you to look through the puck at the image below, allowing you to trace it more accurately.

Electromagnetic Tablets

Some graphics tablets work using the principles of electromagnetic induction: small currents are induced by moving a magnetic field relative to a conductor. The tablet contains a grid of wires which may either generate a signal that's detected by the tablet cursor; or the cursor itself can generate a signal that is picked up by the tablet.

Capacitive Tablets

Capacitive tablets use the capacitance between the tablet and the tablet cursor to deduce the cursor's position. These have the advantage of being able to detect the cursor even when it is hovering above the tablet rather than in contact with it. Capacitive tablets use a similar principle to the touch pad used in place of a mouse on many laptops.

Other Tablets

Other kinds of graphics tablets include optical tablets, which use a small digital camera underneath the tablet to track the position of the cursor; and acoustic tablets, also known as spark tablets, which have a small sound generator in the cursor and microphones placed near the surface of the tablet to detect the location of the cursor.

References

• PC Magazine Encyclopedia; Digitizer Tablet Definition
• "Computer Graphics"; Isrd Group; 2005
• "Comp Architecture and Organization, 2nd Edition"; Govindarajulu; 2010

Resources

• "Understanding Computers: Today and Tomorrow, Introductory"; Deborah Morley, et al.; 2010