Graphics Tablets

A graphics tablet is a computer input device that allows one to hand-draw images and graphics, similar to the way one draws images with a pencil and paper. more...

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Graphics tablets consist of a flat surface upon which the user may "draw" an image using an attached stylus, a pen-like drawing apparatus. The image generally does not appear on the tablet itself but, rather, is displayed on the computer monitor.

It is interesting to note that the stylus, as a technology, was originally designed as a part of the electronics, but later it simply took on the role of providing a smooth, but accurate "point" that would not damage the tablet surface while "drawing".

Graphics tablets should not be confused with the tablet PC.

History and background

Early graphics tablets, known as spark or acoustic tablets, used a stylus that generated clicks with a spark plug. The clicks were then triangulated by a series of microphones to locate the pen in space. The system was fairly complex and expensive, and the sensors were susceptible to interference by external noise..

The first graphics tablet resembling contemporary tablets was the RAND Tablet, also known as the Grafacon (for Graphic Converter), introduced in 1964. The RAND Tablet employed a grid of wires under the surface of the pad that encoded horizontal and vertical coordinates in a small magnetic signal. The stylus would receive the magnetic signal, which could then be decoded back as coordinate information.

Digitizers were popularized in the mid 1970's and early 1980's by the commercial success of the ID (Intelligent Digitizer) and BitPad manufactured by the Summagraphics Corp. These digitizers were used as the input device for many high-end CAD (Computer Aided Design) systems as well as bundled with PC's and PC based CAD software like AutoCad.

Summagraphics also made a OEM version of its BitPad which was sold by Apple as an accessory to their Apple II. These tablets used a magneto-strictive technology which used wires made of a special alloy stretched over a solid substrate to accurately locate the tip of a stylus or the center of a digitizer cursor on the surface of the tablet. This technology also allowed Proximity or "Z" axis measurement.

The first home computer graphics tablet was the KoalaPad. Though originally designed for the Apple II, the Koala eventually broadened its applicability to practically all home computers with graphics support, examples of which include the TRS-80 Color Computer, Commodore 64, and Atari 8-bit family. Competing tablets were eventually produced; the tablets produced by Atari were generally considered to be of high quality.

Modern graphics tablets operate in a fashion similar to the RAND Tablet. In modern devices, though, the horizontal and vertical wires of the grid are separated by a thin insulator. When pressure is applied to the tablet, the horizontal wire and vertical wire associated with the corresponding grid point meet each other, causing an electric current to flow into each of these wires. Since an electric current is only present in the two wires that meet, a unique coordinate for the stylus can be retrieved. Pointing device detection is additionally aided by a weak magnetic field projected approximately one inch from the tablet surface. It is important to note that, unlike the RAND Tablet, modern tablets do not require electronics in the stylus and any tool that provides an accurate "point" may be used with the pad (though the stylus itself is likely designed with both the resolution of the grid and the durability of the tablet in mind and, therefore, should be used).

Read more at Wikipedia.org