07-12-2012, 04:57 PM
Graphics tablet Drawing tablet
Graphics tablet Drawing tablet.doc (Size: 103.5 KB / Downloads: 23)
A graphics tablet or digitizer is a computer input device that enables a user to hand-draw images and graphics, similar to the way a person draws images with a pencil and paper. These tablets may also be used to capture data or handwritten signatures. It can also be used to trace an image from a piece of paper which is taped or otherwise secured to the surface. Capturing data in this way, either by tracing or entering the corners of linear poly-lines or shapes is called digitizing.
The device consists of a flat surface upon which the user may "draw" or trace 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.
Some tablets are intended as a general replacement for a mouse as the primary pointing and navigation device for desktop computers.
History
The first electronic handwriting tablet was the Telautograph, patented by Elisha Gray in 1888.[1] Elisha Gray is best known as a contemporaneous inventor of the telephone to Alexander Graham Bell.
The first graphics tablet resembling contemporary tablets and used for handwriting recognition by a computer was the Stylator in 1957.[2] Better known (and often mis-stated as the first digitizer tablet) is the RAND Tablet[3] 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.
The acoustic tablet, or spark tablet, 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.[4] The system was fairly complex and expensive, and the sensors were susceptible to interference by external noise.
Digitizers were popularized in the mid 1970s and early 1980s 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 an OEM version of its BitPad which was sold by Apple Computer as the Apple Graphics Tablet accessory to their Apple II. These tablets used a magnetostriction 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.
In 1981, musician Todd Rundgren created the first color graphics tablet software for personal computers, which was licensed to Apple as the Utopia Graphics Tablet System.[5]
In the 1980s, several vendors of graphics tablets began to include additional functions, such as handwriting recognition and on-tablet menus.[6][7]
Operation
There have been many attempts to categorize the technologies that have been used for graphics tablets:
Passive tablets
Passive tablets,[8] most notably those by Wacom, make use of electromagnetic induction technology, where the horizontal and vertical wires of the tablet operate as both transmitting and receiving coils (as opposed to the wires of the RAND Tablet which only transmit). The tablet generates an electromagnetic signal, which is received by the LC circuit in the stylus. The wires in the tablet then change to a receiving mode and read the signal generated by the stylus. Modern arrangements also provide pressure sensitivity and one or more switches (similar to the buttons on a mouse), with the electronics for this information present in the stylus itself, not the tablet. On older tablets, changing the pressure on the stylus nib or pressing a switch changed the properties of the LC circuit, affecting the signal generated by the pen, which modern ones often encode into the signal as a digital data stream. By using electromagnetic signals, the tablet is able to sense the stylus position without the stylus having to even touch the surface, and powering the pen with this signal means that devices used with the tablet never need batteries. Activslate 50, the model used withPromethean Ltd white boards, also uses a hybrid of this technology.[9]
Embedded LCD tablets
Some graphics tablets incorporate an LCD into the tablet itself, allowing the user to draw directly on the display surface.[14]
Graphics tablet/screen hybrids offer advantages over both touch screens and ordinary tablets. Unlike touch screens, they offer pressure sensitivity, and their resolution is generally higher.[citation needed] While their pressure sensitivity and resolution are typically no better than those of ordinary tablets, they offer the additional advantage of directly seeing the location of the physical pen device relatively to the image on the screen. This often allows for increased accuracy and a more tactile, "real" feeling to the use of the device.
Uses
Graphics tablets, because of their stylus-based interface and ability to detect some or all of pressure, tilt, and other attributes of the stylus and its interaction with the tablet, are widely considered[according to whom?] to offer a very natural way to create computer graphics, especially two-dimensional computer graphics. Indeed, many graphics packages can make use of the pressure (and, sometimes, stylus tilt or rotation) information generated by a tablet, by modifying the brush size, shape, opacity, color, or other attributes based on data received from the graphics tablet.
In East Asia, graphics tablets, known as "pen tablets", are widely used in conjunction with input-method editor software (IMEs) to write Chinese, Japanese, Korean characters (CJK). The technology is popular and inexpensive and offers a method for interacting with the computer in a more natural way than typing on the keyboard, with the pen tablet supplanting the role of the computer mouse. Uptake ofhandwriting recognition among users who use alphabetic scripts has been slower.
Graphics tablets are also very commonly found in the artistic world. Using a pen on a graphics tablet combined with a graphics-editing program, such as Adobe Photoshop, gives artists a lot of precision while creating digital drawings. Photographers can also find working with a graphics tablet during their post processing can really speed up tasks like creating a detailed layer mask or dodging and burning.