Graphics tablet
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A graphics tablet (or digitizing tablet, graphics pad, drawing tablet[1]) 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. These tablets may also be used to capture data of handwritten signatures.
A graphics tablet (also called pen pad) consists 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.
Some tablets are intended as a general replacement for a mouse as the primary pointing and navigation device for desktop computers.
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[edit] History and background
Early graphics tablets are most commonly 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[2] 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 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 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.
[edit] Operation
- Passive tablets
- Passive tablets, 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 pen. The wires in the tablet then change to a receiving mode and read the signal generated by the pen. 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 pen itself, not the tablet. On older tablets, changing the pressure on the pen nub or pressing a switch changed the properties of the LC circuit, affecting the signal generated by the pen, which modern ones often encode a digital data stream onto the signal. 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. Wacom's patents don't permit their competitors to employ such techniques.
- Active tablets
- Active tablets differ in that the stylus used contains self-powered electronics that generate and transmit a signal to the tablet. These pens rely on an internal battery rather than the tablet for their power, resulting in a bulkier pen. Eliminating the need to power the pen means that such tablets may listen for pen signals constantly, as they do not have to alternate between transmit and receive modes, which can result in less jitter.
For both technologies, the tablet can use the received signal to also determine the distance of the stylus from the surface of the tablet, the tilt (angle from vertical) of the stylus, and other information in addition to the horizontal and vertical positions.
Compared to a resistive or capacitive touchscreen, a graphics tablet offers much higher precision, the ability to track an object which is not touching the tablet, and can gather much more information about the stylus, but is typically more expensive, and can only be used with the special stylus or other accessories.
Some tablets, especially inexpensive ones aimed at young children, come with a corded stylus, using technology similar to older RAND tablets, although this design is no longer used on any normal tablets.
[edit] Accessories
The first accessories were special mouse-like pucks designed for CAD applications, typically with a clear plastic area containing crosshairs for precise tracing of drawings, followed by a basic stylus. Today, a graphics tablet will come with a stylus for all models and a mouse for all but the cheapest or smallest models, and typically have a wide variety of other accessories available too. Many tablets use a digital data stream to encode information on the pen, often also transmitting a unique serial number, allowing the software to recognize if the user has multiple input devices, and assign different properties (brush type, color, etc) to each one.
[edit] Stylus
A modern stylus has a pressure sensitive tip capable of sensing many levels of pressure against the tablet. A very inexpensive tablet might be able to sense 256 levels of pressure, while a normal tablet 512 levels, and a professional tablet a full 1024 levels of pressure. The increase in sensitivity of the tablet tip allows more precise control, especially if software scaling is used to allow a large response to a light increase in pressure. Most styli contain at least one button, with two being the most common number, that are typically assigned to the same functions as mouse buttons would be. High-end tablets will also measure the tilt of the pen, giving the angle from vertical along both the X and Y axis (typically up to 60 degrees), allowing the graphics program to change the shape or other attributes of the brush depending on how the stylus is held. Some manufacturers also sell a stylus that uses a ball-point pen cartridge in the tip, allowing the user to place a sheet of paper onto the tablet, and draw a hard-copy on the paper in addition to the digitized version.
[edit] Stylus eraser
Many modern styli have an eraser-shaped tip on the top of the pen, and additional circuitry to allow the pen to be used upside-down with the eraser end against the tablet, often very similar or identical to the circuitry used for the tip. The pressure-sensitive eraser is typically assigned a function similar to a real eraser, removing recent or all layers of coloring from the image, although it can be assigned other functions, such as a differently shaped brush, a selection tool, or other feature of the application.
[edit] Mouse
Unlike a regular computer mouse, a graphics tablet mouse is capable of being used in "absolute mode," where the mouse position on the screen directly corresponds with its physical location on the tablet, or in "relative mode," where it emulates a regular mouse, for high-speed pointing. Graphics tablet mice typically contain several buttons, and often pressure-sensitive thumb wheels or other controls allowing similar capabilities as the pressure-sensitive tip of a stylus. Many tablets can also detect the rotation of the mouse on the tablet, allowing applications to use this data.
[edit] Puck
A puck is typically distinguished from a mouse as having crosshairs for accurately tracing diagrams, a large number of buttons (12 buttons laid out similar to a telephone pad is not uncommon), or other features aimed at CAD usage. They are far less common than a regular tablet mouse, and only available for some tablets.
[edit] Airbrush
Some tablets come with a speciality stylus designed to emulate an airbrush, often with additional finger-operated wheels to mimic the paint flow, nozzle shape, and other adjustments found on the genuine article. These are significantly less common than a regular stylus, and often much more expensive.
[edit] Art pens
Like a regular stylus, they typically resemble a pen with a pressure-sensitive tip, but have additional features, such as allowing the tablet to recognize the rotation of the pen in addition to the standard tilt and pressure, allowing the application to rotate the brush, reshape the brush, or otherwise make use of this additional information, often to generate more realistic brush strokes.
[edit] Screen
A graphics tablet/screen hybrid (or tablet/LCD hybrid, Tablet LCD Monitor[3]) is a graphics tablet that incorporates an LCD into the tablet itself, allowing the user to draw directly "on" the display surface. It should not be confused with tablet PC hybrids.
[edit] Uses
[edit] General 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 to offer a very natural way to create computer graphics, especially two-dimensional computer graphics. Indeed, many graphics packages (e.g. The GIMP, Corel Painter, Inkscape, Photoshop, Pixel image editor, Studio Artist, the Crosfield imaging system, Quantel Paintbox, and others) are able to make use of the pressure (and, in some cases, 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, or pen tablets as they are known, 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 methodology for interacting with the computer in a more natural manner than typing on the keyboard, with the pen tablet supplanting the role of the computer mouse.
Tablets are also popular for technical drawings and CAD, as one can put a piece of paper on them without interfering with their function.
Many of the most successful webcomic artists use tablets, including Hawk of AppleGeeks, Jorge Cham of Piled Higher and Deeper, Tim of Ctrl+Alt+Del and Gabe of Penny Arcade, who uses a graphics tablet to color directly into the computer.
Finally, tablets are gaining popularity as a replacement for the computer mouse as a pointing device. They can be more intuitive to some users than the mouse, as the position of the pen on the tablet typically corresponds to the location of the pointer on the GUI shown on the computer screen. Those artists using the pen for graphics work will as a matter of convenience use the tablet and pen for standard computer operations rather than put down the pen and find the mouse.
Graphics tablets are available in various sizes and price ranges; A6-sized tablets being relatively inexpensive and A3-sized tablets being far more expensive. Modern tablets usually connect to the computer via a USB interface.
[edit] A solution for injuries
Advocates of tablets and pens cite relief from occupational overuse syndrome varieties such as repetitive strain injury [1]. Sufferers of carpal tunnel syndrome also report good results. This is because the use of a computer mouse tends to be very repetitive on the wrist, whereas operating a pen is more natural and tends to involve the movement of the entire arm [2].
[edit] Similar devices
Some Interactive Whiteboards operate on the induction principle, with some brands offering high resolution wall size graphic tablets up to 95" along with options for pressure and multiple input based on different resonance patterns from tuned pens. Interactive Whiteboards are proving to be immensely popular in schools in the UK, US and Mexico[citation needed].
Touch screens like those found on some Tablet PCs and the Nintendo DS are operated in similar ways, but they usually use either optical grids or a pressure sensitive film instead, and therefore they do not need a special pointing device.
The graphics tablet are also used for Audio Haptic products where blind or visually impaired people touch swelled graphics on a graphic tablet and get audio feedback from that.[4] The product that is using this technology is called Tactile Talking Tablet or T3.
[edit] References
- Repetitive Stress. WACOM Technology United States Website. Retrieved on 2005-08-24.
