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GRAPHICS TABLET

A graphic tablet (also known as a digitizer, drawing tablet, drawing pad, digital drawing tablet, pen tablet, or digital art board) is a computer input device that enables a user to hand-draw images, animations and graphics, with a special pen-like stylus, 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 tablet surface. Capturing data in this way, 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 the attached stylus, a pen-like drawing apparatus. The image is displayed on the computer monitor, though some graphic tablets now also incorporate an LCD screen for a more realistic or natural experience and usability.

Some tablets are intended as a replacement for the computer mouse as the primary pointing and navigation device for desktop computers.

Characteristics:

Typically tablets are characterized by size of the device, drawing area, its resolution size («active area», which is measured in lpi), number of buttons and types and number of interfaces: bluetooth, usb; etc. The actual drawing accuracy is restricted to pen's nib size.

A large-format graphic tablet by manufacturer Summagraphics (OEM'd to Gerber): The puck's external copper coil can be clearly seen.

Types:

There have been many attempts to categorize the technologies that have been used for graphic tablets:

Passive tablets

Passive tablets, most notably those manufactured by Wacom and Parblo, for example, 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 buttons, with the electronics for this information present in the stylus. On older tablets, changing the pressure on the stylus nib or pressing a button 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 with Promethean white boards, also uses a hybrid of this technology.

Active tablets

Active tablets differ in that the stylus used contains self-powered electronics that generate and transmit a signal to the tablet. These styluses rely on an internal battery rather than the tablet for their power, resulting in a bulkier stylus. 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.

Optical tablets

Optical tablets operate by a very small digital camera in the stylus and then doing pattern matching on the image of the paper. The most successful example is the technology developed by Anoto.

Acoustic tablets

Early models were described as spark tablets—a small sound generator was mounted in the stylus, and the acoustic signal picked up by two microphones placed near the writing surface. Some modern designs are able to read positions in three dimensions.

Capacitive tablets

These tablets have also been designed to use an electrostatic or capacitive signal. Scriptel's designs are one example of a high-performance tablet detecting an electrostatic signal. Unlike the type of capacitive design used for touchscreens, the Scriptel design is able to detect the position of the pen while it is in proximity to or hovering above the tablet. Many multi-touch tablets use capacitive sensing.

For all these 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, such as clicking buttons of the stylus or the rotation of the stylus.

Адрес публикации: https://www.prodlenka.org/metodicheskie-razrabotki/325175-graphics-tablet