Lecture
Graphics tablet (from the English. Graphics tablet or graphics pad , drawing tablet , digitizing tablet , digitizer - digitizer , digitizer ) - a device for entering drawings by hand directly into the computer. Consists of a pen and flat tablet, sensitive to pressure or proximity of the pen. Also a special mouse can be attached.
The first graphic tablet was the Television Autograph, patented by Elisha Gray in 1888 [1] . Elisha Gray is better known as a contemporary of the inventor of the telephone, Alexander Bell.
The first graphics tablet, similar to the modern ones, was used for handwriting recognition by the Stylator computer [2] in 1957. The better known and often mistakenly referred to as the first, the graphic tablet RAND Tablet [3] is also known as “Grafacon” (GRAPHIC Converter), introduced in 1964 The RAND Tablet used a grid of conductors beneath the surface of the tablet, to which electrical impulses coded with the threefold Gray code were applied. A capacitively connected pen received this signal, which could then be decoded back into coordinates. [four]
Another graphics tablet is known as an “acoustic tablet,” the pen of which generated sparks with a spark gap. The clicks were triangulated by a series of microphones to locate the pen [5] . The system was quite complex and expensive, the microphones were sensitive to extraneous noise.
Graphic tablets were popularized due to their commercial success in the mid-1970s - early 1980s. ID (Intelligent Digitizer) and BitPad manufactured by Summagraphics Corp. These tablets were used as an input device for a variety of Hi-End CAD (Computer Aided Design) systems connected to PCs and software like AutoCAD.
The first tablets for the consumer market were called “KoalaPed”. Although they were originally created for the Apple II computer, over time the Koala spread to other personal computers. Then other companies began to produce their tablet models.
In modern tablets, the main working part is also a network of wires (or printed conductors), similar to the one that was in Grafaconah. This grid has a fairly large pitch (3-6 mm), but the pen position recording mechanism allows you to get a step of reading information much smaller than the grid step (up to 200 lines per mm).
According to the principle of operation and technology, there are various types of tablets. In electrostatic tablets, a local change in the electrical potential of the grid under the pen is recorded. In electromagnetic - the pen emits electromagnetic waves, and the grid serves as a receiver. In both cases, the pen must be powered.
Wacom has created technology based on electromagnetic resonance, when the grid both radiates and receives a signal. At the same time, the signal emitted by the grid is used to power the pen, which, in turn, sends a response signal, which is not just a reflection of the original, but newly formed, which, as a rule, carries additional information identifying the particular pen, as well as data on the pressing force, fixing / positioning of controls on the pointer, on whether the working tip of the pen or its “eraser” is used (if such functions are provided for in it). Therefore, a separate power supply for such a device is not required. But with electromagnetic plates, interference from radiating devices, in particular monitors, is possible. Some touchpads are based on the same principle of operation [6] .
There are tablets, the kit which includes feathers that can record the force of depression. As a rule, the registration mechanism is based on the use of a variable capacitor capacitor. In particular, this type of sensor is used in pens for Wacom tablets [7] . Registration can also be performed using a component with variable resistance [8] or variable inductance. There are implementations based on the piezoelectric effect [ source not specified 1676 days ] . When you press the pen within the working surface of the tablet, under which the grid of conductors is laid, a potential difference arises on the piezoelectric plate, which allows you to determine the coordinates of the desired point. Such tablets do not require a special pen at all and allow drawing on the working surface of the tablet as on a conventional drawing board.
In addition to the pen coordinates, modern graphics tablets can also determine the pen pressure on the working surface, the slope, the direction of rotation in the plane of the tablet, and the force of the pen compressed by hand.
Also, a set of graphics tablets with a pen can be supplied with a mouse, which, however, does not work like a normal computer mouse, but according to the same principle as a pen. Such a mouse can only work on a tablet. Since the tablet resolution is much higher than the resolution of a conventional computer mouse, the use of a bundle of mouse + tablet allows you to achieve significantly higher accuracy when entering.
The resolution of the tablet is the step of reading information. Resolution is measured by the number of lines per inch (eng. Lines per inch , lpi). Typical resolution values for modern tablets are several thousand lpi.
The number of degrees of freedom describes the number of quasi-continuous characteristics of the relative position of the tablet and pen. The minimum number of degrees of freedom is 2 (X and Y positions of the projection of the sensitive center of the pen), additional degrees of freedom can include pressure, pen inclination relative to the plane of the tablet, rotation (position of the pen relative to its vertical axis).
Graphic tablets are used both to create images on a computer in a manner as close as possible to how images are created on paper, as well as for normal work with interfaces that do not require relative input (although entering relative movements using a tablet is possible, it is often inconvenient).
In addition, it is convenient to use them for transferring (drawing) already finished images into a computer.
Some instant messaging programs (for example, MSN Messenger (now Windows Live Messenger) and Skype) allow a user with a graphics tablet to interactively display a drawing to the subscriber at the other end.
Some of these applications have an image sharing ( whiteboard ) feature using, for example, Jabber protocols. Among them - Coccinella IM-client ( English ), IM client Tkabber and graphical editor Inkscape. Whiteboard support is also being developed in the Jabber Psi client.
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Electromechanical devices of electronic devices
Terms: Electromechanical devices of electronic devices