Two. Liquid-crystal displays

Another type of monitors - liquid-crystal (LCD). The first liquid crystal materials were discovered more than 100 years ago, the Austrian scholar FA Renittserom. Over time, it was found a large number of materials that can be used as liquid crystal modulators, but the practical use of technology has begun relatively recently. Technology for LCD-displays based on the unique properties of liquid crystals, which simultaneously possess certain properties as a liquid (eg, fluidity), and solid crystals (in particular the anisotropy (from the Greek. Anisos - uneven and tropos - direction - the dependence of properties of the medium on the direction. The anisotropy is characterized by, for example., mechanical, optical, magnetic, electrical and other properties of crystals.). In the LCD-panels use the so-called nematic liquid crystals, whose molecules are in the form of elongated plates, united in a twisted spiral. LCD-element, in addition to the crystals includes transparent electrodes and polarizers. When voltage is applied to the electrodes of the helix straightened. Using the input and output polarizers, one can use such a spiral effect as an electrically controlled valve, which is missing, it does not transmit light. screen LCD-display is from the matrix LCD-items. In order to obtain an image, you need to address the specific LCD-items. There are two main methods of addressing and, accordingly, two types of matrices: passive and active. In the passive matrix image point is activated by applying a voltage on the conductors, the row and column electrodes. The electric field occurs not only at the point of intersection of address conductors, but on the whole pathway of current, which prevents the achievement of high contrast. In an active matrix of each point of the image controls the electronic switch, which provides a high level of contrast. active matrix usually implemented on the basis of thin-film field-effect transistors (Thin Film Transistor, TFT). TFT-screens, otherwise known as active matrix displays have the highest resolution of flat panel devices are widely used in notebook computers, car navigation devices and a variety of digital set-top boxes. LCD-display does not radiate, and works as an optical shutter. Therefore, to reproduce the image it needs a light source which is located behind the LCD-panel. The lifetime of the inner light TFT LCD-monitor depends on its type. Typically, the light sources for 15-inch monitors are losing about 50% of initial luminance of 20,000 hours.

Three. Gas-discharge or plasma display panels (pdp).

The operating principle of plasma display panel based on the emission of special phosphors (phosphorescent material) when exposed to ultraviolet radiation. In turn, this radiation is produced when an electric discharge in the environment of highly rarefied gas. When such a discharge between the electrodes to a control voltage is formed a conductive "cord", consisting of ionized gas molecules (plasma) (a similar principle of operation is implemented in the fluorescent light - gas in the flask (glass tube) begins to glow by passing a voltage through it). That is why the gas-discharge panel, working on this principle, and were called "discharge" or "plasma" panels. By applying control signals to the vertical and horizontal conductors deposited on the inner surface of the glass panel, the control circuit panel shall, respectively, "lower case" and "personnel" of the raster scan television picture. In this case the brightness of each pixel is determined by the glow of the respective "cell" plasma display: the most striking elements of the "burn" all the time, but in the darkest places they did not "set on fire." The bright areas of an image on the PDP (Plasma Display Panel) are smooth with light, and so the image is absolutely no flicker than favorably with the "picture" on the screen of traditional picture tubes. Plasma displays are created by filling the space between two glass surfaces with an inert gas. The whole space is divided into many pixels (picture elements), each of which consists of three sub-pixel corresponding to one of three colors (red, green and blue) (see Fig.) By combining these three colors can be reproduced any other color. In each sub-pixel are small transparent electrodes to which a high-frequency voltage. Under the influence of this voltage electrical discharge occurs. The interaction of gas-discharge plasma with the particles of phosphorus in each sub-pixel corresponding to the emission arises colors (red, green or blue). The work of each subpixel is controlled entirely by electronics, which allows each pixel to reproduce up to 16 million different colors. At the present time to create a flat panel display (Flat Panel Display, FPD) using various technologies and solutions, although the market is still dominated by LCDs. As you know, technologies that are used in creating modern displays can be conditionally divided into two groups. The first is a device based on the emission of light, such as traditional, made on the basis of cathode ray tubes (CRTs) and plasma displays PDP (Plasma Display Panel). The second group includes devices such as translational, including LCD monitors. Devices of both groups have very definite advantages and disadvantages. If you talk about the future, long-term solutions in the field of modern displays do often combine features of both technologies. So, today, much attention is paid to the creation of displays based on field emission (Field Emisson Display, FED). Unlike LCD screens, which work with reflected light, FED-panel itself generate light, which makes them with screens, CRT and plasma displays. However, if all three CRT electron guns, the FED-units for each pixel is its own electrode, so that the thickness of the panel does not exceed a few millimeters. In this case, each pixel is controlled directly, as in LCDs with active matrix. The genealogy of FED-unit developments are from the mid-1990s, when engineers tried to create a truly flat CRT.