Shadow mask crt pdf Continue In Shadow Mask CRT, tiny holes in the metal plate separate colored phosphorus in the layer behind the front glass of the screen. The holes are placed so that the electrons from each of the three cathode tube guns reach only the corresponding phosphorus on the display. All three beams pass through the same holes in the mask, but the angle of approach at each gun is different. The distance between the holes, the distance between the phosphorus and the placement of the guns are arranged so that, for example, the blue cannon has only an unobstructed path to blue phosphorus. Red, green and blue phosphorus for each pixel are usually arranged in a triangular form (sometimes called triad). All early color TVs and most computer monitors, past and present, use shadow mask technology. Traditionally, shadow masks have been made of materials, temperature fluctuations cause expansion and contract to the point affecting performance. The energy that the shadow mask absorbs from the electronic cannon in normal operation, causes it to heat up and expand, leading to blurred or discolored (see dome-shaped) images. The mask of the brewed shadow consists of a nickel-iron alloy in a brew. Therefore it expands and contracts much less than other materials in response to temperature changes. This property allows displays made with this technology to provide a clearer and more accurate picture. It also reduces the amount of long-term stress and damage to the shadow masks, which can be the result of re-expansion/contract cycles, thereby increasing the life expectancy of the display. In other words, in shadow Mask CRT, before the flow of electrons produced by the CRT cathode reaches the phosphorous face plate, it collides with a shadow mask, a sheet of metal engraved with a pattern of holes. The mask is located in a glass CRT funnel during manufacture and the phosphorus is covered on the screen so that the electrons coming from the red, green and blue positions of the cannon only land on the corresponding phosphorus. Stray electrons turn the shadow into the mask and are absorbed by it, generating a lot of heat, which in turn leads to the expansion of the metal. To allow flatter CRTs to be made, the metal is most commonly used nowadays for the shade of the Invar mask, the alloy of iron and nickel. The metal has a low expansion rate, and its name comes from the supposed immutability of its size when applying heat. In fact, its dimensions are not completely unchanged and the accumulation of heat in the mask of the shadow can lead to a form of distortion known as domining, where the center of the mask bulges to faceplate a bit. An alternative to the shadow mask, which is less prone to distortion, the diaphragm grille, was incorporated as part of the design of Trinitron CRTs sony in 1968 and Mitsubishi in its Diamond tron products in the early 1990s. This article is about Ray Tube (CRT) displays. To mask shadows in 3D computer graphics, see the shadows display. The metal sheet with hundreds of thousands of holes used in CRTs to properly align the colors of the Shadow Mask close-up in-line (left) and the triad (right) shadow mask based on the CRT's close-up shadow mask is one of two technologies used in the production of cathode-ray tubes (CRT) TVs and computer monitors that produce clear, targeted color images. Another approach is the aperture lattice, better known as the trade name Trinitron. All early-color TVs and most CRT computer monitors used shadow mask technology. Both of these technologies are largely obsolete, having been increasingly replaced since the 1990s by the liquid crystal display (LCD). The shadow mask is a metal plate punctured by tiny holes that separate colored phosphorus in the layer behind the front glass of the screen. Shadow masks are made by photochemical treatment, a method that allows for drilling of small holes on metal sheets. The three electronic guns at the back of the screen sweep through the mask, with beams only reaching the screen if they pass through the holes. Because the cannons are physically separated at the back of the tube, their beams approach the mask from three slightly different angles, so after passing through the holes they hit a slightly different place on the screen. The screen is patterned with dots of colored phosphorus arranged so that each can be struck by only one of the rays coming from three electronic guns. For example, blue phosphorous dots are hit by a beam from the blue cannon after passing through a certain hole in the mask. The other two guns do the same for red and green dots. This arrangement allows three guns to tackle individual color points on the screen, even if their beams are too large and too poorly directed to do so without a mask in place. Red, green and blue phosphorus are usually arranged in a triangular form (sometimes called a triad). Sometimes they were called game masks. For use on television, modern displays (since the late 1960s) use rectangular slots instead of round holes, improving brightness. The development of Color Television Color Television was explored even before commercial broadcasting became common, but it was not until the late 1940s that the problem was seriously addressed. At that time, a number of systems were offered that used separate red, green and blue signals (RGB) that were broadcast sequentially. Most experimental systems broadcast entire footage sequentially, with a color filter (or gel) that rotates in front of a conventional black-and-white television tube. Each frame is encoded by one color image, and the wheel rotates in sync with the signal, so the correct gel was in front of the screen when Colored frame is now being Because they broadcast individual signals for different colors, all of these systems were incompatible with existing black-and-white sets. Another problem was that the mechanical filter made them flicker if very high rates of upgrades were used. (This is conceptually similar to a DLP-based projection display, where one DLP device is used for all three color channels.) RCA worked in different lines completely, using the brightness-chromanza system first introduced by George Valenci in 1938. This system does not directly encode or transmit RGB signals; instead, he combined these colors into one common brightness figure called brightness. This closely corresponded to the black-and-white signal of existing transmissions, which allowed the image to be displayed on black and white TVs. The remaining color information was separately encoded in the signal as a high-frequency modulation to produce a composite video signal. On black and white television, this additional information will be seen as a small randomization of the intensity of the image, but the limited resolution of existing sets has made this invisible in practice. On color sets, additional information will be detected, filtered and added to the brightness to re-create the original RGB for display. Although the RCA system had huge advantages, it was not successfully developed because it was difficult to produce a tube display. Black-and-white televisions used a continuous signal, and the tube could be covered with uniform phosphorus painting. With the RCA system, the color is constantly changing along a line that was too fast for any kind of mechanical filter to follow. Instead, the phosphorus had to be broken down into a discrete pattern of colored spots. Concentrating the correct signal on each of these tiny spots was beyond the capabilities of the electronic guns of the era. In the 1940s and early 1950s, numerous attempts were made to solve the color problem. A number of large companies continued to work with separate colored channels with different ways of re-combining the image. RCA was included in this group; On February 5, 1940, they demonstrated a system using three conventional tubes combined to form a single image on a glass plate, but the image was too dim to be useful. John Logie Baird, who made the first public colour television broadcast using a semi-mechanical system on February 4, 1938, has already progressed on the all-electronic version. His design, Telechrome, used two electronic guns aimed at both sides of the phosphorus plate in the center of the tube. Development did not go far when Baird died in 1946. A similar project was the Geer tube, which used a similar arrangement of guns aimed at part of one plate covered with small three-sided pyramids covered with phosphorus. However, all of these projects have had problems color of bleeding from one phosphorus to another. Despite their best efforts, the wide electronic beams simply could not concentrate tightly enough to hit individual points, at least throughout the entire screen. In addition, most of these devices were cumbersome; The location of the electronic cannons around the outside of the screen led to a very large display with significant dead space. The rear gun forces a more practical system to use one gun in the back of the tube, firing one multicolored screen at the front. In the early 1950s, several large electronics companies began to develop such systems. Another contender was Penetron General Electric, which used three folded layers of phosphorus and tried to change the power of the electronic beam to write the correct one. More common were attempts to use secondary focus just behind the screen to get the accuracy required. Paramount Pictures worked long and Chromatron, which used a set of wires behind the screen as a secondary gun, further focusing the beam and directing it to the correct color.