Prev NEXT. Computer Peripherals. Computer Monitors. Display History In , IBM introduced the Color Graphics Adapter CGA , which was capable of rendering four colors, and had a maximum resolution of pixels horizontally by pixels vertically. EGA allowed up to 16 different colors and increased the resolution to x pixels, improving the appearance of the display and making it easier to read text. Read More. The control grid regulates the brightness of the spot on the screen. By controlling the number of electrons by the anode and hence the focusing anode ensures that electrons leaving the cathode in slightly different directions are focused down to a narrow beam and all arrive at the same spot on the screen.
The whole assembly of cathode, control grid, focusing anode, and accelerating electrode are called the electron gun. Two pairs of deflecting plates allow the beam of electrons. An electric field between the first pair of plates deflects the electrons horizontally, and an electric field between the second pair deflects them vertically, the electrons travel in a straight line from the hole in the accelerating anode to the center of the screen when no deflecting fields are present, where they produce a bright spot.
This may be circular or rectangular. The screen is coated with a special type of fluorescent material. Fluorescent material absorbs its energy and re-emits light in the form of photons when the electron beam hits the screen.
When it happens some of them bounces back just like bouncing off a cricket ball from a wall. These are called secondary electrons.
They must be absorbed and returned to the cathode if it is not so they accumulate near the screen and produce space charge or electrons cloud. To avoid this, aqua day coating is applied on the funnel part of CRT from inside. The use of CRT technology has quickly declined since the introduction of LCDs but they are still unbeatable in certain ways. The electrons collide with the phosphor atoms, causing them to gain energy or become "excited. Older CRT TVs use just a single color phosphor and so can only produce black-and-white, or monochrome, pictures.
Later CRT TVs use phosphors colored in the three primary colors -- red, green and blue -- and therefore can produce full color pictures. In the latter case, manufacturers apply multiple color coatings to the screen through a device known as an aperture mask, made from perforated metal, to create thousands of narrow, colored lines of phosphor.
The electron guns generate sharply focused electrons which are accelerated at high voltage. This high-velocity electron beam when strikes on the fluorescent screen creates luminous spot. After exiting from the electron gun, the beam passes through the pairs of electrostatic deflection plate. These plates deflected the beams when the voltage applied across it.
The one pair of plate moves the beam upward and the second pair of plate moves the beam from one side to another. The horizontal and vertical movement of the electron are independent of each other, and hence the electron beam positioned anywhere on the screen.
The working parts of a CRT are enclosed in a vacuum glass envelope so that the emitted electron can easily move freely from one end of the tube to the other.
The electron gun emits the electron beam, and through deflecting plates, it is strikes on the phosphorous screen. The detail explanation of their parts is explained below. The electron gun is the source of the electron beams. The electron gun has a heater, cathode, grid, pre-accelerating anode, focusing anode and accelerating anode.
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