Display and types of display_Display's types

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                Displays and types of displays 

Display-A display is an electronics output device that displays information in pictorial form is called display.
  Different types of display.
·        CRT (cathode ray tube) display.
·        LCD (liquid crystal display) display.
  1.          Light-emitting diode (LED) backlit LCD
  2.       Thin-film transistor (TFT) LCD
·        Plasma display.
·        LED(light emitting diode) display
  1.                OLED display
  2.            AMOLED display
·        Plasma Screen display


CRT display 
CRT displays are widely used with computers to display alphanumeric characters and graphs. CRT stands for cathode ray tube. To display characters on a CRT screen an electron beam is swept back and forth across the screen. The beam is also swept up and down. This method of displaying images is known as raster scan method. The cursor points the spot on the screen where one can enter the desired character. The cursor moves left and right, up and down. A CRT terminal also contains a keyboard to enter programs. The typed texts are displayed on the screen. If there are errors, they can be corrected. To correct an error the cursor is brought at the spot where correction is to be made. Then key for the correct character is pressed. A character is formed by light dots. To display a character the required light dots are energised to glow. The screen of a commonly used CRT terminal can accommodate 25 lines. Each line contains 80 characters. A CRT controller is an IC which contains the necessary circuitry to control the operation of a CRT. A television screen can be used as a CRT screen. A suitable interfacing circuitry is to be incorported for the purpose.
                              Raster Scan Colour Graphics- For a monochrome display inner side of the screen is coated with a single phosphor which produces the images of desired colour. For colour display the screen is coated with red, green and blue phosphors. One technique of coating is to have dots of the three phosphors in a triangular pattern over the entire Screen. The three different phosphors are bombarded by three separate electron beams. By turning on and off different combinations of red, blue and green beam 16 colours can be produced. Instead of switching on and off beams, if their intensity is controlled using D/A converters, a variety of colours can be produced.   
                                                     
                   Vector Scan CRT Display- The electron beam is scanned over the entire screen in A raster scan CRT. In certain applications only lines are to be shown on the screen. For such applications it will be wasteful to scan the electron beam over the entire screen. A diagonal line drawn on raster CRT looks like stair steps. A vector scan CRT does not have these disadvantages. If a line between points A and B is to be drawn on a vector scan CRT, the electron beam moves directly from A to B. This is achieved using D/A converters in horizontal and vertical deflection circuitry. The values of inputs to these converters decides the position of the beam on the screen. The vector scan CRT is good to display graphics containing straight lines, but is not suitable for curves.


·        LCD (liquid crystal display) display.

LCD stands for liquid crystal display. LCD display is a kind of flat-panel display. It is also called TFT (Thin Film Transistors) screen. TFT screen are widely used in notebook computers. They are also being used in desktop computers. An element of LCD contains crystalline liquid material sandwitched between two glass or plastic plates. When exposed to electrical signal, the molecules of liquid crystal change their alignment to either transmit or block light, which ultimately creates an image. A matrix of tiny switching transistors (TFT) is placed on a glass substrate to control on/off state of each pixel depending on the electrical signal applied. LCDS are used in watches, calculators, notebook computers, desktop computers etc. In screen type of LCD, the liquid crystal elements are arranged in a large X-Y matrix of dots. The LCD elements are connected together row-wise and column-wise for energizing purpose.
                             Light-emitting diode (LED) backlit LCD- A LED-backlit LCD is a flat panel display that uses LED backlighting instead of traditional cold cathode fluorescent (CCFL) backlighting.LED-backlit displays use the same TFT LCD (thin-film-transistor liquid-crystal display) technologies as CCFL-backlit displays, but offer reduced energy consumption, better contrast and brightness, greater color range (using more expensive RGB LEDs, blue LEDs with RG phosphors, or a quantum dot enhancement film (QDEF)), more rapid response to changes in scene (with dynamic backlight dimming), and photorefractive effects.


                 Thin-film transistor (TFT) LCD- A thin-film-transistor liquid-crystal display (TFT LCD) is a variant of a liquid-crystal display (LCD) that uses thin-film-transistor (TFT) technology to improve image qualities such as addressability and contrast. A TFT LCD is an active matrix LCD, in contrast to passive matrix LCDs or simple, direct-driven LCDs with a few segments.
EX-TFT LCDs are used in appliances including television sets, computer monitors, mobile phones, 

Plasma display
                                                                         
Display It is also a kind of flat-panel display. A plasma display contains ionized gas sandwitched between two glass plates. Several parallel wires run horizontally as well as vertically. An electrical signal is applied to one of the horizontal wires as well as one of the vertical wires. This causes the gas to glow at the spot lying at the intersection of the energized wires. Plasma displays are brighter than LCD and they can easily be built in large sizes, larger than 40 inches. They use simplified controlling circuits. They are less expensive. In plasma display phosphor material is used for each cell. Red, green and blue phosphors are used in three adjacent cells, for colour display.
·        LED(light emitting diode) display
It working principle is electroluminescence.A LED display is a flat panel display that uses an array of light-emitting diodes as pixels for a video display. Their brightness allows them to be used outdoors where they are visible in the sun for store signs and billboards. In recent years, they have also become commonly used in destination signs on public transport vehicles, as well as variable-message signs on highways.
                       OLED display-OLED (Organic Light Emitting Diodes) is a flat light emitting technology, made by placing a series of organic(carbon-hydrogen bond) thin films between two conductors. When electrical current is applied, a bright light is emitted.

AMOLED display-AMOLED is an 'active-matrix organic light-emitting diode'. It adds a layer of semiconducting film behind the OLED panel which allows it to more quickly activate each pixel. That increased speed makes it ideal for larger, higher definition displays with a lot of pixels.
 EX- smartwatches, mobile devices, laptops, and televisions. 

    NOTE-The AMOLED screen is considered to be the best type of screens for mobile phones, and some the best phones today like the Samsung S8 and Note-8 use AMOLED screens.



Location: India

Comments

  1. liuamy29 December 2020 at 03:56

    I am thankful to this blog giving unique and helpful knowledge about this topic.
    lcd display screen

    ReplyDelete

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