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CRT Moniters

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Definition - What does Cathode-Ray Tube (CRT) mean?


A cathode-ray tube is a display device used in television sets and computer monitors. It is a kind of vacuum tube which contains one or more electron guns, electrostatic deflection plates and a phosphor target which is located at the back of the glass screen. A cathode for which the CRT got its name is a positive terminal at which electrons may enter.

In a computer monitor or in a television set, the entire front of the tube is being scanned systematically and rapidly in a fixed pattern which is called a raster. Images and color are produced by shooting and controlling the electron beams representing each additive color light (red, blue and green) using the video signal as the reference.

Modern CRT monitors use magnetic deflection to bend the electron beams. This is done by varying the magnetic field generated by coils which is driven by electronic circuits located along the neck of the tube.

Techlover9 explains Cathode-Ray Tube (CRT)


A cathode ray tube is a specialized vacuum tube where images can be created by shooting electrons beams at the phosphorescent surface. The CRT also known as the picture tube was the only choice for a display device up until the less bulky and less power hungry LCD was invented. They usually employ magnetic deflection for changing the orientation of the electron beams but other types use electrostatic deflection. These are usually used in oscilloscopes as magnetic deflection which would lessen the inductive reactance of the magnetic coils and limit the frequency response of the oscilloscope.

The brightness, color and persistence of the illumination can be varied by using different kinds of phosphor. This is especially useful for making CRTs for different applications.

LCD Moniters

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Definition - What does Liquid Crystal Display Monitor (LCD Monitor) mean?


A liquid crystal display (LCD) monitor is a computer monitor or display that uses LCD technology to show clear images, and is found mostly in laptop computers and flat panel monitors. This technology has replaced the traditional cathode ray tube (CRT) monitors, which were the previous standard and once were considered to have better picture quality than early LCD variants. With the introduction of better LCD technology and its continuous improvement, LCD is now the clear leader over CRT, in terms of color and picture quality, not to mention capabilities for large resolutions. Also, LCD monitors may be made much more cheaply than CRT monitors.

Techlover9 explains Liquid Crystal Display Monitor (LCD Monitor)


Various different LCD technologies are used today, including:

  • In Plane Switching (IPS) Panel Technology: These panels are considered to have the best color accuracy, viewing angles and image quality in LCD technology.
  • Super Plane to Line Switching (PLS): Developed by Samsung, this LCD panel is very similar to the IPS panel but reportedly, it is 10 percent brighter, has wider viewing angles and is cheaper to produce.
  • Vertical Alignment (VA) Panel Technology: These panels are considered to be in the middle of TN and IPS technology. Compared to TN panels, they offer wider viewing angles and better color quality but have slower response times. They have higher contrast ratios, compared to the other panels but have a downside, in terms of color shifting, where the brightness display is unevenly distributed throughout the screen.
  • Twisted Nematic (TN) Panel Technology: These panels are the most commonly used type of panel in LCD technology. They are cheaper and offer faster response times, making them a preferred choice for gamers. The downside is that the viewing angles, contrast ratios and color production are considered the lowest of LCD panel types.

LED Moniters

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The latest marketing innovation to hit TV's and monitors is the term LED. This is being marketed as a new type of screen to supersede the Plasma and the LCD (Liquid Crystal Display). LED means Light Emitting Diode and relates to the way the display is illuminated. LED monitors still use the same Liquid Crystals as the previous LCD displays. The way the backlight works however with the LED's will lead to a number of improvements in the display as we will discover in this article.

Types of LED backlighting

The LED monitor is a new way of lighting a monitor display but there is more than one method being used with relative advantages and disadvantages to them. The three types we will be looking at are W-LED (White-LED), Edge LED, and RGB LED. We are going to start with the Edge LED.

Edge LED monitors

This is the most common method for backlighting in the LED model. Edge LED monitors have diodes placed all around the edge of the screen to light up the display. This is by far the cheapest method and still comes up with some good results. This technology is primarily used in computer monitors. In this model all the diodes produce white light and are laid out as data.
While it may look like this will give the edges of the screen more light than the center of the screen, a little piece of tech called a Light Guide Plate equalizes all the light around the display giving it an equal brightness balance across the entire display. Since the launch of the Edge LED monitors, manufacturers have perfected the technology to the point where they only need to have LED's on a single edge of the screen. This dramatically reduces the production costs of the displays, making LED monitors even more affordable. LED's have now become the mainstream tech for computer monitors because they are now affordable to the masses.

Direct LED Monitors

Direct LED monitors use LED directly behind the liquid crystal display (LCD) in order to light up the screen. This technique is very effective and gives each area of the screen its own diode, which can be on or off. Still using white light, the direct LED screens can produce massive contrast ratio's making the difference between the lights and the blacks appear almost perfect. The problem with the Edge LED's is that some of the deepest blacks can appear a little grey. So Direct LED's are the better option then? Yes however this technology is expensive and also leads to screen being deeper and heavier than the Edge LED counterparts, something the industry is trying to get away from.
Direct LED screen are only found in high end HDTV's at the moment due the cost of manufacturing. But they are the way to go if you can afford them. Its unlikely that the sales person at your local electronics store is going to know what type the TV is so its always worth searching on the net before you make a purchase to see what your really getting for your money. These types of screen may also be referred to as WLED (White LED). Check out the video below on Edge vs. Direct LED's

 

RGB LED monitors work in much the same way as the Direct LED screen only that in these panels the LED's are capable of emitting not white light but RGB (Red, Green, Blue). Because the diodes can produce these colours the actual onscreen colours are much more accurate and also they have a much broader range of colours available. The downside to this method is none other than our good old friend, price. The cost of these panels prices most of the market out of these types of screens. On average you are looking at £2000+ for a TV with RGB LED technology. RGB LED's are also heavier and have more panel depth than the other two.

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