A monitor is an output device that displays information in pictorial form. A monitor usually comprises the display device, circuitry, casing, and power supply. The display device in modern monitors is typically a thin film transistor liquid crystal display (TFT-LCD) or a flat panel LED display, while older monitors used a cathode ray tube (CRT).
Monitors are connected to computers via VGA, DVI, HDMI, DisplayPort, Thunderbolt, or USB Type-C cables. The first computer monitors used cathode ray tubes. Data was displayed on a screen by firing electrons at it. The electrons were produced by electron guns mounted on each side of the screen. The guns were aimed at the screen by magnetic coils or by electrostatic deflection, depending on the type of CRT. The screen had a coating of phosphor on it, which glowed when hit by the electrons. The glowing phosphor produced the images on the screen. Each phosphor dot on the screen was actually a tiny phosphor-coated bead, with the three colors (red, green, and blue) being produced by different phosphors. The beads were very close together so the human eye could not resolve them. The screen had to be large enough so the guns could fire the electrons across the entire screen without them missing the phosphor beads.
The first monitors were monochrome, displaying only white and black colors. Color monitors were developed next, using a shadow mask. A shadow mask is a thin piece of metal with tiny holes in it. The holes are aligned over the phosphor dots on the screen. The guns fire the electrons through the holes. The electrons can only hit the phosphor dots that are directly behind the holes in the shadow mask. This way, each phosphor dot is only hit by the electrons that are supposed to produce the color for that dot. This method is still used in CRTs today.
LCD monitors work in a completely different way. They don’t use electron guns or phosphor dots. Instead, they use a backlight to produce the images on the screen. The backlight is a bank of LEDs (light emitting diodes) that shine through a diffuser. The diffuser spreads the light evenly over the entire screen. The backlight is usually located at the bottom of the LCD panel.
A layer of liquid crystal is placed over the backlight. The liquid crystal is a special type of material that can change its properties when an electric field is applied to it. The liquid crystal is sandwiched between two polarizing filters. One filter is placed over the backlight and the other filter is placed over the LCD panel. The filters are oriented so that the light can only pass through them if the liquid crystal is in the correct state.
When no electric field is applied to the liquid crystal, it is in a state called “twisted nematic.” In this state, the light can pass through the two filters and is then polarized by the liquid crystal. The light then passes through the LCD panel to the front of the screen, where it is visible to the user.
When an electric field is applied to the liquid crystal, it untwists and the light can no longer pass through it. This state is called “homeotropic.” In the homeotropic state, the light is blocked and the pixel is turned off. By applying different voltages to the liquid crystal, it is possible to control how much light passes through it. This is how images are produced on an LCD screen.
LCD monitors have several advantages over CRT monitors. They are thinner, lighter, and use less power. They also produce less electromagnetic interference. LCD monitors are available in a wide range of sizes, from small screens that are only a few inches wide to large screens that are several feet wide. LCD monitors are also available in a wide range of resolutions, from 640×480 to 2560×1440 and beyond.
LED monitors are similar to LCD monitors, but they use LEDs (light emitting diodes) instead of a backlight. The LEDs are located around the edge of the screen. They shine light onto the LCD panel, which then produces the images on the screen. LED monitors have the same advantages as LCD monitors, but they are even thinner and lighter. They also have better color reproduction and use even less power than LCD monitors.
Monitors are an important part of any computer system. They allow the user to see what the computer is doing and interact with it. Without a monitor, a computer would be much less useful.