A monitor or display (sometimes called a visual display unit) is an electronic visual display forcomputers. The monitor comprises the display device, circuitry, and an enclosure. The display device in modern monitors is typically a thin film transistor liquid crystal display (TFT-LCD) thin panel, while older monitors use a cathode ray tube about as deep as the screen size.Originally computer monitors were used for data processing and television receivers for entertainment; increasingly computers are being used both for data processing and entertainment and TVs implement some typical computer functionality. Displays exclusively for data use tend to have an aspect ratio of 4:3; those used also (or solely) for entertainment are usually 16:9 widescreen, Sometimes a compromise is used, e.g. 16:10[1].
Screen size
The size of an approximately rectangular display is usually given as the distance between two opposite screen corners, that is, the diagonal of the rectangle. One problem with this method is that it does not take into account the display aspect ratio, so that for example a 16:9 21 in (53 cm) widescreen display is far less high, and has less area, than a 21 in (53 cm) 4:3 screen. The 4:3 screen has dimensions of 16.8 × 12.6 in (43 × 32 cm) and area 211 sq in (1,360 cm2), while the widescreen is 18.3 × 10.3 in (46 × 26 cm), 188 sq in (1,210 cm2). For many purposes the height of the display is the main parameter; a 16:9 display needs a diagonal 22% larger than a 4:3 display for the same height.
This method of measurement is inherited from the method used for the first generation of CRT television, when picture tubes with circular faces were in common use. Being circular, only their diameter was needed to describe their size. Since these circular tubes were used to display rectangular images, the diagonal measurement of the rectangle was equivalent to the diameter of the tube's face. This method continued even when cathode ray tubes were manufactured as rounded rectangles; it had the advantage of being a single number specifying the size, and was not confusing when the aspect ratio was universally 4:3.
A problematic practice was the use of the size of a monitor's imaging element, rather than the size of its viewable image, when describing its size in publicity and advertising materials. On CRT displays a substantial portion of the CRT's screen is concealed behind the case's bezel or shroud in order to hide areas outside the monitor's "safe area" due to overscan. These practices were seen as deceptive, and widespread consumer objection and lawsuits eventually forced most manufacturers to instead measureviewable size[citation needed].
Performance measurements
Comparison
[edit]CRT
Pros:- High dynamic range (up to around 15,000:1),[2] excellent color, wide gamut and low black level. The color range of CRTs is unmatched by any display type except OLED.
- Can display natively in almost any resolution and refresh rate
- No input lag
- Sub-millisecond response times
- Near zero color, saturation, contrast or brightness distortion. Excellent viewing angle.
- Usually much cheaper than LCD or Plasma screens.
- Allows the use of light guns/pens
Cons:Cons:- Large size and weight, especially for bigger screens (a 20-inch unit weighs about 50 lb (23 kg))
- High power consumption
- Generates a considerable amount of heat when running
- Geometric distortion caused by variable beam travel distances
- Can suffer screen burn-in
- Produces noticeable flicker at low refresh rates
- Normally only produced
Phosphor burn-in
Phosphor burn-in is localized aging of the phosphor layer of a CRT screen where it has displayed a static image for long periods of time. This results in a faint permanent image on the screen, even when turned off. In severe cases, it can even be possible to read some of the text, though this only occurs where the displayed text remained the same for years.Screensavers were developed as a means to avoid burn-in, which was a widespread problem on IBM Personal Computer monochrome monitors in the 1980s. Monochrome displays are generally more vulnerable to burn-in because the phosphor is directly exposed to the electron beam while in colour displays, the shadow mask provides some protection. Although still found on newer computers, screen savers are not necessary on LCD monitors.Phosphor burn-in can be "fixed" by running a CRT with the brightness at 100% for several hours, but this merely hides the damage by burning all the phosphor evenly. CRT rebuilders can repair monochrome displays by cutting the front of the picture tube off, scraping out the damaged phosphor, replacing it, and resealing the tube. Colour displays can theoretically be repaired, but it is a difficult, expensive process and is normally only done on professional broadcasting monitors (which can cost up to $10,000).
GlareGlare is a problem caused by the relationship between lighting and screen or by using monitors in bright sunlight. Matte finish LCDs and flat screen CRTs are less prone to reflected glare than conventional curved CRTs or glossy LCDs, and aperture grille CRTs, which are curved on one axis only and are less prone to it than other CRTs curved on both axes.
Colour misregistration
With exceptions of correctly aligned video projectors and stacked LEDs, most display technologies, especially LCD, have an inherent misregistration of the color channels, that is, the centers of the red, green, and blue dots do not line up perfectly. Sub-pixel renderingdepends on this misalignment; technologies making use of this include the Apple II from 1976[3], and more recently Microsoft (ClearType, 1998) and XFree86 (X Rendering Extension).Analog monitors
Most modern computer displays can show the various colors of the RGB color space by changing red, green, and blue analog video signals in continuously variable intensities. These are almost exclusively progressive scan. Although televisions used an interlaced picture, this was too flickery for computer use. In the late 1980s and early 1990s, some VGA-compatible video cards in PCs used interlacing to achieve higher resolution, but the event of SVGA quickly put an end to them. While many early plasma and liquid crystal displays have exclusively analog connections, all signals in such monitors pass through a completely digital section prior to display.CRTs remained the standard for computer monitors through the 1990s. The first standalone LCD displays appeared in the early 2000s and over the next few years, they gradually displaced CRTs for most applications. First-generation LCD monitors were only produced in 4:3 aspect ratios, but current models are generally 16:9. The older 4:3 monitors have been largely relegated to point-of-service and some other applications where widescreen is not required.
Comparison
[edit]CRT
Pros:
- High dynamic range (up to around 15,000:1),[2] excellent color, wide gamut and low black level. The color range of CRTs is unmatched by any display type except OLED.
- Can display natively in almost any resolution and refresh rate
- No input lag
- Sub-millisecond response times
- Near zero color, saturation, contrast or brightness distortion. Excellent viewing angle.
- Usually much cheaper than LCD or Plasma screens.
- Allows the use of light guns/pens
Cons:
Cons:
- Large size and weight, especially for bigger screens (a 20-inch unit weighs about 50 lb (23 kg))
- High power consumption
- Generates a considerable amount of heat when running
- Geometric distortion caused by variable beam travel distances
- Can suffer screen burn-in
- Produces noticeable flicker at low refresh rates
- Normally only produced
Phosphor burn-in
Phosphor burn-in is localized aging of the phosphor layer of a CRT screen where it has displayed a static image for long periods of time. This results in a faint permanent image on the screen, even when turned off. In severe cases, it can even be possible to read some of the text, though this only occurs where the displayed text remained the same for years.
Screensavers were developed as a means to avoid burn-in, which was a widespread problem on IBM Personal Computer monochrome monitors in the 1980s. Monochrome displays are generally more vulnerable to burn-in because the phosphor is directly exposed to the electron beam while in colour displays, the shadow mask provides some protection. Although still found on newer computers, screen savers are not necessary on LCD monitors.
Phosphor burn-in can be "fixed" by running a CRT with the brightness at 100% for several hours, but this merely hides the damage by burning all the phosphor evenly. CRT rebuilders can repair monochrome displays by cutting the front of the picture tube off, scraping out the damaged phosphor, replacing it, and resealing the tube. Colour displays can theoretically be repaired, but it is a difficult, expensive process and is normally only done on professional broadcasting monitors (which can cost up to $10,000).
GlareGlare is a problem caused by the relationship between lighting and screen or by using monitors in bright sunlight. Matte finish LCDs and flat screen CRTs are less prone to reflected glare than conventional curved CRTs or glossy LCDs, and aperture grille CRTs, which are curved on one axis only and are less prone to it than other CRTs curved on both axes.
Colour misregistration
With exceptions of correctly aligned video projectors and stacked LEDs, most display technologies, especially LCD, have an inherent misregistration of the color channels, that is, the centers of the red, green, and blue dots do not line up perfectly. Sub-pixel renderingdepends on this misalignment; technologies making use of this include the Apple II from 1976[3], and more recently Microsoft (ClearType, 1998) and XFree86 (X Rendering Extension).
Analog monitors
Most modern computer displays can show the various colors of the RGB color space by changing red, green, and blue analog video signals in continuously variable intensities. These are almost exclusively progressive scan. Although televisions used an interlaced picture, this was too flickery for computer use. In the late 1980s and early 1990s, some VGA-compatible video cards in PCs used interlacing to achieve higher resolution, but the event of SVGA quickly put an end to them. While many early plasma and liquid crystal displays have exclusively analog connections, all signals in such monitors pass through a completely digital section prior to display.CRTs remained the standard for computer monitors through the 1990s. The first standalone LCD displays appeared in the early 2000s and over the next few years, they gradually displaced CRTs for most applications. First-generation LCD monitors were only produced in 4:3 aspect ratios, but current models are generally 16:9. The older 4:3 monitors have been largely relegated to point-of-service and some other applications where widescreen is not required.
Most modern computer displays can show the various colors of the RGB color space by changing red, green, and blue analog video signals in continuously variable intensities. These are almost exclusively progressive scan. Although televisions used an interlaced picture, this was too flickery for computer use. In the late 1980s and early 1990s, some VGA-compatible video cards in PCs used interlacing to achieve higher resolution, but the event of SVGA quickly put an end to them. While many early plasma and liquid crystal displays have exclusively analog connections, all signals in such monitors pass through a completely digital section prior to display.
CRTs remained the standard for computer monitors through the 1990s. The first standalone LCD displays appeared in the early 2000s and over the next few years, they gradually displaced CRTs for most applications. First-generation LCD monitors were only produced in 4:3 aspect ratios, but current models are generally 16:9. The older 4:3 monitors have been largely relegated to point-of-service and some other applications where widescreen is not required.
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