Computer display
From Free net encyclopedia
A computer display, monitor or screen is a computer peripheral device capable of showing characters and/or still or moving images generated by a computer and processed by a graphics card. Monitors generally conform to one or more display standards. Sometimes the name "display" suits better than the word "monitor", as the latter term can also ambiguously refer to a "machine-level debugger" or to a "thread synchronization mechanism". Some people also refer to computer displays as "heads", especially when talking about multiple displays connected to a single physical computer. Once an essential component of a computer terminal, computer displays have long since become standardized peripherals in their own right.
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Hardware
Technologies
As with television, several different hardware technologies exist for displaying computer-generated output:
- Cathode ray tube (CRT)
- Liquid crystal display (LCD). [LCD-based monitors can receive television and computer protocols (SVGA, PAL, SECAM; NTSC).)
- Plasma display
- Surface-conduction electron-emitter display (SED)
- Video projector
- Organic light-emitting diode (OLED) display.
A modern CRT display has considerable flexibility: it can usually handle a range of resolutions from 320 by 200 pixels (320×200) up to 2048 by 1536 pixels (2048×1536) or 2304 by 1440 pixels (2304×1440), with unlimited colours and a variety of refresh rates.
As of 2005, the highest known maximum native resolution for any type of monitor is 3840 by 2400 pixels (3840×2400) on an LCD screen.
Dot pitch measures the sharpness of a display. In general, the lower the dot pitch, (e.g. .24), the sharper the picture will appear.
Early CRT-based VDUs (Visual Display Units) without graphics capabilities gained the label "glass teletypes", because of the functional similarity to their electromechanical predecessors.
Black-and-white displays can only display one colour: either as on or off. Monochrome displays can show only levels of a single colour. In both cases the display usually uses green, orange (amber) or gray (white).
Image:Monitor.jpg Colour monitors may show either digital colour (turning each of the red, green and blue signals either on or off, giving eight possible colours: black, white, red, green, blue, cyan, magenta and yellow - sometimes with an extra "brightness" signal producing a total of up to 16 colours) or analog colour (red, green and blue signals vary continuously, allowing the display of any combination). Early digital monitors are sometimes known as TTLs because the voltages on the red, green and blue inputs are compatible with TTL logic chips. Later digital monitors support LVDS, or TMDS protocols.
Most modern computer displays can show thousands or millions of different colours in the RGB colour space by combining red, green, and blue dots in varying intensities.
With exceptions of DLP, most display technologies (especially LCD) have an inherent misregistration of the colour planes, that is, the centers of the red, green, and blue dots do not line up perfectly. Subpixel rendering depends on this misalignment; technologies making use of this include the Apple II from 1976 [1], and more recently Microsoft (ClearType, 1998) and XFree86 (X Rendering Extension).
Moving texts can appear in italics, even when the display resolution is too low to show static italics: a fractional time delay causes an apparent corresponding shift of a fraction of a pixel.
Note the sometimes disputed issue of screen emissions. Most computer monitors have analog signal relay, but some (mostly LCD screens) start supporting digital input signals. It is a common misconception that all computer monitors are digital. For several years, Televisions, composite monitors and computer displays have had significant distinction, however it has blurred as newer TVs have become versatile to accommodate these purposes.
History
A trend of miniaturization within computer displays has seen a general move away from the older, bulky CRT devices in the general direction of flat screens as found in modern laptops.
Major manufacturers
- Apple Computer
- BenQ
- Dell, Inc.
- Eizo
- Iiyama Corporation
- LaCie
- LG Electronics
- NEC/Mitsubishi
- Philips
- Samsung
- Sony
- ViewSonic
Performance Measurements
The relevant performance measurements of a monitor are:
- Luminance
- Size
- Dot pitch
- Color temperature
- Contrast ratio
- Interface (DVI or VGA, commonly)
- H-sync rate
- V-sync rate
- Response time
- Refresh rate
Configuration and usage
Multi-head
Template:Main Some users use more than one monitor. The displays can operate in multiple modes. One of the most common spreads the entire desktop over all of the monitors, which thus act as one big desktop. The X Window System refers to this as "Xinerama".
A monitor may also clone another monitor.
Terminology:
- Dualhead - Using two monitors
- Triplehead - using three monitors
- Display assembly - multi-head configurations actively managed as a single unit
Virtual displays
The X Window System provides configuration mechanisms for using a single hardware monitor for rendering multiple virtual displays, as controlled (for example) with the Unix DISPLAY global variable or with the -display command option.bs:Monitor ca:Monitor (informàtica) cs:Monitor (obrazovka) da:Skærm (monitor) de:Bildschirm es:Pantalla de ordenador eu:Pantaila (ordenagailua) fi:Näyttö fr:Moniteur d'ordinateur gl:Monitor he:צג hr:Zaslon ja:ディスプレイ (コンピュータ) ln:Emónisi lt:Monitorius nds:Kieker (Reekner) nl:Beeldscherm pl:Monitor (ekran) pt:Monitor ru:Монитор (дисплей) simple:Monitor sl:Monitor sr:Монитор sv:Bildskärm zh:显示器