Computer monitor
A monitor or display (sometimes called a visual display unit) is an electronic visual display for computers. 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.
The first computer monitors used Cathode ray tubes (CRTs), which was the dominant technology until they were replaced by LCD monitors in the 21st Century.
Originally computer monitors were used for data processing while television receivers were used for entertainment. From the 80s onwards, computers have been used for both data processing and entertainment, while televisions have implemented some computer functionality. The common aspect ratio of televisions, and then computer monitors, has also changed from 4:3 to 16:9.
Technologies
Different image techniques have been used for Computer monitors. Until the 21st century most monitors were CRT but they have been phased out for LCD monitors.
Cathode ray tube
The first computer monitors used cathode ray tubes (CRT). Until the early 1980s, they were known as video display terminals and were physically attached to the computer and keyboard. The monitors were monochrome, flickered and the image quality was poor. In 1981, IBM invented the Color Graphics Adapter, which could display four colors with a resolution of 320 by 200 pixels. They introduced the Enhanced Graphics Adapter in 1984, which was capable of producing 16 colors and had a resolution of 640 by 350.[1]
CRT remained the standard for computer monitors through the 1990s. CRT technology remained dominant in the PC monitor market into the new millennium partly because it was cheaper to produce and offered viewing angles close to 180 degrees.[2]
Liquid Crystal
TFT-LCD is a variant of liquid crystal display (LCD) which is used for computer monitors. [3]
The first standalone LCD displays appeared in the early 2000s and over the next few years, they gradually displaced CRTs.[2] The main advantages of LCD over CRT are that they are lighter and consumes less power. The technology also has less flickering, which reduces eye strain.[4]
Future
Organic light-emitting diode (OLED) monitors provide higher contrast and better viewing angles than LCDs, and are predicted to replace them. In 2011 a 25 inch OLED monitor costs $6000, but the prices are expected to drop.[5]
Performance measurements
The performance of a monitor is measured by the following parameters:
- Luminance is measured in candelas per square meter (cd/m2 also called a Nit).
- Aspect ratios is the ratio of the horizontal length to the vertical length. Monitors usually have the aspect ratio 4:3, 16:10 or 16:9.
- Viewable image size is usually measured diagonally, but the actual widths and heights are more informative since they are not affected by the aspect ratio in the same way. For CRTs, the viewable size is typically 1 in (25 mm) smaller than the tube itself.
- Display resolution is the number of distinct pixels in each dimension that can be displayed. Maximum resolution is limited by dot pitch.
- Dot pitch is the distance between subpixels of the same color in millimeters. In general, the smaller the dot pitch, the sharper the picture will appear.
- Refresh rate is the number of times in a second that a display is illuminated. Maximum refresh rate is limited by response time.
- Response time is the time a pixel in a monitor takes to go from active (black) to inactive (white) and back to active (black) again, measured in milliseconds. Lower numbers mean faster transitions and therefore fewer visible image artifacts.
- Contrast ratio is the ratio of the luminosity of the brightest color (white) to that of the darkest color (black) that the monitor is capable of producing.
- Power consumption is measured in watts.
- Viewing angle is the maximum angle at which images on the monitor can be viewed, without excessive degradation to the image. It is measured in degrees horizontally and vertically.
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. 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 measure viewable size[citation needed].
The estimation of the monitor size by the distance between opposite corners does not take into account the display aspect ratio, so that for example a 16:9 21 in (53 cm) widescreen display has less area, than a 21 in (53 cm) 4:3 screen. The 4:3 screen has dimensions of 16.8 in × 12.6 in (43 cm × 32 cm) and area 211 sq in (1,360 cm2), while the widescreen is 18.3 in × 10.3 in (46 cm × 26 cm), 188 sq in (1,210 cm2).
Aspect ratio
Until about 2003, most computer monitors had a 4:3 aspect ratio and some had 5:4. Between 2003 and 2006, monitors with 16:9 and mostly 16:10 (8:5) aspect ratios became commonly available, first in laptops and later also in standalone monitors. Reasons for this transition was productive uses for such monitors, i.e. besides widescreen computer game play and movie viewing, are the word processor display of two standard letter pages side by side, as well as CAD displays of large-size drawings and CAD application menus at the same time.[6][7] 2008 16:10 became the most common sold aspect ratio for LCD monitors and the same year 16:10 was the mainstream standard for laptops and notebooks.[8]
In 2008 the computer industry started to move over from 16:10 to 16:9. According to a report by displaysearch the reasons for this were/are:[8]
- Innovative product concepts drives a new product cycle and stimulating the growth of the notebook PC and LCD monitor market.
- 16:9 provides better economic cut (panelization) in existing TFT LCD fabs.
- 16:9 products provide higher resolution and wider aspect ratio.
- The widespread adoption of High Definition in the consumer entertainment sector will help end users readily adopt the new products with the wider aspect ratio.
- The 16:9 panels provide an opportunity for PC brands to further diversify their products.
In 2011 Bennie Budler, product manager of IT products at Samsung South Africa, confirmed that monitors capable of 1920 × 1200 resolutions are no longer being manufactured. “It is all about reducing manufacturing costs. The new 16:9 aspect ratio panels are more cost effective to manufacture locally than the previous 16:10 panels”[9]
In 2011 non-widescreen displays with 4:3 aspect ratios were only being manufactured in small quantities. According to Samsung this was because the “Demand for the old 'Square monitors' has decreased rapidly over the last couple of years,” and “I predict that by the end of 2011, production on all 4:3 or similar panels will be halted due to a lack of demand.”[9]
Resolution
The resolution for computer monitors have increased over time. From 320 by 200 during the early 80s, to 800 by 600 during the late 90s. In March 2011 1920 x 1080 became the most common used resolution among Steam users. The earlier most common resolution was 1680 x 1050.[10]
Configuration and usage
Multiple monitors
More than one monitor can be attached to the same device.
- Mirroring (sometimes cloning,) in which at least two displays are showing the same image. It is commonly used for presentations. Hardware with only one video output can be tricked into doing this with an external splitter device, commonly built into many video projectors as a pass through connection.
- Extension allows each monitor to display a different image, so as to form a contiguous area of arbitrary shape. This requires software support and extra hardware, and may be locked out on "low end" products by crippleware.
- Spanning a very large virtual display is created, and then pieces are split into multiple video outputs for separate monitors. Hardware with only one video output can be made to do this with an expensive external splitter device, this is most often used for very large composite displays made from many smaller monitors placed edge to edge.
Multiple video sources
Multiple devices can be connected to the same monitor using a video switch. In the case of computers, this usually takes the form of a "Keyboard Video Mouse switch" (KVM) switch, which is designed to switch all of the user interface devices for a workstation between different computers at once.
Virtual displays
Much software and video hardware supports the ability to create additional, virtual pieces of desktop, commonly known as workspaces. Spaces is Apple's implementation of virtual displays.
Additional features
Power saving
Most modern monitors will switch to a power-saving mode if no video-input signal is received. This allows modern operating systems to turn off a monitor after a specified period of inactivity. This also extends the monitor's service life.
Some monitors will also switch themselves off after a time period on standby.
Most modern laptops provide a method of screen dimming after periods of inactivity or when the battery is in use. This extends battery life and reduces wear.
Integrated accessories
Many monitors have other accessories (or connections for them) integrated. This places standard ports within easy reach and eliminates the need for another separate hub, camera, microphone, or set of speakers. These monitors have advanced microprocessors which contain codec information, Windows Interface drivers and other small software which help in proper functioning of these functions.
Glossy screen
Some displays, especially newer LCD monitors, replace the traditional anti-glare matte finish with a glossy one. This increases color saturation and sharpness but reflections from lights and windows are very visible.
Directional screen
Narrow viewing angle screens are used in some security conscious applications.
Autostereoscopic (3D) screen
A directional screen which generates 3D images without headgear.
Touch screen
These monitors use touching of the screen as an input method. Items can be selected or moved with a finger, and finger gestures may be used to convey commands. The screen will need frequent cleaning due to image degradation from fingerprints.
Tablet screens
A combination of a monitor with a graphics tablet. Such devices are typically unresponsive to touch without the use of one or more special tools' pressure. Newer models however are now able to detect touch from any pressure and often have the ability to detect tilt and rotation as well.
Touch and tablet screens are used on LCD displays as a substitute for the light pen, which can only work on CRTs.
Well-known manufacturers
See also
References
- ^ "Cathode Ray Tube (CRT) Monitors". Infodingo.com. Retrieved 2011-05-20.
- ^ a b "CRT Monitors". PCTechGuide.Com. Retrieved 2011-05-20.
- ^ "TFT Central". TFT Central. 2011-04-30. Retrieved 2011-05-20.
- ^ "Is the LCD monitor right for you?". Infodingo.com. Retrieved 2011-05-20.
- ^ Agoraquest, LLC - The only place for the Sony Enthusiast. "Sony's Outs Two New OLED Monitors". Agoraquest. Retrieved 2011-05-20.
- ^ NEMATech Computer Display Standards http://www.millertech.com/Technical_Specs.htm
- ^ "Introduction--Monitor Technology Guide". necdisplay.com. Archived from the original on 2007-03-15. (currently offline)
- ^ a b "Product Planners and Marketers Must Act Before 16:9 Panels Replace Mainstream 16:10 Notebook PC and Monitor LCD Panels, New DisplaySearch Topical Report Advises". DisplaySearch. 2008-07-01. Retrieved 2011-05-20.
- ^ a b http://mybroadband.co.za/news/hardware/17621-Widescreen-monitors-Where-did-1920x1200.html
- ^ "Steam Hardware & Software Survey". Store.steampowered.com. Retrieved 2011-05-20.
External links