Information about Liquid Crystal Display Television
Liquid crystal display television (LCD TV) is television that uses LCD technology for its visual output. The technology used is generally TFT. In the early 2000s, LCD flat-panels captured a large part of the computer monitor market from traditional CRTs. Continuing advances in LCD TV technology enable it to compete against Plasma flat panels and rear-projection televisions (DLP, LCD, and LCoS) for large-screen HDTV.
Early LCD television had drawbacks relative to traditional visual display technologies. It displayed fast-moving action with "ghosting" and could be viewed best only when looking directly at the screen or from a slight angle. Most of these problems were solved in recent years, and LCD televisions, along with plasma displays, have become more popular worldwide than cathode ray display televisions. The LCD design is also known for being more energy efficient than the CRT design.
For a long time it was widely believed that LCD technology was suited only to smaller sized flat-panel televisions, and could not compete with plasma technology at sizes of 40" or larger. At the time, plasma held the edge in cost and performance. Presently, LCD TV's can offer the same performance with the announcements of seventh-generation panels by major manufacturers such as Samsung, Sony, LG.Philips LCD, and Sharp Corporation:
Improvements in LCD technology have narrowed the technological gap with plasmas. The lower weight, falling prices, higher available resolution which is crucial for HDTV, and lower electrical power consumption of LCDs make them competitive against plasma displays in the television set market. As of late 2006, analysts note that LCDs are overtaking plasmas, particularly in the important 40" and above segment where plasma had enjoyed strong dominance a couple of years before. [1][2]
This pixel has darkened. The pixel darkens in proportion to the voltage applied to it: for a bright detail, a low voltage is applied to the pixel; for a dark shadow area, a higher voltage is applied. LCDs are not completely opaque to light, however; some light will always go through even the blackest LCD pixels.
Moving pictures on a CRT TV do not exhibit any sort of "ghosting" because the CRT's phosphor, charged by the strike of electrons, emits most of the light in a very short time, under 1 ms, compared with the refresh period of e.g. 20 ms (for 50 fps video). In LCDs, each pixel emits light of set intensity for a full period of 20 ms (in this example), plus the time it takes for it to switch to the next state, typically 12 to 25 ms.
The second time (called the "response time") can be shortened by the panel design (for black-to-white transitions), and by using the technique called overdriving (for black-to-gray and gray-to-gray transitions); however this only can go down to as short as the refresh period.
This is usually enough for watching film-based material, where the refresh period is so long (1/24 s, or nearly 42 ms), and jitter is so strong on moving objects that film producers actually almost always try to keep object of interest immobile in the film's frame.
Video material, shot at 50 or 60 frames a second, actually tries to capture the motion. When the eye of a viewer tracks a moving object in video, it doesn't jump to its next predicted position on the screen with every refresh cycle, but it moves smoothly; thus the TV must display the moving object in "correct" places for as long as possible, and erase it from outdated places as quickly as possible.
Although ghosting was a problem when LCD TVs were newer, the manufacturers have been able to shorten response time to 2ms on many computer monitors and around an average of 8 ms for TVs.
There are two emerging techniques to solve this problem. First, the backlight of the LCD panel may be fired during a shorter period of time than the refresh period, preferably as short as possible, and preferably when the pixel has already settled to the intended brightness. This technique resurrects the flicker problem of the CRTs, because the eye is able to sense flicker at the typical 50 or 60 Hz refresh rates.
Another approach is to double the refresh rate of the LCD panel, and reconstruct the intermediate frames using various motion compensation techniques, extensively tested on high-end "100 Hz" CRT televisions in Europe.
The best approach may be a combination of two, possibly allowing the viewer to switch them on or off when viewing video- or film-based material.
Some manufacturers are also experimenting with extending colour reproduction of LCD televisions. Although current LCD panels are able to deliver all sRGB colours using an appropriate combination of backlight's spectrum and optical filters, manufacturers want to display even more colours. One of the approaches is to use a fourth, or even fifth and sixth colour in the optical colour filter array. Another approach is to use two sets of suitably narrowband backlights (e.g. LEDs), with slightly differing colours, in combination with broadband optical filters in the panel, and alternating backlights each consecutive frame.
Fully using the extended colour gamut will naturally require an appropriately captured material and some modifications to the distribution channel. Otherwise, the only use of the extra colours would be to let the viewer boost the colour saturation of the TV picture beyond what was intended by the producer, but avoiding the otherwise unavoidable loss of detail ("burnout") in saturated areas.
Digital Light Processing (DLP) is a technology used in projectors and video projectors. It was originally developed at Texas Instruments, in 1987 by Dr. Larry Hornbeck.
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Early LCD television had drawbacks relative to traditional visual display technologies. It displayed fast-moving action with "ghosting" and could be viewed best only when looking directly at the screen or from a slight angle. Most of these problems were solved in recent years, and LCD televisions, along with plasma displays, have become more popular worldwide than cathode ray display televisions. The LCD design is also known for being more energy efficient than the CRT design.
For a long time it was widely believed that LCD technology was suited only to smaller sized flat-panel televisions, and could not compete with plasma technology at sizes of 40" or larger. At the time, plasma held the edge in cost and performance. Presently, LCD TV's can offer the same performance with the announcements of seventh-generation panels by major manufacturers such as Samsung, Sony, LG.Philips LCD, and Sharp Corporation:
- In October 2004, 40" to 45" televisions were widely available, and Sharp had announced the successful manufacture of a 65" panel.
- In March 2005, Samsung announced an 82" LCD panel.http://www.samsung.com/PressCenter/PressRelease/PressRelease.asp?seq=20050307_0000101589
- In August 2006, LG.Philips Consumer Electronics announced a 100" LCD television http://www.newscenter.philips.com/About/news/article-15499.html
- In January 2007, Sharp displayed a 108" LCD panel branded under the AQUOS brand name at CES in Las Vegas.http://www.foxnews.com/story/0,2933,242431,00.html
Improvements in LCD technology have narrowed the technological gap with plasmas. The lower weight, falling prices, higher available resolution which is crucial for HDTV, and lower electrical power consumption of LCDs make them competitive against plasma displays in the television set market. As of late 2006, analysts note that LCDs are overtaking plasmas, particularly in the important 40" and above segment where plasma had enjoyed strong dominance a couple of years before. [1][2]
LCD Technology
LCD technology is based on the properties of polarized light. Two thin, polarized panels sandwich a thin liquid-crystal gel that is divided into individual pixels. An X/Y grid of wires allows each pixel in the array to be activated individually. When an LCD pixel darkens, it polarizes at 90 degrees to the polarizing screens.This pixel has darkened. The pixel darkens in proportion to the voltage applied to it: for a bright detail, a low voltage is applied to the pixel; for a dark shadow area, a higher voltage is applied. LCDs are not completely opaque to light, however; some light will always go through even the blackest LCD pixels.
Developments in LCD televisions
TVs based on PVA and S-PVA LCD panels deliver a broad angle of view, up to 178 degrees. They also deliver an adequate contrast ratio for viewing bright scenes, as well as dark scenes in bright rooms. The dynamic contrast technique improves contrast when viewing dark scenes in a dark room. Alternatively, some manufacturers produce LCD TVs that throw light on the wall behind it to help make dark scenes look darker. PVA and S-PVA panels generally have difficulty with ghosting when going between different shades of dark colours, however in new televisions this is compensated to some degree using a technique called overdriving.Moving pictures on a CRT TV do not exhibit any sort of "ghosting" because the CRT's phosphor, charged by the strike of electrons, emits most of the light in a very short time, under 1 ms, compared with the refresh period of e.g. 20 ms (for 50 fps video). In LCDs, each pixel emits light of set intensity for a full period of 20 ms (in this example), plus the time it takes for it to switch to the next state, typically 12 to 25 ms.
The second time (called the "response time") can be shortened by the panel design (for black-to-white transitions), and by using the technique called overdriving (for black-to-gray and gray-to-gray transitions); however this only can go down to as short as the refresh period.
This is usually enough for watching film-based material, where the refresh period is so long (1/24 s, or nearly 42 ms), and jitter is so strong on moving objects that film producers actually almost always try to keep object of interest immobile in the film's frame.
Video material, shot at 50 or 60 frames a second, actually tries to capture the motion. When the eye of a viewer tracks a moving object in video, it doesn't jump to its next predicted position on the screen with every refresh cycle, but it moves smoothly; thus the TV must display the moving object in "correct" places for as long as possible, and erase it from outdated places as quickly as possible.
Although ghosting was a problem when LCD TVs were newer, the manufacturers have been able to shorten response time to 2ms on many computer monitors and around an average of 8 ms for TVs.
There are two emerging techniques to solve this problem. First, the backlight of the LCD panel may be fired during a shorter period of time than the refresh period, preferably as short as possible, and preferably when the pixel has already settled to the intended brightness. This technique resurrects the flicker problem of the CRTs, because the eye is able to sense flicker at the typical 50 or 60 Hz refresh rates.
Another approach is to double the refresh rate of the LCD panel, and reconstruct the intermediate frames using various motion compensation techniques, extensively tested on high-end "100 Hz" CRT televisions in Europe.
The best approach may be a combination of two, possibly allowing the viewer to switch them on or off when viewing video- or film-based material.
Some manufacturers are also experimenting with extending colour reproduction of LCD televisions. Although current LCD panels are able to deliver all sRGB colours using an appropriate combination of backlight's spectrum and optical filters, manufacturers want to display even more colours. One of the approaches is to use a fourth, or even fifth and sixth colour in the optical colour filter array. Another approach is to use two sets of suitably narrowband backlights (e.g. LEDs), with slightly differing colours, in combination with broadband optical filters in the panel, and alternating backlights each consecutive frame.
Fully using the extended colour gamut will naturally require an appropriately captured material and some modifications to the distribution channel. Otherwise, the only use of the extra colours would be to let the viewer boost the colour saturation of the TV picture beyond what was intended by the producer, but avoiding the otherwise unavoidable loss of detail ("burnout") in saturated areas.
See also
- Ambilight
- ATS euro plus
- Comparison of display technologies
- DLP
- Digital Terrestrial Television
- Picture in Picture
- Pixel Plus
- Plasma display Panel Television (PDP TV)
- Progressive scan
- Teletext
- Television
- Touch Screens
- Wake-up and sleep timer
- Wide XGA, SVGA and DVI PC interfaces
External links
- Plasma.com LCD TV vs PDP TV vs DLP TV
Television (often abbreviated to TV, T.V., or more recently, tv; sometimes called telly, the tube, boob tube, or idiot box in British English) is a widely used telecommunication system for broadcasting and receiving moving pictures
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liquid crystal display (commonly abbreviated LCD) is a thin, flat display device made up of any number of color or monochrome pixels arrayed in front of a light source or reflector.
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thin film transistor (TFT) is a special kind of field effect transistor made by depositing thin films for the metallic contacts, semiconductor active layer, and dielectric layer.
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Flat panel displays encompass a growing number of technologies enabling video displays that are lighter and much thinner than traditional television and video displays that use cathode ray tubes, and are usually less than 4 inches (100 mm) thick.
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A computer display monitor, usually called simply a monitor, is a piece of electrical equipment which displays viewable images generated by a computer without producing a permanent record.
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1. Electron guns 2. Electron beams 3. Focusing coils 4. Deflection coils 5. Anode connection 6. Mask for separating beams for red, green, and blue part of displayed image 7.
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plasma display panel (PDP) is a type of flat panel display now commonly used for large TV displays (typically above 37-inch or 940 mm). Many tiny cells located between two panels of glass hold an inert mixture of noble gases (neon and xenon).
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Flat panel displays encompass a growing number of technologies enabling video displays that are lighter and much thinner than traditional television and video displays that use cathode ray tubes, and are usually less than 4 inches (100 mm) thick.
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- For , see .
Digital Light Processing (DLP) is a technology used in projectors and video projectors. It was originally developed at Texas Instruments, in 1987 by Dr. Larry Hornbeck.
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An LCD projector is a type of video projector for displaying video, images or computer data on a screen or other flat surface. It is the modern equivalent of the slide projector or overhead projector.
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Liquid crystal on silicon (LCOS or LCoS) is a "micro-projection" or "micro-display" technology typically applied in projection televisions. It is a reflective technology similar to DLP projectors; however, it uses liquid crystals instead of individual mirrors.
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High-definition television (HDTV) is a digital television broadcasting system with a significantly higher resolution than traditional formats (NTSC, SECAM, PAL). While some early analog HDTV formats were broadcast in Europe and Japan, HDTV is usually broadcast digitally,
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Flat panel displays encompass a growing number of technologies enabling video displays that are lighter and much thinner than traditional television and video displays that use cathode ray tubes, and are usually less than 4 inches (100 mm) thick.
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Samsung Group
삼성
三星
Public (traded on the Korea Stock Exchange)
Founded 1938
Headquarters Seoul, South Korea
Key people Lee Byung-chul, Lee Kun-Hee
Industry Conglomerate
Revenue $142 billion (2005)
Net income $9.
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삼성
三星
Public (traded on the Korea Stock Exchange)
Founded 1938
Headquarters Seoul, South Korea
Key people Lee Byung-chul, Lee Kun-Hee
Industry Conglomerate
Revenue $142 billion (2005)
Net income $9.
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Sony Corporation
ソニー株式会?
Public (TYO: 6758 ; NYSE: SNE )
Founded May 7 1946 (adopted current name in 1958) by Masaru Ibuka and Akio Morita[1]
Headquarters Minato-ku, Tokyo, Japan[1]
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ソニー株式会?
Public (TYO: 6758 ; NYSE: SNE )
Founded May 7 1946 (adopted current name in 1958) by Masaru Ibuka and Akio Morita[1]
Headquarters Minato-ku, Tokyo, Japan[1]
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LG.Philips LCD (hangul:엘지필립스엘씨디, LG필립스LCD) was formed as a joint venture by the Korean electronics company LG Electronics and the Dutch company Koninklijke Philips Electronics in 1999 to manufacture active
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Sharp Corporation
シャープ株式会社
Corporation (TYO: 6753 , LuxSE: SRP )
Founded Tokyo, Japan (1912)
Headquarters Osaka, Japan
Key people Toshihiko Fujimoto, President
Industry Electronics
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シャープ株式会社
Corporation (TYO: 6753 , LuxSE: SRP )
Founded Tokyo, Japan (1912)
Headquarters Osaka, Japan
Key people Toshihiko Fujimoto, President
Industry Electronics
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Samsung Group
삼성
三星
Public (traded on the Korea Stock Exchange)
Founded 1938
Headquarters Seoul, South Korea
Key people Lee Byung-chul, Lee Kun-Hee
Industry Conglomerate
Revenue $142 billion (2005)
Net income $9.
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삼성
三星
Public (traded on the Korea Stock Exchange)
Founded 1938
Headquarters Seoul, South Korea
Key people Lee Byung-chul, Lee Kun-Hee
Industry Conglomerate
Revenue $142 billion (2005)
Net income $9.
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Sharp Corporation
シャープ株式会社
Corporation (TYO: 6753 , LuxSE: SRP )
Founded Tokyo, Japan (1912)
Headquarters Osaka, Japan
Key people Toshihiko Fujimoto, President
Industry Electronics
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シャープ株式会社
Corporation (TYO: 6753 , LuxSE: SRP )
Founded Tokyo, Japan (1912)
Headquarters Osaka, Japan
Key people Toshihiko Fujimoto, President
Industry Electronics
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The of this article or section may be compromised by "weasel words".
You can help Wikipedia by removing weasel words. The Sharp Aquos is a range of LCD televisions and component screens made by Sharp Corporation. It encompasses small, portable models (e.g.
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You can help Wikipedia by removing weasel words. The Sharp Aquos is a range of LCD televisions and component screens made by Sharp Corporation. It encompasses small, portable models (e.g.
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The International Consumer Electronics Show (CES) is a trade show held each January in Las Vegas, Nevada, and is sponsored by the Consumer Electronics Association. At the show, many previews of products are introduced, or new products are announced.
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A computer display monitor, usually called simply a monitor, is a piece of electrical equipment which displays viewable images generated by a computer without producing a permanent record.
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High-definition television (HDTV) is a digital television broadcasting system with a significantly higher resolution than traditional formats (NTSC, SECAM, PAL). While some early analog HDTV formats were broadcast in Europe and Japan, HDTV is usually broadcast digitally,
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polarization (Brit., polarisation) is the property of electromagnetic waves, such as light, that describes the direction of the transverse electric field. More generally, the polarization of a transverse wave describes the direction of oscillation in the plane
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degree (in full, a degree of arc, arc degree, or arcdegree), usually denoted by ° (the degree symbol), is a measurement of plane angle, representing 1⁄360 of a full rotation.
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pixel (short for picture element, using the common abbreviation "pix" for "pictures") is a single point in a graphic image. Each such information element is not really a dot, nor a square, but an abstract sample.
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A shadow is a region of darkness where light is blocked. It occupies all of the space behind an opaque object with light in front of it. The cross section of a shadow is a two-dimensional silhouette, or reverse projection of the object blocking the light.
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liquid crystal display (commonly abbreviated LCD) is a thin, flat display device made up of any number of color or monochrome pixels arrayed in front of a light source or reflector.
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The contrast ratio is a measure of a display system, defined as the ratio of the luminosity of the brightest color (white) to that of the darkest color (black) that the system is capable of producing.
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