27 Lcd With Led Backlight @ Amazon.com
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LCD is winning the race to be the dominant display technology for HDTV. According to DisplaySearch, in 2007, the market for LCD (liquid crystal diode) TVs was approximated at $27.4 billion. LCD TV shipments rose a more inviolable than expected 52% year to year in the second quarter of 2008 to closely 7.5 million units (79.8% of total HDTV sales). The LCD screen on a LCD HDTV is a selective light filter. It does not in itself emit light, but selectively filters light passing through the display from the back. Most HDTVs include either a single sheet of luminescent plastic or sidelighting with fluorescent lamps to provide the backlight. Both proficiencies are difficult to control. Many buyers focus on screen solution when selecting a High Def (HDTV) system. Is this HDTV 720p, 1020i, or 1020p? However, when an expert group, the SMPTE (Society of Motion Pictures and Television Engineers), not so long ago ranked the importance of screen resolution, it ranked fourth. The SMPTE ranked contrast ratio, color saturation, color temperature and grayscale in front of screen solution in importance. The Imaging Science Foundation reached a similar conclusion. Backlighting is the key factor to betterment in contrast symmetry and grayscale. It is primary that an LCD system allows for adjustment of the level of backlighting, and preferably, performs this function automatically. This will improve the contrast of the picture. Also, a scaled down backlight level will also reduce power consumption and extend lamp life, as the power employed and lamp lifetime is directly related to the backlight level. A lamp with a 50,000 hour lifetime at 6 milliamps may only have a 30,000 hour lifetime if the current is 7 milliamps, just 1 milliamp higher (Example: Sharp Electronics LCD Display). Another important factor in the choice of backlighting is the thoughtfulness of “blur”. Blur occurs when there is rapid motion in the programming, such as sports. When the picture changes quickly, the pixels may lag in response. Effective backlight technology may reduce this significantly by strobing the backlighting, so that the person pixels do not stay lit longer than needed. Examples of this technique include the Philips “Aptura” and the Samsung “LED Motion Plus”. Sidelighting With sidelighting, the backlight is located in the back of the LCD panel, and to each side to create panel illumination. To make the light more uniform, a light diffuser is located amidst the lamps and the rear of the optical filter module. Most LCD systems that use sidelighting use cold cathode fluorescents (CCF) lamps. This technology provides a very bright white light. The lifetime of the lamps is commonly amid 10,000 to 20,000 hours (6-12 years at a rate of 5 hours of use per day). The most crucial disfavor is that the intensity of light can not be varied locally, and sidelighting may look non-uniform. Some CCF lamps comprise mercury. This is an ecological disadvantage. The major drawbacks:
Conventional Backlighting Most backlighting is performed with a single sheet of electroluminescent plastic. These panels may age (though improvements in this area have scaled down this problem). Electroluminescent Panel backlighting uses colored phosphors to generate light. Displays using this technique may be thin and lightweight, and provide even light distribution. The major drawbacks:
LED Backlighting LED backlighting uses a matrix of LEDs that may be controlled on an individual basis to offer very good control. In this configuration, a huge number of LEDs are mounted uniformly behind the display. Brightness improvements in LEDs have made them more practical for backlighting. NEC initiated this technique with their monitor, the 2180WG. Other companies, such as Samsung, have not long ago introduced versions of this technology. This ought to push prices down (the Samsung model cost less than 1/3 the price of a comparable NEC monitor). This system offers local dimming engineering and may achieve 1,000,000:1 dynamic contrast ratio. True actual black levels (the “Holy Grail” of LCD) are attainable by shutting off a pixel’s light source. This may eliminate the grayish black picture typical of galore LCD HDTVs. Groups of LEDs may be locally controlled to fabricate more light, increasing the luminance when necessary. The problem with conventional white LEDs is that their spectrum is not idealisti for photographic replica because they are basically blue LEDs with a yellow phosphor on top. Their color spectrum has two peaks, one at blue and another at yellow. White LEDs that are based on a group of red, green and blue LEDs are idealisti for the RGB color filters of an LCD and may result in the most completely filled colors. Sony’s “Triluminos” LED backlight scheme is an example of this technique. LED backlights are much more effective that substitute techniques. And since the LED backlight waste less energy, less heat is generated, that ought to be managed with air conditioning. LED backlights offer a long operating lifetime of more than 50,000 hours (more than 25 years of use at a rate of 5 hours a day). LED backlit schemes may not show well in a typical retail environment. Typically, the screens are more or less reflective in order to achieve the high contrast ratio, and subsequently, a brightly lit showroom may not flatter this technology. In a more typical less-lit environment, this problem ought to not be as noticeable. Engineering Concerns The electrical technology is less complicated with LED backlights. Cold cathode fluorescent lamps (CCF) require high AC voltages (1,500 VAC) at startup, and operating voltages of 700 VAC or more. When the lamp is new it may take much less voltage to start, but with age the voltage requisites commonly increase, complicating a designer’s problem. An electroluminescent panel requires a voltage of with regards to 100 VAC @ 400 Hertz. A power inverter (to generate VAC) is necessitated for both CCF and electroluminescent panels to operate with a DC power supply. This is a significant expense, in cost, size, and weight of the system. The best inverter for this application permits the output voltage to mechanically increase as the lamps age, extending the utile life of the lamps. LCD systems with LED backlighting utilize low voltage DC, ordinarily 12 or 24 VDC. This results in a smaller, simpler, and more authenti system. LED backlit schemes must be well cooled or their performance may suffer. The LEDs generate less heat than CCF lamps, but the heat is very concentrated. Operating at high temperatures reduces the LED lifetime and shifts their light spectrum, while reducing output luminance. OLED A new technology that you will be hearing with regards to in the future is Organic LED (OLED). This engineering science has a altogether dissimilar backlight technology, it doesn’t need one. Because of this, they draw much less power. And because there is no backlight, an OLED scheme has a more spectacular watching angle than an LED system. An OLED display is much thinner than an LCD display. The response time for OLED is rapidly and without delay than normal LCD screens. An intermediate of 8 to 12 milliseconds in response time is normal for a LCD equated to 0.01 milliseconds in response time for an OLED. Sony introduced an 11″ HDTV at the Consumer Electronics Show in Vegas. The new 11″ Sony TV is called the “XEL-1″. It’s very thin (1/10″) and presently sells for $2500. Samsung demonstrated a 31″ OLED HDTV with 1080P solution at a tradeshow in Asia in November. LG, Toshiba, Matsushita (Panasonic), and others are investing hundreds of millions of dollars, fabricating this exceedingly promising technology. Toshiba has plans to trade a 30″ OLED display in 2009. Samsung has declared they will trade big screen OLED HDTVs in 2010. OLED displays have already been used for a great deal of time in digital cameras, cell phones and other gimmicks with comparatively little panels, because they are very energy efficient, which is very indispensable in portable devices. In theory, OLED displays may be more cheaply fictitious than LCD or plasma displays, meaning that they ought to not be as expensive. Remember that the firstborn big LCD and Plasma displays were much more costly when they were introductory introduced. Summary LCD HDTVs and monitors with LED array backlighting are now the approach of choice because they exhibit better effigy quality while saving power. The capacity to locally control light output is key to achieving high contrast ratios. Most helpful customer reviews 115 of 116 people found the following review helpful. 122 of 134 people found the following review helpful. |
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