Keanu Corea

I. LED SCREEN A. What is LED screen? - a flat-screen device in which an array of light-emitting diodes can be selectively activated to display numerical and alphabetical information, used esp in pocket calculators, digital timepieces, measuring instruments, and in some microcomputers - Stands for "Light-Emitting Diode." An LED is an electronic device that emits light when an electrical current is passed through it.Early LEDs produced only red light, but modern LEDs can produce several different colors, including red, green, and blue (RGB) light. Recent advances in LED technology have made it possible for LEDs to produce white light as well. LEDs are commonly used for indicator lights (such as power on/off lights) on electronic devices. They also have several other applications, including electronic signs, clock displays, and flashlights. Since LEDs are energy efficient and have a long lifespan (often more than 100,000 hours), they have begun to replace traditional light bulbs in several areas. Some examples include street lights, the red lights on cars, and various types of decorative lighting. You can typically identify LEDs by a series of small lights that make up a larger display. For example, if you look closely at a street light, you can tell it is an LED light if each circle is comprised of a series of dots. The energy efficient nature of LEDs allows them to produce brighter light than other types of bulbs while using less energy. For this reason, traditional flat screen LCD displays have started to be replaced by LED displays, which use LEDs for the backlight. LED TVs and computer monitors are typically brighter and thinner than their LCD counterparts. B. History of LED screen -The first edge-lit LED TV was introduced by Sony in 2008. Because they are just an improved LCD screen, they are replacing normal LCD TVs rapidly. Discoveries and early devices Electroluminescence as a phenomenon was discovered in 1907 by the British experimenter H. J. Round of Marconi Labs, using a crystal of silicon carbide and a cat's-whisker detector.[10][11] Russian Oleg Losev reported creation of the first LED in 1927.[12] His research was distributed in Russian, German and British scientific journals, but no practical use was made of the discovery for several decades.[13][14] Rubin Braunstein[15] of the Radio Corporation of America reported on infrared emission from gallium arsenide (GaAs) and other semiconductor alloys in 1955.[16] Braunstein observed infrared emission generated by simple diode structures using gallium antimonide (GaSb), GaAs, indium phosphide (InP), and silicon-germanium (SiGe) alloys at room temperature and at 77 Kelvin. In the fall of 1961, while working at Texas Instruments Inc. in Dallas, TX, James R. Biard and Gary Pittman found that gallium arsenide (GaAs) emittedinfrared light when electric current was applied. On August 8, 1962, Biard and Pittman filed a patent titled "Semiconductor Radiant Diode" based on their findings, which described a zinc diffused p–n junction LED with a spaced cathode contact to allow for efficient emission of infrared light underforward bias. After establishing the priority of their work based on engineering notebooks predating submissions from G.E. Labs, RCA Research Labs,IBM Research Labs, Bell Labs, and Lincoln Labs at MIT, the U.S. patent office issued the two inventors the first patent for the infrared (IR) light-emitting diode (U.S. Patent US-), the first modern LED.[17] Texas Instruments immediately began a project afterward to manufacture infrared diodes and announced the first LED commercial product in October 1962, the SNX-100. The SNX-100 used the zinc diffusion and gold-zinc P-type contact from the varactor diode and the tin alloy from the tunnel diode for the N-type Ohmic contact, which was achieved by plating molybdenum wires with tin and alloying them into the N-type surface of the die using a strip heater. The first visible-spectrum (red) LED was developed in 1962 by Nick Holonyak, Jr., while working at General Electric Company.[8] Holonyak first reported this breakthrough in the journal Applied Physics Letters on the December 1, 1962.[18] Holonyak is considered by some people as the "father of the light-emitting diode".[19] M. George Craford,[20] a former graduate student of Holonyak, invented the first yellow LED and improved the brightness of red and red-orange LEDs by a factor of ten in 1972.[21] In 1976, T. P. Pearsall created the first high-brightness, high-efficiency LEDs for optical fiber telecommunications by inventing new semiconductor materials specifically adapted to optical fiber transmission wavelengths.[22] Commercial development The first commercial LEDs were commonly used as replacements for incandescent and neon indicator lamps, and in seven-segment displays,[23] first in expensive equipment such as laboratory and electronics test equipment, then later in such appliances as TVs, radios, telephones, calculators, and even watches (see list of signal uses). Until 1968, visible and infrared LEDs were extremely costly, in the order of US$200 per unit, and so had little practical use.[6] The Monsanto Company was the first organization to mass-produce visible LEDs, using gallium arsenide phosphide (GaAsP) in 1968 to produce red LEDs suitable for indicators.[6] Hewlett Packard (HP) introduced LEDs in 1968, initially using GaAsP supplied by Monsanto. These red LEDs were bright enough only for use as indicators, as the light output was not enough to illuminate an area. Readouts in calculators were so small that plastic lenses were built over each digit to make them legible. Later, other colors became widely available and appeared in appliances and equipment. In the 1970s commercially successful LED devices at less than five cents each were produced by Fairchild Optoelectronics. These devices employed compound semiconductor chips fabricated with the planar process invented by Dr. Jean Hoerni at Fairchild Semiconductor.[24][25] The combination of planar processing for chip fabrication and innovative packaging methods enabled the team at Fairchild led by optoelectronics pioneer Thomas Brandt to achieve the needed cost reductions.[26] These methods continue to be used by LED producers.[27] As LED materials technology grew more advanced, light output rose, while maintaining efficiency and reliability at acceptable levels. The invention and development of the high-power white-light LED led to use for illumination, and is slowly replacing incandescent and fluorescent lighting[28][29](see list of illumination applications). Most LEDs were made in the very common 5 mm T1¾ and 3 mm T1 packages, but with rising power output, it has grown increasingly necessary to shed excess heat to maintain reliability,[30] so more complex packages have been adapted for efficient heat dissipation. Packages for state-of-the-art high-power LEDs bear little resemblance to early LEDs C. Understanding LED TVs Televisions that are referred to as LED TVs actually have LCD front panels that are backlit by light-emitting diodes, or LEDs, instead of cold-cathode fluorescent lighting. All LCD televisions require a source of backlighting because LCD, or liquid crystal diode, chips and pixels do not emit light on their own. The only true LED TVs are the giant screens found in stadiums, arenas, and on high-resolution billboards. Thus, although commonly described as LED televisions, consumer-level LED televisions actually have LCD screens, which is why some companies more accurately refer to them as "LED-based LCD televisions." LED TVs come in a few different configurations depending on the placement of the LED lights and whether or not a particular model employs what is known as local dimming. LED-based LCD televisions are more expensive than those that use CCFL for backlighting, but with that comes improved picture quality and energy efficiency. Although overall picture quality is said to rival that of plasma televisions, it suffers a bit when viewed from side angles or from above or below eye level. II. Types of LED There are two main configurations for backlighting on LED televisions: edge lighting and direct lighting. Both edge-lit and direct-lit LED televisions come in models with and without a technology called local dimming. There are slight differences in all four of these configurations, and the advantages and disadvantages of each should be taken into account when shopping for an LED-backlit LCD television. A. Full- or Direct-Lit LED TV Full - LED televisions, sometimes referred to as full-array or direct-lit LED, have the LED lights arranged behind the entire LCD panel. They are thicker than edge-lit LCD TVs and have a picture quality similar to that of CCFL-backlit LCD televisions, although black-level performance is considered to be on par with that of plasma televisions. B. Edge-Lit LED TV Edge - lit LED televisions have a series of LED backlights that run along the outside edges of the screen, which is dispersed across the entire screen by light guides. By placing the LEDs along the edges only, manufacturers are able to make screens very thin and further reduce costs. This configuration sometimes creates a brightness around the edge of the screen and decreases the depth of blacks, but this is not often noticeable when viewing in brightly lit rooms. Spotlighting in the corners or white blotches across the screen may also be noticeable when viewing in a dark room. Aside from these minor uniformity issues, picture quality is similar to CCFL-backlit LCD TVs. C. Edge LED vs. Direct LED Which is better depends on what consumers want. "Edge LED offers various advantages over Direct LED such as a thinner chassis (meaning a larger TV in a smaller position in the home), it is more power efficient (saving the consumer money on utility bills), and picture clarity is improved," a Samsung spokesperson told TechRadar. "Direct LED can create a 'halo effect' meaning that clarity from source content is lost. However, Edge LED suffers less from halo effect as the LEDs themselves are positioned around the edge of the TV, meaning the light source is emitting from the guide plate, producing less blurring of the image." As you might have gathered from that, Samsung is committed to Edge LED tech, citing it as the "superior technology." It's 'halo' argument is valid; clusters of LED lights in the behind the screen can cause bright objects to appear with a slight ring around them. Edge sets do, however, struggle to produce as high a contrast - especially when compared to that other big-screen technology: plasma. III. Characteristics A. PICTURE QUALITY BRIGHTNESS An LCD (both with CCFL and LED backlight) can produce an image a lot brighter than any type of screens. In an LCD screen, the source of light is separate than the color of the pixel. The source of light behind the screen, just needs to be white and has no real size constraint. This enables the uses of very bright sources of light, like LEDs. In a plasma screen, each color of a pixel emits their own light. The gas inside a cell is excited to produce an ultraviolet light, which then excites a phosphor. This method has a lot less potential to produce a strong light. COLORS There are no major differences between the main technologies in the accuracy of the hue of the color (the actual color, not the intensity of it). It will mostly depends on the actual model and brand of the television. Since a few years, most TVs are really good in that aspect. Calibrated correctly, 99% of the people will not be able to say if the colors are slightly off compared to another television. The eye of humans are sensible a lot more to the intensity of the color or the clarity of the picture than the accuracy of the color. A few televisions claims to have more colors than the others, some even add a fourth yellow pixel to the normal 3 colors (red, green and blue). The truth is, you will not see a difference. This is why the fourth yellow component always stayed as a novelty instead of becoming mainstream on all TVs; it is not worth it. Motion Blur Motion blur is a problem usually found on lower end LCD televisions. It happens when an image stays on the screen longer than intended, superposing the next image. The pixels do not change fast enough to keep up with the video, making it look blurry. The next animation shows a screen with a motion blur problem and one without. A plasma TV does not have a motion blur problem because the pixels stop emitting light as soon as the electricity ceased to be applied on them. In an LCD screen, the pixels take some time to adjust its opacity based on their polarization. If the pixels do not switch fast enough, motion blur will happen. In the last few years, LCD screens response time improved a lot, especially the higher end models and it is not a real issue anymore. Also, manufacturers introduced panels with 120Hz refresh rate. A 120Hz refresh rate does not guarantee the absence of motion blur but is a good indication that the response time of this panel is better. Also, a 120Hz televisions will create new interpolated frames between the real frames to further prevent any motion blur. B. LESS ENERGY CONSUMPTION As shown in the chart, the power consumption of a plasma television is higher than an LED television. The difference is more noticeable for big televisions. A plasma TV consume significantly more power than an LED TV because each gas cell need to be excited enough to produce a bright color. In an LED display, the light is independent and shared across all the pixels so a more efficient way to produce the light can be used. The chart displays the average advertised power consumption for the 2013 models. This is the average case scenario; the power consumption varies depending on the content viewed and the settings of the television. The TV consumes a lot more power when displaying a very bright white screen compared to a dark one, especially for Plasma televisions. ELECTRICITY COST The next chart shows the yearly cost if the television is watched 5 hours per day for 365 days, at a cost of electricity of 0.11$ per kWh. As you can see in the chart, a plasma television does cost more electricity than an LED TV. However, the resulting cost at the end of the year is not very big, about 10$ more for a 50" plasma. On a 5 years period, the total amount saved would be 50$. As mentioned previously here, a plasma TV cost on average 350$ less than an LED TV for the same size. Based on this, it will take 35 years for the total cost of ownership (initial cost + electricity cost) of a plasma television to surpass its LED counterpart. C. Price D. Longevity In the earlier years of the technology, the life span of a plasma TV was really bad. This problem has been greatly reduced now by the manufacturers with the help of technologies like cycling the pixels if it detects a still image and improving the quality of the phosphor. In newer models, only temporary image retention can sometimes happen. LCDs suffer a lot less from that problem and it is what made them very popular during plasma's early years. Most TVs are now advertised with a life span of 60,000, the equivalent of 6.85 years of continuous playing. Of course, this is a made up number from the manufacturers, they did not test a model for 7 years before selling it. That number is usually made by extrapolating a stress test on the assumed worst individual component of the television, tested separately. Comparing the advertised life span between television is not worth much. E. SIZE On average, an edge-lit LED TV is the thinnest, with only 1.8". Smaller LED TVs are thicker because they are usually direct lit. Plasmas are not so bad anymore, about 2.5" deep in average. Thickness is mostly for the appearance and impressing your friends. A very slim television looks a lot better in your living room than a bulky one. It is also easier to mount on the wall, because it will be closer to the wall. You should not base your buying decision on only this factor, unless the esthetic of your television is very important to you and how it fits into your room. Consider the thinness a bonus if you are buying an LED TV. F: ADVATAGES AND DISADVANTAGES Advantages of LED TVs LED-backlit LCD televisions have several advantages when compared to traditional CCFL-backlit LCD models, and even a few advantages over plasma televisions. One real advantage is that LED TVs use somewhat less power than CCFL-backlit LCD televisions, and significantly less power than plasma sets. Many consumers are more comfortable with them as they do not use any mercury in the lighting system, as do some other types of LCD televisions. LED backlighting results in screen thickness, meaning LED televisions weigh less and take up less space. They are, therefore, easier to mount on walls or hang from ceilings. It should also be noted that although many LED televisions use white backlights, those that use RGB-colored LED backlights display more realistic colors than CCFL-backlit LCD models. LED TV models with local dimming offer the most advantages, as this feature produces wider viewing angles, more contrast in black levels, and increased depth in the picture. LED lights typically have very long lives, and they do not have the same tendency as CCFL-backlit LCD TVs to develop white-balance color changes as they age. Disadvantages of LED TVs Though LED-backlit LCD televisions have many advantages over their CCFL counterparts, some disadvantages should also be noted. Consumers may feel more limited when it comes to size options with LED-backlit LCD televisions. Typically, they are not manufactured in as wide a size range as traditional CCFL LCD TVs. LED technology is also more expensive than CCFL, which means a higher cost for the consumer. Some consumers may not feel the increased price for an LED LCD television is worth the increase in picture quality, as it is less than significant in many models. Uniformity of picture suffers with the thinner screens found on LED-backlit televisions, and off-angle viewing is not very good, although LED-backlit LCD models with local dimming do give a much better picture. However, models with local dimming consume more power than models without it. In some instances, models with local dimming consume as much energy as power-hungry plasma televisions.