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Big Screen TV

Large-screen television technology developed rapidly in the late 1990s and 2000s. Various thin screen technologies are being developed, but only the liquid crystal display (LCD), plasma display (PDP) and Digital Light Processing (DLP) have been released on the public market. These technologies have almost completely displaced cathode ray tubes (CRT) in television sales, due to the necessary bulkiness of cathode ray tubes. However, recently released technologies like organic light-emitting diode (OLED) and not-yet released technologies like surface-conduction electron-emitter display (SED) or field emission display (FED) are making their way to replace the first flat screen technologies in picture quality. The diagonal screen size of a CRT television is limited to about 40 inches because of the size requirements of the cathode ray tube, which fires three beams of electrons onto the screen, creating a viewable image. A larger screen size requires a longer tube, making a CRT television with a large screen (50 to 80 inches) unrealistic because of size. The aforementioned technologies can produce large-screen televisions that are much thinner.

The following are important factors for evaluating television displays:

  • Display size: the diagonal length of the display.
  • Display resolution: the number of pixels in each dimension on a display. In general a higher resolution will yield a clearer, sharper image.
  • Dot pitch: This is the size of an individual pixel, which includes the length of the subpixels and distances between subpixels. It can be measured as the horizontal or diagonal length of a pixel. A smaller dot pitch generally results in sharper images because there are more pixels in a given area. In the case of CRT based displays, pixels are not equivalent to the phosphor dots, as they are to the pixel triads in LC displays. Projection displays that use three monochrome CRTs do not have a dot structure, so this specification does not apply.
  • Response time: The time it takes for the display to respond to a given input. For an LC display it is defined as the total time it takes for a pixel to transition from black to white, and then white to black. A display with slow response times displaying moving pictures may result in blurring and distortion. Displays with fast response times can make better transitions in displaying moving objects without unwanted image artefacts.
  • Brightness: The amount of light emitted from the display. It is sometimes synonymous with the term luminance, which is defined as the amount of light per area and is measured in SI units as candela per square meter.
  • Contrast ratio: The ratio of the luminance of the brightest color to the luminance of the darkest color on the display. High contrast ratios are desirable but the method of measurement varies greatly. It can be measured with the display isolated from its environment or with the lighting of the room being accounted for. Static contrast ratio is measured on a static image at some instant in time. Dynamic contrast ratio is measured on the image over a period of time. Manufacturers can market either static or dynamic contrast ratio depending on which one is higher.
  • Aspect ratio: The ratio of the display width to the display height. The aspect ratio of a traditional television is 4:3, which is being discontinued; the television industry is currently changing to the 16:9 ratio typically used by large-screen, high-definition televisions.
  • Viewing angle: The maximum angle at which the display can be viewed with acceptable quality. The angle is measured from one direction to the opposite direction of the display, such that the maximum viewing angle is 180 degrees. Outside of this angle the viewer will see a distorted version of the image being displayed. The definition of what is acceptable quality for the image can be different among manufacturers and display types. Many manufacturers define this as the point at which the luminance is half of the maximum luminance. Some manufacturers define it based on contrast ratio and look at the angle at which a certain contrast ratio is realized.
  • Color reproduction/gamut: The range of colors that the display can accurately represent.

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