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FrontlightA frontlight is a system of illuminating a screen, commonly an LCD, so that it can be used in dark environments or those where ambient lighting is poor. An LCD (liquid crystal display) operates on a refractive medium, that is to say, it displays colors by moving crystals in such a way that the light moving through them appears to change color due to refraction, the same mechanism that separates white light into various colors in a prism. LCD screens are not self-illuminating. In their "normal" form they require light to be supplied from outside, which is then reflected back through the LCD so it can be viewed. In the more common backlight system, a light source is placed behind the LCD in place of the reflective medium so that the screen appears to glow, like a more conventional Cathode ray tube (CRT) display. This requires a different form of LCD to be manufactured, and the light source to be of equal area to the display. In a frontlight setup, the LCD is as it normally would be, no light source and a reflective backing. But a light source is placed directly in front of the LCD, and then is then reflected back as if in normal operation. This has the advantage or requiring minimal additional engineering, because the LCD itself is unmodified. It also retains the reflective backing of the original LCD, so that if conditions warrant, the front light can be deactivated and the LCD can still retain useful visibility. The biggest drawback to using a frontlight system is that it can often create a "washed out" look to the colors, especially if the color of the light source is too bright or is not very close to pure white light. It also has the potential to be a physically bulkier solution (although this is minimal with current technology) because in addition to the light source, the display still retains the reflective backing as well. Also, because a frontlight has to be clear in nature, the light source is restricted to being around the edges of the display, so larger-size screens would suffer from being dark in the center, which is why they are not used for most laptop or notebook computer displays. The source of the light is usually a light emitting diode (LED), as they are small and consume very little power. Backlight systems are usually flourescent in nature, due to the fact that the bulbs are capable or covering a larger area. Often a flourescent bulb is used to project a bright, white light from the top of an LCD screen, which brightens the image. This technology has replaced backlights on some LCD screens, and consumes less power.
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