1. Field of the Invention
This invention generally relates to an LCD TV, and more particularly to an LCD TV using a projection-based backlight system.
2. Description of the Related Art
In recent years, liquid crystal displays (LCDs) have been widely used in a variety of applications, including LCD televisions (LCD TVs), portable computers, and vehicle, ship and aircraft instrumentation, due to the advantage of a thin profile and brilliant display. Most LCDs require an illumination source or backlight unit for backlighting LCD panels so that the image displayed on the LCD can be seen by a viewer.
In those applications, LCD TVs are gradually gaining in popularity due to their thin, light features and low power consumption in comparison with conventional cathode ray tube televisions (CRT TVs). An LCD TV comprises an LCD screen panel and a backlight unit placed at the back of the LCD screen panel and configured to light the LCD screen panel so that an image can be formed on the LCD screen panel. In the backlight unit, cold cathode fluorescent lamps (CCFLs) are generally adopted as the light source to provide a uniform backlighting of the LCD screen panel. It is necessary to illuminate the whole surface of the LCD screen panel with the light from a so-called linear light source by such a fluorescent lamp.
In general, as to features of a cold cathode fluorescent lamp (CCFL) used for a light source in an LCD screen panel, its luminance is inversely proportional to its lifetime. That is, if the CCFL is driven with a high current to increase the luminance, its lifespan is reduced, and if the CCFL is driven at a low current to increase its lifetime, it is difficult to obtain high luminance. However, actual commercial products generally require high luminance and a long lifetime concurrently.
Further, when an LCD TV, particularly over 40 inches, is to be manufactured, it is necessary to have a large backlight unit with more numbers of CCFL tubes for supplying sufficient light to the LCD screen panel of the LCD TV. However, the yield for such a large backlight unit having more numbers of CCFL tubes not only has lower yield rate but also has even higher cost. In additions, a more uniformly bright and effectively polarized light for such an LCD TV is not easy to be achieved by these CCFL tubes.
Due to the above shortcomings of the CCFL and its use in an LCD TV, it is needed to provide an LCD TV using a projection-based backlight system so as to solve the above-mentioned problems in the prior art.