Samsung demonstrated an LCD TV panel that used field emission technology to power the backlight, simply called field emission backlight (FEB). By using FEB, Samsung was able to improve the contrast ratio to 300,000:1. This is a major development. The FEB has an array of pixels that can be turned on or off depending on the image that is being shown. The FEB implementation in Samsung’s demonstration is divided into 2,800 squares (70 x 40) that are 1cm (~0.39″) on each side and allows for precise control of luminance. This type of backlight control technology is called local dimming and has been enabled first by use of LED backlights. But even the best prototype implementations of LED backlight based local dimming is limited to less than 2,000 areas.
For instance, Dolby‘s High Dynamic Range technology was implemented by SIM2 on a prototype LCD TV with 1,838 LEDs with individual control over them. This SIM2 LCD TV prototype was considered one of the best showcases for improving contrast ratio based on local dimming. The SIM2 LCD TV prototype was able to improve contrast up to a minimum of 25x the LCD’s native contrast ratio. If for example a LCD TV panel has 1,000:1 contrast ratio, by implementing Dolby’s HDR technology to the fullest, you can expect a minimum improvement to 25,000:1. This is still considerably less than Samsung’s FEB-based 300,000:1 contrast ratio.
Field emission technology is a variation on how CRTs and plasmas work by using electrons to excite phosphors on a screen. In Samsung’s example the control is fine tuned by the use of carbon nanotubes and a unique structure. The carbon nanotubes are used as emissive tips. Nanotubes are deposited on a flat surface and is treated with an elastomer. The elastomer allows the exposed nanotubes to stand up, which then can be used as emissive tips. A TFT-like grid is layered above the nanotubes to control the movement of electrons to excite the red, green and blue phosphors. The FEB generates brightness of 6,000 cd/m2. The layers in the LCD, especially the color filter, absorbs about 95% of that brightness and allowing just 300 cd/m2 to be seen by the viewer.
This is just the beginning, but it’s a complicated beginning. FEB-based LCDs require two different display technologies and likely will be very expensive at first. But the technology’s logical end would be to map individual pixels to a light source. We already have the technology to do this. For instance, this can be accomplished by using a plasma display panel or a rear projection system. By mapping individual pixels to a light source, I am sure the contrast ratio can be improved to close to 1,000,000:1, similar to what we see with OLED technologies today but without the incredibly difficult challenge of scaling to larger sizes.
Source: Electronics Weekly
[tags]Samsung, LCD TV, Field Emission, Carbon Nanotube, Contrast Ratio, Field Emission Backlight, FEB, OLED, LED, LED Backlight, Dolby, High Dynamic Range, SIM2, Plasma Display Panel, Rear Projection[/tags]