Xigga

SED stands for Surface-conduction Electron-emitter Display. Pretty long name, so lets just call it SED. SED technology is going to compete with LCD and OLED technologies. Plasma has no chance, read my previous article to see why. SED was created jointly by Canon and Toshiba.

LCD is good, but you don’t get a high contrast ratio (yet). Even though we have Samsung out with a 500,000:1 conrast ratio, it’s not static. It’s dynamic contrast ratio. Read my article on contrast ratio here. High contrast ratio will be the biggest advantage for SED TVs. To find out why we first need to know how LCDs work.

LCD TVs have pixels that are arranged in a nice grid. Each pixel can be any color, but the pixel doesn’t have it’s own light source to control the brightness of the color. Behind the grid panel, there is a light source called the back light. When LCDs first came out the backlight was a powerful tubelight. Now they have LEDs for the backlight, but it’s still one light source for all the pixels. So the pixels can only have a small contrast range. If one side of the screen is all white and the other side is black, the black side will look washed out, because the backlight is at it’s full brightness.

Before I explain SED technology I need to explain CRT. CRT is the old picture tube technology that has been around for more than half a century. CRT stands for Cathode Ray Tube. CRT works by shooting an electron at a phosphorus screen with an electron gun. When the electron is shot at the screen it goes through a mask which allows the electron to hit only specific locations on the screen. when the electron hits the screen, it light’s that section up. The electron gun shoots electrons one by one in an orderly fashion. It starts from the left of the screen and goes all the way to the right, then it moves down to the next line and repeats the process until the whole frame is drawn. This happens very fast, so you don’t notice it at all.

SED brings the best of both worlds together. In a SED TV each pixel is like a small CRT television. Each pixel has an electron gun and it shoots straight. In a conventional CRT, the electron gun shoots an electron, but since it has to draw on the whole screen the electron is deflected with a magnet at whatever angle it needs to be to hit the exact point on the screen. With SED you only need to shoot straight because you are using a grid of CRTs to display a picture. So in a SED TV, we have a grid of pixels, but the pixels are tiny CRT’s. This gives us the benefit of a higher refresh rate, because CRTs are fast at changing colors. LCDs are slow compared to CRTs. If you play videos games you will notice a ghosting effect in fast moving scenes. You can also notice this in movies with fast-motion scenes.

With SED we also get higher contrast ratios because each pixel will have it’s own brightness. When an electron hits a phosphorus screen it emits light. And the light can be any color you wish and brightness. So SEDs don’t have a backlight, they don’t need one. An electron hitting a phosphor creates light! Simple put, an SED is like a LCD, but each pixel is a tiny CRT.

You may think that we are moving backwards because CRT is old, but that’s not the case. CRT had some limitations, such as a maximum screen size it could shoot the electrons on. You can only change the electron’s trajectory so much. That’s why you never saw a 60″ CRT.

Will SED make LCD obsolete? It’s possible, but LCD is always being improved. Let’s not forget Sony and how they like to push their technologies. When VHS was coming out they were pushing their Betamax, they lost. For the HD media they were pushing Bluray, and they won. Sony is going to be pushing OLED technology against SED. OLED is similar to SED, but instead of having tiny CRTs for pixels, it uses (Organic) LEDs. That’s all I can say about OLED for now. I’ll leave that for another article.