HDTV, Plasma Screens and OLED Screens

HDTV
We happen to be alive at a very cool time in TV history. Two things are happening. The first thing is there are now lots of different ways to make a TV. For 50 years, the CRT was the only technology available. Now there are several different technologies, including Plasma TVs, LCD TVs, DLP TVs and OLED TVs. And they are all getting cheaper every day. The second thing is we are now making the switch to high definition TV, or HDTV.

Ever since the 1940s, TV has been the same. Today we call it "analog TV." The TV screen had about 500 pixels across each line, and about 400 lines of pixels in an image. In HDTV, there are lots more pixels – about 1,920 pixels across a line, and 1,080 lines of pixels. In other words, an HDTV has about 10 times more pixels than an old analog TV. That makes the pictures on the screen a lot clearer.

In the United States, there's an average of two TVs in every household. There is almost one TV for every person in the United States.

How Plasma Screens Work
When we talked about a CRT display, you learned how phosphor creates colored light. A plasma screen uses phosphor as well. But it activates it in a very different way.

In an HDTV plasma screen, there are approximately six million tiny glass cups embedded in a single piece of glass. Each cup is lined with red, green or blue phosphor, and three cups make a pixel. A second sheet of glass covers and seals all the cups.

Now, using clear electrodes etched onto the top and bottom glass, the phosphor inside the cups can be energized. If a cup gets energized, the phosphor inside the cup glows. A computer controls all six million cups, so that every one produces exactly the right amount of light to create moving images.

How OLED Screens Work
Everyone has seen LEDs. An LED is a Light Emitting Diode. They are the little colored lights you see on video game consoles, computers, printers and many other electronic devices. Lots of flashlights now use LEDs too, because LEDs are very energy efficient.

You can make TVs out of LEDs. In fact, most of the "Jumbo TVs" that you see in stadiums are made using LEDs. But if you want to create a home-size TV, normal silicon LEDs are hard to manufacture in a small enough size.

That's where OLEDs, or Organic LEDs, come in. Organic LEDs are made of layers of organic polymers. It's kind of like a very special plastic. When you energize the plastic, it creates red, green or blue light. A computer can control a grid of electrodes and energize the OLEDs in the right pattern to create color pictures.

The advantage of OLEDs is that, once scientists and engineers work out all the kinks, these displays should be inexpensive and very thin. They may also be able to flex enough to roll up. And they will be very bright and crisp. The problem is, right now, there are still kinks, so today's OLED displays are small and expensive.