A plasma TV is sometimes called an "emissive" display — the panel is actually self-lighting. The display consists of two transparent glass panels with a thin layer of pixels sandwiched in between. Each pixel is composed of three gas-filled cells or sub-pixels (one each for red, green and blue). A grid of tiny electrodes applies an electric current to the individual cells, causing the gas (a mix of neon and xenon) in the cells to ionize. This ionized gas (plasma) emits high-frequency UV rays, which stimulate the cells' phosphors, causing them to glow the desired color.
Each individual plasma cell is switched on and off by its own electrode. An HDTV-capable plasma TV can have up to 3 million of these cells!
Because a plasma panel is illuminated at the sub-pixel level, images are extremely accurate, and the panel's light output is both high and consistent across the entire screen area. Plasma TVs also provide very wide horizontal and vertical viewing angles, especially when compared to conventional rear-projection TVs. Picture quality looks sharp and bright from virtually anywhere in the room. Because plasma TV screens do use a phosphor coating (like direct-view and projection CRT TVs), the potential for image burn-in exists, so it's important to follow the manufacturer's recommendations on day-to-day use.
Until recently, all flat-panel TVs were progressive displays — at any given moment all of the pixels are illuminated. But plasma TVs based on innovative AliS technology (Alternate Lighting of Surfaces) are proving that a non-progressive picture can look outstanding. Typical plasma panels have a strip of electrodes for each horizontal row of plasma cells, while ALiS panels share an electrode strip between two rows of cells. At any given instant only half the panel's pixels are turned on. It's somewhat similar to interlaced-scanning on a CRT-based TV — in fact, ALiS technology was developed as a way to make a simpler, lower-cost plasma panel capable of displaying interlaced HDTV signals (1080i).
Two HDTV-capable plasma panel designs. The ALiS panel (left) is a simpler design that uses a "trough" structure instead of the conventional "cell" structure, while also streamlining the drive electronics (fewer electrodes). Bottom line: Both panel designs can deliver outstanding picture quality!
Two HDTV-capable plasma panel designs. The ALiS panel (left) is a simpler design that uses a "trough" structure instead of the conventional "cell" structure, while also streamlining the drive electronics (fewer electrodes). Bottom line: Both panel designs can deliver outstanding picture quality!
Because there is less screen "real estate" taken up by electrode strips, there's more illuminated area, and as a result, ALiS panels provide a seamlessly clear, bright image. Other ALiS benefits include high-efficiency — they require only half the voltage of conventional plasma drive systems — and extended panel life. |
