Comparing Video Display Types
As you shop for a video display (or TV), you’ll need to decide what type of display you want — beyond the brand and size choices that are available. You can more easily compare display types when you understand the primary technologies that underlie different types of TVs.
For many people, a display means the traditional tube television that’s been around for decades. But new technologies have made flat-panel screens, which have no tube and are only a few inches deep, a viable choice as well. And projection TVs, which shoot the picture onto a screen, have never been better, cheaper, and bigger.
Direct-view displays vs. projection systems
The first distinction revolves around how the picture gets to your eyeballs:
With some displays, you are directly viewing the image created by the imaging hardware within the TV. In other words, the image is created on the screen you are watching. These displays are known as direct view. The most common type of direct-view display is the old-fashioned tube TV, but flat-panel (hang-on-the-wall) plasma and LCD TVs can also be considered direct-view displays.
Other displays create the image in one place and then project it onto a screen elsewhere. These projector displays work much like a movie projector in a theater and can offer the biggest image size of any type of display.
There are two types of projectors:
Rear-projection systems, which display an image on the back of the screen, which you then view from the front.
Front-projection systems, which display an image on the front of a screen (the same side you view the image on).
Video display technologies
Displays are also categorized by the underlying technology that creates the image. Most of these technologies can be used for either direct-view or projection displays, depending on how they are implemented:
CRT: CRT, or cathode ray tube, is the traditional technology behind TVs and home theater displays (for a long time, CRT was the only technology). CRTs can be used in both direct-view and projector applications.
Plasma: Plasma (sometimes called PDP, or plasma display panel) displays use a grid of electrical circuits sandwiched between two plates of glass to electrically excite a gas and cause it to put out light. Plasma displays are the thin TVs (often less than 4 inches thick) that everyone’s dying to hang on their walls.
LCD: LCDs do exactly what their name implies — they have liquid crystal particles within them that can be aligned in different ways to create different colors. When a bright light shines through these crystals, you get a video picture.
LCDs can be flat-panel TVs (like a plasma display), or they can be used in projection TVs. If you’ve seen a laptop computer (or a desktop PC with a flat-panel display), you’ve seen an LCD.
OLED: The newest flat panel technology is known as Organic Light Emitting Diode, or OLED. OLED displays are built of an organic material that is printed onto the display, and like plasma, OLED creates its own light (so there’s no backlight).
OLED displays are even thinner than plasma or LCD displays and use less electricity than either. They also have extremely high contrast ratios and extraordinary color reproduction. OLED technology is still in its infancy and is mainly used in very small displays for cell phones and similar devices.
Microdisplays: Traditionally, projection systems used CRT tubes to create the projected image. Most current projection systems use a microdisplay technology to do so instead. A microdisplay is exactly what the name says it is — basically a tiny display that uses some sort of miniaturized display technology to create an image that is then enlarged when it is beamed onto the projection screen.
Several different technologies are within the microdisplay family:
LCD: The same LCD technology used for flat-panel screens can be shrunken down and used in a projector.
DLP: A DLP, or digital light processor, uses a special video chip from Texas Instruments that includes millions of microscopic mirrors that are moved by computer command to create an image.
LCoS: Liquid Crystal on Silicon microdisplays use a special variant of LCD technology that’s shrunken down to the chip level.