Applications of LCDs:

• Telecommunications / Mobile Phones
• Datacommunications
• Consumer Electronics
• Security + CCTV
• Amusement / Gambling Machines
• Signs and Displays
• Projectors
• Automotive
• Point of Sale / Terminals and PDAs

LCD Systems

Common-plane-based LCDs are good for simple displays that need to show the same information over and over again. Watches and microwave timers fall into this category.

Passive-matrix LCDs use a simple grid to supply the charge to a particular pixel on the display.

Active-matrix LCDs depend on thin film transistors (TFT). Basically, TFTs are tiny switching transistors and capacitors. They are arranged in a matrix on a glass substrate. To address a particular pixel, the proper row is switched on, and then a charge is sent down the correct column. Since all of the other rows that the column intersects are turned off, only the capacitor at the designated pixel receives a charge. The capacitor is able to hold the charge until the next refresh cycle. And if we carefully control the amount of voltage supplied to a crystal, we can make it untwist only enough to allow some light through. By doing this in very exact, very small increments, LCDs can create a gray scale. Most displays today offer 256 levels of brightness per pixel.

LCD Advances

LCD technology is constantly evolving. LCDs today employ several variations of liquid crystal technology, including super twisted nematics (STN), dual scan twisted nematics (DSTN), ferroelectric liquid crystal (FLC) and surface stabilized ferroelectric liquid crystal (SSFLC). For an in-depth (and pretty technical) article that addresses all of technologies, see Liquid Crystal Materials.

Display size is limited by the quality-control problems faced by manufacturers. Simply put, to increase display size, manufacturers must add more pixels and transistors. As they increase the number of pixels and transistors, they also increase the chance of including a bad transistor in a display. Manufacturers of existing large LCDs often reject about 40 percent of the panels that come off the assembly line. The level of rejection directly affects LCD price since the sales of the good LCDs must cover the cost of manufacturing both the good and bad ones. Only advances in manufacturing can lead to affordable displays in bigger sizes.

Projectors

Comparison between LCD and DLP technologies: http://www.projectorcentral.com/lcd_dlp.htm

Color LCD Projectors.
LCD (liquid crystal display) projectors usually contain three separate LCD glass panels, one each for red, green, and blue components of the image signal being fed into the projector. As light passes through the LCD panels, individual pixels ("picture elements") can be opened to allow light to pass or closed to block the light, as if each little pixel were fitted with a Venetian blind. This activity modulates the light and produces the image that is projected onto the screen.

1. How Stuff Works:
   http://electronics.howstuffworks.com/lcd.htm
   
2. More information on display technologies:
   http://www.exhibitresearch.com/display.html