Flat Screen TFT Displays
 As
the cost of TFT (thin-film-transistor) displays drops and the desire for more user-friendly and graphical interfaces increases, more companies are asking engineers to design these products into their own. Although many engineers have designed with monochrome, passive, graphic-LCD modules, the task of selecting and working with a
TFT, or active-matrix, display may seem somewhat confusing and daunting.
Manufacturers of Flat Screen TFT Displays
You can save lots of money by designing with monochrome graphic-LCD modules. They are inexpensive, relatively easy to interface and control, and readily available. Monochrome displays require less overhead in hardware and less complex software. It's easier to manage one color per pixel than three (red, green, and blue) per pixel. Also, "monochrome" doesn't necessarily refer to just black and white.
The first thing to consider is whether you need a flat screen TFT
display. Management, marketing requirements, or design specifications often answer this question.
Depending on the backlight and LCD material, so-called monochrome LCDs come in a variety of colors, including black and white, yellow, green, blue, and a host of variations in between.
Color passive-LCD modules also exist. Depending on the design criteria, a color passive panel may have benefits over TFT panels, such as outdoor brightness or overall color brilliance. When deciding between a TFT and a color passive panel, keep in mind update speed and viewing angle.
Flat screen TFT displays can provide viewing angles of nearly 180[degrees] degrees, whereas passive color modules, although constantly improving, usually provide only 70 to 80[degrees].
LCD panels comprise a layer of LCD material and one or more polarizing layers made of plastic, glass, or some other material. When you align two polarizing materials with each other, light passes through. However, when one polarizing agent is at a 90[degrees] angle to the other, light is blocked. LCD fluid acts as a dynamic polarizing agent. When you place a voltage across an LCD cell, the cell twists by 90[degrees], which, depending on the orientation of the polarizing agent under the LCD layer, either blocks or passes light.
Flat Screen TFT Displays : Liquid Crystal Displays
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In passive-LCD technology, the cells act as capacitors. Once charged, they bleed off their voltage and slowly twist back to their original position. Because of this, passive panels cannot quickly change the state of their cells and are unsuitable for fast-moving graphics. To overcome this weakness,
flat screen TFT displays LCDs use transistors to drive the LCD cells. Although this approach is more complex and expensive, it allows for faster control of the LCD cell. A TFT can therefore display full-motion video and graphics, whereas a passive-LCD module starts to blur with images moving faster than eight to 15 frames/sec, depending on the manufacturer.
See also Liquid Crystal Displays, and pages relate to Flat Screen TFT Displays
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