How do lcd

Your start with the sandwich of glass and liquid crystals described above and add two transparent electrodes to it. For example, imagine that you want to create the simplest possible LCD with just a single rectangular electrode on it.

The layers would look like this:. The LCD needed to do this job is very basic. It has a mirror A in back, which makes it reflective. Then, we add a piece of glass B with a polarizing film on the bottom side, and a common electrode plane C made of indium-tin oxide on top. A common electrode plane covers the entire area of the LCD. Above that is the layer of liquid crystal substance D. Next comes another piece of glass E with an electrode in the shape of the rectangle on the bottom and, on top, another polarizing film F , at a right angle to the first one.

The electrode is hooked up to a power source like a battery. When there is no current, light entering through the front of the LCD will simply hit the mirror and bounce right back out. But when the battery supplies current to the electrodes, the liquid crystals between the common-plane electrode and the electrode shaped like a rectangle untwist and block the light in that region from passing through. That makes the LCD show the rectangle as a black area. Note that our simple LCD required an external light source.

Liquid crystal materials emit no light of their own. Small and inexpensive LCDs are often reflective , which means to display anything they must reflect light from external light sources.

Look at an LCD watch: The numbers appear where small electrodes charge the liquid crystals and make the layers untwist so that light is not transmitting through the polarized film. Most computer displays are lit with built-in fluorescent tubes above, beside and sometimes behind the LCD. A white diffusion panel behind the LCD redirects and scatters the light evenly to ensure a uniform display.

On its way through filters, liquid crystal layers and electrode layers, a lot of this light is lost -- often more than half! If you take the layer that contains the single electrode and add a few more, you can begin to build more sophisticated displays. 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. Although the hexagonal bar shape illustrated previously is the most common form of electrode arrangement in such devices, almost any shape is possible.

Just take a look at some inexpensive handheld games: Playing cards, aliens , fish and slot machines are just some of the electrode shapes you'll see. Today, LCDs are everywhere we look, but they didn't sprout up overnight. It took a long time to get from the discovery of liquid crystals to the multitude of LCD applications we now enjoy. Liquid crystals were first discovered in , by Austrian botanist Friedrich Reinitzer. Reinitzer observed that when he melted a curious cholesterol -like substance cholesteryl benzoate , it first became a cloudy liquid and then cleared up as its temperature rose.

Upon cooling, the liquid turned blue before finally crystallizing. Since then, LCD manufacturers have steadily developed ingenious variations and improvements on the technology, taking the LCD to amazing levels of technical complexity. And there is every indication that we will continue to enjoy new LCD developments in the future!

Passive-matrix LCDs use a simple grid to supply the charge to a particular pixel on the display. Creating the grid is quite a process! It starts with two glass layers called substrates. One substrate is given columns and the other is given rows made from a transparent conductive material. This is usually indium-tin oxide. The rows or columns are connected to integrated circuits that control when a charge is sent down a particular column or row.

The liquid crystal material is sandwiched between the two glass substrates, and a polarizing film is added to the outer side of each substrate. To turn on a pixel, the integrated circuit sends a charge down the correct column of one substrate and a ground activated on the correct row of the other. The row and column intersect at the designated pixel, and that delivers the voltage to untwist the liquid crystals at that pixel.

The simplicity of the passive-matrix system is beautiful, but it has significant drawbacks, notably slow response time and imprecise voltage control. Response time refers to the LCD's ability to refresh the image displayed. The easiest way to observe slow response time in a passive-matrix LCD is to move the mouse pointer quickly from one side of the screen to the other. You will notice a series of "ghosts" following the pointer. Imprecise voltage control hinders the passive matrix's ability to influence only one pixel at a time.

When voltage is applied to untwist one pixel, the pixels around it also partially untwist, which makes images appear fuzzy and lacking in contrast. 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. Liquid-crystal display LCD is a popular type of technology used in electronic displays. Because liquid crystals have light-modulating properties, LCDs are particularly effective for this purpose.

To learn more about LCD displays and how they work, keep reading. While there are several different configurations for LCD displays, most are designed in the same basic manner. They work by using liquid crystals to produce an image.

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