How does lcd work video

LCD screen technology is rather straightforward: LCD monitors are made of a substance that is permanently in a liquid state but has some properties inherent in crystal bodies. A Liquid crystal display is a passive device, which means it doesn't produce any light to display characters, images, video and animations. But it simply alters the light traveling through it. The internal construction of LCD describes how the light altered when it passes through it in order to produce any characters, images etc.

The American inventor J. Fergason created the first working liquid crystal display in Before that, such devices consumed too much energy, their operating life was limited, and the contrast of the image was on a low level. A new LCD monitor was introduced in Despite the fact that liquid crystals were discovered a long time ago, at first, they were applied for different purposes.

Molecules of liquid crystals under the influence of electricity can change their orientation and, as a result, change the properties of the light beam passing through them. Based on this discovery and because of further research, it became possible to discover a connection between the increase of electric voltage and the change in the orientation of the crystal molecules to ensure the creation of the image.

Firstly, liquid crystals found their application in the displays for calculators and quartz watches, and then they were utilized in monitors. Today, due to progress in this area, such screens have become very popular in desktop computers and many other devices. LCD screens are an array of small segments called pixels, which can be manipulated for information displaying.

Such displays have several layers, where two panels, made of glass material free of sodium and called substrate, play a crucial role. The substrate contains a thin layer of liquid crystals between them. The panels have flutes that direct the crystals, giving them a distinctive orientation. Flutes are parallel on each panel but are perpendicular between the two of them.

Longitudinal flutes are obtained as a result of placing on the glass surface thin films of transparent plastic, which are then processed in a particular way. In contact with the flutes, the molecules are oriented identically in all the cells. The liquid crystal panel is illuminated by a light source, depending on where it is located, as the LCD panels operate on reflection or light transmission.

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. 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 levels of brightness per pixel. An LCD that can show colors must have three subpixels with red, green and blue color filters to create each color pixel.

Through the careful control and variation of the voltage applied, the intensity of each subpixel can range over shades. Combining the subpixels produces a possible palette of These color displays take an enormous number of transistors. For example, a typical laptop computer supports resolutions up to 1,x If we multiply 1, columns by rows by 3 subpixels, we get 2,, transistors etched onto the glass! If there is a problem with any of these transistors, it creates a "bad pixel" on the display.

Most active matrix displays have a few bad pixels scattered across the screen. LCD technology is constantly evolving. 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.

Sign up for our Newsletter! Mobile Newsletter banner close. Mobile Newsletter chat close. Mobile Newsletter chat dots. Mobile Newsletter chat avatar. Mobile Newsletter chat subscribe. TV Technology. How LCDs Work. By: Jeff Tyson. Depending on the direction from which you're viewing it, you can see one of three different images. See more HDTV pictures. Image courtesy Sharp Corporation. Nematic Phase Liquid Crystals " ". Image courtesy Dr. Oleg Lavrentovich, Liquid Crystal Institute. Creating an LCD " ".

Light can be polarized. See How Sunglasses Work for some fascinating information on polarization! Liquid crystals can transmit and change polarized light.