Lcd tv how does it work

It was this move that gave LCDs something of a boost over plasma TVs, which were often thick, heavy and sometimes even ugly. An LED illuminated TV can be hung on a wall, and that captured the imagination of both reviewers and the public.

In these TVs, especially early on, it would be quite common to have bright spots at the edges, often concentrated in the corners. This was undesirable, but on more expensive models the backlight was often very even, and looked great.

Some degree of dimming control was possible, so blacks would appear better than CCFL TVs, but it was still not perfect. Later on things advanced again, and we got LED backlights. This was a more expensive solution, but using this method you could have a direct source of light behind the LCD. This, as a rule, gave the most even picture and allowed for very bright TVs. However, there was an update to this technology that also allowed these LED backlights to be dimmed in zones.

Depending on the number of LEDs and zones used, you could get an impressive level of control over the image contrast. For example, in a shot of a dark room with a bright window, the TV could dim all of the zones in the dark parts of the room, to bring out the detail, but increase the brightness in the window to bring out the detail in the light part of the image. This technology allowed black levels to approach those of plasma for the first time.

Although early sets using this technology would sometimes show a white halo around objects, this was noticeable on end-credits of movies. There are several great things about LCDs. The first is that they offer a lot of brightness, really good colour and an incredibly sharp picture. Then there was the burn-in issue, where a plasma could retain an image left on screen for too long - another problem LCD just didn't have. Of course, plasmas had a lot going for them too.

Much better black levels being crucial, and with it a better contrast ratio and more realistic image. Plasmas also have a much faster refresh rate, which meant when 3D came along you'd get less crosstalk. But more importantly, if you're a sports fan, then plasma would give you a much sharper image on moving objects.

In theory though, OLED trumps them both. It takes all the good things about plasma, like amazing black levels and contrast, super-fast refresh rates and great viewing angles, and merges them with the strengths of LCD like the ability to do 4K - which is a problem for plasma - and amazing colour and brightness. It's fair to say plasma TVs have had their day as we enter a world of 4K.

These TVs look better than ever, and it's likely that they will remain the number one selling display technology for a really long time. In an LCD screen there is every little emission of electromagnetic radiation. A great advantage in an LCD screen is that it can be made into almost any size or shape. Another advantage is that is associated with an LCD screen is the masking effect.

In an LCD screen there is no theoretical resolution limit. One of the great disadvantages using an LCD screen is that it is very limited viewing angle which causes the brightness and saturation to very. The brightness distortion and also caused due to uneven backlighting in some of the monitors. One of the great disadvantage that may arise in intensity is that the liquid crystal sometimes cannot completely block all of the light that is passing through them this causes the black levels to be unacceptably bright.

Another important disadvantage that may occur in the LCD's dad they may become dead or stuck pixels during the manufacturing of this problem may occur during the use.

In an environment where there is a very high temperature a loss of contrast may occur in an LCD. Another important disadvantage that is associated with an LCD is that in the direct sunlight the LCD shows a poor display and it cannot be used with the light guns.

If a person is wearing polarized sunglasses it would be very hard for him to see on an LCD. The difference lies in the brightness of the image. However, LED is more preferred and used now a day. Email : info mepits. Login Sign up Cart 0. Toggle navigation. Tutorial by Mepits. Introduction A liquid crystal display also known as LCD is a display that uses a flat panel, electronic visual display.

Construction The LCD consists of a thin layer of liquid crystal that is present between the two glasses. Advantages The LCD screen as compared to other screen is very compact and light in weight. Disadvantages One of the great disadvantages using an LCD screen is that it is very limited viewing angle which causes the brightness and saturation to very.

LED vs. User Review 0. Please login to add review. Related Items. 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.

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