LCD LED backlight. Principles of LED TV and LED backlighting. Edge LED: Better color rendering

LED LED backlighting is another characteristic of TVs and monitors, which recently complicates the choice of the buyer, requiring him to think too much and make a responsible decision ... The fact is that LCD (LCD) TVs are becoming more and more, and its types are all time is multiplying.

Indeed, when purchasing a TV, one wants not to make a mistake, not to buy something representing yesterday or the day before yesterday, which will soon be impossible to use ...

Fortunately, there are no big difficulties in this matter, its importance is greatly exaggerated - more on this below on the page ...

There is a good rule of thumb: when buying a TV, it is recommended to pay less attention to the names of the technologies used, and more guided by your impressions of its look and picture quality.

In this case, of course, more modern (and expensive) TV in most cases will be of better quality.

The best results in terms of image quality today are, perhaps, given by the type of backlight - Direct (Full) LED. Moreover, it is being improved all the time - now a very large number of LEDs can be used in this technology, which, of course, has a very positive effect.

Edge LED or its derivatives also show more and more best performance, allowing, moreover, to make the TV very thin.

In both cases, in best models TVs also use the "Local dimming" method - Local dimming... In LG TV, the backlight using it is called LED plus.

The LCD elements that make up LCD TV panels will not produce images on their own unless they are backlit. Therefore, this or that type of highlighting in modern TVs necessarily present. At the same time, it should be borne in mind that technologies are constantly being improved, and the type of highlighting with the same or a similar name in the next year may be very different in performance from last year. For example, Full LED screens are now almost as thin as Edge LEDs.

Among the types of TV backlight used or used by SONY are the following:

CCFL (Cold Cathode Fluorescent Lamp Illumination).

WCG-CCFL (Wide Backlight colors on cold cathode fluorescent lamps).

RGB LED, or dynamic rgb led (Provides color backlighting of individual parts of the monitor or TV screen. Potentially a very promising technology, since in theory it makes it possible to illuminate the desired area of \u200b\u200bthe screen with a certain color. In practice, its theoretical advantages over other types are not always possible to translate into life. For more details see page below).

Full LED. Another name is Direct LED (the backlighting diodes are evenly located behind the screen throughout its entire area. This simplifies control and improves quality. But negatively affects the thickness of the screen.) - Edge LED (The LCD screen is backlit by white LEDs installed at the top and bottom or on the sides . Allows to manufacture very thin Slim-TVs).

Dynamic Edge LED (In addition, Local Dimming technology is used, which controls the amount of luminescence of individual groups of LEDs depending on the displayed image).

Intelligent Dynamic LED. Another name is Full LED or Direct LED (Compared to previous technologies, there are many more white backlighting LEDs located right behind the TV screen evenly throughout its entire area and illuminating the image. By controlling the glow of individual LED blocks, the system can illuminate specific areas of the image, leaving others dark. This technology simplifies operation and improves quality, but negatively affects screen thickness.)

Other TV makers such as Samsung, Sharp, LG or Toshiba use different technologies to varying degrees. Accordingly, the TV backlight options may also have a different name (you can find a lot of information on the Internet for more information on technologies, but from the point of view of choosing an option for a purchase, this information will not give much. It is more important, as we have already said, to evaluate the TV picture visually).

By the way, Sony's Full LED (Intelligent Dynamic LED) is not the same as full LED backlighting as originally understood in the early days of technology, when the fluorescent lamp backlight of LCD TVs was simply replaced by thousands of individual light-emitting diodes (LEDs).

Compared to previously used technologies, lED LED LCD backlighting (LCD) TVs have enough advantages, but there are also disadvantages (inherent in the technology itself):

Disadvantages of LED technology

Initially, this type of backlight does not improve the viewing angles of the LCD display.
- Thinner models with side LED backlighting may suffer from uneven backlighting
- LED backlighting can cause local unwanted dimming.

Of course, these disadvantages in most cases are successfully overcome in specific models TVs and monitors, since the technology itself is constantly being improved. Besides, not only the backlight affects the quality of the picture on the screen.

Benefits of LED TVs

All types of LED backlighting are more economical
- Technologies such as Edge LED allow you to create TVs with an extremely thin screen
- LED leds does not contain mercury (although their manufacturing technology uses gallium and arsenic)

Of course, miracles do not happen. As a rule, the more expensive model will have both a better image and the type of screen backlight that is considered the most promising at the moment. But the image will be good not only and not necessarily because of the backlight. All other TV devices, including the video processor, can be of very good quality. The TV can be very well tuned (what used to be called "calibrated"). In the end, the adjustments can be correctly and appropriately for the given lighting ...

From all this, in our opinion, we can conclude:

When choosing a TV, you should not pay much attention to the type of backlight. It will be better if you personally compare the image quality of several models, and choose the one for which the picture seems more pleasant.

And it is up to the manufacturers to choose which type of backlighting is better. So far, they themselves cannot come to an established opinion (which is natural, because technologies are moving forward very quickly).

Take for example RGB LED backlight. It is believed to provide a much richer color gamut, extremely crisp and contrasting images on the screen, but has not been seen ubiquitously over time. On the contrary, it seems that manufacturers are abandoning it. First, it is much more expensive than other types. And it also has technical limitations: the number of backlighting elements is limited, since it is too difficult and costly to control every part of the monitor. As a result, some of the scene illumination that should have been bright may decrease.

Addition:

Recent times there are reports of successful improvements to this technology by Mitsubishi. Moreover, they are developing a completely new type of RGB Backlit using a tri-color laser. Perhaps, soon about RGB backlighting will again start talking in full voice.

Sergey Filinov

LED backlighting in modern TVs with LCD screens today has several technological solutions. In an effort to increase the color gamut for better display of colors, TV display manufacturers have developed new backlighting techniques that differ from conventional LEDs.

RGB LED

To obtain a wide spectrum of white light, they began to use triads of LEDs consisting of blue, green and red colors in the backlight.

It was an alternative to WLED with white LED and lower color gamut. The lighting system with three different LEDs is called RGB LED. The color gamut of RGB backlit screens was greater than with white LEDs alone or with fluorescent lamp CCFL. But there were also disadvantages: price, size, weight, different aging times of LEDs different color, which over time led to a color detuning of the image. Therefore, they abandoned RGB LED backlighting in favor of WLED.

RGB LED

WLED

Given the disadvantages of RGB backlighting, TV manufacturers have opted for "white" LEDs. They are located either on the sides of the case or in one array behind the LCD matrix. With the help of special diffusers, the light from the diodes is evenly distributed over the entire screen.

Although we call these LEDs "white", they actually emit blue light, which passes through a yellow filter and becomes white. Therefore, the use of white LEDs in screens as early as 2010 gave a bluish tint to the image.

Over time, manufacturers have improved the components, and the WLED backlight has become quite workable, but as far as the light spectrum is concerned, some color imbalances are noticeable.

This peak in blue is due to the blue LED. Using a light filter, you can get white light. And that filtered light hits the subpixels of red, blue and green to form the entire gamut-limited spectrum. Passing through the filters, part of the spectrum is lost, and the flux intensity at a frequency corresponding to blue will be greater than at red and green. You can get the correct colors by calibrating the screen, but these reasons allow a WLED backlit screen to display colors in sRGB only.

If the display with WLED will display colors in the picture close to blue (shades of blue), then the advantage in the spectrum is precisely of blue color may put pressure on other colors to be mixed in to create a hue. Therefore, the display of shades close to blue may not be correct.

There was a similar problem when using a CCFL lamp, but there was a problem with green. It was on the green that the intensity peak was visible.

Increased color gamut

To expand the color gamut beyond sRGB and move to the next color standard, changes were made to the WLED backlighting.

And after the changes, they began to use the name GB-R LED or GB-r LED. Now, instead of a white LED, a combined blue and green LED coated with a red phosphor is used.

This technology makes it possible to obtain peaks in the spectrum in red, green and blue.

This technology is currently used in LG on AH-IPS matrices and in Samsung on PLS. GB-r LED technology achieves 99% Adobe RGB coverage.

Some manufacturers in their screens use a different way to increase the color gamut. They take a mixture of blue and red LED and use a green phosphor for the light filter. This technology is called RB-LED or RB-G LED.

LED TVs have gained particular popularity among users due to their characteristics and quality. However, not everyone understands what a led TV is, how it differs from others and how it works this technology... Therefore, today we decided to talk about the advantages and disadvantages of this technology, as well as answer other questions.

In television equipment, LED stands for liquid crystal LCD TVbacklit light emitting diodes edge or direct. Older TVs used a cold cathode backlight. Thanks to the new backlight technology, the image quality has improved, which means that the brightness, contrast, color depth and color reproduction itself have improved.

A large number of small, individual LEDs are used to create this edge-lit monitor. In this case, each of the diodes is responsible for the backlighting of a certain area of \u200b\u200bthe screen. This technology allows you to reduce the thickness of the TV. In addition, unlike the fluorescent lamps used in LSD TVs, the LEDs used in both direct and edge backlighting last much longer.

Features of LED backlight

In fact, most of the parameters in ice TV depend on the quality used. It affects parameters such as:

• Contrast;
• Brightness;
• Viewing angle;
• Black level;
• Color gamut;
• Color rendering;
• Response time;
• Update frequency.

The increase in screen contrast has led to the emergence of such a thing as dynamic contrast. This means that the brightness of the glow of each of the diodes with direct backlighting is controlled separately from the rest of the sections. The static contrast does not change, since it depends on the display matrix.

In addition, both direct and edge backlit LED TV new technology local dimming, which provides local dimming through which groups of LEDs can be controlled. This dimming method is quite popular, but it also has some drawbacks.

1. The color is not uniform, so you may notice dark and bright spots where there is no backlight or it is very bright.
2. Fine details of the image disappear in dark areas.
3. Colored halos appear at the junctions of contrasting colors.

However, do not worry, as they are not visible in the usual picture.

Types of ice backlights

The backlight in such screens is divided into several main types:

• Direct - blue, red and green diodes are evenly spaced from the back of the matrix, forming a screen. Direct technology achieves the most optimal color gamut and the best color reproduction. However, it should be noted that displays with direct technology consume more electricity and are thicker.
• Edge - White LEDs along with a diffuser panel are located around the perimeter of the screen. Edge TVs are more energy efficient and thinner, but good local dimming is difficult to achieve. Edge-type backlighting is the most popular, especially on small diagonal TVs.

Composite LEDs

Direct lighting in TVs is different from the classic RGB LED. Composite LEDs of three colors are used to improve color gamut. However, the desired color gamut did not work out, as it was often too small. Therefore, on the basis of this technology, other light diodes were invented, allowing to achieve desired result... So, today quantum dots or GB-R LED and RB-G LED diodes are used in ice TV.

In GB-R technology, blue and green LEDs are combined into one, covered with a red phosphor, and in RB-G, red and blue are combined, which is eventually covered with a green phosphor.

Disadvantages and advantages of LED TVs

As a result, it can be noted that such TVs have a large number of advantages, and of the disadvantages, in fact, only a "biting" price.

In this article we will look at what LED technology is and where it is applied. I must say right away that not only the matrices of monitors and televisions () are illuminated, but in general everything from the bottom of the car to water from the tap. Now let's talk about this in more detail.

Generally speaking, a liquid crystal monitor is a device that consists of just a few major components. These are the pixel matrix, backlight and top protective layer. In this case, the image itself is generated by a matrix of pixels, but since it does not emit light at all, you have to illuminate it from behind. You can shine a flashlight from the front, but hardly anyone will sit and shine into the monitor during operation;) For this, a backlight is used.

Earlier, in older models of LCD monitors, it was electroluminescent, that is, a tube filled with gas, as in lamps for lighting schools, offices, and so on. It is clear that in monitors and TVs such lamps are much smaller, and the gas there is different, but the main principle of operation is the same. Now, most of the new models use LED backlighting, that is, LED (light emitting diodes).

When using lamps, they are installed along the perimeter of the screen, and in order to spread the light evenly from the perimeter to the center, reflectors and light-scattering filters are used.

When using the same lED backlight two options are possible. The first is traditional, cheap and practical - the same perimeter installation. In this case, everything is done in the same way as with lamps - diodes are installed along the perimeter and their light is carried to the center by reflectors and various filters. But, of course, there will be no improvement in the quality (uniformity) of the backlight compared to electroluminescent lamps. But, nevertheless, there are pluses! Reducing energy consumption when using LED-backlighting is reduced several times. As, in fact, and the release of heat.

All of the above applies to the budget - white backlighting (although it is actually blue, additional yellow filters are simply used). It is installed on the sides for the same purpose - to save money. Such monitors are sold out faster, as they do not frighten off consumers with their price. But there is another option for installing the backlight - over the entire surface of the matrix. It is already much more uniform and of better quality, and in addition, it is also colored. Yes, this is the so-called RGB LED backlight. It consists of RGB LEDs in three colors: red, green and blue. Located across the entire area of \u200b\u200bthe matrix, such a backlight can be turned off to obtain absolutely black color on the screen, but it can be highlighted in a certain color, giving the picture brightness and saturation to the color.

However, since the cells can be quite large, when part of the illumination is completely turned off to obtain black, the part of the image that should be bright may be affected. But, most likely, all this will be solved simply by increasing the number of LED cells or even controlling individual diodes on their own, it will simply require more computing power of the central processor at the monitor.

LED lighting everywhere

In fact, backlighting can be applied anywhere. For example, I have selected for you some successful, in my opinion, pictures with diodes.

LED bike lights

Backlit sofa

As you can see, it all depends on fantasy. LED lights are perfect for cars, bicycles, furniture and even showers or faucets. Get enough interesting effects and hands start to itch to do something like that, well, go ahead! Don't hold yourself back :)

LED TV - TV with a liquid crystal screen, which uses LEDs to illuminate it. For example, other LCD TVs that came before used a cold cathode to illuminate the screen. It is believed that it is LED TVs that have best quality images, in contrast to previous TV models, namely: color quality, contrast, color depth, brightness and other parameters.

The image quality is affected by a new technology called local dimming. This technology is responsible for local dimming of the screen, due to which the picture quality is increased several times. Unfortunately, this technology has some drawbacks, for example: poor color uniformity in the image, color halos may appear on contrasting transitions, and some of its details may disappear in the dark areas of the image.

Varieties of LED TVs

It is worth noting that LED TVs are divided into two subspecies according to the way the LEDs are arranged, these are: Direct and Edge. Direct implies the arrangement of the LEDs evenly behind the screen, and when using Edge technology, in turn, the LEDs will be located around the entire perimeter of the screen, together with the diffusing panel.

Each of these technologies has its own advantages and disadvantages. For example, Direct, allows you to get a more uniform backlight, but this will increase the thickness of the screen itself, and therefore the TV, and in addition, the power consumption will increase. This is due to the fact that when using this method the number of LEDs increases. Thin or ultra-thin TVs are built with Edge technology, which is the exact opposite.

As mentioned above, the cost of LED TVs is decreasing today. This is due to the emergence of televisions with improved iPS technology... These TVs have better color reproduction than LED TVs, high level brightness and contrast, high image clarity and many other advantages.

As a result, choosing a TV by the type of backlighting, a person can make a mistake, since it does not always have a decisive effect on the image quality. An important role in this is played by the type of GPU, as well as the image processing technology.