edge lit led lcd panel factory

Lightboxes can be built to your specifications regarding size, color temperature, and frame color. Single and double-sided [illuminated on the front and rear face] light panels are also available. Edge-lit panels are 8mm or about 1/3-inch thick a light panel including a flip-open frame [now called a lightbox] has a thickness of 0.625 to 1.50-inches. Illumination across the LED light panel from edge-to-edge is within 10% so a dark center is not a concern. Read more

Light panels have many uses in retail environments such as lighted shelves, signs or as a lightbox for photographic transparencies, stained glass and faux windows. For interior lighting applications, the panel performs well as a ceiling troffer, lighted wall, under cabinet light and under stone such as Onyx, quartzite or translucent man-made countertops. Read more

In signage, edge-lit panels can be a substitute for fluorescent tubes. Panels are thin, evenly illuminated and last for years without maintenance. Several color temperatures are available and RGB.

When displaying stained glass or some other translucent material in a window, you can use our clear edge-lit panel to let natural light through during the day and illuminate your art at night.

When comparing different models of televisions, you might see the term "edge-lit LED." All LED TVs are a type of LCD TV; the "LED" refers only to the kind of lighting source used to illuminate the LCD pixels in the television. There is more than one way to light the pixels. The two primary technologies are edge-lit and full-array.

In an edge-lit television, the LEDs that illuminate the LCD pixels are located only along the edges of the set. These LEDs face inward toward the screen to illuminate it.

These models are thin and light at the mild expense of some picture quality—specifically in the area of black levels. Black areas of the picture, such as a dark night scene, are not truly black but more like a very dark gray since the lighting is coming from the edge and illuminating the dark areas a bit more.

In some poorer-quality edge-lit LEDs, uniform picture quality can be a problem. Because the LEDs are along the edges of the panel, quality declines as you approach the middle of the screen because a uniform amount of illumination is not reaching the pixels further from the edges. Again, this is more noticeable during scenes of darkness; the black along the sides of the screen is more gray than black (and corners can appear to have a flashlight-like quality of illumination emanating from the edges).

Full-array LED televisions use a full panel of LEDs to illuminate the pixels. Most of these sets also have local dimming, which means the LEDs can be dimmed in different regions of the panel while other areas are not. It helps improve black levels, which appear closer to black than dark gray.

In general, full-array LED is a superior technology when it comes to picture quality, but edge-lit sets have one significant advantage: depth. Edge-lit LED TVs can be much thinner than those lit with either a full LED panel or traditional fluorescent (non-LED) backlight. For that reason, most of the super-thin sets you see in stores will be edge-lit.

If you"re looking for the best possible picture quality, you are most likely to find it in a full-array LED display with local dimming. If you are primarily concerned about the appearance of the television and want an extremely thin screen, edge-lit is the style that will fit your needs.

The local dimming on LED TVs is a key way of introducing contrast. With this technology, the intensity of lighting adapts to the image shown achieving contrast ratios.

LED-backlit LCD, which uses light-emitting diodes for backlighting is a common type of display on televisions and laptops. Unlike pure LED screens these LCDs are not self-illuminating and are reliant on the backlighting for illuminating the display. It is an advancement on the preceding cold cathode fluorescent technology and some manufacturers and retailers may advertise this type of screen as an LED TV.

Edge-lit is a type of screen backlighting that has LED lights lining either the top and bottom edges of the screen or the perimeter of the screen. This form of backlighting differs from others as the screen is not lit from behind, and often produces a more muted effect. An opaque piece of plastic called a diffuser light guide distributes the lighting across the rear of an LCD panel.

Edge-lit LEDs can be individually brightened or dimmed to provide the high degree of backlight control that screened content demands. Edge-lit screens can achieve this in one of two ways:

Direct-lit backlighting uses LED lighting across a television back panel. This form of backlighting initially used Cold Cathode Fluorescent Lamps (CCFLs) before transitioning to LED. The lighting is behind the LCD panel to provide consistent lighting across the entire screen.

The use of LEDs creates an extremely bright picture. This can lead to black and naturally dark tones appearing too bright, a phenomenon known as ‘elevated black levels’. This appearance can really affect wide-screed films, especially as there is no way to alter the backlight of specific portions of the screen. This has led to the development of alternative backlighting arrangements that minimize the greying of black sections of the screen.

Both types of backlighting provide the illumination LED screens required to produce a visible image. The main difference is that direct-lit backlights sit behind the LCD panel to provide the necessary lighting whereas edge-lit screens have LEDs sitting at the perimeter of the screen. Here are some other notable differences:

The first generation of LED backlighting was edge-lit. However, this early form of edge-lit technology caused the development of hotspots on the screen and the overall lighting was inadequate. As LED design became more efficient and effective, Samsung revisited this type of backlighting with a market-leading edge-lit LED television in 2009.

Direct-lit panels use a simple array of LEDs to provide uniform lighting across an entire LCD panel. The adoption of direct-lit screen technology in the 2000s was driven by the availability of white LEDs that could replace existing CCFL technology.

Direct-lit performs across a range of viewing angles and colors, but it is limited by not being able to increase contrast, as the entire backlight has to be dimmed to change color intensity. This affects the ability of a screen to achieve a deep black tone. Full array lighting and flexible backlight technologies have superseded direct-lit lighting. They are more advanced and can achieve more nuanced imaging effects.

Edge Lit screens can achieve full, deep blacks as they can use local dimming technology to reduce lighting in areas of the screen that display black or dark colors.

I would guess that LCD TV enthusiasts, owners, and potential buyers that lean more toward the videophile/home-theater end of the spectrum represent a fairly small percentage of the overall market. If you are part of this minority and follow discussions on AV forums dedicated to such topics, you will learn about quality control issues that plague just about every make and model of flat-panel TV on the market. In some cases you will learn about flaws that you may never have noticed on your own, and once they are seen they usually can’t be unseen. But it is better to be able to spot a problem immediately within a return or warranty period than to suddenly discover it on your own when it is too late. Being informed can assist you in making a better choice in selecting a TV; it can also cause frustration to find out that no matter what make or model you choose,luck almost always plays a role.

It is pure speculation on my part, but it seems plausible that the Edge-Backlit LCD TV business model has settled on this general quality control philosophy:

LCD TVs, once scorned by those who care about things like black blacks and color uniformity, have made substantial improvements in a very short time. These improvements are partly due to improved panel processes, and also partly due to clever backlight dimming techniques that help offset some of the inherent shortcomings in the LCD panel itself.

Note: While it is common to use the term “panel” to refer to the entire assembly of the LCD array and the layers and components associated with backlighting, I will at times be referring only to the active liquid crystal panel.

HDTV and monitor LCD panel technologies and signal processing have advanced dramatically in just the past couple of years. 70″ to 80″screens are found lining dealer’s walls and aisles, and gone are the laggy, low contrast, narrow viewing angle displays that marked the beginning of the flat screen era.

Unfortunately some of these technological advances have been stunted by the trend of using a system of edge-lights and a sandwich of thin film layers to provide the distributed backlight for the LCD panels.

Early flat screen TVs and computer monitors used a parallel array of thin CCFL (cold-cathode fluorescent) tube lamps spaced behind a translucent diffuser. Banding of the backlight was minimized by optimizing the quality of the diffuser, minimizing the spacing between adjacent lamps, and providing adequate distance between the diffuser and the lamps. CCFL backlit TVs could not be very thin, and were usually several inches thick depending on the screen size. While reasonably efficient, CCFLs, much like hot-cathode fluorescent lights, have a limited life and require the use of high voltage switching power supplies.

LED backlighting if implemented properly is a natural fit for LCD panel lighting. LEDs are a more energy-efficient light source and generally have an extremely long life, although the active driver circuits that provide a constant current to the LEDs can fail before the LEDs themselves. LEDs can also be dimmed easily (unlike CCFLs) and some more advanced TVs will allow the backlights in dark areas of the image to be intelligently dimmed, enhancing the black level beyond the darkening capability of the LCD panel alone. More on this later.

The natural progression for transitioning to LED backlighting of LCD panels involved replacing the tubular CCFL lamps with distributed arrays of point-source LEDs. This is known as full array backlighting. As in the case of CCFL lighting, uniformity was a function of the spacing between adjacent LEDs and the spacing of the LED array from the diffuser panels. This need to keep the LEDs some distance away from the diffuser panel prevents the full-array TV from getting as thin as an edge-lit design.

Ignoring any variations in the LCD panels themselves, which is a separate issue, the uniformity of full array backlighting is quite consistent. Any deficiencies in light uniformity (which I have never really seen) using full-array LED backlights would be seen as hot-spotting rather than banding as is the case with CCFL tube lamps. But with this type of design the expectation would be that if you did see any backlighting-related deficiencies on the display model at Best Buy, you would probably see the same deficiencies on the next one in the stack or one purchased at a CostCo 2000 miles away. This is a consistent lighting method – one whose uniformity depends on the design, not production variations, and not luck-of-the-draw.

Full-array backlighting also allows groups of LEDs, allocated into zones, to be dynamically dimmed under black areas of the screen, and the full-array can handle dimming scenarios that no other form of backlighting can handle (a white screen with a black center, for example).

At some point, thin became sexy. Bezels became narrower and panels grew larger and in some cases became ridiculously thin. It should also be noted that regardless of the apparent thinness of the panel edge, other electronics and connectors that can’t be contained within that thin form factor contribute to the need for the hump or pod that is present on the back of all of the thin sets.

But whatever is driving the trend toward LED edge-lighting with ultra-thin panels – cost reduction, marketing studies, who knows what- it certainly isn’t picture quality. It is also a fair question to ask how much the drive toward thin packages has compromised the designs of support electronics and cooling. Perhaps this is a contributor to the perception that you should not expect your lovely new HDTV to last more than a few years, or sometimes much less than that.

The fundamental problem of poor uniformity with LED edge-lighting is not in any way the fault of the LEDs; they are merely the light source, and a good one at that. The real problem lies in the technology of the light distribution panel, and more specifically in the sensitivity of that technology to manufacturing and material inconsistencies. Flashlighting, Clouding, DSE (Dirty Screen Effect), Banding, Non Uniformity, and Backlight Bleed are all terms used to describe the flaws present in far too many (dare I say the majority?) of edge-lit LCD TVs right out of the box.

Read the AV forums and you will see that there are potential buyers that are tracking which panels are getting used in which TVs (by serial number) in an attempt to “find a good one”. Some owners with blotchy screens are rubbing them with microfiber cloth in an attempt to massage out some lighting anomalies, with varying degrees of success. And others are loosening the screws on the perimeter of the screen, because they have found that minor variations in panel stresses caused by a different screw torquing sequences can sometimes help.

This all points to one thing, and you don’t need to be a backlight panel expert to understand it: the sensitivity of edge-lit panel uniformity to manufacturing and material variations – over which manufacturers clearly have inadequate control- is too high. An example case describing the astounding out-of-the-box differences between two identical TVs will be given later.

An inside look at the construction of the light distribution layers of an edge-lit TV is fascinating in its hidden complexity, and yet it’s disheartening when you to see how a fundamentally compromised design can get signed off and in effect contribute to an entire industry trending toward a lowest common denominator product that customers will still tolerate.

The light distribution layers of edge-lit panels can vary somewhat, but a key element is the panel that reflects incoming light from the edge-mounted LEDs at a right angle toward the viewer. This is a thin, flexible panel sometimes called a light guide. All of this reflection occurs due to very many small ridges contained within the thickness of the light guide, like many thousands of small mirrors all carefully aimed to catch any light coupled to the guide’s edges and aim it directly at you. The ridges have to be graded in height so that the ridges near the center, those farthest away from the edge light source, receive their fair share of light to reflect and are not obscured by the ridges closer to the edge.

It is this stackup of thin, flexible film layers, including the active LCD panel, that appears to be highly variable. Anyone who has ever pushed a finger into an LCD laptop screen knows how sensitive it is to stresses and distortion.

The sandwich of flexible films that comprise the edge-light distribution system cannot be squeezed into flat submission in a 10 ton platen press; it’s more like trying to flatten the lettuce in your sandwich by pinching only the crusts together. The protective glass screen front is flexible. The active LCD panel is flexible. The back of the whole panel is flexible. And they are all trying to contain and flatten the inner films that, on a macro scale, appear very compliant, but on a more micro scale have wrinkles, bows, and waves. These deviations from perfect flatness all require some degree of pressure to overpower – pressure that is difficult to apply in the center of a large screen when the outer faces that apply the pressure can themselves flex and bow.

It is also no wonder that some of the techniques that owners are using to try to improve their screens do, in some cases, have an effect . With a full black signal input (0%), and with the backlight fully on, a common flaw called clouding will show up as lighter patches on the dark background. It takes very little pressure on the screen – often no more than you would use to clean it – to be able to chase the clouds around like bubbles in a water bed (if you remember water beds!). Sometimes they change permanently; more often they stay the same or just move a little. The active LCD panel itself could be a contributor; it is difficult to identify the real source of the problem without risking the TV, but it seems to be generally accepted that the worst problems are correlated directly to edge-lit designs.

Through chance and fate, and a truly helpful sales person, I was steered to a sister store that had a few Sony KDL55HX800 models. I bought one, and it was very, very good. The panel blacks were good to start with, but it also had dynamic edge lighting which actively turns off the LEDs in regions that are black, enhancing the contrast. The LED dimming was so effective and so well implemented that we bought a second identical set a few days later for use in another room. Unfortunately, the second set was not up to the standard of the first. There was a vertical, faintly dark band visible on blue green backgrounds that I noticed right away. I didn’t like it, but I would live with it if it did not get worse.

Well, it took a while, but it got worse. I waited until near the end of the warranty and submitted pictures to Sony; they concurred that the panel was defective and needed to be replaced. Arrangements were made, a repair visit was scheduled, and then I got a call. Their message: We have no panels, they are not economical to replace anyway, and your HX800 is therefore considered unrepairable (still in warranty!). But We would like to offer you one of our lovely reconditioned current R550A models as a replacement.

After doing some more research, I semi-reluctantly decided to try a 70″ passive 3D TV by made by a top name manufacturer. There had been some issues with this particular model, but it did have some terminology implying an LED dimming feature emblazoned on the box, and that feature had become of utmost importance at this point. By now I had learned that the best way to compensate for lousy backlight and panel uniformity is to turn off backlights before your eyes can adapt to a dark screen. Of course the panel still had to be reasonably good at the darkest gray levels when the light has to be on.

I picked out a lucky one, brought it home and set it up in a dark room with the backlight level at minimum. I loaded a test disk with gray fields, and went to 0%, full black. There was some flashlighting, but I wasn’t worried about that for now. There was some clouding with full black, but the acid test for me is whether you see it during film credits. Usually even credits put enough white on the screen that your pupils constrict to the point that light clouding is not a problem. And with the LED dimming feature, full black – where the clouding would normally be most obnoxious – is presumably accompanied by LED shutdown, and hence total blackness. I could live with this, even though I couldn’t figure out how to get the dimming to work in a useful way.

With the correct settings I was eventually able to get the LED backlights to shut off when transitioning from 1% near black to 0% black, but it would only happen about 6 or 7 seconds after the transition to full black. This told me that LED dimming functionality was there, but the delay, which I did not understand and could not disable, rendered it useless. The LEDs are supposed to transition to off almost simultaneously as the LCD goes full dark. After trying virtually every setting that should make this happen, but with no success, I called the manufacturer.

To be fair I should point out that the dark picture on the right is taken with an automatic exposure on the camera, and the clouds are not as bright as the picture would indicate. However, it is a true indication of the relative variations that you seen in a dark room. The background leakage glow is there, as is every feature of the clouding. This was a show stopper, and not surprisingly it failed the movie credit test miserably as well.

And at this point it came as no great surprise when I proceeded to test the backlight dimming feature and found it to behave exactly the same as the first set – the LEDs would go black 6 to 7 seconds after a full black input signal was applied. This behavior made the dimming feature useless for its intended purpose, and the manufacturer had agreed that this was not the correct behavior.

Support attempted to duplicate the problem while I was on the phone, but it turned out they did not have the correct model set available. When questions came up on how exactly to duplicate the test, it became very telling about what their capabilities were, and they did not even have the capability of providing test patterns that were needed. I sent links on where they could obtain the test pattern files, and left them to do what they could do. I really did not expect to hear from them again.

A few days later I received a follow-up call from the support liaison. At the time it was funny in that he sounded nervous or excited, and perhaps a little practiced on how he was going to say what he had to say. Engineering had been contacted and my results had been duplicated in their lab, on their test set. And the kicker? They had identified the LED dimming behavior as a design flaw and they had no immediate solution for it, but they would be looking into it. He also thanked me profusely for bringing it to their attention. Admissions like this are surprising when you hear them, but they have happened before, and that may be a good topic for a future article.

Unfortunately, I never even got to the point of discussing those with the manufacturer. If the dimming feature problem had been solvable, there would be the possibility of still finding that model of set that might have a good panel. A verified hardware or firmware problem with dimming on an unknown number (or all) sets ruled that out. In the end, discussing panel quality issues with support would probably have ended in no real satisfaction anyway.

In more than two months I have not heard of any follow-up on the dimming problem (they offered to keep me informed to satisfy my own curiosity) but after returning both sets I washed my hands of any of the problems associated with this make and model TV. The downside is that between the wasted time spent on performing field QA and the risk of getting blacklisted for returning defective TVs, purchasing another TV is currently off the table. The immediate goals are to keep the HX800 running and wait for OLED TVs to become mainstream.

Edge lit BLUs using light guide plates are mature technology and remain a cost effective back light for many types of displays. It creates uniform and bright light output in computer monitors, mobile devices, and commercial displays. LCDs driven by edge lit back light units are a mainstay in cost effective displays found in mobile phones, laptops, tablets, and automotive displays, to name a few. They are reliable and produce uniform light, but extracting the maximum light output can prove challenging. BrightView now offers Gain Enhancement films (GEFs) based on our micro lens array technology that provides a boost in brightness for edge lit displays. The GEF replaces the traditional down diffuser, resulting in a brighter, more efficient backlight.Up to 30% improvement in brightness compared to traditional down diffuser films

Most people find themselves entangled in a perplexing situation while choosing the right TV for themselves. Buyers of big brands like Sony, Samsung and LG see their purchase as a safe deal as they are established brands and we have seen their performance for a long time now. However, individuals seeking to choose from amongst the budget offerings are the ones who are more likely to get confused in selecting the right TV that could be the best bang for their buck.

This article will give you an insight into the technical aspects of different TVs and by the end of this write-up, you yourselves would be armed with adequate technical knowledge to choose the best TV for yourself.

Most television companies, as well as sellers, misguide consumers by saying that this particular TV is not LCD but LED. So, first of all, we need to understand that all TVs are basically only

LCDs. What we refer to as LED is simply an update to the existing LCD panels. The panel technology is the same, however, the backlight is entirely different. Those LCDs that use LEDs as a light source are generally termed as LEDs. In short, a LED-backlight is a replacement for the uniform CCFL (Cold Cathode Fluorescent Light) backlight that previously gave LCD TVs its brightness.

Initially, there were only CCFL-backlit LCDs, but with advancement in technology, these CCFL were replaced by LEDs, as not only they dramatically reduced power consumption by over 40 percent compared to conventional CCFL-backlit LCDs, we got more control over the image quality by modulating these individual LEDs.

In the LED-backlit LCDs, LED lights can switch on and off individually, which allows the image to have greater contrast, bright whites and deep black in the same image. Thus, producing a superior picture when compared to CCFL-backlit LCDs. LCD TVs with LEDs also offer better response time in comparison to CCFL-backlit LCDs.

In the traditional LCDs, the CCFL lights were spread all across the surface behind the display screen, but there was no control over them. It means that when we switched on our TV, the entire surface behind the screen used to get illuminated by these CCFL lights that were always ON, and we were unable to control their dimming in specific areas of the screen.

Because of this, even the dark part of the picture used to be illuminated like the rest and we were unable to achieve images with convincing blacks, as light passed through the dark part of the picture and made it appear grey. In other words, the contrast of CCFL-backlit LCD panels isn’t very good. However, a plasma TV doesn’t have this problem as each pixel can light up or switch-off according to the demand of the picture.

Now coming to LCDs that use LEDs as the source of illumination, there are basically three types. One is Full-array backlighting, another is Edge-lit backlighting (ELED) and third is direct-lit LED backlights (DLED).

The term full-array is used where LEDs cover the entire back-side of the LCD panel. Full-array TVs are high-ends TVs that are heavier and often thicker, but they provide better picture quality as all parts of the screen are evenly backlit. They offer the most effective local dimming, as the LEDs are more in number and are spread over the entire back surface of the panel. The independent dimming of each LED in these TV sets helps in achieving perfect blacks. But, as they are costlier to manufacture, they are rare.

Edge LEDs use an array of LED backlights along the outer edges of the screen that use lightguides or diffusers to fire light across into the centre of the screen.

This technology allows the designing and manufacturing of exceptionally thin TV sets. Edge-lit sets also have a cost-benefit over direct, local dimming versions (DLED) as fewer LEDs are used in them. Because of which, they are power efficient too.

However, technically, it is the least effective system in terms of achieving a high contrast ratio as it does not offer ‘local dimming’. The black levels are not as deep and the edge area of the screen has a tendency to be brighter than the centre area of the screen. The Edge TVs not only struggle to produce a high contrast, they can also get affected by Murra Effect, which can cause light to bleed from sides to gradually overpower the entire screen.

Direct-lit LED backlights are an offshoot of full-array backlighting, though they use significantly fewer LEDs across the back of the panel. In this technology, several rows of LEDs are placed behind the entire surface of the screen.

As the LEDs are behind the LCD panel in DLED TVs, dual modulation works far more efficiently and the TVs can have better overall brightness and contrast. Using a feature called local dimming, the LEDs are divided into a number of zones that can be individually controlled, so some portions of the backlight can be dimmed while other remain illuminated.

Direct-lit LEDs can have around 200+ LED lights arranged all over the screen in clusters. Visually it is the most impressive technology, though it’s more expensive and adds extra millimetres to the depth of the TV, these TVs have local dimming that improves the blackness of an image and produce best in class picture quality, with an exceptional contrast ratio of up to 10,000,000:1. They have the ability to implement new levels of peak light output and give superb motion reproduction. Some EDGE LEDs also stake claim to local dimming, but in these TVs, it is hardly able to bring the desired effect.

Apart from being more expensive and adding to the depth of the TV, these DLED TVs might display ‘Halo Effect’ for bright images on a dark background, in which constellations of LED lights from behind the screen can cause bright objects to appear with a slight ring around them.

Though different brand TVs might be using the same DLED or ELED backlighting, their image quality might differ considerably depending on how many lights are used and how they are aligned. In some budget Edge-lit TVs, LEDs are aligned on only one side, either upper or lower edge of the TV panel, while others might have LEDs on both upper and lower edges of the panel. The high end TVs might even have a row of LEDs on all four edges of the panel. Some manufacturers use both Edge and Direct LED systems for LCD TVs. The best professional monitors use direct LEDs.

Though bigger brands like Sony, Samsung and LG also prefer EDGE-lit LED backlighting in their TVs, they complement it with some of their indigenously formulated technology to enhance the picture quality.

TV manufacturers lay more stress on producing TVs with ELED technology as it not only cut down upon their expenditure but allows them the liberty of producing ultra-slim TV sets that can appeal the masses with their aesthetically designed panels.

Traditional LCDs use CCFLs, or cold-cathode florescent lamps, as their backlight. While cheap, they"re not as energy efficient as LEDs. More importantly, all contain mercury, and aren"t able to do some of the fancy area-lighting of which some LED backlit models are capable. Because of these issues and the falling prices of LEDs, CCFL backlit LCD TVs will disappear entirely very soon. In 2013

Most LED LCDs on the market today are edge-lit, which means the LEDs are in the sides of the TV, facing in toward the screen. In the image at the top, the LED strips are above and to the side of this exploded-view of an LCD panel. There"s a close-up view here (full article with more images

There are a few models that are have their LEDs arrayed on the back of the TV, facing you. These are less common, though are making a comeback in the form of cheaper, but thicker, mostly low-end LED LCDs. There are a handful of high-end TVs that use full-array LED backlighting in a slightly different way, which we"ll discuss later.

Because the light is brightest nearest the LEDs, it"s common for edge-lit LED LCDs to have poor uniformity. This is especially noticeable on dark scenes, where areas of the screen will appear brighter than others. Corners or edges can have what looks like tiny flashlights shining on the screen. Check out

Each manufacturer has a preferred method for edge-lighting, but some models may feature one type, while other models feature another type. Generally speaking, the fewer LEDs the cheaper the TV is to produce. Fewer LEDs also mean better energy efficiency, but LED LCDs are already so efficient that this is a tiny improvement. Unfortunately, specific details about where a TV"s LEDs are located (beyond "direct" or "edge"), the number of LEDs, and other useful information about the backlighting, are rarely listed on a TV"s spec sheet.

The biggest difference between all the LED back/edge-lighting methods is how effective their "local dimming" is, which as you"ll see, has become a pretty broad term.

This design has all the LEDs along the bottom of the TV. Though manufacturers don"t like to reveal how many LEDs they use, this is likely the type with the least number of LEDs.

Though TVs of this style claim to have "local dimming" you can see how this is a pretty broad definition of "local." Even if each LED is dimmable independently (highly unlikely), you"re still only able to dim columns that stretch from top to bottom. Something like this:

As you can guess, this design has LEDs on the top and bottom edges of the screen. The local dimming here is a little better, where the zones can be slightly smaller areas of the screen, like this:

This is a less common method now, as it requires more LEDs than any of the other edge-lighting methods. The local dimming can get a little more accurate, but is still limited to large-ish zones. If we used our moon example image, the result with an all-sides edge-lit would look just like top and bottom. But with regular video (that has more light sources than just the moon), it will have a more zones to work with, sort of like this:

All Sides used to be the most common edge-lighting method. But as the light guides improved, and costs had to come down (to make cheaper LED LCDs), this method became fairly rare.

Nearly all "backlit" LED LCDs use this method. The LEDs are arrayed on the back of the TV, facing you, but there is no processing to dim them individually. They work instead as a uniform backlight, like most CCFL LCDs. The least expensive LED LCDs use this method, as do most of Sharp"s

This is the ultimate LED LCD, offering performance that rivals the better plasmas. Like the "direct-lit" TVs, these have their LEDs behind the screen (the image above for direct-lit works as a visual aid for this type as well). The full local-dimming aspect means the TV is able to dim zones behind the dark areas of the screen in fairly specific areas to make the image really pop, drastically increasing the apparent contrast ratio.

However, they basically don"t exist. The LG LM9600 wasn"t great last year, and LG has yet to announce any full-array local-dimming TVs for 2013. The only other local-dimming LED LCD was the Sony HX950, which was excellent, and is still current. In his review David Katzmaier called

The two biggest-selling TV makers in the U.S. are Samsung and Vizio, and neither has sold a full-array local-dimming LED TV for the last couple years. At CES 2013, Samsung"s only such TV announced was the insanely-expensive E420i-A1, saying "Sure, black levels get darker, but the trade-off in shadow detail is one I"m not willing to make," and concluded that its "local dimming does nothing to improve picture quality."

As I mentioned at the top, there"s no easy way to tell, just by looking at a spec sheet, what kind of backlight a TV has. By extension, there"s no way to tell how good its local dimming will be. Bad local dimming can, at worst, just be marketing hyperbole. At best, it does little to improve the picture. Good local dimming, however, can make a punchy image, with lots of apparent depth and realism. Or to put it differently, the best LCDs on the market have the best local dimming, allowing them to rival plasmas on the picture quality front. The better TV reviews, like ahem those here on CNET, will talk about all this, so you"re not duped into paying for a "feature" that"s little more than a check mark on a spec sheet.

ST. PAUL, Minn.--(BUSINESS WIRE)--In an effort to meet LCD manufacturer design flexibility demands, the 3M Optical Systems Division today announced that it has developed a unique solution called Uniformity Tape that will allow LCD manufacturers to reduce the number of LEDs required for edge-lit LED LCD panels at a low cost, without sacrificing brightness or efficiency.

"As LED technology continues to improve and becomes even brighter, some backlight designs are currently using more LEDs than needed for a brightness specification in order to avoid head lighting or thick bezels. Uniformity constraints have also prevented manufacturers from removing LEDs to save on cost"

LEDs are becoming brighter and even more efficient-requiring fewer bulbs to achieve target brightness for a given display. Until now, there have been limitations as to how far LEDs can be spaced apart at the edge of an LCD panel because of dark areas that appear between LEDs when they are too far apart. This scenario is commonly referred to as "head-lighting" because it looks like the dark space on the road between the headlights of a car.

3M"s Uniformity Tape is a clear tape, which has adhesive on one side and a micro-replicated optical pattern on the other side. It is adhered to the edge of the light guide, which faces the LED light sources. The tape is designed to increase the spreading of light in the light guide from each LED, which greatly increases the allowable LED spacing. The optical pattern is spatially uniform, meaning that no positional registration of LEDs is required along its length. The Uniformity Tape keeps the edge of the display closest to the LEDs uniform in brightness when the spacing of light sources is increased. This allows panel manufacturers to save money by removing unnecessary LEDs. Uniformity Tape can also increase LED spacing by up to three times the current spacing, while maintaining edge uniformity for a given bezel size.

"As LED technology continues to improve and becomes even brighter, some backlight designs are currently using more LEDs than needed for a brightness specification in order to avoid head lighting or thick bezels. Uniformity constraints have also prevented manufacturers from removing LEDs to save on cost," noted Gilles Georges, 3M global marketing manager. "By spacing LEDs further apart for edge-lit LED LCD panels, 3M"s Uniformity Tape allows light to travel inside the light guide at wider angles-allowing manufacturers to design wider spacing between LEDs without any dark areas."

When combined with 3M"s Dual Brightness Enhancement Film (DBEF), Uniformity Tape allows display manufacturers even more design freedom to innovate and use less LEDs to create a backlight that not only meets energy standards, but also remains competitive at a low cost. Furthermore, Uniformity Tape helps device manufacturers meet the growing number of energy efficiency standards around the world.

There are two types of LED TV - edge-lit and back-lit televisions. So what is the difference, and is it important? Find out everything you need to know.

This type of lamp has managed to produce high-quality televisions. But, there have always been disadvantages to this technology, such as poor contrast ratios and color reproduction.

Different parts of the screen can have the blocks of lights switched on or off at any time, which gives the TV a much better contrast ratio than a traditional LCD TV.

Therefore, a back-lit LED TV with local dimming produces a better picture, which helps it to create an image comparable with other TV technologies like OLED.

A downside is that the power consumption of these TVs can be greater than standard LCD or edge-lit televisions – especially those models which use RGB LEDs.

The advantage over an edge-lit TV is that the lighting will usually be more uniform across the screen – eliminating the light-pooling of edge-lit screens.

The lights in edge-lit LED televisions are placed around the perimeter of the LCD screen – and the light they emit spreads across the back of the panel using a series of ‘light guides.’

An LED-backlit LCD is a liquid-crystal display that uses LEDs for backlighting instead of traditional cold cathode fluorescent (CCFL) backlighting.TFT LCD (thin-film-transistor liquid-crystal display) technologies as CCFL-backlit LCDs, but offer a variety of advantages over them.

While not an LED display, a television using such a combination of an LED backlight with an LCD panel is advertised as an LED TV by some manufacturers and suppliers.

A 2016 study by the University of California (Berkeley) suggests that the subjectively perceived visual enhancement with common contrast source material levels off at about 60 LCD local dimming zones.

LED-backlit LCDs are not self-illuminating (unlike pure-LED systems). There are several methods of backlighting an LCD panel using LEDs, including the use of either white or RGB (Red, Green, and Blue) LED arrays behind the panel and edge-LED lighting (which uses white LEDs around the inside frame of the TV and a light-diffusion panel to spread the light evenly behind the LCD panel). Variations in LED backlighting offer different benefits. The first commercial full-array LED-backlit LCD TV was the Sony Qualia 005 (introduced in 2004), which used RGB LED arrays to produce a color gamut about twice that of a conventional CCFL LCD television. This was possible because red, green and blue LEDs have sharp spectral peaks which (combined with the LCD panel filters) result in significantly less bleed-through to adjacent color channels. Unwanted bleed-through channels do not "whiten" the desired color as much, resulting in a larger gamut. RGB LED technology continues to be used on Sony BRAVIA LCD models. LED backlighting using white LEDs produces a broader spectrum source feeding the individual LCD panel filters (similar to CCFL sources), resulting in a more limited display gamut than RGB LEDs at lower cost.

Using PWM (pulse-width modulation), a technology where the intensity of the LEDs are kept constant but the brightness adjustment is achieved by varying a time interval of flashing these constant light intensity light sources,

A first dynamic "local dimming" LED backlight was public demonstrated by BrightSide Technologies in 2003,Sony in September 2008 on the 40-inch (1,000 mm) BRAVIA KLV-40ZX1M (known as the ZX1 in Europe). Edge-LED lighting for LCDs allows thinner housing; the Sony BRAVIA KLV-40ZX1M is 1 cm thick, and others are also extremely thin.

LED-backlit LCDs have longer life and better energy efficiency than plasma and CCFL LCD TVs.mercury, an environmental pollutant, in their manufacture. However, other elements (such as gallium and arsenic) are used in the manufacture of the LED emitters; there is debate over whether they are a better long-term solution to the problem of screen disposal.

Because LEDs can be switched on and off more quickly than CCFLs and can offer a higher light output, it is theoretically possible to offer very high contrast ratios. They can produce deep blacks (LEDs off) and high brightness (LEDs on). However, measurements made from pure-black and pure-white outputs are complicated by edge-LED lighting not allowing these outputs to be reproduced simultaneously on screen.

Quantum dots are photoluminescent; they are useful in displays because they emit light in specific, narrow normal distributions of wavelengths. To generate white light best suited as an LCD backlight, parts of the light of a blue-emitting LED are transformed by quantum dots into small-bandwidth green and red light such that the combined white light allows a nearly ideal color gamut to be generated by the RGB color filters of the LCD panel. In addition, efficiency is improved, as intermediate colors are no longer present and do not have to be filtered out by the color filters of the LCD screen. This can result in a display that more accurately renders colors in the visible spectrum. Companies developing quantum dot solutions for displays include Nanosys, 3M as a licensee of Nanosys, QD Vision of Lexington, Massachusetts, US and Avantama of Switzerland.Consumer Electronics Show 2015.quantum dot displays at CES 2017 and later formed the "QLED Alliance" with Hisense and TCL to market the technology.

Mini LED displays are LED-backlit LCDs with mini-LED–based backlighting supporting over a thousand full array local dimming (FALD) zones, providing deeper blacks and a higher contrast ratio.

LED backlights are often dimmed by applying pulse-width modulation to the supply current, switching the backlight off and on more quickly than the eye can perceive. If the dimming-pulse frequency is too low or the user is sensitive to flicker, this may cause discomfort and eyestrain similar to the flicker of CRT displays at lower refresh rates.

Novitsky, Tom; Abbott, Bill (12 November 2007). "Driving LEDs versus CCFLs for LCD backlighting". EE Times. Archived from the original on 28 November 2010. Retrieved 21 November 2020.

LED TVs: 10 things you need to know; David Carnoy, David Katzmaier; CNET.com/news; 3 June 2010; https://www.cnet.com/news/led-tvs-10-things-you-need-to-know/

LCD Television Power Draw Trends from 2003 to 2015; B. Urban and K. Roth; Fraunhofer USA Center for Sustainable Energy Systems; Final Report to the Consumer Technology Association; May 2017; http://www.cta.tech/cta/media/policyImages/policyPDFs/Fraunhofer-LCD-TV-Power-Draw-Trends-FINAL.pdf Archived 1 August 2017 at the Wayback Machine

Polarisation-sensitive beam splitter; D.J. Broer; A.J.S.M. de Vaan; J. Brambring; European patent EP0428213B1; 27 July 1994; https://worldwide.espacenet.com/publicationDetails/biblio?CC=EP&NR=0428213B1&KC=B1&FT=D#

The Samsung QN90B QLED is the best TV with an LED panel we"ve tested. It"s an impressive TV with amazing picture quality and a great selection of gaming features. It uses a Mini LED backlight, with way more dimming zones than most LED TVs, which allows for greater control over the local dimming feature for better dark room performance, with less distracting blooming around bright objects. It also gets exceptionally bright, meaning it can handle lots of glare in a bright room.

Unlike most high-end LED TVs, it"s also a good choice for a wide seating arrangement, as the image remains consistent when viewed at an angle thanks to Samsung"s "Ultra Viewing Angle" technology. It also has a great selection of extra features like a built-in Tizen smart interface that"s easy to use and has a ton of apps available to download, so you can easily find your favorite shows. It"s also excellent for gaming, as it supports 4k @ 120Hz gaming from the new-gen consoles, and it supports a variable refresh rate to reduce tearing.