Despite the quarantine, virtual CES 2021 was able to fully present the main technological innovations in the consumer electronics segment. As usual, smart gadgets, new robot vacuums, and smartphones got a lot of attention. But high-tech TVs have been in the spotlight.
Probably, this year can be considered the end of the next technological stage in the development of LCD TVs. This year, virtually every industry leader announced innovative mini LED backlight, including Samsung Neo QLED, LG QNED and TCL OD-Zero TVs. A short excursion into history will make it possible to appreciate the significance of this epoch-making event.
10 years ago, companies only offered LED LCD TVs, which form an image using the polarization of particles. In fact, liquid crystals act as light filters, passing or absorbing the colors, depending on the polarization.
But this technology requires the mandatory use of backlight.
The invention of OLED technology based on self-emitting diodes marked the beginning a new direction. The rejection of the backlight allowed the developers to reduce the display thickness and radically increase the contrast, significantly improving the image quality. With no electrical current from a thin-film transistor (TFT), self-emitting diodes provide absolutely black. LCD TVs cannot provide this due to partial passage of scattered light from the backlight. Later, it split into two technologies, which are today called OLED and MicroLED.
Of course, the term “organic” in the OLED (organic light emitting diode) acronym has nothing to do with animal or vegetable origin. These diodes are made from carbon compounds that are products of organic chemistry. In fact, it’s a solid semiconductor with a thin layer of carbon material that emits light under the influence of an electric current.
Micro LED pixel arrays mainly use GaN (Gallium Nitride) carbon-free diodes. Otherwise, these technologies use a similar operating principle.
Unfortunately, OLED technology has a number of significant cons, including relatively low brightness (500-1,000 nits), short blue pixel life (15,000 hours), and a sharp rise in manufacturing costs when increasing the display size. The use of GaN diodes eliminates these problems. Micro LED matrices have a huge resource (from 100,000 hours), provide high brightness from 2,000 nits and above, and their modular design eliminates restrictions on the size and even shape of the screen. At CES 2019, Samsung first showed the13-inch Micro LED modules, which are assembled using brackets with powerful magnets.
And at CES 2020, the company unveiled MicroLED bezel-less panels with unprecedented 5,000 nit brightness. But the fabulous price tag drastically limits their popularity. For example, Samsung’s newest 110-in Micro LED panel costs $ 156,000.
Of course, companies have continued to improve reliable and low-cost LCD technology, reducing the difference in image quality compared to self-emitting diode technology. As follows from the operation principle, the picture quality directly depends on the quality of the LED backlight, which, ideally, should be uniform and provide absolutely white.
As known, its spectrum has a uniform distribution of the power of electromagnetic radiation for all wavelengths in the visible part and is an achromatic color (black, white and gray shades).
For example, a sunny color is perfectly white. The natural adaptation of the eye provides an additive synthesis (interference of simple waves), allowing us to perceive colors and their shades.
To describe this process, current standards use the concept of color temperature, including D65 (color temperature 6500K), and D55 (5500K), which are close to the radiation of the solar spectrum. Absolute white has the highest brightness, and its spectrum is identical to that of the sun.
Quantum Dot technology
Elegant idea of using quantum dots to form perfect white was first introduced in the 1990s. But it got real development only in 2004, when the QD Vision laboratory (USA, Lexington (Massachusetts)) was created. QD Vision originally planned to develop an electroluminescent quantum dot display similar to self-emitting OLED technology. But then the developers returned to the idea of using quantum dots only to form backlight with a pure spectral color. Already in 2013, it was first used in Sony TV.
In fact, quantum dots are an additional film with a layer of nanoparticles that is placed between the LED backlight and the liquid crystal matrix.
Importantly, nanoparticles have different sizes, corresponding to the green and red spectrum. Blue light from the blue LED backlights passes through the quantum dot matrix. They partially absorb blue, emitting green or red, depending on their size.
Mixing the blue from the backlight with the fluorescent colors of the quantum dots produces near-perfect white, which is then sent to a color filter to form a color image. In fact, this technology allowed the developers to create a small artificial sun into TV with almost perfect white.
Today, Quantum Dot technology is used by many companies under different names, including Samsung QLED, Sony Triluminos, LG NanoCell, and Hisense ULED. Almost all modern Quantum Dot TVs use Nanosys QDEF (quantum-dot enhancement film) film.
At a low manufacturing cost, this technology has significantly expanded the color gamut, increased contrast, peak brightness and color accuracy, dramatically narrowing the gap compared to self-emitting panels.
The development of HDR (High Dynamic Range) has given impetus to the development of a new direction for improving LCD technology. As known, in 2012, Dolby Vision developed an innovative HDR technology with 12-bit color. Later, Samsung and other members of the UHD (Ultra High Definition) Alliance developed several more HDR standards, including HDR 10, HDR 10+, HDR 10+ Adaptive (for bright lit room) and HLG (Hybrid Log-Gamma). At the same time, HDR 10+ supports the transfer of dynamic metadata for each frame, but it requires support for HDMI 2.1 in TV. HDR has dramatically improved image quality.
It solves the problem of lighting, which has traditionally been one of the main for any shooting. For example, the scene with a spy in a black cloak in gray bushes, who is watching an object relaxing on a sunny beach, is very difficult for the operator. Low brightness will not provide a clear image of a person under bright sun, but increasing the frame brightness will destroy the gray gradations, displaying the spy in the bushes as a gray spot on a dark background. To solve this problem, the filmmakers used bulky structures with powerful lighting lamps that moved along rails on the set.
HDR solves this problem gracefully. For example, modern cameras in smartphones in HDR mode take a shots series of the same frame with with different exposures. Then, the digital image processing algorithm assembles one frame by selecting fragments from different frames in the series. As a result, the smartphone generates a Frankenstein-frame with optimal brightness for each area of the frame.
Mini LED backlight
In LCD TVs with traditional LED backlight brightness is the same across the entire screen. Local Dimming technology providing brightness control for different areas of the frame. For several years, companies have developed several generations of FALD (full-array local dimming), the last of which is called mini LED backlight.
It’s based on the use of a huge number of miniature LEDs, which are grouped into a large number of Local Dimming zones.
Until this year, the Chinese TCL dominated in this direction, annually introducing a new generation:
– 2018 – TCL 6-Series Roku TV with Contrast Control Zones technology;
– 2019 – TCL 8-Series Roku TV with improved mini LED Quantum Contrast technology (over 1,000 Local Dimming zones);
– 2020 – Vidrian mini LED technology.
This year company presented C825 with superinnovation TCL OD-Zero (Optical Depth Zero) mini LED technology at CES 2021.
According to the company, OD Zero technology has reduced the optical distance between the backlight and diffuser plates to “zero” (151 microns).
For comparison, the diameter of LEDs in conventional LCD panels reaches 12mm. Given this size, TCL OD Zero TV will be able to group LEDs into a huge number of zones.
However, the rest of the leaders also did not stand aside. Samsung unveils an excellent Samsung Neo QLED series with 12-bit luminance (4096 gradations) and 30,000 mini LEDs, which can form about 5,000 zones. LG announced LG NanoCell QNED TVs with 2,500 local dimming zones and with a very tempting price from $ 1,000.
In fact, mini LED backlight further increases the contrast and peak brightness for individual sections of the frame, reducing the difference between the HDR-content reproduction by LED LCD vs OLED TVs.
Thus, Quantum Dot technology has significantly improved the white quality for backlight, and the use of a huge number of miniature LEDs has dramatically increased the brightness control accuracy for each individual screen area in LCD TVs. As a result, their color gamut, color accuracy, contrast and peak brightness have come very close to the premium segment of OLED TVs.
Of course, LG and Sony are also showing impressive strides in improving their OLED models, increasing their brightness and cutting production costs. For example, LG already offered 55-in 4K OLEDs from $ 1,500 last year, which was unrealistic just a few years ago.
Nevertheless, the new LCD TVs with Quantum Dot technology and mini LED backlighting will provide them with stiff competition.
Curiously, LG NanoCell QNED TVs will compete with LG OLED models. This is not relevant for Samsung due to the huge gap between the Samsung Neo QLED Series and Samsung micro LED panels starting at $ 100,000.
Today Samsung Neo QLED vs LG QNED vs TCL OD-Zero comparison is hardly correct without regard to price. But given the pricing policy of the Chinese giant, its mini LED models may be quite affordable. However, the announced price of $ 1,000 for LG NanoCell QNED TVs is also encouraging.
But a huge 75″ LCD Vizio V-Series Class (V755-G4) worth $ 850 on the company’s website might be a more pragmatic choice for viewing conventional content.
In addition, the successful completion of the announced Samsung QD-OLED and QD-MicroLED technologies could end long-standing competition between technologies by replacing them with a more efficient hybrid TVs.
The video shows Samsung’s new Neo QLED TVs.
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