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OLED, short for Organic Light Emitting Diode, heralds a new era in display technology, poised to supersede LCD, amalgamating the strengths of both Plasma and LCD technologies.
1. Delving into the WRGB OLED Technology on LG TVs
Today, I'm excited to share insights into the WRGB OLED technology, which LG employs in its TV lineup. Fundamentally, OLED operates more akin to CRT/Plasma than LCD. However, did you know that in practice, LG's implementation of WRGB OLED bears more resemblance to LCD than CRT/Plasma?
What is OLED?
Before delving into the WRGB OLED technology utilized by LG in their TVs, let me introduce some basic aspects you should know about OLED technology.
OLED TVs utilize organic light-emitting diodes capable of self-emission - LG image
OLED, short for Organic Light Emitting Diode, heralds a new era in display technology, poised to supersede LCD, amalgamating the strengths of both Plasma and LCD technologies. We say OLED operates closer to CRT and Plasma because each pixel consists of 3 sub-pixels, each corresponding to an emissive diode. Similar to Plasma and CRT pixels, which are essentially chemical cells that emit light when stimulated by electricity (Plasma) or cathode rays (CRT), respectively.
The operation mechanism of OLED is akin to Plasma - www.edsavhandbook.com
The advantage of this method lies in its fastest response time and high contrast, thanks to deep blacks (due to fully turned-off pixels). In contrast, each LCD sub-pixel is a liquid crystal block with a front color filter, indirectly illuminated by a backlight system behind (or alongside for edge-lit LED). Since the backlight is always on and the LCD crystals cannot completely block all light passing through, the black color of LCD/LED TV cannot be as deep as OLED TV.
The Super AMOLED display on phones epitomizes RGB OLED technology - gsmarena image
When discussing OLED displays, what we often think of is RGB OLED. RGB OLED technology employs 3 diodes with 3 basic colors (red, green, blue) to form a pixel. However, manufacturing organic diodes with 3 different colors in large sizes is not easy. In reality, Samsung failed to commercialize RGB OLED TVs, although they almost dominated the OLED screen segment (AMOLED) for small mobile devices. The main reason is that for each different color, each organic diode is composed of different organic compounds. Not only is production difficult, but their degradation rates also differ, making the balance between lifespan and image quality of manufacturers even more complex.
For phone screens, the solution we often see is arranging pixels in a Pentile layout, meaning sub-pixels will have different sizes depending on degradation rates (usually blue will be the largest, followed by red, and the smallest is green). However, this imbalanced setup reduces the eye's perception of sharpness (even though the number of main pixels remains unchanged compared to RGB), so manufacturers do not apply it to TVs (which have much lower pixel densities than mobile devices). LG's WRGB OLED technology used on LG TVs
LG can be considered the largest OLED TV manufacturer today with a series of models launched in recent years. A common feature of LG OLED TVs is that they do not use conventional RGB architecture but rather employ WRGB architecture. So, how does WRGB OLED differ from RGB OLED?
The operation mechanism of WRGB OLED is quite similar to current LCD - image www.newspim.com
Although the name WRGB sounds similar to RGB, their mechanisms are entirely different. Instead of creating sub-pixels with 3 different colors, complex and facing degradation issues, LG's WRGB solution utilizes all white organic diodes. To produce three basic colors, the company uses a color filter similar to LCD. Simply put, the organic diodes in the WRGB setup merely act as backlight, with the actual colors filtered through (red, green, blue). This method is akin to LCD's color creation, using filters to generate colors for white light emitted by the backlight.
The LED backlight system of LCD TVs - image www.em.avnetasia.com
Nevertheless, WRGB still surpasses LCD in light control capability. The organic diodes themselves allow LG to control light 'on each sub-pixel' with the highest possible accuracy. The highest-end LED TVs currently attempt to mimic this effect through local dimming feature; however, due to the large size of LED bulbs (even compared to main pixels), the effectiveness cannot match OLED. Additionally, the light from the diodes goes directly to the filter, so the quality does not deteriorate as when passing through the liquid crystal layer of LCD. This control capability is the key to enabling OLED (both WRGB and RGB) to turn off organic diodes when displaying black, thus achieving extremely high contrast.
Macro shot of LG OLED TV screen - image Digital Versus
One point to note is that instead of having 3 sub-pixels for each main pixel, WRGB has up to 4 sub-pixels including: white, red, green, blue. Perhaps the most frequently asked question is why LG adds a white sub-pixel to the basic 3 colors, and what its purpose is. In fact, OLED has a weakness in that its nature is ultra-small self-emissive diodes, so the brightness of early-generation OLED TVs is relatively low. The white sub-pixel is essentially the optimal intensity light from the organic diode at its brightest, helping to increase the brightness for the entire frame. However, in terms of color reproduction, the white sub-pixel has no effect other than enhancing brightness when displaying white (optimizing contrast). Moreover, this is perhaps partly why in scenes with low contrast, the recently evaluated EG930T cannot demonstrate color superiority compared to traditional LED TVs.
The display mechanism differs from RGB OLED, however, WRGB OLED still maintains the advantage in black color depth - image LG
If you pay attention, most OLED TV demo videos mainly showcase scenes with very high contrast and emphasize the extremely deep black performance of the TV. Meanwhile, LED TV demo videos often highlight vibrant eye-catching colors with high brightness, limiting the display of black details on the screen. The LG G6 Signature unveiled at CES 2016 was announced with a maximum brightness of up to 1000 nits, equivalent to the highest-end LED TV models, promising to address this weakness of OLED. Which provides better image quality: RGB OLED or WRGB OLED?
Back in 2013, when the race to develop OLED TVs was arguably at its peak, the debate between RGB OLED (Samsung, Sony-Panasonic alliance) and WRGB (LG) technologies for producing better images was intense. Each side had its own rationale, but unfortunately, it was all just theoretical. By the time I'm writing this, all those debates have lost much of their significance. Why?
Temporarily setting aside the technology and image quality aspects, LG is the only winner in the race to commercialize OLED TVs. Not only does LG produce OLED TVs en masse, but it also lowers the price of OLED TVs to nearly match LED TVs (for example, the retail price of the EG910T OLED TV is 56 million, which is even lower than the 60 million for the UF950T LED TV). During that time, Samsung also introduced OLED TVs using RGB architecture, but they were mainly used to showcase the technology and were priced very high, so they did not sell widely. And since 2015, Samsung has officially stopped developing OLED TVs to focus on LCD/LED TVs using quantum dot technology. Although there have been rumors that Samsung will return to the OLED TV race in 2017, currently, you have no choice other than WRGB OLED TVs.
