Despite the love of gamers for OLED displays, a persistent issue known as burn-in has been firing up gaming forums and Reddit. LG has recently taken the very noticeable step of revising its warranty terms, now offering a two-year burn-in warranty service for its OLED gaming monitors in the US.
Christopher De Maria, the head of consumer communications at LG North America, has confirmed that this new warranty period is applicable retroactively. This applies to consumer use where burn-in falls within the parameters of standard use and not to commercial environments where the displays might be used such as as digital signage.
Although Acer and Asus also employ LG panels in their monitors, they do not currently offer a similar warranty. By comparison, Dell’s gaming brand Alienware and Corsair provide a 3-year burn-in warranty for their OLED displays. Alienware even goes a step further by offering next-business-day replacement services. While Corsair uses panels, Alienware is using Samsung’s QD-OLED panels.
What is Burn-in on OLED Displays?
Each OLED pixel is made up of three subpixels: red, green, and blue. When an electric current is applied to an OLED pixel, the organic material inside the pixel emits light. The amount of light emitted depends on the strength of the current. OLED burn-in is a phenomenon that occurs when the pixels in an OLED display degrade at different rates, causing some pixels to appear brighter or darker than others. This can create a ghost image of a previous image on the screen, even when the new image is displayed.
This is because, over time, the organic material in an OLED pixel can degrade. This degradation can happen faster for some pixels than for others. If a particular pixel is displaying a bright image for a long period of time, the organic material in that pixel will degrade faster than the organic material in pixels that are displaying darker images. This can lead to the pixel appearing brighter than the other pixels, creating a ghost image. The red subpixels in an OLED display tend to degrade the fastest, followed by the green and blue subpixels. This is because the red subpixels use a different type of organic material than the green and blue subpixels.
That’s why some people suggest you avoid prolonged display of identical content and, in some cases, even hiding interface elements like the Windows taskbar and browser to reduce the risk of burn-in or ghosting of images on the screen. It’s not really very practical to ask gamers to do that or, for that matter, to ask anyone to the same. It’s like putting plastic covers on your furniture to protect them from use when the whole point of getting the furniture was to have something nice to sit on, not plastic sheets.
You can reduce the brightness of your OLED display. This will help to slow down the degradation of the organic material in the pixels. But that also means reducing the brightness of a display you may have bought because of its brightness. There are some features that can be enabled on some OLED displays to help reduce the risk of burn-in. For example, some displays have a pixel shift feature that can move the image around on the screen slightly every few minutes. This helps to prevent any one pixel from displaying the same image for too long. Again, not something that is very practical for gamers. So burn-in is a real potential issue with OLED displays.
The Lifetime of an OLED Based on Burn-in
There is no way to completely prevent burn-in on an OLED display. In a research review of lifetime modeling for OLEDs, the authors shows how the product lifetime of OLED displays is closely tied to the onset of burn-in. It is defined as the average amount of time it takes for burn-in to become visible to users. This concept is quantified by a parameter denoted as TX, where X represents a certain percentage of the initial luminance (L0). In other words, TX indicates the time it takes for the OLED display to reach X% of its original brightness. This parameter is determined while the device operates at a specific current density (J0).
For example, if the lifetime threshold is set at T95 (meaning 95% of initial luminance), then TX would be the time it takes for the OLED display to lose 5% of its original brightness while operating at the specified conditions. Similarly, other lifetime thresholds like T80 (80% of initial luminance) or T70 (70% of initial luminance) can be defined based on the desired level of luminance degradation that is considered acceptable.
The calculation to measure the OLED lifetime based on burn-in involves monitoring the luminance degradation over time under specified operating conditions. This is usually done through accelerated testing, where OLED devices are operated at higher current densities or temperatures than normal usage conditions to simulate the effects of long-term usage in a shorter period. The data collected from these accelerated tests are then used to extrapolate the expected lifetime at regular operating conditions. However, there is a lack of a universal framework capable of explaining degradation in various types of OLEDs, spanning PHOLEDs, triplet–triplet fusion, TADF, and hyperfluorescent OLEDs.
One way to get around the problem of burn-in is to implement burn-in compensation for OLED displays, which requires recording the usage history of individual OLED pixels within the display system’s memory. This usage history includes essential information such as the duration of pixel usage, the specific luminance levels at which the pixel has been operated, and optionally, the corresponding operating temperatures. This data collection process enables the display system to track how each pixel has been utilized over time.
Once the usage history is collected, the burn-in compensation algorithm employs this information to estimate the reduction in luminance for each pixel based on its unique usage pattern. The algorithm calculates a compensation factor that can be used to restore the pixel’s original luminance value.
In practical terms, this means that if a pixel has aged and its luminance has decreased over time, the algorithm determines the compensation necessary to bring the pixel’s luminance back to its initial level. To achieve this, the algorithm adjusts the operating current level for the aged pixel. By assigning a new operating current level that corresponds to the pixel’s original luminance value, the pixel’s appearance can be restored. This reassignment of the operating current is typically done using an 8-bit display input, which ranges from 0 to 255, allowing for a precise adjustment.
Reference
Jaesang Lee (2023) Lifetime modeling for organic light-emitting diodes: a review and analysis, Journal of Information Display, 24:1, 57-70, DOI: 10.1080/15980316.2022.2126018
