Will LCDs be Replaced in VR?
2023年9月20天 Sam Dale
In 2023, almost every VR device uses LCDs (Liquid Crystal Displays) to replace the real world with digital content, but a shift might be underway in 2024.Apple's Vision Pro is set to be one of the earliest VR devices to use OLED-on-Si technology, also known as micro-OLED, in a move to shrink headsets down whilst offering extremely high-quality images.
IDTechEx's recent report, "Displays for Virtual, Augmented and Mixed Reality 2024-2034: Forecasts, Technologies, Markets", explores the future of the VR display market in more detail, alongside other head mounted display systems. It predicts the VR display market to grow at a CAGR of 7.5% to 2034, with innovation in display technology driving this growth ahead of the whole VR market. However, the use of emerging display choices like OLED-on-Si could bring almost as many difficulties as benefits, and the long-dominant LCD could prove a tough contender to beat.
The commercial status of VR display technologies. Today, edge-lit LCDs are in almost every VR headset. Source: IDTechEx
Why LCDs have held their own in VR
Today, Sony's PlayStation VR2 stands alone amongst mainstream VR headsets in using AMOLED (Active Matrix Organic Light Emitting Diode) panels, commonly found in smartphone displays. Unlike LCDs, AMOLED panels are emissive, offering higher contrast ratios and much deeper blacks. They offer fast refresh rates, wide color gamuts and are well-established in production - at first, AMOLED displays might seem like the perfect fit for VR, and they looked like the winning display technology until about 2019. Why, then, did LCDs displace them as the dominant VR display choice?
Firstly, the capabilities of VR-specific LCDs improved: their manufacturers focused on this emerging market as AMOLEDs began to take over market share in the much larger smartphone industry. A key problem solved was performance at fast refresh rates, which suffered in older LCDs as the pixel response time was too slow, giving the appearance of motion blur as frames transition.
Moving towards faster response liquid crystal materials and innovation in electrode structures formed part of the solution, but backlight strobing stops motion blur completely by turning off the backlight while the display updates. Sharp, Japan Display Inc., and BOE all use this technology. This reduced the advantage of AMOLED displays in this area.
As this problem was solved, VR headset designers saw the other advantages of LCDs, as well as their lower cost. The biggest benefits of LCD vs. OLED are the smaller gaps between pixels, reducing the "screen door effect" (visible gaps between pixels for a display seen up close), and the higher maximum pixel density, increasing immersion without making headsets bulkier. The former is due to the diamond pixel layout that helps contribute to extending the life of the display. The latter is due to limitations in the shadow fine metal mask (FMM)-based shadow mask deposition technology used to pattern OLEDs, which limits pixel density to around 800PPI (pixels per inch), vs. >1200PPI for LCD. Combine these factors with the lower cost of LCDs, and the reason for the transition becomes obvious.
How the dominance of LCDs is being challenged - and how LCDs might keep their place
AMOLED displays are making progress past this PPI limit. A move towards photolithographic patterning of OLEDs offers a step change here whilst solving additional issues like limited substrate size when using FMMs to allow the patterning of more displays on a single piece of glass. Chinese firm Visionox's ViP (Visionox Intelligent Pixelization) will allow RGB AMOLED pixel densities of up to 1700PPI, and the company says it will be ready to manufacture displays through this photolithographic process next year. JDI's competitor process, eLeap, can go as high as 2000PPI, with a strategic alliance with Chinese LCD manufacturer HKC being established in 2023 to establish mass production of OLED displays via eLeap in 2025.
However, OLED-on-Si panels could offer even more advanced capabilities. Most often found in camera viewfinders today, these displays use OLED emitters on a CMOS silicon chip backplane, with color filters for RGB color. This allows them to achieve pixel densities >4000PPI, so extremely small displays can provide high resolutions. This allows the lenses that are used to magnify and focus the displays to shrink down, helping the entire headset become smaller and places the cameras used to pass video of the real-world view to the wearer closer to the position of the eyes, increasing performance in passthrough mixed reality mode.
Sony Semiconductor leads the OLED-on-Si market in terms of revenue and is expected to be Apple's supplier for the Vision Pro, but investment from across the display industry is increasing as demand is expected to grow alongside the spatial computing market. Samsung Display is in the process of acquiring OLED-on-Si pioneer eMagin, which has the technology to directly pattern emitters, so color filters are not required (unlike in Sony's panel designs). BOE, which formerly established a joint venture with US company Kopin to develop OLED-on-Si production, showed off 4K panels intended for VR headsets at SID Display Week 2023, with this demo being one of the best-received of the event. The display industry clearly views this technology as extremely important, and IDTechEx expects OLED-on-Si to be a leading VR display technology by 2034.
The LCD industry is fighting back with the use of mini-LED backlights, which up the contrast ratio of LCDs around 75% by selectively varying backlight power depending on local brightness. However, increased costs and lack of contrast ratio competitiveness with OLED-based displays persist. LCDs' true potential lies in providing immersive VR experiences cost-effectively. While LCDs are expected to remain dominant due to price competition in the near term, their future becomes less certain in a landscape where VR's utility is better demonstrated.
Future developments and further insight
In the years ahead, as price competition wanes and VR's value solidifies, LCDs might face a more uncertain future. As the VR landscape evolves, OLED-on-Si and other emerging technologies, including micro-LED, are expected to reshape the VR display landscape, eventually ending LCDs' current reign.
IDTechEx's new report, "Displays for Virtual, Augmented and Mixed Reality 2024-2034: Forecasts, Technologies, Markets", offers detailed analysis of the spatial computing display landscape including granular ten-year market forecasts and assessments of the potential for success of the technologies covered.