LG and Google are working together to improve display technology for VR HMDs and what they’ve come up with so far blows currently available displays out of the water. LG and Google created a 4.3” OLED display which boasts a 120Hz refresh rate (30Hz higher than the Rift and Vive) and a staggering 4,800x3,840 resolution.
SID International Display Week is going on this week, and LG and Google used the platform to reveal the details about a new display that the two companies are building for future VR devices. Representatives from both companies will present a research paper today that outlines the recently developed OLED panel, but the team published the paper publicly yesterday.
LG and Google’s new display is an ambitious project. The paper’s authors explain that they sought to create OLED panels that more closely match the human visual system. The goal was to engineer an on-glass OLED display which would offer higher than 100-degrees field of view (FoV), 1,000 to 2,200 pixels per inch (PPI), and 15-25 million pixels per eye. To put that into perspective, the Vive Pro and Samsung Odyssey, which include the highest-resolution VR displays available today, feature 615 PPI and 2.3 million pixels per eye.
The engineering teams at LG and Google have created a panel that meets the project’s criteria. The two companies developed a 4.3” OLED panel that features 4,800x3,840 pixels, which equates to 1443 PPI, or 18-megapixels. The panel also operates at 120Hz, which enables a motion-to-photon latency of 8.3ms/frame. The display also supports short persistence illumination, which is designed to reduce motion blur. LG and Google said the illumination process takes 20% of the frame time, which leaves 6.4ms/frame for the host device to render each frame. The current design also offers up to 120-degrees horizontal FoV and 96-degrees vertical FoV.
The team isn’t satisfied with the current results, and it is striving for even better results in the future. The paper’s authors suggest that the theoretical upper limits would be 9,600x9,000 pixels per eye, 2,183 PPI, and 160-degrees by 150-degrees FOV. We can’t imagine what type of graphics system would drive such a panel, though, so we don’t expect to see the upper limit panel anytime soon. However, LG and Google have already built working prototypes of the 18-megapixel display, which make them the highest density on-glass OLED panels ever created.
LG and Google used a two subpixel per pixel arrangement, which is often found in mobile phone displays. Each pixel features a green subpixel and either a red or a blue subpixel. The team used a white OLED structure with color filters to simplify mass production of the new panels because the traditional Fine Metal Mask processes used to build display panels don’t work well for displays with upwards of 1000 PPI.
LG and Google’s engineering teams designed two 18-megapixel displays to use in tandem in a VR HMD. The 4.3-inch panels feature electronics on three sides and a 1.7mm bezel on the forth side. When two panels are used together, the thin bezel sides should touch. The left-eye panel would draw diagonally from the top right to the bottom left, and the right side would draw from the bottom left to the upper right.
LG and Google’s engineers also focused on ways to help the GPU drive the 18-megapixel display. The team created a foveated rendering technique which breaks the image into two acuity levels. The high-acuity zone, which is the visual sweet spot of the panel, is a relatively small portion of the display that is rendered at full resolution. The low-acuity zone, which includes everything outside the sweet spot, is rendered at the lower detail level to conserve bandwidth in the rendering pipeline. The display panels feature a built-in FPGA that combines the data from the low and high-acuity zones to create a full-screen image. The low acuity images come in at 1280x1922 pixels, and the FPGA upscales them to the panel resolution.
LG and Google didn’t give us any hints as to when we would see these 18-megapixel displays featured in a VR headset, but the team suggested that they would be ideal for standalone VR devices, so we would guess that LG is building a Daydream-compatible standalone VR device behind closed doors.
|Header Cell - Column 0||LG, Google 18-Megapixel OLED|
|Subpixel count||3840 × 2 (either RG or BG) × 4800|
|Pixel pitch||17.6 µm (1443 ppi)|
|Brightness||150 cd/m2 @ 20% duty|
|Color depth||10 bits|
|Viewing angle2||30°(H), 15° (V)|
|Refresh rate||120 Hz|