Introduction

SID Display Week (DW) 2025 is coming to San Jose, CA, May 11–16. My last two articles discussed LCOS technology I saw at DW 2024 and MicroLEDs for AR at DW 2024. This article will concentrate on Micro-OLED (also known as OLEDs on Silicon), which could be used in optics-see-through (OST) Augmented Reality (AR) or Virtual Reality (VR) headsets.

If you have a product or concept or want to discuss a topic from this blog at Display Week 2024, please email me at meet@kgontech.com. I’m planning on being there every day of the exhibits (May 13-15).

Partnering with SID and Discount Code

I’ve partnered with SID to share my insights from Display Week (DW) — past, present, and future. If you’re planning to attend Display Week, SID has provided the code DW25KARL for a free exhibit hall pass — don’t miss the chance to explore the latest innovations shaping the future of displays.

Brighter Micro-OLEDs to Overcome Optical Inefficiencies and Support Higher Dynamic Range

Today’s Micro-OLEDs have much better image quality, resolution, and cost than MicroLEDs and have better image quality, particularly in terms of contrast, than LCDs and LCOS, which may cost less. These characteristics make Micro-OLED the best quality pick for VR Headsets as well as Birdbath and LetinAR’s Pintilt optical see-through (OST) AR glasses.

Micro-OLEDs, with their Lambertian-like light output, larger light-emitting area, and brightness limitations, are impractical to use with diffractive and reflective waveguides, which typically output to the eye less than 1% of a microdisplay’s “raw” nits. These waveguide optics use MicroLED, LCOS, DLP, and Scanning, which can output hundreds of thousands to several millions of nits.

Even the brightest Micro-OLEDs with about 10,000 nits have on the order of 1/100th the nits necessary for use with waveguides. Still, they have image quality advantages over other display devices when using more efficient optics than waveguides. While many VR headsets used Fresnel Lenses and aspherical lenses, which lose little of the display’s light, many of the newer, smaller, and lighter-weight headsets use “pancake optics,” which typically output only about 10% of the display’s light/nits.

The diagrams below show example light paths for optical see-through (OST) birdbath optics (e.g., Nreal/Xreal) and VR pancake optics (e.g., Quest 3, and Apple Vision Pro ). With both optical designs, only about 10% of the display’s nits reach the eye, so it takes an OLED with about 10x the desired output nits to reach the eye.

Both eMagin (acquired by Samsung in 2024) and LG discussed 10,000-nit Micro-OLEDs. These would seem to be much more than necessary for VR, but they would be useful in (non-waveguide) OST AR in situations, like outdoors, where the ambient light would be much brighter.

Nreal Birdbath Overview (left) and AWE 2024 VR – Hypervision, Sony XR, Big Screen, Apple, Meta, & LightPolymers (right)

How Many Nits are Needed (to the Eye)?

Nits, or more scientifically, candela per square meter (cd/m²), measure light in a specific direction, and for head-worn displays, into the eye. To calibrate things a bit, typical computer monitors and TVs output 100 to 300 nits, which is a little brighter than a piece of white paper in typical room lighting. High-dynamic-range (HDR) TVs can go to (perhaps for small bright regions) 1,000 to 10,000 nits. Typical VR headsets output 80 to 200 nits today, but are starting to add higher dynamic range. VR headsets don’t have to be as bright as, say, a monitor, since they block out ambient lighting.

Whereas direct-view displays have a black background, optical AR headsets have to compete with the reflections of objects in the real world. Depending on the room lighting combined with the angles of the light, reflectivity of the paper, and the direction to the eye, a piece of white paper indoors might have 50 to 300 nits. Outdoors in sunlight, grass has about 2,000 to 3000 nits, white concrete as much as 10,000 nits, and clear sky (not looking directly at the sun) about 7,000 nits. The simultaneous dynamic range is huge, as things can be in shadow. For text to be easily readable, you want at least 2:1 contrast where the image would be as bright as the background (contrast = {content+background}/background). To reasonably distinguish colors, at least an 8:1 contrast is necessary.

While adding some level of dynamic shutters/dimming to glasses can help, they A) can’t block so much that the real world cannot still be seen well, and B) they have to deal with the real world’s dynamic range. Thus, even with dynamic dimming, AR glasses for outdoor use would like to have more than 1,000 nits, and preferably more than 2,000 nits to the eye.

Today, Common micro-OLED displays used in birdbath and pancake optics output between 1,000 and 3,000 units, which translates to about 100 to 300 nits to the eye. Both eMagin and LG were at DW 2024 talking about 10,000-nit Micro-OLED microdisplays.

3M Dominance in Higher End Pancake Optics

As discussed in 3M Dominates Polarized Light Plastic Films for Pancake Optics, 3M has a major presence in beam-splitting polarizer films and other optical films used in both Pancake and Birdbath optics. At DW 2024, 3M showed Meta (Quest Pro and Quest 3) and Pico VR pancake (and Quest 2, which used Fresenel lenses) headsets using their films, and it is widely believed that the Apple Vision Pro also used 3M films in their pancake optics.

Samsung/eMagin

Founded in 1996, micro-OLED maker eMagin has had some success in military and industrial applications. Still, it has seemingly always lost out to Sony and, more recently, others in higher-volume consumer products, including camera viewfinders as well as VR and AR headsets. Samsung started acquiring eMagin in 2023, but the acquisition wasn’t completed until June 2024. The eMagin name branding is still being used. Samsung is expected to add capital and manufacturing muscle to eMagin’s technology, which will be necessary to compete with other large display companies.

In addition to a lineup of micro-OLEDs with various resolutions and brightnesses, eMagin has a micro-OLED that can reach as bright as 24,000 nits for a green-only device (likely for military and industrial applications). They also have a prototype of a 10,000-nits full-color device. The pictures below were taken in eMagin’s DW 2024 booth. Interestingly, they were showing an 8″/200mm wafer in the booth (below right). I suspect that Samsung will help eMagin transition to 12″/300mm wafers with Samsung’s help to take advantage of more modern CMOS technology (see Lighting Silicon (Formerly Kopin Micro-OLED), where I discuss their transition to 12″/300mm wafers ).

I was able to take direct photographs (with a camera macro-lens) of eMagin’s 2.5K by 2.5K with a 7.2 micron pixel pitch that can output 3,000 nits (I used neutral density filters on the camera lens). Click on the images below to see them in higher resolution (note that these displays were unprotected, and some dust can be seen in the pictures).

LG 10K Nits Micro-OLED

LG is perhaps best known for its displays for large-view LCD and OLED televisions and monitors, but it makes displays of all sizes, including cell phones and microdisplays. Of particular interest to the field of XR is its development of very high-brightness micro-OLED microdisplays.

High-brightness Micro-OLEDs are particularly interesting to VR systems with pancake optics that want to support high dynamic range. It would also be of interest to some non-waveguide AR systems (for example, using birdbath optics or LentinAR’s PinTilt for use outdoors). Even at 10K nits, LG’s Micro-OLEDs are not bright enough for Waveguide optics that need many hundreds of thousands to millions of nits due to pupil expansion and efficiency losses.

At DW 2024, LG demonstrated a “10-K Nits 4K x 4K” 1.3″ (3840×3840 pixels, 4175 PPI = ~ 6.08 Microns/Pixel). In their booth, LG made clear that this was a “laboratory prototype” and that there was no immediate plan to make it a product.

They had a demo prototype with optics, and I first took a picture through the optics with an iPhone 15 Pro Max (right).

LG allowed me to remove their lens and get a direct picture with an Olympus 60mm macro lens. This picture has much more detail and eliminates the distortion from the demo optics. One thing I saw in the high-resolution picture was that there was a dead vertical line of red (only) pixels (click on the images below to see it in high resolution).

I’m not faulting LG for this as it is just a prototype, but it is an example of what cannot be seen based on content, and how well you can see the demo device. Many demos of “prototypes” will structure the content and/or only let you see a small display without great optics, so that you can see their defects.

BOE

BOE and SeeYa (not at DW 2024) are the two Micro-OLED companies I hear most as an alternative to the current Sony Micro-OLED dominance. BOE was showing a “4K x 4K” (more exactly 3552 x 3840) 1.35″ MicroLED. I took the picture below via the optics of their demo system.

Lumicore (Nanjing Lumicore Technology)

Lumicore was founded in 2019, but DW 2024 was my first encounter with their Micro-OLED technology. They have devices with 1920 x 1080 (1080p) and 2560 x 2560 (2.5K x 2.5K) pixels.

The booth included a prototype system with their 1080p device and birdbath AR optics. The 1080p device was also running independently, driven by a development board.

The image quality looked reasonably good but I was not able to make a serious evaluation on the show flow.

Fraunhofer Semi-Transparent Micro-OLED

Fraunhofer is an applied research institution funded by the German government. As of 2022, its budget was €3.0 billion, and they have diverse efforts in the field of display devices and MEMS devices. In SID Display Week 2024 – MicroLEDs for AR, I discussed their paper on quantum dot color conversion for MicroLEDs.

Fraunhofer has shown their “semi-transparent Micro-OLED” at many conferences, including the SPIE’s AR/VR/MR 2024 and 2025 and DW 2024. This technology combines multiple lenses on top of a transparent OLED to make a somewhat see-through microdisplay.

In recent years, I have seen several companies, including Newsight Reality and LUSOVU (below), with similar “see-through” microdisplay concepts (below). Conceptually, they “work” by doing a form of pupil replication by having optics (either refractive or reflective) over multiple subdisplays. In this way, the user can see the image as their eyes/pupils move. The optics serve to move the focus of the images far enough away that the eye can focus and to direct the image light such that multiple sub-images will combine into a single image.

Unfortunately, this whole concept, Fraunhofer’s variation included, fails for many reasons. First and foremost, there is no way to make the optics and sub-display combinations small enough that they won’t cause a major disturbance to the view through the display, and the effects of diffraction make this fundamental problem worse. Secondly, the eye is never perfectly aligned with various replicated images. The ideal spacing of the replicated displays is based on the pupil size, which is variable both due to the light’s effect on the pupil size and the variability from person to person. The technique needs many replicated pixels to form the various pupil replications, resulting in a high-resolution display being required for a low-resolution image.

The net result of this technique is that the user will see circles in both the real world view and in that of the virtual image. While a technical curiosity, I can’t imagine this ever having a volume practical application.

Conclusion

Revisiting my experience at DW 2024 reminded me of how much I learned, and it has helped me prepare for DW 2025. While this series of articles has concentrated on the microdisplay technology for XR headsets, this is only a small subset of all the display and optics technology shown at Display Week.