Meta and Stanford’s “synthetic aperture waveguide holography” study aims to supply “VR glasses” with a total optical stack thickness of less than 3mm.
Called “Synthetic Aperture Waveguide Holography for Compact Mixed Reality Displays Using Large-Scale Ethendue,” the paper comes from two researchers, Meta’s Display Systems Research Team, associate professor at Stanford and Stanford Ph.D. Students supported by Metal Research Fellowships.
In the context, the current VR/MR headset thickness is almost entirely driven by optics and display. Pancake lenses have thinned the headset in recent years, but by shortening the optical path between the lens and the display, the pancake lens stack itself is still relatively thick and heavy – much more than glasses.
Douglas Lanman, director of Meta’s Display Systems Research team, often spoke about his desire to help out with “VR Glasses” one day. Of course, this requires a fundamentally different kind of display system than what is shipped today. This is what brings this type of research into the meta.
A new display system from researchers at Meta & Stanford.
The word “holographic” has many different meanings in the industry and is often misused and abused. But to clarify, the prototype shown in the new paper is a true holographic display, providing realistic true 3D images with cues of intrinsic depth, thus reducing the major flaws with today’s headsets called vertical and harmony conflicts.
The prototype uses small fiber-coupled lasers for small colors (red, green, blue). These are steered by small, extremely fast mirrors (MEMS mirrors) that extend and guide light into the optical waveguide (SLM).
“One of the major innovations in display systems is the compact, custom designed waveguides for holographic neer eye displays that support large-scale effective étendues.
It is co-designed with a new AI-based algorithm framework that combines an implicit large waveguide waveguide model, an efficient wave propagation model with partially coherent mutual strength, and a new computer-generated holography (CGH) framework.
Waveguides are typically used in transparent AR systems such as Hololens, Magic Leap, Snap Specs, and Meta’s Orion Prototype, but this system uses a Volume Bragg Grating (VBG).
The prototype also uses AI calibration, a neural network that learns how light changes as it passes through the entire system, to tune the SLM to provide a higher quality output to the eye, improve image quality and reduce artifacts.
Facebook researchers show the most compact VR optics ever
Facebook’s VR Research Division presents prototype VR optics that are smaller than you’ve seen at its annual Siggraph Computer Graphics Conference. The idea behind the “holographic Near Eye Display” could one day enable a VR headset with a sunglass form factor, but for now this is only limited research.
This is far from seeing a research prototype for an ultra-thin VR display system for the first time. But it is an important advancement to what we have seen before.
In 2020, Facebook researchers showed off a fixed-focus holographic lens approach that is less than 9mm thick. However, the prototype was only green, not full color, and the listed 18 gram weight did not include laser backlight.
In 2022, NVIDIA researchers achieved a thickness of 2.5mm with a true 3D holographic approach using pupil supplemental waveguides, spatial light modulators (SLMs), and geometric phase lenses. However, its field of view was only 23° diagonal, with the eyebox being just 2.3mm or 8mm without eye tracking.
Eyebox refers to the maximum distance from the center of the lens. The eyes can get an acceptable image without blurry. If it’s too small, many people won’t be able to use the device, but others will need to constantly adjust it.
Nvidia researchers still built the thinnest VR display system
Nvidia researchers have developed the thinnest VR display system, only 2.5 mm thick. Called holographic glasses, this could one day lead to a thin VR headset like sunglasses. But for now, this is a research technique with serious practical limitations. Today’s size and most major drivers.”
A new prototype from researchers at Meta and Stanford is a key advance, achieving a 38° diagonal field of view and a large 9x8mm static eyebox.
Researchers also say that the AI image calibration approach is a major step towards image quality. I have tried many holographic display system prototypes, many of which are large systems mounted on desks and image quality has always been the biggest drawback, so this is a very promising advancement.
We may not have been away from holographic optical shipping on actual XR products for years yet. The 38° oblique field of view on this system is much narrower than the approximately 115° of Quest 3. Additionally, there is no commercial scale supply chain of high quality SLM, fiber-coupled lasers, and VBG waveguide types.
However, research into holographic display systems continues to steadily improve, with each breakthrough bringing another step closer to VR devices that are more cumbersome than reading glasses.
For more information about this study, read the complete “synthetic aperture waveguide holography” of a compact mixed reality display with a large-scale Etendue “full paper.”
