Meta and Stanford's "Synthetic Aperture Waveguide Holography" research aims to deliver "VR glasses", with a total optical stack thickness of less than 3mm.The paper, called "Synthetic aperture waveguide holography for compact mixed-reality displays with large étendue", comes from two researchers from Meta's Display Systems Research team, an associate professor at Stanford, and a Stanford Ph.D. Student supported by a Meta research fellowship.For context, today's pancake lenses have delivered thinner headsets, but they're still very thick compared to glasses.For context, the thickness of current VR/MR headsets is almost entirely driven by the optics and displays. While pancake lenses have in recent years enabled thinner headsets, by shortening the optical path between the lens and display, the pancake lens stack itself is still relatively thick and heavy - far more so than glasses.Douglas Lanman, the director of Meta's Display Systems Research team, has often spoken of his desire to one day help ship "VR glasses" - a head-mounted display system that can deliver VR in a form factor no more cumbersome than regular glasses. This will, of course, require a fundamentally different kind of display system than anything shipping today, and that's what this kind of research moves Meta closer to. 0:00 /0:12 1× The new display system from the Meta & Stanford researchers. The word "holographic" has many different meanings in this industry, and is often misused and abused. But to be clear, the prototype presented in the new paper is a true holographic display, providing a realistic truly 3D image with inherent depth cues, and thus mitigating a major flaw with today’s headsets called the vergence-accommodation conflict – the discomfort your eyes feel because they’re pointing toward the virtual distance of virtual objects but focusing to the fixed focal distance of the lenses.The prototype uses tiny fiber-coupled lasers for each color (red, green, and blue) which are steered by tiny, very fast mirrors (MEMS mirrors) into an optical waveguide, which expands and guides the light into a spatial light modulator (SLM), which modulates it back to a holographic eyepiece lens in front of your eye."One of the key innovations of our display system is a compact, custom-designed waveguide for holographic near-eye displays that supports a large effective étendue.This is co-designed with a novel AI-based algorithmic framework combining an implicit large-étendue waveguide model, an efficient wave propagation model for partially coherent mutual intensity as well as a novel computer-generated holography (CGH) framework."Waveguides are normally used in transparent AR systems, such as HoloLens, Magic Leap, Snap Specs, and Meta's Orion prototype, but whereas those use surface relief gratings, this system uses volume Bragg gratings (VBGs), which are angle-encoded to diffract a very specific band of colors at very narrow angles, improving efficiency to enable a thinner form factor.The prototype also uses AI calibration, a neural network that learned how the light changes as it passes through the entire system, to adjust the SLM to deliver a much higher quality output to the eye, with improved image quality and fewer artifacts.Facebook Researchers Show The Most Compact VR Optics YetFacebook’s VR research division is presenting prototype VR optics smaller than any we’ve seen yet for the annual SIGGRAPH computer graphics conference. The ideas behind the “holographic near-eye display” could one day enable VR headsets with sunglasses form factor- but for now this is solely research with limitations.UploadVRDavid HeaneyThis is far from the first time we've seen a research prototype for ultra-thin VR display system. But it is a significant advancement over what we've seen before.Back in 2020, Facebook researchers showed off a fixed-focus holographic lens approach with a thickness of less than 9mm. However, the prototype was green-only, not full-color, and the stated 18 gram weight didn't include the laser backlight.In 2022, researchers at Nvidia achieved 2.5mm thickness, with a true 3D holographic approach, by using a pupil-replicating waveguide, a spatial light modulator (SLM), and a geometric phase lens. However, its field of view was just 23° diagonal, and its eyebox just 2.3mm without eye tracking, or 8mm with it.The eyebox refers to the maximum distance from the center of the lens your eyes can be and still get an acceptable image without blur. If it's too small, many people won't be able to use the device, while others will need to constantly adjust it.NVIDIA Researchers Built The Thinnest VR Display System YetNVIDIA researchers developed the thinnest VR display system yet, just 2.5 mm thick. Called Holographic Glasses, this could one day lead to VR headsets as thin as sunglasses. But for now this is research technology with severe practical limitations. The primary driver of the size and bulk of today’UploadVRDavid HeaneyThe new prototype from the Meta and Stanford researchers achieves a 38° diagonal field of view and a large 9x8mm static eyebox, a significant step forward.The researchers also say the AI image calibration approach brings a significant step forward for image quality. I've tried many holographic display system prototypes, many of which are large desk-mounted systems, and the image quality has always been the biggest drawback, so this is a very promising advancement.Image quality with and without the AI calibration approach.We're likely still many years off holographic optics shipping in actual XR products. The 38° diagonal field of view of this system is far narrower than the roughly 115° of Quest 3. And there exists no commercial-scale supply chain for the kind of high-quality SLMs, fiber-coupled lasers, and VBG waveguides this display system uses.But there continues to be steady improvements in research on holographic display systems, with each breakthrough bringing us another step closer to VR devices no more cumbersome than your reading glasses.For more details on this research, read the full ""Synthetic aperture waveguide holography for compact mixed-reality displays with large étendue" full paper in Nature.