Cutting-edge micro-lED Image Source
In the world of AR, there are many competing display technologies, such as LCoS, OLED, and LBS. In this menagerie of displays, one novel technology - micro-LED’s, or uLED’s, stands out. uLED’s displays have the true black performance of OLEDs, are very bright, and don’t suffer from speckle artifacts like laser display systems do.
There’s just one problem - currently, large uLED area displays don’t exist, and full-color uLED panels have poor performance due to fabrication issues. In order to take advantage of currently manufacturable displays, we use a compact, custom-designed panel in conjunction with a novel projection system to create a high-resolution area display.
Novel Structured Geometric Waveguide Eyepiece
The goal of any AR optical system is simple - to get an image from somewhere on the user’s head to “out there”; that is, some distance (usually a few meters) in front of the wearer, superimposed on the the real world. Any AR system will have a few lenses and mirrors, and an eyepiece, or “combiner”, which serves as the final element in the relay.
The choice of eyepiece technology is the heart of a headset design; it strongly influences the form factor, field of view, and image quality of the system. Popular designs include diffractive waveguides, giant reflectors, and birdbath designs, all of which have their pros and cons. Diffractive waveguides are compact, but have a limited field of view, suffer from artifacts in bright light, are hard to mass produce, and are optically inefficient. Giant reflectors have a relatively wide field of view and are cheap to manufacture but, as their name implies, are very large - such headsets literally mount a smartphone screen to the user’s head. Birdbath designs are relatively compact and wide, but are heavy and extremely dark; because the light passes twice through 50% transmissive beamsplitters, over 75% of the light is lost.
Our system uses a structured geometric waveguide as the combiner. Like in a diffractive waveguide, light is coupled down the eyepiece via total internal reflection, but unlike a diffractive system, the structures in the eyepiece are explicitly much larger than a wavelength, which prevents colored ghosts in ambient light. Furthermore, the out-coupling elements are ordinary geometric optics, which mitigates the narrow angle of acceptance from which diffractive elements suffer from. In addition, a careful multi-layer design allows the out-coupling elements to cover about 5% of the eyepiece’s area, allowing us to maintain very high transparency.
Easy-to-Use, cross-platform software Development Platform
In the end, the strength of a product depends on what its users do with it. This is especially true in an emerging field like AR, where rapidly advancing hardware innovations change possible applications overnight.
Kura’s unmatched transparency, field of view, and form factor enable applications that were previously impossible. For example, architectural visualization and automotive design clients benefit immensely from the wide field of view, which immediately allows them to see and interact with the entire model at arm’s range. Technical training and service applications greatly value the high transparency - in a potentially dangerous industrial setting, it would be unacceptable to obstruct the outside view. Likewise, collaboration and telepresence uses require a highly transparent headset to preserve eye contact and expressiveness. Moreover, our bright, high-resolution, and ghost-free image enables a whole new class of entertainment applications.
To enable our users to implement what they want without being held back, we provide a full suite of sensors, including cameras, eye tracking, head tracking, and depth tracking. We also provide API’s for integration with popular game engines such as Unity and Unreal, as well as lower-level access through OpenXR. Finally, we have several useful, off-the-shelf applications for common tasks such as 3D visualization and conferencing on which users can build.
AR Display and Optics Technologies Comparison
| Structured Geometric Waveguide + Customized Optical Architecture + Customized Micro-LED Display + Customized ASICs | Diffractive Waveguide | Birdbath/Freeform Prism | Giant Reflector | Reflective Waveguide | Pin Mirror | Holographic Reflector | |
|---|---|---|---|---|---|---|---|
| Examples | Kura Gallium | Hololens, Magic Leap, WaveOptics, Digilens, Vuzix, Dispelix, Sony | Nreal, 0Glass, Google Glass, Realwear, Hisene, Ned+, LLVision | Mira, Realmax, Leap Motion North Star, Meta, Ximmerse, Dreamworld, Lenovo Mirage AR | Lumus, Lochn, Optivent | Letinar | Focals By North |
| Field of View | Very Wide (150°) | Narrow (10-55°) | Narrow (10-55°) | Medium/Wide (50-100°, depends on the size) | Narrow (40-55°) | Medium (10-80°) | Very Narrow (10°) |
| Transparency | High (95%) | Very Low (<25%, filter required due to dim image) | Very Low (<25%) | Low (20-50%) | Medium (40-85%) | High (80-95%) | High (~90% or higher) |
| Brightness/Outdoor Usability | High | Low | Medium | Low | Medium | Low | Medium |
| Contrast | High | Medium | Medium/High (depends on image source) | Low | Low | Medium | Medium |
| Size | Compact | Medium | Medium | Large | Compact | Compact | Compact, but FOV is very narrow |
| Depth of Field * | Unlimited | 1-2 discrete focal planes | 1 focal plane | 1 focal plane | 1 focal plane | Unlimited | 1 focal plane |
| Mass Producibility * | High | Low | Medium | High | Low | High | Medium |
Depth of Field: Typical AR headsets relay the image to one or two discrete focal planes. This results in what is called “accommodation-vergence mismatch” - for example, depth cues and parallax may suggest that a virtual object is six feet away, but the wearer’s eyes are need to focus 1 foot away to see a sharp image. Accommodation-vergence mismatch can lead to eyestrain and discomfort after prolonged periods of usage. A select few technologies (our’s and Letinar’s pin mirrors) have unlimited depth of field - the in-focus regions extends from a few centimeters in front of the wearer all the way to infinity.
Mass Producibility: The manufacturability of a design largely depends on its material and tolerance requirements. Systems that can leverage well-developed, large-scale manufacturing techniques and automated assembly will be much cheaper than those requiring niche and exotic manufacturing processes and precision hand-assembly. For example, molded plastic lenses cost next to nothing thanks to the smartphone camera industry, whereas freeform glass prisms and diffractive waveguides are rather costly owing to the novelty and low volume of their respective processes. Manufacturing advances over time, but there is always strong value in a product that can be manufactured now, rather than a product that might be manufacturable years from now.
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