Waveguides vs Laser Displays: What You Need To Know

In this article we will make a comparison between waveguides and laser to holographic combiners. In doing so we will also look at North (formerly Thalmic Labs), their business success, and their IP, and place that into the context of the greater smartglasses market, and near-eye optics IP.

What The Reader Will Gain

This article is not meant to be a scholarly treatise, but rather an accessible overview, providing the reader with a baseline understanding of the competition between waveguides and laser displays, and how advances in the field of optics are changing the landscape in the consumer smartglasses market.

Simple Displays

A “combiner,” as the name implies, combines virtual content with the user’s view of the real world. The simplest combiner is essentially a two-way mirror. It may also be referred to as a “Pepper’s Ghost” display, referencing a Vaudeville era magic trick that employed two-way mirrors. A birdbath display is one that employs a curved combiner, a trick used to expand the display’s field-of-view.

Simple beam-splitter displays were employed in early ODG glasses, such as the model R-7. A birdbath display was used in the META 2, and a miniature birdbath display was employed by ODG’s model R-9. It is also notable that ODG’s assets were put up for auction in January, and META was recently declared insolvent.

So Let’s Look Instead At Waveguides

Waveguides are employed in conjunction with a light-engine (a micro-display that projects into the optics). The light-engine feeds an input grating on one side of the waveguides. The light moves through the lens, and exits the waveguide through an output grating in front of the eye. Depending on whether the waveguide is a surface-relief or holographic waveguide, the optical elements are either engraved into the lens (subtractive), applied onto the lens (additive), or exposed within the lens as holographic mirrors.

Now Let’s Look At Laser to Holographic Combiners

Retinal lasers were pioneered in near-eye optic display systems by MicroVision, but their combiner was a more basic beam splitter. A collection of Swiss companies perfected the use of a laser reflected off of a holographic combiner, into the wearer’s eye. A holographic combiner uses a similar technique as a holographic waveguide: a series of micro-mirrors are holographically exposed into a lens, and a laser is directed—typically using a MEM Chip with a nano-scale mirror mounted on a dual-axis gimbal—to reflect the imagery into the eye.

Where Have Laser to Holographic Combiners Been Deployed?

Laser displays are “having a moment,” most notably with Focals by North—which employ a laser to holographic combiner display, and have recently launched to much fanfare and success.

After initial work by MicroVision, laser displays saw more recent advancements coming out of Switzerland. A startup named Lemoptix developed some of the most advanced micro-opto-electromechanical systems (MOEMS)—essentially a laser and nano-mirror projection system—and Composyt Light Labs then employed Lemoptix laser projector into an RGB composited near-eye optics display module. Subsequently Intel acquired the combined companies. Composyt’s early devices stumbled with color compositing, and early last year a monochrome red version based on their technology was briefly deployed by Intel under the name Vaunt. However, mere weeks later Intel dissolved their wearables business unit, and discontinued Vaunt almost as quickly as they launched.

Meanwhile, a small startup in Canada named Thalmic Labs whose most notable prior accomplishment was launching crowd-funded muscle tracking gesture control armband, discretely raised $120M from Intel Capital and Amazon’s Alexa Fund to develop laser to holographic combiner based smartglasses. They seemed an unlikely candidate… until last fall, when Thalmic rebranded as North, and launched Focals. Their color display shows that they solved the color composite registration problem that had bedeviled Composyt Light Labs’ previous implementation. North then took additional investment from the Canadian government, and after a highly successful go to market they acquired the IP behind Intel’s Vaunt glasses (principally Lemoptix and Composyt Light Lab’s laser display patents). This has consolidated most of the laser to holographic combiner IP under one roof.

Laser displays also have one clear advantage over waveguides: they’ve been shown to work within a prescription lens, and further that these lenses can be mass manufactured at scale.

Does This Mean Laser Display Tech Has Pulled Into The Lead?

Not so fast.

One issue that has always plagued near-eye optics, when built in low profile form factor, is field-of-view (FOV). Microsoft’s HoloLens is a mere ~35º FOV. Though insolvent, the META 2 has a 90º FOV, almost triple that of HoloLens… but META 2 is also staggeringly large compared to Focals by North, which are available in a consumer accessible form factor. If HoloLens’ FOV is narrow compared to META’s, then Focals by North’s FOV is positively minuscule, at ~15º. This is of course fine for the alerts use-case they have been developed for, but are far insufficient for any kind of immersive AR experience. In Focals implementation they are also monoscopic, so there will be no depth or dimensionality.

Laser displays also have another disadvantage compared to waveguides: they are “through-the-air projection,” meaning that anything that obstructs the line of sight between the laser projecting from the eye-frame’s temple, and the lens (such as hair) can obstruct the projected image. Buyer-beware, don’t wear Focals with bangs.

So Where Do Waveguides Shine?

Waveguides are enclosed, so they don’t have the obstruction issues of a lasers’ through-the-air projection system. Further, in recent months we’ve seen FOV breakthroughs in waveguide displays. Not much is known about Apple’s acquisition of Akonia Holographics, but it is clear at this point between hires, acquisitions and IP, that Apple is betting on holographic waveguides. The industry leader and pioneer of holographic waveguides, DigiLens, recently disclosed a FOV breakthrough at CES, noting that lenses with a staggering 150º FOV are imminent—the technological limitation no longer being the waveguides themselves, but in developing a light-engine of high enough resolution to drive their FOV.

This would seem to imply that laser to holographic combiner displays’ time in the limelight may be limited, but waveguides are not out of the dark yet. No one has yet demonstrated a waveguide display embedded within a prescription lens, as others have been able to show with laser projectors. Indeed, another Swiss startup named Interglass also makes a waveguide, but their principal IP concerns the robotic manufacturing of resin lens that contain embedded elements, including holographic combiners used for laser displays, not unlike those employed in Focals by North.

Getting a waveguide embedded within a prescription lens, using resin based manufacturing method is the most likely path to a consumer viable stereoscopic 3D, augmented reality smartglasses display system… and last October, North (as Thalmic Labs) was awarded a patent for just that.

A spokesperson for Interglass tells us that embedding a waveguide within a prescription lens is for them a current R&D priority, working together with “other partner companies” for which they are prohibited from disclosing. They noted an imminent patent filing that is of “a different design” than depicted by North’s prescription lens waveguide patent. Joining the competition, DigiLens noted that they too have already been awarded a patent, not for embedding a planar waveguide within a prescription lens, but rather for a “curved diffractive waveguide… that could be laminated to a [prescription] lens,” and they’re confident their design will scale at a substantially lower cost than a waveguide embedded into a resin lens. Interglass says they expect to meet an important development milestone in “about 12 months,” and will then “be in a position for a more reliable prediction” for when such lenses will be ready for mass production. If they had to predict now, “we assume that it will take about another year [from then, to achieve] mass production.” So it is a reasonable expectation that we could see the first prototype waveguides embedded within (or applied onto) a prescription lens by as early at CES 2020.

Will Interglass have their own waveguide into a prescription lens and reveal a prototype before North debuts their own design? Will another player unexpectedly emerge? The race is on.

Where To Now?

The smartglasses field is narrowing. ODG has shut down, META has declared insolvency, and many more should be expect to fold in the coming year. This is not a bad thing, it is a sign that the market is maturing, and we are approaching consumer viability. Keep your eyes open, things are just getting good.

This article was originally published at UploadVR, on February 1, 2019.