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Updated Jan 23, 2023 – Corrections:
This series on CES 2023 is starting with foundation technologies for AR/MR rather than products with Meta Materials’ non-polarizing dimming and Porotech’s MicroLED display technologies. Addoptics 3-D printable optics molds are a third in this series of foundation technology.
Brad and I briefly discussed Luxexcel (and Meta Materials ARFusion) in a video I made with SadlyIsBradley on AWE 2022 in the section on Printable Lenses. In that video, made before I knew of Meta’s (Facebook) acquisition of Luxexcel, I expressed some reservations about volume manufacturing with the Luxexcel direct 3-D printing approach, something I think Addoptics better addresses.
This article will briefly cover some of the strengths and weaknesses of Addoptics and Luxexcel, along with Meta Materials ARFusion approaches to customizable optics in prescription lenses. To avoid confusion, Meta Materials was a company before Facebook changed its name to Meta.
Addoptics’ ability to make customized optics takes on added significance with Meta (Facebook) buying the 3-D optical printing technology company Luxexcel. Luexcel claimed to work with over 20 companies. Those companies are now left in a lurch with Meta’s acquisition.
The similarities and differences between Addoptics and Luxexcel are not purely coincidental. Joris Biskop, the founder and CEO of Addoptics, was with Luxexcel for about eight years. I find it interesting that Meta, with the Meta Quest Pro and soon-be-released Meta Quest 3, which both used pancake optics, bought Luxexcel, which can’t make usable pancake optics due to the inherent birefringence of its process. At the same time, Addoptics can make custom optics without this problem.
The basics of Addoptics are simple to explain. Whereas Luxexcel directly 3-D prints the lenses, Addoptics 3-D prints limited run molds, which they say are good for about 100 “runs” per mold. Then a thermal hardening lens material fills the mold to form the finished part.
Printing the mold may seem like an added step, but there are significant advantages to Addoptic’s 3-D method over Luxexcel’s direct optical 3-D print when making mass quantities of lenses. At first glance, it might seem better and simpler to print the optics directly. Addoptics was giving away samples (right) on the show floor, which hints at lower lens production costs.
Addoptics separates the mold’s need for good 3-D printing characteristics from needing good optical characteristics in the molded part. Luxexcel is limited to optically clear resins that are very thin for printing optical structures with very fast UV curing properties. Luxexcels current prototypes are known to turn yellow in sunlight, and its printing process results in high birefringence, meaning that they won’t work with polarized light. Addoptics should be able to include features in molded optics that are not possible with a 3-D printed optic.
Addoptics claims advantages in using better, slower-curing resins with better mechanical and optic properties, non-yellow, and low birefringence. Addoptics, for example, says that they can make pancake optics that use polarized light. A downside to the Addoptics method compared to Luxexcel is that it can take several days to go from making a mold to a finished lens.
Volume manufacturing seems to be better addressed with the Addoptics method. Luxexcel throughput is limited by needing a large, expensive printer to make each device. With Addoptics, many lower-cost molds can make many lenses in parallel.
It would seem the cost per print could be more than 10x lower with the Addoptics approach. The much lower cost means that the Addoptics could be used to make not just one-off prototypes but in volume production without making costly metal injection molds, and would even enable the stocking of standard prescription lenses (more on this later).
What got Luxecel all the attention, including Meta, which bought them, was that Luxexcel had a way to make custom prescription lenses formed around waveguides. Luxexcel made two key points; the first was the ability to leave an air gap, and the second was to print prescription optics. This made me think about how Addoptics might address these same issues concerning prescription optics for VR and AR.
This whole section on prescription is speculation on my part in trying to see if Addoptics could be used for prescription lenses and whether it would be better than Luxexcel’s approach. Addoptics is not currently talking about supporting prescription AR optics.
While some VR headsets have a built-in diopter adjustment, even these don’t address astigmatism, affecting about 1 in 3 people. I have rather mild nearsightedness but significant astigmatism, which is different in each eye.
Luxexcel also pointed to having the ability to leave an air gap before and after a waveguide to support the waveguides that need total internal reflection (TIR) to work. While this sounds good initially, it would seem that if this were done while printing, it would leave a non-AR-coated surface with an air gap that would cause reflections/transmission losses due to the index of refraction mismatch. I have not seen anywhere how Luxexcel creates the air gap around waveguides, how the waveguide is introduced and printed around, or anything about the index of refraction mismatch.
It seems that if custom optics were to support air gaps, it would need to be made in two parts, and then each part would need AR coating on both sides. The two parts would then be glued together with indexed match glue (to ensure no air gap/refraction mismatch).
Typically, the outer part of a prescription lens will have a nominal curvature that does not change. The inner curvature between the waveguide and the eye must be customized.
Related to the air gap issue, at CES 2023, Lumus said their new Z-Lens waveguides don’t require an air gap, what Lumus calls “direct bonding.”
Lumus’ Z-Lens architecture also allows for direct bonding of optical elements for Rx prescription glasses, which can be licensed and utilized by manufacturing partners. This feature allows consumers to customize their AR eyeglasses to their vision without bulky, heavy inserts, enabling them to be utilized as normal eyewear.Lumus CES 2023 News Release
Even if it is optically permissible to mold directly to the waveguide, it would seem problematic due to the different thermal expansion characteristics between the waveguide and the plastic. Perhaps something like an index-matched gel could be used as a mechanical buffer.
The advantage of the Luxexcel direct 3-D method is that you can print custom prescriptions into each device, whereas with the Addoptics, you would have to print a mold and then mold the lens. With conventional lenses, about 400 different lens prescriptions cover the common range of diopters and astigmatism (not including varifocal lenses). While 400 is a large number, with the finish lenses costing a few dollars a piece, all the most common prescriptions could easily be kept in stock.
Certainly, for VR, it would seem much better to have custom optics with built-in prescriptions than to have a custom insert or a diopter adjustment that does not support astigmatism.
The combinations and permutations explode when including varifocal lenses for (typically older people with Presbyopia). This would not be an issue for VR-type displays as they have a fixed focus distance, but it might be an issue for a glasses replacement optical AR/MR headset. Conventional glasses prescription lens makers use a “semi-finished lens” where one side of the lens is later custom ground to support variable focal length. Either Addoptics would have to use a resin that supports post-mold grinding, or they would have to make a custom mold to support varifocal.
While discussing prescription molded optics, Meta Materials’ ARFusion technology should be mentioned. ARFusion is an automated process that selects premade glass molds and UV-cured resins to make custom lenses that can embed electronic devices, holographic films, and their metamaterial films.
This method might be useful for making custom lenses for VR applications, particularly when they want to embed something like eye tracking. It is harder to imagine how it could be used with waveguides or for many applications that could use Addoptics or Luxexcel devices.
On the surface, I prefer Addoptics’ approach of 3-D printing molds over Luxexcel’s 3-D printing optics. I don’t have direct experience or reports on the quality of their products. On a technical level, I think Addoptics printing the molds has major advantages in using better optical resins, and in a production environment, it supports much lower costs. I can imagine many more ways companies could leverage Addoptics’ approach.