Supercon: Designing Your Own Diffractive Optics

Aug 06, 2023

Kelly Peng is an electrical and optical engineer, and founder of Kura AR. She's built a fusion reactor, a Raman spectrometer, a DIY structured light camera, a linear particle accelerator, and emotional classifiers for likes and dislikes. In short, we have someone who can do anything, and she came in to talk about one of the dark arts (pun obviously intended): optics.

The entire idea of Kura AR is to build an immersive augmented reality experience, and when it comes to AR glasses, there are two ways of doing it. You could go the Google Glass route and use a small OLED and lenses, but these displays aren't very bright. Alternatively, you could use a diffractive waveguide, like the Hololens. This is a lot more difficult to manufacture, but the payoff will be a much larger field of view and a much more immersive experience.

The lens that Kelly is using in her AR headset is basically a diffraction grating, or a series of parallel lines on a piece of plastic. These diffraction gratings reflect light, but it's dependent on the wavelength. Therefore, for a full-color system, you need three layers, one for red, one for blue, and another for green. The trick here is how to manufacture this. Kelly took a Hololens lens apart and took a look at it with an electron microscope, which appears to be made via fancy, and expensive, photolithography.

There is another way, though. The feature sizes on this diffraction grating aren't too small, and this could conceivably be done through injection molding. With a lot of coding, simulation, and testing, Kelly realized this was manufacturable with somewhat standard injection molding processes, would cost only about $60,000 upfront, and would produce a part for one dollar. That's much better than whatever process is going into the Hololens, and an amazing technical feat that's bring the future of AR closer than ever before.

This talk gets deep into diffractive optics. It's jam-packed with the kind of technical detail you’ll need to know if you’re going to hack together your own AR / VR system. In short, it's the kind of real-world technical talk that we love. Sit back with some popcorn and your notepad.