The geometric waveguide glass of the Meta Ray-Ban Display glasses. (Credit iFixit)
Recently the avid teardown folk over at iFixit got their paws on Meta’s Ray-Ban Display glasses, for a literal in-depth look at these smart glasses. Along the way they came across the fascinating geometric waveguide technology that makes the floating display feature work so well. There’s also an accompanying video of the entire teardown, for those who enjoy watching a metal box cutter get jammed into plastic.

Overall, these smart glasses can be considered to be somewhat repairable, as you can pry the arms open with a bit of heat. Inside you’ll find the 960 mWh battery and a handful of PCBs, but finding spare parts for anything beyond perhaps the battery will be a challenge. The front part of the glasses contain the antennae and the special lens on the right side that works with the liquid crystal on silicon (LCoS) projector to reflect the image back to your eye.

While LCoS has been used for many years already, including Google Glass, it’s the glass that provides the biggest technological advancement. Instead of the typical diffractive waveguide it uses a geometric reflective waveguide made by Schott, with the technology developed by Lumus for use in augmented reality (AR) applications. This is supposed to offer better optical efficiency, as well as less light leakage into or out of the waveguide.

Although definitely impressive technology, the overall repairability score of these smart glasses is pretty low, and you have to contest with both looking incredibly dorky and some people considering you to be a bit of a glasshole.

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The worst thing about a volume knob is that, having connected it to a computer, it might be wrong: if you’ve manually altered the volume settings somewhere else, the knob’s reading won’t be correct. [I Got Distracted] has a quick tutorial on YouTube showing how to use a BLDC, a hall effect sensor, Pi Pico and the SimpleFOC library to make a knob with active haptic feedback and positioning.

We covered the SimpleFOC library a few years ago, but in case you missed it, it’s, well, a simple library for FOC on all of our favorite microcontrollers, from Arduino to ESP to Pico. FOC stands for field-oriented control, which is a particular way of providing smooth, precise control to BLDCs. (That’s a BrushLess DC motor, if the slightly-odd acronym is new to you.) [I Got Distracted] explains exactly how that works, and shows us just how simple the SimpleFOC project is to use in this video. Why, they even produce their own motor controllers, for a fully-integrated experience. (You aren’t restricted to that hardware, but it certainly does make things easy.)

The haptic feedback and self-dialing knob make for an easy introductory project, but seeing how quick it hacks together, you can doubtless think of other possibilities. The SimpleFOC controller used in this video is limited to relatively small motors, but if you want to drive hundreds of kilowatts through open source hardware, we’ve covered that, too.

Arguably, using a motor as a knob isn’t within the design spec, and so could almost qualify for our ongoing Component Abuse Challenge, had [I Got Distracted] thought to enter.

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hackaday.com/2025/10/09/motors…