This "BS" Wearable Computer Doubles as a Lesson in Optics

Google Glass may have been very controversial when it first launched, but it had (and still has, in current versions) some very interesting technology. The most obvious is the heads-up display (HUD), which puts a digital screen right in front of your eye on a clear piece of glass. It lets you see both the real world and whatever virtual content you want. But Google Glass and similar products are very expensive. Many makers have attempted to create DIY versions using transparent screens. In a recent video, Zack Freedman tackled just such a project and even worked in a lesson on optics

One of Freedman's trademarks, aside from his delightful sense of humor, is the headset that he wears in every video. That is very similar to Google Glass, so he is no stranger to the technology. Before he even started this cheap DIY build, he knew that it wouldn't work. That's why he was clear from the beginning that this wearable computer sucks. It includes a small transparent OLED screen, a Crystalfontz driver board, a small LiPo battery, and an Adafruit Feather nRF52 development board with Bluetooth capability. A 3D-printed frame contains all of those components and distributes the weight across Freedman's noggin.

But the build isn't the interesting part of the video. The real meat of the video is Freedman's explanation of how HUD optics work. It all comes down to the fact that your eye cannot focus on a screen that close. The light is too scattered. If the screen were further away, only the mostly-parallel photons would hit your eye and you would see them clearly. You could also focus on the screen if you put a lens in front of it, but that would distort everything further away, which would defeat the purpose of a HUD. So how does Google Glass work? It uses a very precise projection system to "straighten" out the photons, making them act like they're coming from far away. The light then reflects off the lens into your eye. As far as your eye is concerned, it is looking a screen several feet away.

Those optics are very complex, which is why Google Glass and others are so expensive. It is disappointing that a transparent OLED isn't a viable alternative, but Freedman's video provides a great explanation for that.