Google Glass might have been a flop, but that doesn't mean that there aren't people with an interest in HUD (heads-up display) headsets. The idea of having a wearable computer with a screen that is always viewable is appealing to many. But consumer HUD devices, including Google Glass (yes, it still exists), are expensive. So Redditor Zoemaestra used a Raspberry Pi to build their own HUD headset.
All HUD headsets must overcome the same optical challenge: human eyes can't focus on anything too close. But nobody wants to wear a headset that sticks a foot out from their face. For this reason, HUD headsets must use special optics to extend the distance that photons travel from the screens to the user's eyes. The most common way to achieve that is by using reflective lenses, which is what Zoemaestra did here.
They started with a cheap AR headset from AliExpress. It has two clear, curved, reflective lenses that hang down a couple of inches front of the wearer's eyes. Two LCD screens, mounted near the user's forehead, reflect off of those lenses and to their eyes. The resulting photon path doubles to around four inches — far enough to focus on without too much eye strain. Zoemaestra can also look through the lenses to see their surroundings.
At this time, the Raspi runs the standard Raspberry Pi OS (previously called "Raspbian") desktop environment. Zoemaestra reports that text is readable, if a bit distorted. In the future, they plan to add a Leap Motion Controller to enable gesture control, which would eliminate the need for a mouse.
The total build cost for this Raspi HUD should have been less than $100, which makes it far more affordable than the devices on the market. Despite that low cost, Zoemaestra gets a real computer and all of its capability to run whatever software they want.