If you’ve never heard of Aerial Imaging by Retro-Reflection, or AIRR for short, you’re probably not the only one. It’s a technique developed by researchers at Utsunomiya University that uses beam splitters and retroreflective foil to create the illusion of an image floating freely in the air. Hackaday alum [Moritz v. Sivers] has been experimenting with the technique to make — what else — a clock, appropriately called the Floating Display Clock.
The most commonly available retroreflective films are typically used for things like street signs and high-visibility clothing, but also work perfectly fine for homebrew AIRR setups. [Moritz] tried several types and found that one called Oralite Superlens 3000 resulted in the best image quality. He combined it with a sheet of teleprompter glass and mounted both in their appropriate orientation in a black 3D printed enclosure.
The projected image is generated by a set of 8×8 RGB LED displays, which are driven by a PCA9685 sixteen-channel servo driver board. A Wemos D1 Mini fetches the time from an NTP server and operates the display system, which includes not only the LED panels but also a set of servos that tilt each digit when it changes, giving the clock an added 3D effect that matches nicely with the odd illusion of digits floating in space.
We can imagine it’s pretty hard to capture the end result on video, and the demonstration embedded below probably doesn’t do it justice. But thanks to [Moritz]’s clear step-by-step instructions on his Instructables page, it shouldn’t be too hard to replicate his project and see for yourself what it looks like in real life.
Although this isn’t a hologram, it does look similar to the many display types that are commonly called “holographic”. If you want to make actual holograms, that’s entirely possible, too.
14 thoughts on “Clever Optics Make Clock’s Digits Float In Space”
A Hackaday contributor writing about a project done by another Hackaday contributor.
It’s Hackaday contributors all the way down.
To be fair, Moritz hasn’t written for us in over a couple of years, but I added a note into the text.
And I think Robin honestly didn’t know. We’ve had a lot of contributors in the last 20 years. They’re like Pokemon — nobody can actually name them all.
That said, when we’re looking for contributors, we look for people who do the sort of stuff that we’d feature on Hackaday, and Moritz ticked all those boxes. He has one of the most lovely bubble chamber builds I’ve seen, and his whole experimentation with themochromic ink is worth a look too! And we wrote those up _before_ he wrote for us.
But yeah. Hackaday writers are Hackaday readers, and we’re all hackers.
I know everybody always bemoans the absence of an “edit” button round here, but sometimes I’d just want to be able to drop a simple heart react. <3
It’s not like they took up one of a limited number of slots that a “more deserving” post could have filled. It’s a blog, you can have as many posts as you need!
Reminds of this sharper image toy.
And wjat happened to the most infamous contributor, Brianchoff, it was thrown under a bus, or he died of severe controversy ?
Buses became expensive. No longer could afford the damage.
I did something like this a while back, but I took a different approach. I used three flat A4 sized Fresnel lenses made from hard plastic, usually used for reading newspapers, stacked on top of each other. It reduces the focal length substantially and adds a slight fisheye effect, but due to the high combined magnification, it almost looks like a hologram. It would be interesting to see that used with the servo mechanism to “spin” the numbers, so you wouldn’t be looking at a reflection.
More Fresnel layers seems to reduce the transparency due to the density of the prism groves, or lack thereof in this case.
>Aerial Imaging by Retro-Reflection, or AIRR for short
Great chutzpah to take Pepper’s ghost and re-name it like that :)
The retroreflector in the mix makes it different, I guess. Makes it work over a wider angle?
Or maybe they just did it b/c they could.
Pepper’s Ghost doesn’t change the focal plane or magnify the image. This retroreflective material is the Pepper’s Ghost mirror covered in a micro lens array.
No, the mirror acts just like the mirror in the Pepper’s Ghost illusion.
The retroreflector is entirely separate, and acts to move the apparent image to float *in front* of the assembly, floating in free space — very different from Pepper’s Ghost.
It’s a neat effect. A shame the video does not show it very effectively.
It would work even better if the retroreflector were much larger so the image would not fall out of view at the extremes left and right.
Scale this up, and I wonder what evil you can do with this on a street, projecting virtual images in front of people or cars.
It’s *not* just pepper’s ghost. The optical path is folded and the final effect is different to just having a simple mirror. But hey, who am I to stand in the way of the obligatory “HUUURRR IT’S NOT A HOLOGRAM” comment?
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