Hackers and makers have built just about every kind of clock under the sun. Digital, analog, seven-segment, mechanical seven-segment, binary, ternary, hexadecimal… you name it. It’s been done. You really have to try to find something that shocks us… something we haven’t seen before. [Moritz v. Sivers] has done just that.
Meet the Caustic Clock. It’s based on the innovative Hollow Clock from [shiura]. It displays time with an hour hand and a minute hand, and that’s all so conventional. But what really caught our eye was the manner in which its dial works. It uses caustics to display the clock dial on a wall as light shines through it.
If you’ve ever seen sunlight reflect through a glass, or the dancing patterns in an outdoor swimming pool, you’ve seen caustics at play. Caustics are the bright patterns we see projected through a transparent object, and if you shape that object properly, you can control them. In this case, [Moritz] used some GitHub code from [Matt Ferraro] to create a caustic projection clockface, and 3D printed it using an SLA printer.
The rest of the clock is straightforward enough—there’s some WS2812 LEDs involved, an Arduino Nano, and even an RP2040. But the real magic is in the light show and how it’s all achieved. We love learning about optics, and this is a beautiful effect well worth studying yourself.
This technique would make for an amazing escape room prop!
“Caustic lenses are really weird”
https://www.youtube.com/watch?v=wk67eGXtbIw
With the right means of producing them, these lenses can create surprising well-defined images.
“Wobbly lenses” sounds so much more friendly than caustic lenses. :-)
“You really have to try to find something that shocks us… ”
Kudo’s to the first to build a taser-based clock.
Really snappy effect. Would love to see a version of this where the hands are also caustic images printed on rotating discs stacked together.
That was actually my first idea. The problem is that each lens distorts the incoming light for the next lens so you would have to account for that. It might still work though
The hands, and therefore their projections, don’t need to overlap at all to be effective. Just use an inner radius for the hour hand marker and an outer radius for the minute hand marker.
You’ve made really impressive progress with this. None of it looks easy.
Now we just need to make an adjustable caustic-generating surface.
We can already make surfaces that deform on demand by electroosmotic pumps, like https://hackaday.com/2024/05/24/dynamic-buttons-are-weird-blobs-you-can-press/
And we have https://hackaday.com/tag/adaptive-optics/ that can undo aberrations that would cause caustics.
So, how about a challenge? Make a deformable-on-demand surface to create the caustics you desire in real time.
Something like a seven segment display, with transparent plastic bags filled with gel. I’m imagining something like a clear air mattress, but with individual cells for the segments, and gel filling the segments driven by servo solenoids.
Does it need to be so fancy? What happens if you fill and empty water from a cylinder?
Clocks based upon germs.
I just fired up an ultrasonic humidifier and noticed a mound of water forms above the disc, or you could gently pump water to deform the surface of water in an overhead projector setup. A reflecting pond could shine the time on a nearby wall at any size.
Nice work. I am the one who built an acrylic lenses shown as a fragment in your video. I also tried resin printing, but with no success. What was a trick in producing caustic lenses by printing?