Caustic Lens Projection Clock
Moritz V. Sivers' Caustic Clock focuses light to project an image through its lens.
As explained here, when light travels through – or is reflected by – a medium, it’s focused in different ways, forming pretty patterns. You may have seen this effect while looking at the bottom of a pool, and perhaps even considered how the ~random lines there are related to the wave movements on the top.
If you were to take this concept a few steps further and substitute a carefully-formed lens for the waves, it should be possible to make not just random patterns, but actual focused images. This concept is called a caustic lens, implemented by Moritz v. Sivers as the Caustic Clock.
The clock itself is rather straightforward, using a modified Hollow Clock design by shiura as the face, while adding a caustic lens and a projector made with a WS2812B LED and Arduino Nano to show the time on the wall. As the LED shines through the clock and lens, the hands, as well as the characters embedded into the caustic lens, can be seen. Notably, these characters are largely invisible (or at least hard to see) on the clock itself, but appear on the wall as if by magic.
Of course, the real magic/struggle with this design was figuring out how to make the caustic lens. This took many iterations of SLA printing, careful design and even ray tracing via Blender. The final build shows four “caustic” digits, as well as eight radial lines via light focused through the glass, plus shadows from the Hollow Clock's hands.
