Innovative Clock Uses Printed Caustic Lens

January 20, 2025 by Lewin Day 11 Comments

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.

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Flashlight shining through gold leaf on glass

Shining Through: Germanium And Gold Leaf Transparency

January 5, 2025 by Heidi Ulrich 26 Comments

Germanium. It might sound like just another periodic table entry (number 32, to be exact), but in the world of infrared light, it’s anything but ordinary. A recent video by [The Action Lab] dives into the fascinating property of germanium being transparent to infrared light. This might sound like sci-fi jargon, but it’s a real phenomenon that can be easily demonstrated with nothing more than a flashlight and a germanium coin. If you want to see how that looks, watch the video on how it’s done.

The fun doesn’t stop at germanium. In experiments, thin layers of gold—yes, the real deal—allowed visible light to shine through, provided the metal was reduced to a thickness of 100 nanometers (or: gold leaf). These hacks reveal something incredible: light interacts with materials in ways we don’t normally observe.

For instance, infrared light, with its lower energy, can pass through germanium, while visible light cannot. And while solid gold might seem impenetrable, its ultra-thin form becomes translucent, demonstrating the delicate dance of electromagnetic waves and electrons.

The implications of these discoveries aren’t just academic. From infrared cameras to optics used in space exploration, understanding these interactions has unlocked breakthroughs in technology. Has this article inspired you to craft something new? Or have you explored an effect similar to this? Let us know in the comments!

We usually take our germanium in the form of a diode. Or, maybe, a transistor.

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An image of a grey plastic carrying case, approximately the size of an A5 notebook. Inside are darker grey felt lined cubbies with a mirror, piece of glass, a viewfinder, and various small printed parts to assemble a camera lucida.

Camera Lucida – Drawing Better Like It’s 1807

May 23, 2024 by Navarre Bartz 15 Comments

As the debate rages on about the value of AI-generated art, [Chris Borge] printed his own version of another technology that’s been the subject of debate about what constitutes real art. Meet the camera lucida.

Developed in the early part of the nineteenth century by [William Hyde Wollaston], the camera lucida is a seemingly simple device. Using a prism or a mirror and piece of glass, it allows a person to see the world overlaid onto their drawing surface. This moves details like proportions and shading directly to the paper instead of requiring an intermediary step in the artist’s memory. Of course, nothing is a substitute for practice and skill. [Professor Pablo Garcia] relates a story in the video about how [Henry Fox Talbot] was unsatisfied with his drawings made using the device, and how this experience was instrumental in his later photographic experiments.

[Borge]’s own contribution to the camera lucida is a portable version that you can print yourself and assemble for about $20. Featuring a snazzy case that holds all the components nice and snug on laser cut felt, he wanted a version that could go in the field and not require a table. The case also acts as a stand for the camera to sit at an appropriate height so he can sketch landscapes in his lap while out and about.

Interested in more drawing-related hacks? How about this sand drawing bot or some Truly Terrible Dimensioned Drawings?

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The History Of The World’s First Planetarium

May 6, 2024 by Al Williams 14 Comments

It shouldn’t be a surprise that the idea of a planetarium originated with an electrical engineer, [Oskar von Miller] from the Deutsches Museum in Munich. According to [Allison Marsh] in IEEE Spectrum, he thought about the invention in 1912 as a way to demonstrate astronomical principles to the general public. While it seems obvious today that you can project the night sky onto a dome, it was a novel thought in 1912. So novel that the Carl Zeiss company first told [von Miller] to take a hike. But they eventually reconsidered and built the first planetarium, the Model I.

The engineer for Zeiss was a mechanical engineer by the name of [Walther Bauersfeld]. He was familiar with mechanical devices — orreries — that tracked the motion of the stars and planets. The goal was to translate those movements into a moving projection of light.

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Tiny Prisms Let You See What Lies Beneath A BGA Chip

May 1, 2024 by Dan Maloney 16 Comments

Compared to through-hole construction, inspecting SMD construction is a whole other game. Things you thought were small before are almost invisible now, and making sure solder got where it’s supposed to go can be a real chore. Add some ball grid array (BGA) chips into the mix, where the solder joints are not visible by design, and inspection is more a leap of faith than objective proof of results.

Unless, of course, you put the power of optics to work, as [Petteri Aimonen] does with this clever BGA inspection tool. It relies on a pair of tiny prisms to bounce light under one side of a BGA chip and back up the other. The prisms are made from thin sheets of acrylic; [Petteri] didn’t have any 1-mm acrylic sheet on hand, so he harvested material from a razor blade package. The edge of each piece was ground to a 45-degree angle and polished with successively finer grits until the surfaces were highly reflective. One prism was affixed to a small scrap of PCB with eleven SMD LEDs in a row, forming a light pipe that turns the light through 90 degrees. The light source is held along one edge of a BGA, shining light underneath to the other prism, bouncing light through the forest of solder balls and back toward the observer.

The results aren’t exactly crystal clear, which is understandable given the expedient nature of the materials and construction employed. But it’s certainly more than enough to see any gross problems lying below a BGA, like shorts or insufficiently melted solder. [Petteri] reports that flux can be a problem, too, as excess of the stuff can crystalize between pads under the BGA and obstruct the light. A little extra cleaning should help in such cases.

Haven’t tackled a BGA job yet? You might want to get up to speed on that.

Apple Vision Pro’s Secret To Smooth Visuals? Subtly Substandard Optics

March 21, 2024 by Donald Papp 32 Comments

The displays inside the Apple Vision Pro have 3660 × 3200 pixels per eye, but veteran engineer [Karl Guttag]’s analysis of its subtly blurred optics reminds us that “resolution” doesn’t always translate to resolution, and how this is especially true for things like near-eye displays.

The Apple Vision Pro lacks the usual visual artifacts (like the screen door effect) which result from viewing magnified pixelated screens though optics. But [Karl] shows how this effect is in fact hiding in plain sight: Apple seems to have simply made everything just a wee bit blurry thanks to subtly out-of-focus lenses.

The thing is, this approach of intentionally de-focusing actually works very well for consuming visual content like movies or looking at pictures, where detail and pixel-to-pixel contrast is limited anyway.

Clever loophole, or specification shenanigans? You be the judge of that, but this really is evidence of how especially when it comes to things like VR headsets, everything is a trade-off. Improving one thing typically worsens others. In fact, it’s one of the reasons why VR monitor replacements are actually a nontrivial challenge.

An Optical Computer Architecture

March 12, 2024 by Al Williams 13 Comments

We always hear that future computers will use optical technology. But what will that look like for a general-purpose computer? German researchers explain it in a recent scientific paper. Although the DOC-II used optical processing, it did use some conventional electronics. The question is, how can you construct a general computer that uses only optical technology?

The paper outlines “Miller’s criteria” for practical optical logic gates. In particular, any optical scheme must provide outputs suitable for introduction to another gate’s inputs and also support fan out of one output to multiple inputs. It is also desirable that each stage does not propagate signal degradation and isolate its outputs from its inputs. The final two criteria note that practical systems don’t depend on loss for information representation since this isn’t reliable across paths, and, similarly, the gates should require high-precision adjustment to work correctly.

The paper also identifies many misconceptions about new computing devices. For example, they assert that while general-purpose desktop-class CPUs today contain billions of devices, use a minimum of 32-bits of data path, and contain RAM, this isn’t necessarily true for CPUs that use different technology. If that seems hard to believe, they make their case throughout the paper. We can’t remember the last scientific paper we read that literally posed the question, “Will it run Doom?” But this paper does actually propose this as a canonical question.

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