optics

77 Articles

Close up of a custom optical HDMI cable on a desk

Let There Be Light: The Engineering Of Optical HDMI

February 18, 2025 by 14 Comments

In a recent video, [Shahriar] from The Signal Path has unveiled the intricate design and architecture of optical HDMI cables, offering a cost-effective solution to extend HDMI 2.0 connections beyond the limitations of traditional copper links. This exploration is particularly captivating for those passionate about innovative hardware hacks and signal transmission technologies.

[Shahriar] begins by dissecting the fundamentals of HDMI high-speed data transmission, focusing on the Transition Minimized Differential Signaling (TMDS) standard. He then transitions to the challenges of converting from twisted-pair copper to optical lanes, emphasizing the pivotal roles of Vertical-Cavity Surface-Emitting Lasers (VCSELs) and PIN photodiodes. These components are essential for transforming electrical signals into optical ones and vice versa, enabling data transmission over greater distances without significant signal degradation.

A standout aspect of this teardown is the detailed examination of the optical modules, highlighting the use of free-space optics and optical confinement techniques with lasers and detectors. [Shahriar] captures the eye diagram of the received high-speed lane and confirms the VCSELs’ optical wavelength at 850 nm. Additionally, he provides a microscopic inspection of the TX and RX chips, revealing the intricate VCSEL and photodetector arrays. His thorough analysis offers invaluable insights into the electronic architecture of optical HDMI cables, shedding light on the complexities of signal integrity and the innovative solutions employed to overcome them.

For enthusiasts eager to take a deeper look into the nuances of optical HDMI technology, [Shahriar]’s comprehensive teardown serves as an excellent resource. It not only gives an insight in the components and design choices involved, but also inspires further exploration into enhancing data transmission methods.

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A Waist Level Viewfinder For Not A Lot

January 26, 2025 by 8 Comments

Photographic accessories are often plagued by high prices, as photography is considered a rich man’s game. It doesn’t have to be that way though, and [Snappiness] is here to get you started on the route to cheaper kit with a waist-level viewfinder project.

If you’ve used a twin-lens reflex camera then you should be familiar with a waist level viewfinder, it’s a lens and mirror arrangement allowing the photographer to frame the shot looking down from above. Modern cameras often have no viewfinder, so this is aimed at digital compacts without flip-up screens.

It has three components, all available for relatively low prices, and mounted in a 3D printed case. There’s a prime lens, a mirror, and a Fresnel lens forming the part the photographer looks through. It’s a simple device, but still one which would cost a lot more off the shelf. The video is below the break.

It might interest you to know that this is not the first viewfinder project we’ve brought you for digital cameras.

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Schematic of quantum measurement basis on whiteboard

Shedding Light On Quantum Measurement With Calcite

January 26, 2025 by 18 Comments

Have you ever struggled with the concept of quantum measurement, feeling it’s unnecessarily abstract? You’re not alone. Enter this guide by [Mithuna] from Looking Glass Universe, where she circles back on the concept of  measurement basis in quantum mechanics using a rather simple piece of calcite crystal. We wrote about similar endeavours in reflection on Shanni Prutchi’s talk at the Hackaday SuperConference in 2015. If that memory got a bit dusty in your mind, here’s a quick course to make things click again.

In essence, calcite splits a beam of light into two dots based on polarization. By aligning filters and rotating angles, you can observe how light behaves when forced into ‘choices’. The dots you see are a direct representation of the light’s polarization states. Now this isn’t just a neat trick for photons; it’s a practical window into the probability-driven nature of quantum systems.

Even with just one photon passing through per second, the calcite setup demonstrates how light ‘chooses’ a path, revealing the probabilistic essence of quantum mechanics. Using common materials (laser pointers, polarizing filters, and calcite), anyone can reproduce this experiment at home.

If this sparks curiosity, explore Hackaday’s archives for quantum mechanics. Or just find yourself a good slice of calcite online, steal the laser pointer from your cat’s toy bin, and get going!

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Innovative Clock Uses Printed Caustic Lens

January 20, 2025 by 13 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. 

Wild. Just wild.

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 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 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 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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