Interference Patterns Harnessed For Optical Logic Gates

The basics of digital logic are pretty easy to master, and figuring out how the ones and zeroes flow through various kinds of gates is often an interesting exercise. Taking things down a level and breaking the component AND, OR, and NOR gates down to their underlying analog circuits adds some complexity, but the flow of electrons is still pretty understandable. Substitute all that for photons, though, and you’ll enter a strange world indeed.

At least that’s our take on [Jeroen Vleggaar]’s latest project, which is making logic gates from purely optical components. As he himself admits in the video below, this isn’t exactly unexplored territory, but his method, which uses constructive and destructive interference, seems not to have been used before. The basic “circuit” consists of a generator, a pair of diffraction patterns etched into a quartz plate, and an evaluator, which is basically a pinhole in another plate positioned to coincide with the common focal point of the generator patterns. An OR gate is formed when the two generators are hit with in-phase monochromatic light. Making the two inputs out of phase by 180° results in an XOR gate, as destructive interference between the two inputs prevents any light from making it out of the evaluator.

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Beam Dump Makes Sure Your Laser Path Is Safely Terminated

Between hot things, sharp things, and spinny things, there’s more than enough danger in the average hacker’s shop to maim and mutilate anyone who fails to respect their power. But somehow lasers don’t seem to earn the same healthy fear, which is strange considering permanent blindness can await those who make a mistake lasting mere fractions of a second.

To avoid that painful fate, high-power laser fan [Brainiac75] undertook building a beam dump, which is a safe place to aim a laser beam in an experimental setup. His version has but a few simple parts: a section of extruded aluminum tubing, a couple of plastic end caps, and a conical metal plumb bob. The plumb bob gets mounted to one of the end caps so that its tip points directly at a hole drilled in the center of the other end cap. The inside and the outside of the tube and the plumb bob are painted with high-temperature matte black paint before everything is buttoned up.

In use, laser light entering the hole in the beam dump is reflected off the surface of the plumb bob and absorbed by the aluminum walls. [Brainiac75] tested this with lasers of various powers and wavelengths, and the beam dump did a great job of safely catching the beam. His experiments are now much cleaner with all that scattered laser light contained, and the work area is much safer. Goggles still required, of course.

Hats off to [Brainiac75] for an instructive video and a build that’s cheap and easy enough that nobody using lasers has any excuse for not having a beam dump. Such a thing would be a great addition to the safety tips in [Joshua Vasquez]’s guide to designing a safe laser cutter.

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Precision Optics Hack Chat With Jeroen Vleggaar Of Huygens Optics

Join us on Wednesday, December 2nd at noon Pacific for the Precision Optics Hack Chat with Jeroen Vleggaar!

We sometimes take for granted one of the foundational elements of our technological world: optics. There are high-quality lenses, mirrors, filters, and other precision optical components in just about everything these days, from the smartphones in our pockets to the cameras that loom over us from every streetlight and doorway. And even in those few devices that don’t incorporate any optical components directly, you can bet that the ability to refract, reflect, collimate, or otherwise manipulate light was key to creating the electronics inside it.

The ability to control light with precision is by no means a new development in our technological history, though. People have been creating high-quality optics for centuries, and the methods used to make optics these days would look very familiar to them. Precision optical surfaces can be constructed by almost anyone with simple hand tools and a good amount of time and patience, and those components can then be used to construct instruments that can explore the universe wither on the micro or macro scale.

Jeroen Vleggaar, know better as Huygens Optics on YouTube, will drop by the Hack Chat to talk about the world of precision optics. If you haven’t seen his videos, you’re missing out!

When not conducting optical experiments such as variable surface mirrors and precision spirit levels, or explaining the Double Slit Experiment, Jeroen consults on optical processes and designs. In this Hack Chat, we’ll talk about how precision optical surfaces are manufactured, what you can do to get started grinding your own lenses and mirrors, and learn a little about how these components are measured and used.

join-hack-chatOur Hack Chats are live community events in the Hack Chat group messaging. This week we’ll be sitting down on Wednesday, December 2 at 12:00 PM Pacific time. If time zones baffle you as much as us, we have a handy time zone converter.

Click that speech bubble to the right, and you’ll be taken directly to the Hack Chat group on You don’t have to wait until Wednesday; join whenever you want and you can see what the community is talking about.

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DIY Lasers Hack Chat

Join us on Wednesday, October 7th at noon Pacific for the DIY Lasers Hack Chat with Les Wright!

It’s not too much of a reach to say that how we first experienced the magic of lasers sort of dates where we fall on the technology spectrum. For the youngest among us, lasers might have been something trivial, to be purchased for a couple of bucks at the convenience store. Move back a few decades and you might have had to harvest a laser from a CD player to do some experiments, or back further, perhaps you first saw a laser in high school physics class, with that warm, red-orange glow of a helium-neon tube.

But back things up only a few decades before that, and if you wanted to play with lasers, you had to build one yourself. It was a popular if niche hobby with a dedicated following of amateur physicists who scrounged around for the unlikely parts needed: ruby rods, quartz-glass tubes, and exotic dyes. Couple them together with high-voltage power supplies, vacuum pumps made from converted refrigerator compressors, and homemade optical benches, and if the stars aligned, these parts could be coaxed into producing a gloriously intense burst of light, which as often as not hooked its creator as a lifelong laser addict.

We’re not sure which camp Les Wright falls into, but from the content of his growing YouTube channel, we’d say he’s caught the laser bug. We recently took a look at his high-performance nitrogen laser, which he’s been having fun with as the basis for a tunable dye laser. Along the way he’s been necessarily mucking around with high-voltage power supplies, oscilloscopes, and the occasional robot or two.

Les will stop by the Hack Chat to talk about everything going on in his lab, with a focus on his laser experiments. Join us with your questions on DIY lasers, and stop by to pick up some tricks that might help you catch the laser bug too.

join-hack-chatOur Hack Chats are live community events in the Hack Chat group messaging. This week we’ll be sitting down on Wednesday, October 4 at 12:00 PM Pacific time. If time zones baffle you as much as us, we have a handy time zone converter.

Click that speech bubble to the right, and you’ll be taken directly to the Hack Chat group on You don’t have to wait until Wednesday; join whenever you want and you can see what the community is talking about.

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Infinity Mirror At Warp Speed

Inventing often combines more than one old ideas into a new one. Even when the fused things are similar, the result can be more valuable than the sum of its parts. Unlike those analog watches with a digital clock below the face, when [Mojoptix] combined the re-reflecting properties of an infinity mirror with the image twisting qualities of a funhouse mirror, we get more than just a pair of mirrors. The resulting images look like a lot of fun. Warping one surface of two parallel mirrors doesn’t just alter the result a bit, because the planes feed off each other’s view, the final product is an exponentially skewed show.

Our host mounts a 3D printed ring with an hubward-facing strip of LEDs to an ordinary glass mirror. Over that, he designs four mated plates that hold semi-reflective film sheets in different shapes. The first is a hyperbolic paraboloid, but it’s probably easier to think of it as shaped like a Pringles chip (crisp). Once the light is applied, it looks like a bowtie made by a deranged god or the start of an infinite rabbit hole of light and reflection. To further the madness, he hits us with four shapes at once, so we hope you’ll take a moment to enjoy the video below.

This guy is no stranger to optics, and we’ve reported on a couple of other cool inventions that teach a concept through demonstration. His precision calipers demonstrate the Moiré effect, and his digital sundial capitalizes on parallel light beams.

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Schlieren On A Stick

Schlieren imaging is a technique for viewing the density of transparent fluids using a camera and some clever optical setups. Density of a fluid like air might change based on the composition of the air itself with various gasses, or it may vary as a result of a sound or pressure wave. It might sound like you would need a complicated and/or expensive setup in order to view such things, but with a few common things you can have your own Schlieren setup as [elad] demonstrates.

His setup relies on a cell phone, attached to a selfie stick, with a spherical mirror at the other end. The selfie stick makes adjusting the distance from the camera to the mirror easy, as a specific distance from the camera is required as a function of focal length. For cell phone cameras, it’s best to find this distance through experimentation using a small LED as the point source. Once it’s calibrated and working, a circular field of view is displayed on the phone which allows the viewer to see any change in density in front of the mirror.

The only downside of this build that [elad] notes is that the selfie stick isn’t stiff enough to prevent the image from shaking around a little bit, but all things considered this is an excellent project that shows a neat and useful trick in the photography/instrumentation world that could be useful for a lot of other projects. We’ve only seen Schlieren imaging once before and it used a slightly different method of viewing the changing densities.

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500 Lasers Are Not Necessarily Better Than One, But They Look Great

If playing with but a single laser pointer is fun, then playing with 500 laser pointers must be 500 times the fun, right? So by extension, training 500 laser pointers on a single point must be the pinnacle of pointless mirth. And indeed it is.

When we first spotted this project, we thought for sure it was yet another case of lockdown-induced  boredom producing an over-the-top build. Mind you, we have no problem with that, but in this case, [nanoslavic] relates that this is actually a project from a few years back. It’s really as simple as it looks: 500 laser pointer modules arranged on a plate with a grid of holes in a 25 by 20 array. As he placed the laser modules on the board with a glob of hot glue, he carefully aimed each one to hit a single point about a meter and a half away.  There are also a handful of blue LEDs nestled into the array, because what project is complete without blue LEDs?

The modules are wired in concentric circuits and controlled by a simple bank of toggle switches. Alas, 500 converging 150-mW 5 mW lasers do not a 75-W 2.5 W laser make; when fully powered, the effect at the focal point is reported to be only a bit warm. But it looks incredible, especially through smoke. Throwing mirrors and lenses into the beam results in some interesting patterns, too.

You’ll still need to take safety seriously if you build something like this, of course, but this one is really just for show. If you’re really serious about doing some damage with lasers, check out the long list of inadvisable laser builds that [Styropyro] has accumulated — from a high-powered “lightsaber” to a 200-Watt laser bazooka.

(Terminate your beams carefully, folks. We don’t want anyone going blind.)

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