Variable Mirror Changes Shape Under Pressure

June 27, 2020 by Dan Maloney 10 Comments

Unless you’re in a carnival funhouse, mirrors are generally dead flat and kind of boring. Throw in some curves and things get interesting, especially when you can control the curve with a touch of your finger, as with this variable surface convex mirror.

The video below starts off with a long but useful review of conic constants and how planes transecting a cone can create circles, parabolas, or ellipses depending on the plane’s angle. As [Huygens Optics] explains, mirrors ground to each of these shapes have different properties, which makes it hard to build telescopes that work at astronomical and terrestrial distances. To make a mirror that works over a wide range of distances, [Huygens Optics] built a mirror from two pieces of glass bonded together to form a space between the front and rear surface. The front surface, ground to a spherical profile, can be deformed slightly by evacuating the plenum between the two surfaces with a syringe. Atmospheric pressure bends the thinner front surface slightly, changing the shape of the mirror.

[Huygens Optics] also built an interferometer to compare the variable mirror to a known spherical reference. The data from the interferometer was fed to a visualization package that produced maps of the surface shape, which you can easily see changing as the pressure inside the mirror changes. Alas, a deeper dive into the data showed the mirror to be less than perfect, but it’s fascinating to think that a mirror can flex enough to change from elliptical to almost parabolic with nothing more than a puff of air.

We’ve seen a couple of interesting efforts from [Huygens Optics] before, including this next-level spirit level. He’s not all about grinding glass, though — witness this investigation into discriminating metal detectors.

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Teardown Of Oddball Night Vision Shows Off Retro-futuristic Vibe

April 8, 2020 by Donald Papp 14 Comments

Night vision aficionado [Nicholas C] shared an interesting teardown of a Norwegian SIMRAD GN1 night vision device, and posted plenty of pictures, along with all kinds of background information about their construction, use, and mounting. [Nicholas] had been looking for a night vision device of this design for some time, and his delight in finding one is matched only by the number of pictures and detail he goes into when opening it up.

The GN1 rocks an irresistible retro-futuristic look.

What makes the SIMRAD GN1 an oddball is the fact that it doesn’t look very much like other, better known American night vision devices. Those tend to have more in common with binoculars than with the GN1’s “handheld camera” form factor. The GN1 has two eyepieces in the back and a single objective lens on the front, which is off-center and high up. The result is a seriously retrofuturistic look, which [Nicholas] can’t help but play to when showing off some photos.

[Nicholas] talks a lot about the build and tears it completely down to show off the internal optical layout necessary to pipe incoming light through the image intensifier and bend it around to both eyes. As is typical for military hardware like this, it has rugged design and every part has its function. (A tip: [Nicholas] sometimes refers to “blems”. A blem is short for blemish and refers to minor spots on optics that lead to visual imperfections without affecting function. Blemished optics and intensifier tubes are cheaper to obtain and more common on the secondary market.)

In wrapping up, [Nicholas] talks a bit about how a device like this is compatible with using sights on a firearm. In short, it’s difficult at best because there’s a clunky thing in between one’s eyeballs and the firearm’s sights, but it’s made somewhat easier by the fact that the GN1 can be mounted upside down without affecting how it works.

Night vision in general is pretty cool stuff and of course DIY projects abound, like the OpenScope project which leverages digital cameras and 3D printing, as well as doing it the high-voltage image intensifier tube way.

Fun With A 200-kW Fiber Laser

December 2, 2019 by Dan Maloney 23 Comments

We’ve all heard the “Do not stare into laser with remaining eye” joke. It’s funny because it’s true, as pretty much any laser a hobbyist can easily come by can cause permanent damage to eyes unless the proper precautions are taken. But a fiber laser with 200kW peak power is in another hazard class entirely.

Granted, outsized power ratings like this are a bit misleading, based as they are on femtosecond-long pulses. And to be sure, the fiber laser that [Marco Reps] tears down in the video below was as harmless as a kitten when he got it, thanks to its output optics having been unceremoniously shorn from the amplifier by its former owner. Reattaching the output and splicing the fiber would be necessary to get the laser lasing again, but [Marco] had other priorities in mind. He wanted to understand the operation of a fiber laser, but the tangle of fibers on two separate levels inside the chassis was somewhat inscrutable. The coils of fiber wrapped around the aluminum drums inside the chassis turned out to be the amplifier; fed by a semiconductor seed laser, the light pulse travels through the ytterbium-doped fiber of the two-stage amplifier, which is the active gain medium where stimulated emission, and therefore amplification, occurs.

With a little reverse engineering and the help of an online manual, he was able to understand the laser’s operation. A laser company helped him splice the optics back together – seeing the splicing rig in action is worth the price of admission alone – and the unit seems to be in more or less working order at this point. Normally the most powerful laser we see around here are the CO₂ lasers in those cheap Chinese laser cutters, so we’re looking forward to learning more about fiber lasers.

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Fast Fresnel Hack Embiggens The Smallest Of Heads

November 20, 2019 by Dan Maloney 17 Comments

Aside from frightening small children, we have absolutely no idea why anyone would need a face-magnifying headpiece. But the video below gives us a chuckle every time we see it, and we figure a good laugh that incorporates a quick optics hack is worth a look.

When he’s not playing geek in a box, [Curious Marc]’s videos usually have more of a retrocomputing theme, like his recent conversion of a vintage terminal to a character set from a made-up language, or helping to revive an Apollo Guidance Computer. Given gems like those, we were surprised to learn that [Marc]’s background is physics – optics, to be precise – and that he studied at École Polytechnique, the same school famed physicist Augustin-Jean Fresnel attended. Which fits right into this build since it features one of those large, plastic Fresnel lenses. After a fascinating detour into the history of Fresnel’s namesake lens, [Marc] proceeds with the build.

It’s simplicity itself – a box big enough to wear on the head with one end replaced by the Fresnel lens. A strip of LEDs – warm white, please, lest the wearer takes on a deathly pall – lines the edge of the box just behind the lens. If you want to get fancy, maybe attaching a hard-hat suspension piece would make it more wearable, but even as is it’s just a hoot to see someone with a magnified and distorted head walking around. One probably should be careful not to look at the sun while wearing this, however, for reasons that become apparent beginning at the 3:24 mark of the video.

Thanks to [Marc] for perhaps the oddest YouTube face-reveal yet, and for a great idea for a quick cosplay hack.

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Next Level Spirit Level Is On The Level

October 18, 2019 by Kristina Panos 10 Comments

Miss your shot and scratch on the eight ball? It’s natural to blame the table for not being level so you can save face, but in all likelihood, you’re probably right. [Huygens Optics]’s father never misses a billiards shot on his home table, until one day he did. [Huygens Optics] rushed to his aid and built an extremely precise spirit level for the table so it will never happen again.

First and foremost, he had to decide how sensitive the spirit level should be. Obviously, the table should be as level as possible, though other factors like the condition of the felt will come into play as well. In doing some calculations, he found that every degree of leveling error in the table translates to several millimeters of ball unevenness and deviation, so he wanted the level to have .01 degrees of accuracy. How he manages this feat of grinding and polishing in a hobbyist workshop is all captured in the fascinating video after the break.

The level is made from two disks cut from leftover 15mm borosilicate glass. Between the disks is a 4mm cavity for the liquid (ethyl alcohol) and the air bubble to move around. To avoid introducing error with uneven adhesive application, [Huygens Optics] tried to join the disks using optical contact bonding, wherein two surfaces stick together through the magic of intermolecular forces, like the one that keeps geckos attached to vertical things. That worked quite well until he added the liquid, which broke the bond. Instead, he used a thin, UV-curable epoxy.

Getting into optics doesn’t have to cost a lot. Instead of buying or grinding lenses for experimentation, you can laser-cut lens profiles out of acrylic.

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[Ben Krasnow] Looks Inside Film Camera Date Stamping

October 15, 2019 by Dan Maloney 6 Comments

Honestly, we never wondered how those old film cameras used to put the date stamp in the lower right-hand corner of the frame. Luckily, [Ben Krasnow] does not suffer from this deplorable lack of curiosity, and his video teardown of a date-stamping film camera back (embedded below) not only answers the question, but provides a useful lesson in value engineering.

For the likely fair fraction of the audience who has never taken a photo on film before, cheap 35-mm cameras were once a big thing. They were really all one had for family snapshots and the like unless you wanted to invest in single-lens reflex cameras and all the lenses and accessories. They were miles better than earlier cartridge cameras like the 110 or – shudder – Disc film, and the cameras started getting some neat electronic features too. One was the little red-orange date stamp, which from the color we – and [Ben] assumed was some sort of LED pressed up against the film, but it ends up being much cooler than that.

Digging into the back of an old camera, [Ben] found that there’s actually a tiny projector that uses a mirror to fold the optical path between the film and a grain-of-wheat incandescent bulb. An LCD filter sits in the optical path, but because it’s not exactly on the plane of the film, it actually has to project the image onto the film. The incandescent bulb acts as a point source and the mirror makes the optical path long enough that the date stamp image appears sharp on the film. It’s cheap, readily adapted to other cameras, and reliable.

Teardowns like this aren’t fodder for [Ben]’s usual video fare, which tends more toward homemade CT scanners and Apollo-grade electroluminescent displays, but this was informative and interesting, too.

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Alternative Photography Hack Chat

September 30, 2019 by Dan Maloney 3 Comments

Join us on Wednesday, October 2 at noon Pacific for the Alternative Photography Hack Chat with Pierre-Loup Martin!

It seems like the physics of silicon long ago replaced the chemistry of silver as the primary means of creating photographs, to the point where few of us even have film cameras anymore, and home darkrooms are a relic of the deep past. Nobody doubts that the ability to snap a quick photo or even to create a work of photographic genius with a tiny device that fits in your pocket is a wonder of the world, but still, digital photographs can lack some of the soul of film photography.

Recapturing the look of old school photography is a passion for a relatively small group of dedicated photographers, who ply their craft with equipment and chemistries that haven’t been in widespread use for a hundred years. The tools of this specialty trade are hard to come by commercially, so practitioners of alternate photographic processes are by definition hackers, making current equipment bend to the old ways. Pierre-Loup is one such artist, working with collodion plates, hacked large-format cameras, pinholes camera, and chemicals and processes galore – anything that lets him capture a unique image. His photographs are eerie, with analog imperfections that Photoshop would have a hard time creating.

Join us as Pierre-Loup takes us on a tour through the world of alternative photography. We’ll look at the different chemistries used in alternative photography, the reasons why anyone would want to try it, and the equipment needed to pull it off. Photography was always a hack, until it wasn’t; Pierre-Loup will show us how he’s trying to put some soul back into it.

Our Hack Chats are live community events in the Hackaday.io Hack Chat group messaging. This week we’ll be sitting down on Wednesday, October 2 at 12:00 PM Pacific time. If time zones have got you down, 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 Hackaday.io. You don’t have to wait until Wednesday; join whenever you want and you can see what the community is talking about.