New Holographic Display Hacks The Light Field

[Petapixel] has an interesting post about a startup company’s new holographic display that claims to be “indistinguishable from reality.” The company behind it, Light Field Labs, claims their system requires no glasses and handles different angles.

You can see a bit in the [C|Net] video below, but — of course — being on YouTube, you can’t get a sense for how good the 3D effect is.

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Projecting Moving Images In Air With Lasers

You’ve seen it a million times in science fiction movies and TV shows: a moving holographic display. From Princess Leia asking for help to virtual tennis on Total Recall, it is a common enough idea. [Dan Smalley]’s team at BYU has made progress in projecting moving 3D images in thin air. While they might not be movie quality, they are a start, and, after all, you have to start somewhere.

The display traps a small particle in the air with a laser beam and then moves that particle around, leaving behind an illuminated path in the air. You can see the effect in the video below. The full paper explains how a type of ray tracing allows the relatively small optical trap display to appear larger and more fluid. While it does make images seem to appear behind the display’s actual volume, it also requires eye tracking to work since the illusion only works from a certain perspective.

These are not, of course, technically holograms. That’s actually an advantage in some cases because holograms require a tremendous amount of data that increases rapidly as the size of a display scales up. The optical trap display uses a much more manageable data rate.

We’ve seen optical trap displays before. In fact, volumetric displays seem to be all the rage lately.

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A Different Kind Of 3D Printer: Desktop Holograms

Holograms aren’t new, but a desktop machine that spits them out could be available soon, presuming LitiHolo’s Kickstarter pans out. The machine will have a $1600 retail price and fits in a two-foot square. It can generate 4×5 inch holograms with 1mm hogels (the holo equivalent of a pixel).

The machine allows for 23 view zones per hogel and can create moving holograms with a few seconds of motion — like the famous kiss-blowing holograms.

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Hello, Holograms

Holograms are tricky to describe because science-fiction gives the name to any three-dimensional image. The science-fact versions are not as flashy, but they are still darn cool. Legitimate holograms are images stored on a photographic medium, and they retain a picture of the subject from certain angles. In other words, when [Justin Atkin] makes a hologram of a model building, (video, embedded below) you can see the east side of the belfry, but when you reorient, you see the west side, or the roof if you point down. Holography is different from stereoscopy, which shows you a 3D image using two cameras. With a stereoscopic image, you cannot tilt it and see a new part of the subject, so there is a niche for each method.

There are a couple of different methods for making a hologram at home. First, you probably want a DIY hologram kit since it will come with the exposure plate and a known-good light source. Far be it for us to tell you you can’t buy plates and a laser pointer to take the path less traveled. Next, you need something that will not move, so we’re afraid you cannot immortalize your rambunctious kitty. The last necessity is a stable platform since you will perform a long-exposure shot, and even breathing on the setup can ruin the image. Different colors come from the coherent light source, so getting the “Rainbow Holograms” advertised in the video is a matter of mixing lights. Since you can buy red, green, and blue laser pointers for a pittance, you can do color remixes to your content.

Another type of hologram appears on things like trading cards as those wildly off-color (chromatic, not distasteful) images of super-heroes or abstract shapes. They’re a different variety, which can be printed en-masse, unlike the one-off [Justin] shows us how to make.

If you’re yearning for volumetric displays, we are happy to point you to this beauty capable of showing a jaw-dropping 3D model or this full-color blocky duck.

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3D POV Display Has The Shakes

Persistence of vision projects are a dime a dozen, but by adding a third dimension [Madaeon] succesfully created one to stand out from the crowd. Instead of waving around a single line of LEDs, he is moving a 2D grid of them vertically to create a volumetric POV display.

The display consists of oscillating 3D printed piston, powered by a small geared motor, on top of which sits a 8 x 8 RGB LED grid and diffusing film. The motor drives a cylindrical cam, which moves a piston that sits over it, while an optical end stop detects the bottom of the piston’s travel to keep the timing correct. [Madaeon] has not added his code to the project page, but the 3D files for the mechanics are available. The current version creates a lot of vibration, but he plans to improve it by borrowing one of  [Karl Bugeja]’s ideas, and using flexible PCBs and magnets.

He also links another very cool volumetric display that he constructed a few years ago. It works by projecting images from a small DLP projector onto an oscillating piece of fabric, to created some surprisingly high definition images.

POV displays are good projects for learning, so if you want to build your own, take a look a simple POV business card, or this well-documented POV spinning top.

Latest FlexLED Milestone Refines The POV Display

With his FlexLED project, [Carl Bugeja] is trying to perfect a simple and affordable persistence of vision (POV) display capable of generating “holographic” characters in mid-air. Traditionally POV systems spin LEDs rapidly to create the desired illusion, but that means motors, slip rings, and noise. As the name implies, the goal with this project is to do away with all that and replace it with a self-actuating flexible PCB.

The device is able to quickly move the LEDs back and forth quietly and efficiently thanks to a permanent magnet and magnetic coils integrated into the flexible PCB. With no motors or gears, the whole unit is smaller and less complex than other POV displays. As an added bonus, there’s no danger to the operator or the device should a curious user stick their finger into it.

The last time we took a look at this project, [Carl] had entered an earlier single-LED version into the 2019 Hackaday Prize. Competition was tough last year, and unfortunately FlexLED didn’t get selected as a Finalist. But we’re still extremely interested in seeing the project develop, and we imagine so are you.

The recently completed second version of the display features an improved coil design, eight RGB LEDs and a 3D printed base with integrated magnet. With more LEDs onboard, a single display is able to show multiple characters and even rudimentary animations. A large array of these flapping elements promises to be quite a sight.

But before you get too excited, [Carl] does have some bad news. For one, the cost of building them in small quantities is high, which is always tough for a single hacker trying to iterate a design. Worse, some of the LEDs seem to have died on this prototype already. He says it likely has something to do with the stress of flexing back and forth so quickly, which is obviously a bit troubling. He’s looking to get some feedback from the community, and is hoping to address these issues in the next version.

For an interesting look into his flexible PCB actuator projects, check out the interview [Carl] did with us at the 2018 Hackaday Superconference.

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Giant LEDs, Ruby Lasers, Hologram Displays, And Other Cool Stuff Seen At Maker Faire Rome

Hackers from all over Europe descended upon Rome last weekend for the Maker Faire that calls itself the “European Edition”. This three-day event is one of the largest Maker Faires in the world — they had 27,000 school students from all over Italy and Europe attend on Friday alone.

This was held at Fiera Roma, a gigantic conference complex two train stops south of the Rome airport — kind of in the middle of nowhere. I was told anecdotally that this is the largest event the complex hosts but have no data to back up that claim. One thing’s for certain, three days just wasn’t enough for me to enjoy everything at the show. There was a huge concentration of really talented hardware hackers on hand, many who you’ll recognize as creators of awesome projects regularly seen around Hackaday.

Here’s a whirlwind tour of some of my favorites. On that list are a POV holographic display, giant cast-resin LEDs, an optical-pump ruby laser built out of parts from AliExpress, blinky goodness in cube-form, and the Italian audience’s appreciation for science lectures (in this case space-related). Let’s take a look.

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