A bright-green laser flashes on, shining into a petri dish full of goo. From nowhere, the shape of a paper clip emerges—ghostly at first, then solid. Five seconds later the clip is fished out, cleaned up, and ready for use.
The basic principle here is an established 3-D-printing technique that uses lasers to cure a light-activated monomer into solid plastic. But unlike other approaches, which scan a laser back and forth to create shapes one layer at a time, this system does it all at once using a 3-D light field—in other words, a hologram. It could make 3-D printing far faster.
At the heart of the device that printed the paper clip is a holographic chip developed by Daqri, a startup that designs and builds augmented-reality devices out of laboratories in San Francisco and in Milton Keynes, U.K. The company makes smart glasses similar to Microsoft’s HoloLens and head-up displays for cars; the latter have been fitted to over 150,000 vehicles made by Jaguar Land Rover.
The advantage of Daqri’s chip, the company says, is that it can create holograms without the need for complex optics. On a silicon wafer, a tiny grid of tunable crystals is used to control the magnitude and time delay, or phase, of reflected light shined at the surface of the chip from a laser. Software adjusts the crystals to create patterns of interference in the light, resulting in a three-dimensional light field.
In experiments, the team has used the chip to create solid objects by projecting holograms into containers of various light-activated monomers. It can currently make small objects, such as a paper clip, in about five seconds—a process that could take a normal 3-D printer several minutes.
Seamus Blackley, Daqri’s principal scientist, says that because the entire form is created in one go, the resulting product doesn’t suffer from weaknesses introduced by the “grain” that forms when an object is 3-D-printed by scanning a laser back and forth. Supporting structures that are required when building objects layer by layer are also unnecessary, he says, and larger objects should take about the same amount of time to print as smaller ones.
There are some limitations. The current hardware only creates shallow forms, for example, such as the paper clip in the video. But the depth should increase with the size of the holographic chip that’s used, and the company is planning to scale up the device accordingly.
Dávid Lakatos, head of product at the 3-D-printing company Formlabs, says that heat could be an issue as well. “Polymerization is an exothermic process,” he says, referring to the process by which the light-activated liquid cures into a solid. “Printing something faster means that there’s a lot of energy from the reaction that gets released.” That might cause parts of a larger object to melt.
Nevertheless, Daqri’s chip has other interesting applications, too. While the company already builds augmented-reality devices, it plans to use its holographic chip to create displays with multiple planes of information. Currently, it has a prototype head-up display that can render one image on a windshield and one many meters ahead, at a resolution equivalent to a 720p HD screen, in real time.
But making displays that create truly 3-D, rather than planar, content is computationally intensive. “If you want to create a 1,000-by-1,000-pixel image, that’s one million points,” explains Daping Chu from the Centre for Advanced Photonics and Electronics at the University of Cambridge. “If you want a 3-D image with the same resolution, [that is] is one billion points. In principle it’s the same problem. But in reality … you don’t have enough hardware capability.”
For now, Daqri is already pushing up against the limits of available processing power with its two-plane devices. But as computational power increases, the company is optimistic that displaying 3-D images in real time will soon be possible.
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