160 — A photophoretic-trap volumetric display

This paper has been receiving a lot of attention because it’s insanely cool — the authors present an Optical Trap Display (OTD), a digital 3D projection display system that looks like something out of a science fiction movie.

There are many “holographic” systems both on the market and in research laboratories around the world. But these systems conventionally “clip” or “vignette.” In other words, the viewer must stand at a certain angle or at a certain position relative to the image in order for it to look like a 3D display. This is obviously not as supercool: Ideally, you could walk all the way around the display without suffering any loss to the image quality.

Other systems like tall sandtables (a display system that drips sandlike particles from a showerhead and projects light down onto it) have significant hardware constraints (and, again, you can’t view the display from above, since there’s a showerhead in the way). Plasma displays can’t project in full color; air or levitation displays don’t have the resolution required to provide an attractive display.

The OTD works by trapping a microscopic particle of cellulose in near-invisible light. These photophoretic traps are generated by projecting a beam of light at the particle and moving it slightly to affect (we think!) the local distribution of heat around the particle. The particle tends to move away from the hotter region and you can read more about that here.

Once the particle is trapped, it can be moved by adjusting the beam of light, in a process known as “literally magic.” By scanning this beam quickly in 3D, like rastering a grid of pixels on a CRT monitor, it’s possible to generate a volumetric display.

The OTD is able to change the color of a supplementary beam of light in the visible light range in order to affect the color of the particle at each point during its raster. This means that both the shape and the color of the projection can change in response to the OTD mechanism.

The display is still only a few centimeters in each dimension, but the authors demonstrate that this technology is scalable with improvements in technology. For example, trapping more than one particle at a time could reduce the speed (and thus inertial distortions) required of the display.

This paper is outrageously cool and the figures are even more fun. I highly recommend giving it a read even if just for the pictures. #THEFUTUREISNOW