Photoswitch Molecules Bring 3D Structured Light to Life

I never get tired of 3D movies; from Sing to Planet of the Apes, I still gasp when objects fly out at me and enjoy the sensation of watching a lone figure moving through what appears to be the depth of a 3D stage. However, the sensation of 3D in movies is just that, a sensation. We all recognize that there is nothing actually 3D about the movie; instead, the viewers are wearing special polarized glasses that feed a different image to each eye which the brain then reconstructs as depth of field. Take the glasses off and you are just watching a slightly blurry movie.

The dream of creating fully 3D objects using light is also not realized in holograms, another trick that plays with perception in order to create the impression of depth, but really projecting figures that only have height and width. However, thanks to work being done by The Lippert Research Group at Southern Methodist University in Dallas, TX, the possibility of shaping light into animated 3D objects has been advanced greatly, as detailed in an article recently published in the journal Nature Communications.

The Lippert Research Group is headed by Assistant Professor of Chemistry Alexander Lippert and their research details a method for utilizing a molecule known as the photoswitch molecule, which can change from fluorescent to a non-fluorescent state in relation to exposure to ultraviolet light. Controlled exposure yields a cluster of molecules that can be created in any shape and that make up a 3D image. As Lippert described:

“When you see a 3D movie, for example, it is tricking your brain to see 3D by presenting two different images to each eye. Our display is not tricking your brain – we have used chemistry to structure light in three actual dimensions, so no tricks, just a real three-dimensional light structure. We call it a 3D digital light photoactivatable dye display, or 3D Light pad for short, and it is much more like what we see in real life.”

The ability to control the the light emissions so that the change between states, fluorescent or clear, could occur rapidly was an advance contributed by Jian Cao, an SMU Chemistry grad student, and was a key component in unlocking the power these molecules have to create these 3D structures, as he explained:

“The chemical innovation was our discovery that by adding one drop of triethylamine, we could tune the rate of thermal fading so that it instantly goes from a pink solution to a clear solution. Without a base, the activation with UV light takes minutes to hours to fade back and turn off, which is a problem if you are trying to make an image. We wanted the rate of reaction with UV light to be very fast, making it switch on. We also wanted the off-rate to be very fast so the image does not bleed.”

In order to create this structured light, group members first created an 50 mm cubed quartz glass imaging chamber that would both contain the photoswitch and serve to capture light. Patterns were projected into this chamber by using a regular Digital Light Processing Projector and the light itself was structured in two dimensions. On the opposite side a series of UV light bars were projected and where the two types of light met, a display of two-dimensional squares stacked across the chamber was created. The light was then patterned in both directions and the first 3D image was created.

The resolution of the image created is measured in voxels, the 3D equivalent of the pixel. The light pad the team is currently running is capable of generating over 183,000 voxels, with the idea being that as the pad is scaled up in size, the voxels will increase as well. This means that incredibly high resolution 3D animations can be created in a way never before seen.

This might remind you of the projection of Princess Leia in Star Wars or the idea behind the holodeck in Star Trek: The Next Generation, and this would come as no surprise to Lippert who found himself fascinated with both of these phenomena since his childhood.

“As a kid, I kept trying to think of a way to invent this. Then once I got a background in chemistry molecules that interact with light, and an understanding of photoswitches, it finally dawned on me that I could take two beams of light and use chemistry to manipulate the emission of light.”

The fact is that while the capacity to project an entire reality is not yet present with the light pad, it is not far-fetched to make the leap from the current capacity to some of its possible applications. Imagine that when participating in a conference call, rather than watching the other people on a video screen, they could be projected in real time into the room. Or a couple in a long distance relationship being able to sit down to dinner with each other’s projections. There are also medical and military applications, the kind of possibilities that are able to garner the funding necessary to continue to advance these kinds of projects. As Lippert so succinctly put it: “The sky’s the limit.”

There are still aspects requiring attention, for example, mechanisms for rendering the 3D light structure in true color. In addition, the team is working on how to create a solid cube table display using optical polymers rather than the current liquid vat required for operation. These potential adjustments are no longer the stuff of science fiction, but an up and coming part of the array of technologies potentially available for widespread use. Discuss in the 3D Light forum at 3DPB.com.

[Source: Novus Light Technologies Today]