Sci-Fi novels and movies have always inspired scientists to expand their limit of imagination. We got the idea of submarines from Jules Verne’s “Twenty Thousand Leagues Under the Sea”. The inventor of the modern helicopter, Igor Sikorsky was inspired by another Verne’s book, “Clipper of the Clouds”. In the early 1970’s the design of the very first mobile phone by Motorola was influenced by the “Star Trek” communicator. There are several examples of such fictional prospects that have been brought to real experimentation. Recently, Daniel Smalley and his team from Brigham Young University has developed a new technique (published in nature on January 24) known as the volumetric display which can generate a 3D image to be viewed from any side or angle. The concept of inventing 3D image was inspired by the iconic Star Wars scene where R2:D2 projects Carrie Fisher‘s Princess Leia character in a holographic form.
Smalley’s invention is not a hologram because holographic display scatters light in 2D space and cannot be viewed without a proper angle. The holographic display is pretty much common in science fiction movies produced in Hollywood. Smalley further adds to his explanation that “The image of Princess Leia is not what people think it is: It’s not a hologram”, its a 3D image that floats in the air and practically you can walk all around observe the image from every angle, specified as the volumetric image. Examples of volumetric images include the 3D displays Tony Stark interacts with “Iron Man” or the massive image-projecting table in “Avatar.”
In this technique two sets of lasers are used – one traps and moves a particle around while other projects a color onto the particles. This works on the principle of photophoretic optical trapping. An optical trap is formed by tightly focusing a laser beam with an objective lens of a high numerical aperture that captures and suspends tiny dust particles in mid-air. The lenses actually create a hole of cold air within a circle of warmer illuminated air. When the particle approaches the margin of warmer air, it is repulsed back to the center. When it tries to move out, gets heated by warmer particles and again pushed back towards the colder particles. This controls the movement of the individual particles. The moving particles act as a screen for the second set of laser projectors which projects red, green and blue – onto the particle, illuminating it as it moves through space.
However, the work of this technique is still limited to smaller images. Because of the limited way human eyes can see images when the particles move faster than a rate of 10 per second, our eye perceives the projection as a solid line. This can be made to appear like it’s moving by changing the images even faster. Larger images can also be projected if they are still, or moving slowly.
The volumetric approach has many advantages over hologram technology. Hologram technology forms a 3D image by scattering of light from the 2D surface. Since holographic technology needs some wave interference between two lasers beams with a high degree of coherence in between them. The system must be kept very stable since even a very slight movement can destroy the image. Therefore, the images in hologram techniques are practically static. Whereas the volumetric display forms the 3D image that scatters from the 3D surface which can be viewed from any angle without using any other devices. It has also many applications in the medical field, for entertainment purpose, to improve technology and many more.
Smalley is quite confident that he will be able to address both these issues. “If we make as much progress in the next four years as we made in the last, I think we will be successful making a display of useful size,” he says.