Spanish researchers have just presented an impressive proof of concept: they designed the very first holographic display system that can be touched and manipulated.
Holograms are a great science fiction classic, where they often serve as a fashion of communication or control system. But at present, these three -dimensional floating images are still quite distant from what is found in works like Star Wars.
Complex technology
What is called light is in fact a particular form of electromagnetic wave. This wave is propagated by following very specific patterns, which depend in particular on the form and texture of the object on which it bounces. These reasons are represented in what is called the front d’ondea surface that represents the points where the light has the same phase at a given moment. In practice, creating a hologram therefore amounts to recreating the front of a luminous wave having “touched” an object.
To save it, we use a second reference light wave which, when it meets the wave from the object, generates interference. These can then be used as an indirect representation of the object; From there, by combining several lasers in a very specific way thanks to different mathematical models, we can reconstruct the original wave front, so that our eyes perceive it as a reconstruction of the object in three dimensions.
The concern is that this technique requires capturing the reasons for interference with an extremely high resolution, which is difficult to perform in practice. Most of the real holograms are therefore small, and confined to research laboratories that have advanced optical equipment.
And the complexity of the problem further increases in an exponential way when it comes to interacting with these holograms. To hope to manipulate them, you have to design an even more elaborate optical system. It must also be supported by a computer powerful enough to resolve many complex equations in real time, such as the famous Fourier transformations. This explains why the rare commercial holographic spotlights like those of Voxon or Brightvox, which even if they are very impressive, are limited to holograms relatively smallto the rather low resolutionet non-interactive.
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The first interactive holograms
This is where the authors of this new study come in. They have designed a pseudo-holographic system which does not make it possible to reveal an image in the middle of an empty space, but which still offers the possibility of manipulating it in real time.
To build this system, the researchers recycled the concept of volumetric diffuser. This term designates a system which is based on retinal persistence – the phenomenon because of which the images put approximately 1/18 of a second to disappear after being projected on the retina. This persistence can be used by projecting an image on an surface that oscillates very quickly. There are many “layers” of different lights, which the brain interprets as a complete 3D representation of the object.
The problem is that such diffusers are generally rigid. It is therefore impossible to interact with the image; Introduce a finger into the space where it appears would block the diffuser, preventing the three -dimensional image of forming. The team therefore designed an extremely fine and above all elastic diffuser, which deforms instead of stopping or breaking when it meets another object.
The difficulty is that this approach radically changes the way of approaching the projection of the image. Since the surface deforms, it is also necessary to adjust this projection in real time so that it remains consistent with the surface of the diffuser. It was this step that requested the most work from the researchers, who had to model the behavior of the surface with great precision to correct the final image. But these efforts paid for: at the end of the process, they obtained the First interactive volumetric diffuser in the worldwhich allows for example to rotate the representation of the object by pinching it.
Real concrete applications
Admittedly, the system remains rather raw of formwork – it must be admitted that the result is quite far from what is generally described as a hologram. But it is nevertheless a very interesting first step which, once refined, could still have a concrete interest – even in its current form.
The authors propose, for example, to use it for education. An apprentice mechanic could use it to view the assembly of an engine, while a surgery student could directly handle an anatomical representation of a patient. The team also quotes museums, where this kind of device could offer visitors a new way of observing objects that are too precious to be exposed in the open air.
While waiting for real free and interactive holograms to appear, it will be interesting to see if this technology succeeds in being a small place in one of these areas.
The text of the study in prepublication is available here.
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