In the Bollywood movie ‘Kick’ the hero, played by Salman Khan, is under tight surveillance of the police. To shake off the trail, he projects a holographic image of himself continuously pacing around the house. The police are totally deceived by the illusion, keeping a close watch on the hologram while the real hero carries out whatever admirable enterprise he has in mind.
Is this technology real? Can we create a convincing likeness of something? The answer is yes, holograms are real and as we will see, they might one day lead us to the key to the mystery of the universe.
What is a hologram? It’s like a photograph, but it is 3D and is entirely made up of light. When projected, it is so much like the original object that it even looks different from different angles.
The way holograms are created are somewhat similar to photography. They also require exposure of light on a photographic film, but making a hologram is more complex and more difficult than taking a photograph.
First, there is no lens to focus the light. Instead, the light falls directly on the film. But the most interesting part is the way light is used. The image that is captured by the film is actually a pattern created by mixing beams from two sources. Usually lasers are used for this purpose.
In your school books on physics, you must have read about ‘interference of light’. When light beams from two sources meet under certain conditions, they create a pattern called ‘interference pattern’. The pattern looks like concentric, alternate dark and bright circles. This weird effect from physics gives rise to holographs. Such is the close relationship between Bollywood and physics.
Now, every single point on the object being holographed makes one interference circle, so the film gets a strange looking pattern that is made up of innumerable such circles. When a hologram are displayed, light is passed through the film. On the other side, we see the original object in 3D, without a screen, in the empty space!
There is just one caveat, which makes the use of holograms as shown in the movie ‘Kick’ impossible. While a hologram is being made, everything has to be absolutely still. Even a small disturbance such as talking can disturb the interference pattern and make the hologram invalid. So the part about anxiously pacing around the house in the film is just that, filmy.
You must have seen holograms on your credit cards, but the are now being used for a whole lot of applications, including storing large amount of information. This area has seen a huge amount of interest from the research community as well as the technology industry.
