Monday, October 3, 2011


Holography has been a technology that has fascinated people for many years. It has featured in movies, books, comics, cartoons.. it’s like a technology that’s just got to be!

Bad hair day..

A hologram is a recording of the interference between light reflected from an object and a pristine reference beam. If later you illuminate the recording with a beam similar to the reference beam, it re-interferes and re-creates the appearance of the original object. The benefit of a hologram compared to a 2D picture is that you can look at the object from different angles and the object retains depth information.

Recording a Hologram. Figure from Wikipedia.
Film or photographic emulsions are common media for recording simple holograms. Lately much progress has been made in Digital Holography where the film is replaced by a sensor like a CCD. This allows us to reconstruct the hologram entirely digitally, without illuminating it with an actual beam of light.

Computer Generated Holography is when you digitally create a hologram of an object; there’s no reference beam illumination, no actual interference of light. That makes it possible to create holograms of completely unreal objects.

The most basic holography (shown in the figure above) is done with coherent laser light. But it is also possible to do holography with white, incoherent light. For instance, techniques like Scanning Incoherent Holography and FINCH (Fresnel incoherent digital holography) give incoherent light holograms. It is also possible to capture multiple images of the object from different angles using a normal digital camera, no reference beam, no interference and then digitally generate a hologram from a combination of those views.

There seem to be several good sessions on holography at Frontiers in Optics this year on Tuesday and Wednesday morning - FTuF, FWJ. They have some of the best speakers giving invited talks on this topic. There is also quite a bit of recent research in holographic microscopy, computer generated holography, synthetic aperture digital holography that I can see in the sessions. Surely worth a dekko!!

Cheers and thanks for stopping by!

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