Holograms

Wednesday April 6, 2005 - 1:45AM EDT

In the car driving tonight I was thinking about holography and it finally clicked. I now have an intuitive understanding of holography that I lacked before. I had read a few books on it (read 1 fully and skimmed though 2 or 3 others) a few years ago but didn't grasp the basic priciples fully. Now I get it, and it is awesome. It is almost too simple. The actual formulas and equations used to do precise calculations involved with holography may be difficult but the concept of what actually goes on is quite simple. And I understand why coherrent light is needed to make better holograms. I'll need to do more studying to confirm my understanding but having a grasp of the basic priciple without equations makes it much easier. I want to explore what type of experiments have been done with holography and what has been examined already. I remember reading a while back about realtime holography using sound waves and crystals. It was a pretty clever setup. One of the issues with creating quality holographs is that you need coherent light(light that is in phase and in step). Coherent light comes from lasers and so far laser light available in the visible light specture are common (red, blue, green). Red being the most common and easily made and the other colors being less common and more difficult to work with and for the average person to get their hands on(very expensive). Also there is the issue of the speed of light varying when different wavelength of light travel through a medium due to refraction. It makes it hard, but not impossible, to create full color holograms. One interesting thing I read about was using LCD screens to generate interference patterns and three different color lasers to generation full color full motion holograms. The would theoretically make it possible to create a hologram of anything without actually having to ever use the original object. I don't know what the status of such work is, but it would be very interesting. I'm not sure what type of calculations would be required to create holograms like that on the fly but they are probably exceedingly difficult to come up with, and probably no one has done it yet. But I firmly believe it is possible. Another interesting thing with holography is the lasers thing. Since you need coherrent light to create good holograms lasers are the only reliable source. But with coherent light the wavelength is in a very narrow part of the spectrum, making full color difficult, as I stated before. Something that they have tried for years to make is the X-ray laser. I hear the first once will be completed in 2009. X-Ray lasers are interesting because coherent x-rays can make holograms of tiny structures. One could, in full 3D, view the structure of cells, chemicals and many other nanoscale things. Maybe even eventualy lead to nanoconstruction by engineers using realtime x-ray holograms to build tiny devices. There are probably a lot of issues surrounding x-ray holography for everyday biological purposes but with more research it may be feasible. Right now the intensity of an x-ray laser will probably instantly kill you, lasers work by exciting electrons until they jump to the next energy level then releasing energy in the form of light(coherent light) when the drop back down.