Holography is considered as one of the most remarkable discoveries in modern times. Nevertheless for its first decades it seems to be getting forgotten.

Originally stepped up back at the end of the 1940s to improve electron microscopy, it can not fulfill this function and the wish of its discoverer hungarian-british physicist Dennis Gábor. Due to sources of pure coherent light, which are indispensable for optical holography, being not yet available, not even Gábor himself can locate a field of application for this phenomenon. He can neither recognize at that point of time the meaning and the potential of his discovery and with it the influence this new medium would have on our daily lives one day. Nor can he imagine the plenty of phantasms emerging from this phenomenen. Phantasms, which seem to be mostly one step ahead of applied holography.

With the discovery of laser light at the beginning of the 1960s, for the first time ever it becomes possible to record and reconstruct a real three-dimensional image of an object. What once simply starts as a little rainbow coloured picture of a toy train, today finds its applications in a vast variety of different optical and acoustical fields.

It is as remarkable as the phenomenon of holography itself, that it could never prevail as a popular medium like movie, TV, radio, the internet, print media, etc. Especially when keeping in mind all the phantasmatic stories which emerge from this medium. A lot of dreams, hopes and promises that holography never made by itself, but some of them is trying to keep.

blog.holographie.eu accompanies my scientific work on holography, which would like to give holography an attention, that elsewhere is mostly refused to it. It is of course initially interested in based techniques and technologies of holography and how it works. Moreover it is also interested in these upcoming phantasms and their stories arising from possible abilities of holography. Especially against the backdrop of holography seems to be reaching a point, where its possibilities and abilities catch phantasms.

This blog would like to serve as a sketch book for unprotected ideas, of which some maybe become expanded, while others are not haunted any further, but wants to be told and should not be unmentioned forgotten.


please visit also www.holographie.eu

2010-06-06

Laser

The term LASER is an acronym for Light amplification by Stimulated Emission of Radiation and describes a physical principle of optical amplification; not the device itself, even the term commonly has to serve as a description for the device.

There is a whole bunch of different lasers: gas laser, solid-state laser, dye laser, semiconductor laser, excimer laser, lasers for every visible colour of light, for ultra-viloet and infra-red light, laser for continuos operation and impulse laser (generates short light impulses, like flashlight). Even not each of the lasers is suitable for making holograms, they all have one thing in common: they generate coherent light, with radiation, behaving as going out from one single point. Vice versa the light rays can be concentrated back to one single point.

In holography usually Helium-Neon gas lasers (He-Ne) are used. The are quite cheap and easy to use. Its mechanics should be should be explained here.
He-Ne lasers consist of a glass tube, which is filled with a mixture of Helium and Neon under low pressure. The tube is sealed. On both transparent ends is a mirror attached. One reflecting light 100% and one reflecting light 98%. First the Helium atoms gets stimulated by energy input. They bump into the Neon atoms. Thereby they get transferred into a higher energy state. When falling back into their previous energy state, they set photons free. These photons stimulate surrounding atoms, and so forth. The emerged light begins to move between the two mirrors back and forth. For the two mirrors are fitted exactly many times over the wave length off each other, the amplitudes adds form wave to wave and amplifies. Finally light becomes so bright, that it passes out as coherent light the laser on that side with 98% reflecting mirror.


Fig. Gas laser

Gasentladungsröhre: Glass tube
Spiegel: Mirror
halbdurchlässiger Spiegel: transparent Mirror
Spannungsquelle: voltage source
Laserlichtbündel: bunch of laser light


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