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

2010-06-01

Wave length

The wave length λ (in nanometer - nm) defines the colour of light. The relation between colour of light and wave length is similar to the relation between intensity of light and amplitude. Therefore different colours of light do have different wave lengths. The human eye can perceive light with a wave length between about 400 nm and 700 nm.

"Lichtquellen, wie die Sonne oder die Glühlampe, senden ein Gemisch aller möglichen Wellenlängen, d. h. Farben aus. Ein derartiges Gemisch von Farben empfinden wir als weißes Licht. Aber selbst, wenn uns Licht einfarbig grün oder rot erscheint, wie etwa das Licht einer Verkehrsampel, enthält es normalerweise noch mehrere, wenn auch nur wenig unterschiedliche Wellenlängen."

[Light sources like the sun or a bulb emit a mixture of all kinds of wave lengths, i. e. colours. Such a mix of colours occurs to the human eye as white light. But even light occurs plain green or red - like light from a traffic light - it normally contains several (although few) different wave lengths.]

Fig. Partition of white light into different-coloured spectra by prism

As the first ever Newton carries out a test as shown in the figure above and publishes his observations in 1704 in his book about optics. About 200 years later physicists like Niels Bohr and Arnold Sommerfeld succeed in assigning different colours of light to different spectral lines with specific wave lengths.


Fig. Wave lengths of visible light

Therefore red light (650 nm, or 6.500 Å - Ångström) is long-wave light, while violet light (430 nm, or 4.300 Å) is short-wave light. Light with a wave length of more than 650 nm is called infra-red. Light with a wave length of less than 430 nm is called ultra-violet. Light of the helium-neon gas laser - which plays an important role later - has got a wave length of 623,8 nm and appears to the human eye as red light.

Every single lightwave illustrated in Fig. Wave lengths of visible light is monochromatic - consists of just one colour of light (respectively has got the same wave length). As coming entries will show, is "[...] monochromatic light [...] of basic importance in holography [...]".


Eingestellt von um

No comments:

Post a Comment

Subscribe to: Post Comments (Atom)

contact

Contact Form