Interferometry

Interferometry is a measuring method, which provides the physical effect of interference using an interferometer information about the object being measured.

Emanating from the measured object waves are superposed by the interferometer to an interferogram. Basically it can be with any kind of wave, be it produce light, sound, matter, or even water waves interference and therefore also operate interferometry.

One of the simplest interferometer is a simple converging lens. Coming from the object is directed by all points on the lens on the image point in the focal plane, and there brought to interference. Likewise, each telescope is an interferometer and the captured images whose interferograms. However, only complex measuring instruments are commonly referred to as an interferometer.

Astronomical interferometry

Great importance is the interferometry in astronomy. Here interferometric methods are used to increase the resolution of the observed objects, ie to obtain more detailed images. The resolving power of a telescope is - under ideal conditions - proportional to its diameter. By appropriately overlaying the signals of multiple telescopes object information can be obtained, corresponding to a resolution that corresponds to the largest distance between the telescopes involved.

Is a prerequisite for successful interference that the waves are superposed coherent. This means that the data coming from different parts of the interferometer interfering waves only when the paths ( run lengths ) are different by less than the coherence length. The coherence length depends on the wavelength and the spectral bandwidth (Filter bandwidth ) of the light used. For the visual V band results in a coherence length of three micrometers, for the near- infrared K-band shall be twelve microns.

It has long been working in radio astronomy with interferometric methods (see interferometer ( radio astronomy ) ). Unlike in optical astronomy is not forced here to superimpose the signals of the participating radio telescopes directly. In radio astronomy, can record the full wave information of each telescope in the form of amplitude and phase. This is not the correct time information has been recorded the signal with the signals of other telescopes can be made in a computer for interference. In this way, even radio telescopes on different continents can be connected together and thus provide high-resolution images (see Very Long Baseline Interferometry ).

Interferometric measurement method

• Speckle interferometry (see also: Speckle )
• White light interferometry
• Phase shift method
• Very Long Baseline Interferometry, interferometers (Radio Astronomy )
• Radar interferometry