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Effect of the reference beam in speckle interferometry

: Maack, T.; Notni, G.; Kowarschik, R.


Optics communications 154 (1998), S.137-144
ISSN: 0030-4018
Fraunhofer IOF ()
autocorrelation; beam ration; frequency spectrum; reference beam; speckle interferometry; speckle width

We investigate the influence of the reference beam in speckle interferometry. An expression is derived in detail, which describes the spatial frequency spectrum of a speckle interferogram, i.e. a speckle field where a smooth reference beam is present. It turns out that the spectrum of a speckle interferogram can be trough of as consisting of various components, which can be attributed to the dc components of the reference beam and the speckle field and to the ac components of the speckle field and the interference between speckle field and reference beam. We particularly concentrate on an imaging geometry of a speckle interferometer. The spectrum of the interference is found to correspond to the intensity transmittance of lens pupil, whereas the spectrum of the speckle field is already known to be the autocorrelation. The portion caused by interference increases with reference intensity and, thus, is important when e.g., studying decorrelation of two speckle fields or modulation of the interference signal. Experimental verification of the results is given.