Phasenmeßfehler und Optimierung eines phasenschiebenden Speckleinterferometers bei Verwendung eines Photosensor-Arrays mit begrenzter Dynamik und ausgedehnten Elementen

If compared to classical interferometers, speckle interferometer exhibit two particular kinds of error sources. In addition to the phase decorrelation of the individual phases, extreme errors can be inflicted while they are calculated. This is caused by the broad- band distribution of the intensities in a speckle field in conjunction with the limited dynamics of a camera, consisting of a saturable photo-detector array and an A/D converter. If the elements of the array are of finite extent, the intensity distribution and the contrast of intensity modulation become altered. The standard variation of the phase difference is found to be as small little as 10.6 mrad when an experimental setup is considered, using either of the common 4-frame or 5-frame algorithms with phase shifts of 90-degrees and an 8-bit digitization depth. Then the beam ratio is 4.0, the mean speckle intenstiy is 1/1 1 of the saturation intensity and the space-bandwidth product of the system of imaging lens plus photo-d etector array is 0.31. The measurement error of the phase difference is derived from that of the individual phases and of the phase decorrelation. The results are confirmed by computer simulation.