Reducing phase singularities in speckle interferometry
Sensors, Devices and Components : Devices
Much more sophisticated unwrapping algorithms than the one used in Figure 1 have been developed, trying to deal with the huge number of phase singularities. Nevertheless, it is highly preferable to reduce the number of phase singularities appearing in the raw phase in the first place. This should be done by a physical mechanism, and not by software.
To this end, a physical averaging of many independent speckle fields has been realized, each giving the same deformation phase, while their combination leads to a much reduced number of phase singularities in the resulting raw phase.
Figure 2 shows the raw and the unwrapped phase for a similar deformation after the physical averaging was applied. Comparing with Figure 1, the raw phase now looks much cleaner and less noisy. Apart from a few, small regions, the unwrapped phase has been correctly unwrapped even by the unsophisticated, standard algorithm used.
- Speckle interferometry is routinely used to determine shape and deformations of rough objects
- The evaluation process is however impaired by the presence of phase singularities
- Here, a physical averaging mechanism is applied to reduce the number of phase singularities in the raw phase
- The resulting, averaged raw phase can then be unwrapped even with standard algortihms
German patent has been filed on 02.08.2016
- Ref.-No.: 1629-5142-WT (602.0 KiB)
PD Dr. Wolfgang Tröger
Phone: +49 89 / 29 09 19-27