B4.2 - Study on preprocessing in array detector based optical spatial filtering velocimetry

AMA Conferences 2017
2017-05-30 - 2017-06-01
Nürnberg, Germany
Proceedings Sensor 2017
B4 - Optical Measurement of Geometrical Quantities
M. Schaeper, N. Damaschke, R. Kostbade - Universität Rostock (Germany)
222 - 226


Spatial filtering velocimetry (SFV) is a technique for optical velocity measurements. In applications the image information of an observed scene is captured by a pixel-based array detector. The pixels’ gray scale values are multiplied by a predefined grating function. By integrating over the weighted image information a signal point of the spatial filtering signal is generated for each frame. The spatial filtering signal is generated out of a sequence of images. The frequency of this alternating
signal is proportional to the velocity of the observed scene. The paper presents a Fourier-based description of spatial filtering velocimetry, which shows the relation to other displacement measurement techniques like cross correlation or auto correlation
methods used in particle image velocimetry (PIV). The spatial filtering signal can be interpreted as a single temporal changing Fourier coefficient. The spatial filtering signal is disturbed by phase jumps. They occur, when the statistical spectral content of the observed scene is temporal changing. The fluctuations of the amplitude and the signal’s phase have a negative impact on the frequency estimation. Our approach is a specific preprocessing of the intensity distribution of the array detector to optimize the spatial filtering signal. Here the incoming and outgoing patterns of the image information are suppressed. So the spectral content is sectional stabilized and the timestamps of spectral changes are known.