Optical image sequence analysis and interpretation of stationary and instationary wave fields

The spatio-temporal distribution and evolution of wave fields is measured by the acquisition of optical video image sequences. As one possible application of the optical image sequence acquisition system an experiment at the wind wave flume of the University of Hamburg has been performed to measure small scale processes at the water surface. From the image sequences image spectra are calculated by a three dimensional fast Fourier transformation (3D FFT). The spectral description by the 3D FFT is limited to stationary wave fields and therefore spectrograms of the wave field are presented which allow to describe instationary/inhomogeneous processes.