Spray Diagnostics & Advanced Imaging
Two-phase SI (right column) generates residual lines (2ν) with a spatial frequency twice that of the ground-frequency. Thus, by increasing the ground-frequency, 1st, of the subimages (left column) the residuals become less apparent and eventually, they reside at border of the observable region were they are nearly indistinguishable.
FT = Fourier transform.
Example of a two-pulse (2P) SI image, in which the ground-frequency is ν = 0.50, thus generating residuals exactly at
resolution limit. These unwanted fringes are easily removed by means of a low-pass filter (LPF), which, because of the carefully chosen ground-frequency, hardly affects the image quality. fc = cut-off frequency.