1 
NIU 
  
     
JL 
sd V, 
2F ORTSRAUMFILTER 
AMPL I TUDE 
   
05+ 
  
  
  
  
  
10.00 185.00 i i i f 
01 0,2 93 FN 
  
Fig.12: One-dimensional Fourier transform and designed filter function 
Figure 12a) shows the power spectrum. There is no longer intensity loss at frequencies 
greater than 0.2 fn (f. = Nyquist frequency). In these frequency areas more noise than 
signals takes place. Outgoing from this analysis a low-pass filter function was designed 
(Figure 12b). which works in the space domain. Filtering in the frequency domain was tested 
too, but gave not essentially better results. 
  
  
  
2D TIEFPR 
  
Fig.13: Filtered ISSS-image with densitometric row-profile 
The filter result can be seen in Figure 13a), again shown with a densitometric profile 
of the same row. The image got blurred, but the profile demonstrates, that an automa- 
tic pattern detection now is possible with additional simple procedures (Ehlers and 
Kolouch, 1982).