The image immediately registered by the RASCAN radars is not exactly an image that describes actual distribution of reflectors in the space behind the sounding plane. What radar registers is an interference pattern created by these reflectors that is also called a hologram. For a distant object its interference pattern has a form of ripples due to diffraction. The diffraction effects, being stronger for a more distant object than for a closer one, may prevent a concealed object from identification.

To compensate for diffraction effects RASCAN-5 software provides a focusing procedure that can be relied on when sounding relatively homogeneous media.

Some results of focusing are shown below.






Area under test


Manual scanning from the opposite side

 







Hologram (3.9 GHz)


Focusing at 10 cm — metal bar


Focusing at 20 cm — metal ruler



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