Method and apparatus for filtering signals

DETAILED DESCRIPTION An object of the present invention is to improve a method of the type initially cited such that a qualitatively high-grade filtering of signals with a low signal-to-noise ratio is enabled.
The alone object is inventively achieved in that signal parts having an amplitude below a prescribable threshold are eliminated for filtering the signal after a band-pass filtering, isolated signal parts are subsequently eliminated within the reference plane, and a signal reconstruction is subsequently implemented by interpolation for coordinates of the reference plane at which the signal amplitude of the filtered signal part is essentially equal to zero.
A further object of the present invention is to improve an apparatus of the type initially cited such that it is suitable for the implementation of the method of the invention.
This object is inventively achieved in that the frequency-dependent filter is designed as a band-pass filter which is followed by a threshold filter that is connected in series with a selector that eliminates isolated signal amplitudes and with an interpolator that reconstructs signal curves.
The assistance of the method of the invention and of the apparatus of the invention make it possible an improvement of the image sharpness and to simultaneously compensate an aperture loss that has arisen due to a sampling.
The method essentially works as a non-linear aperture correction which reconstructs the image sharpness in the detail signal and implements a reduction of noise parts at the same time.
There is a high probability that significant noise parts are initially removed due to the signal parts having an amplitude below a prescribable threshold being filtered out.
The subsequent, selective extinction of picture elements also makes it possible to eliminate noise signals having an extremely high amplitude.
Useful signal parts with low amplitude that may be potentially eliminated can be reconstructed with high reliability by the interpolation due to the charging with the threshold characteristic line