Bidimensional noise reduction system for television

A bidimensional noise reduction system for processing a television video signal of recurrent fields of sequentially displaced parallel scanning lines of equal length, said system comprising a vertical dimension noise reduction subsystem including:

• (a) a system input;
• (b) delay and separation means connected to said system input for providing three outputs:
• a first output corresponding to said system input, a second output corresponding to said system input delayed by one time period of each said scanning lines, a third output corresponding to said system input delayed by two time periods of each of said scanning lines, said delay and separation means having an output;
• (c) first combiner-matrix means connected to said vertical delay and separation means for combining said first, second and third outputs in accordance with a predetermined formula to provide an output which is a function thereof;
• (d) first subtractor matrix means connected to said delay and separation means and to said first combiner matrix means for subtracting said output of said combiner matrix means from said second output of said delay and separation means and having an output being the difference therebetween;
• (e) first adjustable threshold coring circuit means connected to said output of said first subtractor matrix means for eliminating noise and other low level components of said difference output below a settable threshold level, and having an output,
• (f) second combiner matrix means connected to said outputs of said first combiner matrix means and said first coring circuit means for combining the signals therefrom, and having an output, and
• a horizontal dimension noise reduction subsystem including:
• (g) low pass filter means having an input connected to said output of said second combiner matrix means for passing low frequency components, and having an output,
• (h) delay means having an input connected to said output of said second combiner matrix means for providing a fixed delay equal to the transit delay through said low pass filter means, and having an output;
• (i) second subtractor matrix means having a minuend input connected to said output of said delay means and having a subtrahend input connected to said output of said low pass filter means, said second subtractor matrix means for subtracting its said subtrahend input from its said minuend input to provide as an output a difference signal in which low frequency components are removed;
• (j) second adjustable threshold coring circuit means connected to said output of said second subtractor matrix means for eliminating noise and other low level components of said difference signal below a settable threshold level, and having an output;
• (k) third combiner matrix means connected to said outputs of said low pass filter means and said second coring circuit means, said third combiner matrix means for providing a system output which is said video signal in which noise has been reduced by processing of both vertical and horizontal dimensions.

A bidimensional noise reduction system for a television video signal of recurrent fields of sequentially displaced, parallel scanning lines of equal length, said system comprising:

• a vertical dimension noise reduction subsystem including:
• (a) a system input for receiving said video signal with noise therein;
• (b) first delay means for providing a fixed delay equal to the time period of each said scanning line having an input connected to said input and having an output;
• (c) second delay means for providing a fixed delay equal to the time period of each said scanning line, having an input connected to the output of said first delay means, and having an output;
• (d) first adder means having three inputs:
• a first input V.sub.1 connected to said system input, a second input V.sub.2 connected to said output of said first delay means, and a third input V.sub.3 connected to said output of said second delay means, said adder means for adding said three inputs and having an output which is the function of:
• ##EQU5## (e) first subtractor means having a minuend input connected to said output of said first delay means and having a subtrahend input connected to said output of said first adder means, said first subtractor means for subtracting said subtrahend input from said minuend input, and having an output of the resulting difference,
• (f) first adjustable coring circuit means having an input for eliminating noise and other low level components of said difference below a settable threshold connected to said output of said subtractor means, and having an output;
• (g) second adder means having a first input connected to said output of said first adjustable coring circuit means and a second input connected to said output of said first adder means and having an output which corresponds to the said V.sub.2 second input of said first adder means for high level signal components and which corresponds to low level signal components to the function:
• ##EQU6## a horizontal dimension noise reduction subsystem including:
• (h) low pass filter means having an input connected to said output of said second adder means and having an output, said filter means for passing low frequency components of the signal output from said second adder means;
• (i) third delay means for providing a fixed delay equal to the transit delay through said low pass filter means, said third delay means having an input connected to said output of said second adder means and having an output;
• (j) second subtractor means having a minuend input connected to said output of said third delay means and having a subtrahend input connected to said output of said low pass filter means, said second subtractor means for subtracting said low pass filter output from said third delay means output to provide an output signal in which low frequency components are removed;
• (k) second adjustable coring circuit means for eliminating noise and other low level components of said output of said second subtractor means below a settable threshold, said second coring circuit means having an input connected to said output of said second subtractor means and having an output;
• (l) third adder means having a first input connected to said output of said low filter means, having a second input connected to said output of said second adjustable coring circuit means, and providing a system output of said video signal with noise therein reduced in both the vertical and horizontal dimensions.