Noise reduction circuit for video signal

A noise reduction circuit for video signal comprising:

• first circuit means supplied with an input video signal including a noise component, said first circuit means comprising a first filter circuit for obtaining from said input video signal a high frequency component including the noise component and a first limiter for limiting large amplitude parts of an output signal of the first filter circuit, said first filter circuit having a first impulse response characteristic;
• second circuit means supplied with said input video signal, said second circuit means comprising a second filter circuit for obtaining from said input video signal a high frequency component including the noise component and a second limiter for limiting large amplitude parts of an output signal of the second filter circuit, said second filter circuit having a second impulse response characteristic wherein an amplitude increases or decays with time, said second impulse response characteristic being complementary to said first impulse response characteristic;
• third circuit means supplied with said input video signal, said third circuit means comprising a third filter circuit for obtaining from said input video signal a high frequency component including the noise component and a third limiter for limiting large amplitude parts of an output signal of the third filter circuit, said third filter circuit having a third impulse response characteristic wherein an amplitude increases with time and thereafter decays with time, said third impulse response characteristic being essentially a combination of said first and second impulse response characteristics, said first through third limiters having identical threshold levels;
• and
• fourth circuit means supplied with said input video signal and output signals of said first through third circuit means for carrying out a subtraction between said input video signal and the output signal of said first circuit means so as to obtain a first signal which is substantially eliminated of the noise component except for a noise component and distortion remaining at parts in vicinities of rises and falls in the video signal caused by said first limiter, carrying out a subtraction between the output signals of the second and third circuit means so as to obtain a second signal which includes the noise component and the waveform distortion of said first signal with an inverted phase, and for adding said first and second signals so as to produce an output video signal which has been substantially eliminated of all the noise component.