Noise reduction circuit for a video signal

Claim 1

A noise reduction circuit comprising: lowpass filter means supplied with an input luminace signal having a noise component of an input video signal, said lowpass filter means having a characteristic which eliminates a high-frequency component including said noise component; delay means for delaying said input luminance signal by a predetermined time period τ so that an output signal of said delay means has a leading edge which occurs after said predetermined time period τ, said time period beginning at the start of a rise in an output signal of said lowpass filter means, said predetermined time period τ being equal to a rise time of the output signal of said lowpass filter means; first subtraction means comprising a first adder means which is directly supplied with the output signals of said delay means and is supplied with the output signal of said lowpass filter means via a first phase inverting means for subtracting the output signal of said lowpass filter means from the output signal of said delay means; limiter means for amplitude-limiting an output signal of said first subtraction means; and second subtraction means comprising a second adder means which is directly supplied with the output signal of said delay means and is supplied with the output signal of said limiter via a second phase inverting means for subtracting an output signal of said limiter means from the output signal of said delay means to produce a luminance signal from which said noise component has been substantially eliminated.