| 摘要 |
PURPOSE:To lower the quantity of noise remaining in a part of video signals after removing noise by raising cut-off frequency of a high-pass filter that extracts high frequency component on which noise component gets in from video signals in a period in which amplitude of high frequency component is above a specified value. CONSTITUTION:The switch SW of a high-pass filter 1 is opened, and cut-off frequency becomes fc1 =1/omegaR1C1. Accordingly, input video signals 100 are inputted to the filter 1 and high frequency component higher than cut-off frequency fc1 is extracted. An amplitude detecting circuit 7 closes the switch SW when the amplitude of high frequency component extracted from the filter became higher than amplitude of noise component. Under this condition, cut-off frequency of the filter 1 becomes fc2, and becomes fc1<fc2. When amplitude of high frequency component becomes smaller than amplitude of noise component on it, an amplitude detecting circuit 6 opens the switch SW. Accordingly, the part where amplitude level of differential waveform of input video signals 100 is large becomes slender. When this is limited by a limiter 2 and finite difference of video signals inputted from a delay circuit 6 is obtained by a difference calculator 3, the noise is reduced.
|
