Patent ID: 7499087

Claim:
A noise reducing device comprising: amplifying means of amplifying a video signal; video signal level reducing means of splitting the video signal amplified by the amplifying means into a plurality of bands in accordance with a spatial frequency thereof, reducing a level of a higher frequency component of the video signal based on a comparison between a first characteristic parameter based on an factor of amplification of the amplifying means and the level of the higher frequency component, and synthesizing the reduced higher frequency component and a component of another band with each other; difference signal extracting means of extracting a difference signal between an output of the video signal reducing means and a predetermined reference signal; difference signal level reducing means of reducing a level of the difference signal; and subtracting means of subtracting an output of the difference signal level reducing means from the output of the video signal level reducing means, wherein an output of the subtracting means is outputted as the video signal whose noise has been reduced, and is used as a new reference signal, wherein the level of the difference signal is reduced based on a comparison between the level of the difference signal and a predetermined second characteristic parameter, wherein the second characteristic parameter of the difference signal level reducing means varies in accordance with the factor of amplification of the amplifying means, wherein when the factor of amplification of the amplifying means is not more than a predetermined value, the second characteristic parameter of the difference signal level reducing means is maintained fixed, and the first characteristic parameter of the video signal level reducing means is increased, and wherein when the factor of amplification is higher than the predetermined value, the first characteristic parameter of the video signal level reducing means is maintained fixed, and the second characteristic parameter of the difference signal level reducing means is increased.