Noise reducer using memory

A noise reducer, comprising:

• separating means for separating an input image signal into a first image signal and a second image signal;
• first noise reducing means having a memory and arranged to apply noise reduction processing of a time-cyclic type to the first image signal by using said memory;
• second noise reducing means for detecting a noise component of the second image signal by using the second image signal and the first image signal to which the noise reduction processing has been applied by said first noise reducing means, and for applying noise reduction processing to the second image signal by using the detected component of the second image signal;
• and
• combining means for combining the first image signal to which the noise reduction processing has been applied by said first noise reducing means and the second image signal to which the noise reduction processing has been applied by said second noise reducing means.

An image signal processing method of reducing noise in an input image signal by employing time-cyclic noise reduction processing, comprising the steps of:

• separating the input image signal into a first image signal and a second image signal, said separating step including a step of obtaining the first image signal by sampling the input image signal at a first timing and for obtaining the second image signal by sampling the input image signal at a second timing different from the first timing;
• applying the time-cyclic noise reducing processing to only the first image signal in the input image signal;
• and
• combining the first image signal processed by said noise reduction step and the second image signal supplied by the separating step.

A signal processing apparatus, comprising:

• generating means for receiving an input signal and for generating a first signal and a second signal, said generating means generating the first signal by sampling the input signal at a first timing and generating the second signal by sampling the input signal at a second timing different from the first timing;
• a memory;
• means for obtaining a difference signal indicative of a difference between the first signal and a signal read from said memory;
• multiplying means for multiplying the difference signal by a predetermined coefficient;
• subtracting means for subtracting an output of said multiplying means from the first signal, said memory storing an output of said subtracting means;
• and
• combining means for combining the output of said subtracting means and the second signal supplied from said generating means.

An image signal processing apparatus, comprising:

• image pickup means for picking up an object image to generate an image signal;
• generating means for generating a predetermined image signal from the image signal generated by said image pickup means, said generating means including sampling means for obtaining the predetermined image signal by sampling, at a first timing, the image signal generated by said image pickup means, and for obtaining an image signal other than the predetermined image signal by sampling, at a second timing different from the first timing, the image signal generated by said image pickup means;
• noise reducing means having a memory and arranged to apply noise reduction processing to the predetermined image signal generated by said generating means, by using said memory;
• and
• combining means for combining the predetermined image signal processed by said noise reducing means and an image signal other than the predetermined image signal supplied from said generating means.