Patent ID: 6356304
Filing Date: 2002-03-12
Classification: H04N

Abstract:
An image signal processing method for processing an image signal of a photographed image provided by a photographing device having an optical system including a zoom lens and an iris diaphragm with a light attenuating filter, said method comprising:isolating a high frequency band of a brightness signal component of said image signal by delaying said brightness signal component to obtain a first delayed signal, delaying said first delayed signal to obtain a second delayed signal, amplifying said first delayed signal relative to said brightness signal component and said second delayed signal, and subtracting said brightness signal component and said second delayed signal from said amplified first signal to obtain an isolated high frequency band of said brightness signal component; determining a zoom position of said zoom lens and an aperture size of said iris diaphragm, wherein variation of said zoom position and aperture size causes variation of resolution of said image signal, and said variation of resolution caused by the aperture size variation has a local minimum within a range of the aperture size variation; selecting a gain, corresponding to the determined zoom position and aperture size, from a plurality of gain values stored in a data table memory; and intensifying said high frequency band at the selected gain, wherein degradation of resolution of said image signal due to said zoom lens and said iris diaphragm with light attenuating filter is corrected, and resolution becomes approximately constant with zoom position and iris diaphragm aperture size variation.