Image signal processing method and image signal processing device

Image signal processing method wherein a display signal is generated from an original image signal acquired from means for image pickup, comprising:

• a step of dividing a screen into a plurality of polygons, finding signal intensities of pixels in the polygons by interpolation from the original image signal intensities of pixels corresponding to the vertices of these polygons, as a signal intensity of a low frequency component;
• a step of finding the signal intensities of high frequency components of the pixels by performing calculation to subtract the signal of this low frequency component from the original image signal at each pixel;
• a step of finding, for the signal intensities of the high frequency components, from a histogram showing the rate of occurrence numbers of the respective signal intensities, a transformation function including the integrated values of these rate of occurrence numbers up to the respective signal intensities;
• a step of transforming the signal intensities of the high frequency components into display signal intensities in accordance with this transformation function;
• a step of finding the display signal of the pixels by adding to the display signals of the high frequency components obtained by the transformation a signal obtained by multiplying the signal of the low frequency component by a weighting coefficient of less than 1;
• and
• a step of displaying image on a display device in accordance with the display signal.

An image signal processing device comprising:

• image pickup;
• an original image signal memory recording an original image signal acquired by the image pickup;
• an image signal processing unit generating a display signal by reading the original image signal from the original image signal memory;
• and
• a display signal memory recording the display signal generated by the image signal processing unit;
• wherein the image signal processing unit has:
• a function of dividing the screen into a plurality of polygons and finding a signal intensities of pixels within the polygons by interpolation from the original image signal intensities of the pixels corresponding to the vertices of the polygons, as a signal intensities of a low-frequency component;
• a function of finding a signal intensities of a high-frequency components of the pixels by performing calculation to subtract the signals of the low-frequency components from the original image signal at each pixel;
• and
• a function of finding the display signal of the pixels by adding to the high-frequency component signal a signal obtained by multiplying the low-frequency component signal by a weighting coefficient of less than 1.

An image signal processing device comprising:

• image pickup;
• an original image signal memory recording an original image signal acquired by the image pickup;
• an image signal processing unit generating a display signal by reading the original image signal from the original image signal memory;
• and
• a display signal memory recording the display signal generated by the image signal processing unit;
• wherein the image signal processing unit has:
• a function of dividing the screen into a plurality of polygons and finding a signal intensities of pixels within the polygons by interpolation from the original image signal intensities of the pixels corresponding to the vertices of the polygons, as a signal intensities of a low-frequency component;
• a function of finding a signal intensities of the high-frequency components of the pixels by performing calculation to subtract the signals of the low-frequency components from the original image signal at each pixel;
• a function of finding, for the signal intensities of the high-frequency components, from a histogram indicating the rate of occurrence numbers of respective signal intensities, a transformation function including the integrated values of these rate of occurrence numbers up to the respective signal intensities;
• a function of transforming the signal intensities of the high-frequency components to display signal intensities in accordance with the transformation function;
• and
• a function of finding the display signal of the pixels by adding to the display signal of the transformed high-frequency component signal a signal obtained by multiplying the low-frequency component signal by a weighting coefficient of less than 1.