Electronic endoscope system, processing apparatus for electronic endoscope, and signal separation method

A processing apparatus connected to an electronic endoscope, the electronic endoscope having an imaging section in which a blue pixel, a green pixel, and a red pixel are arranged, the imaging section capturing an image of a tissue site in a body cavity during emission of white broadband light and narrow band light, the tissue site including a blood vessel, the broadband light being sensed by the three color pixels, and the narrow band light being sensed by only one or two of the three color pixels, the processing apparatus comprising:

• a signal obtaining section for obtaining a mixed image signal during the emission of the broadband light and the narrow band light, the mixed image signal including a first color signal which is outputted from the pixel having sensitivity to the narrow band light and has a sum of a brightness value of the broadband light and a brightness value of the narrow band light, and a second color signal which is outputted from the pixel not having sensitivity to the narrow band light and has only a brightness value of the broadband light;
• a correlation information storage for storing correlation information between a brightness value of the pixel having sensitivity to the narrow band light and a brightness value of the pixel not haying sensitivity to the narrow band light when only the broadband light is emitted;
• and
• a signal separator configured to calculate a brightness value of the broadband light contained in the first color signal from a brightness value of the broadband light contained in the second color signal and the correlation information, and subtract the calculated brightness value from the first color signal to obtain a brightness value of the narrow band light contained in the first color signal.

A signal separation method for separating an image signal of an electronic endoscope, the electronic endoscope having an imaging section in which a blue pixel, a green pixel, and a red pixel are arranged, the signal separation method comprising the steps of;

• emitting white broadband light and narrow band light to a tissue site in a body cavity, the tissue site including a blood vessel, the broadband light being sensed by the three color pixels, and the narrow band light being sensed by only one or two of the three color pixels;
• capturing an image of the tissue site with the imaging section during emission of the broadband light and the narrow band light and obtaining a mixed image signal, the mixed image signal including a first color signal which is outputted from the pixel having sensitivity to the narrow band light and has a sum of a brightness value of the broadband light and a brightness value of the narrow band light, and a second color signal which is outputted form the pixel not having sensitivity to the narrow band light and has only a brightness value of the broadband light;
• reading correlation information from a correlation information storage, the correlation information representing a correlation between a brightness value of the pixel having sensitivity to the narrow band light and a brightness value of the pixel not having sensitivity to the narrow band light when only the broadband light is emitted;
• and
• calculating a brightness value of the broadband light contained in the first color signal from a brightness value of the broadband light contained in the second color signal and the correlation information, and subtracting the calculated brightness value from the first color signal to obtain a brightness value of the narrow band light contained in the, first color signal.