Endoscope system, processor apparatus for endoscope system, and method for operating endoscope system

An endoscope system comprising:

• an illumination unit that irradiates a test body with first illumination light and second illumination light having a spectral property different from a spectral property of the first illumination light and including different-absorption-wavelength light that has different absorption coefficients for oxygenated hemoglobin and reduced hemoglobin;
• an endoscope including a CMOS image sensor that captures an image of the test body illuminated by the illumination unit by using a plurality of pixels arranged in two dimensions in a row direction and in a column direction;
• a controller that enables a normal observation mode and a special observation mode to be selectively executed, the normal operation mode being a mode in which signal reading from the image sensor is performed in a state where the first illumination light is being emitted from the illumination unit, the special observation mode being a mode in which the first illumination light and the second illumination light are alternately emitted from the illumination unit while a turn-off period is interposed and signal reading from the image sensor is performed during the turn-off period;
• and
• an image processor that generates an oxygen saturation image on the basis of a first image capture signal read from the image sensor during the turn-off period after emission of the first illumination light and a second image capture signal read from the image sensor during the turn-off period after emission of the second illumination light in the special observation mode, wherein
• the controller controls the image sensor in the special observation mode to make a second read time taken to read the second image capture signal shorter than a first read time taken to read the first image capture signal and a reciprocal of the second read time taken to read the second image capture signal larger than a reciprocal of the first read time taken to read the first image capture signal.