Electronic endoscope system

An electronic endoscope system used for observing living tissues inside a body cavity, comprising

• a single imaging device configured to receive an optical image and output image signals obtained from the optical image;
• an illuminating apparatus having a white light source emitting white light and an excitation light source that emits excitation light having a predetermined wavelength, the living tissues emitting autofluorescence when irradiated with the excitation light;
• an image forming system configured to form the optical image of the living tissues illuminated with each of the white light and the excitation light on the imaging device,
• a display device;
• an image processing system that receives the image signals outputted from the single imaging device, the image processing system transforming the received image signals into signals which are allowed to be displayed on the display device;
• and
• a control system configured to control the whole of the electronic endoscope system,
• wherein the control system controls the illuminating apparatus to illuminate the living tissues alternately with the white light and excitation light,
• wherein the control system controls the image processing system to obtain normal image signals when the living tissues are illuminated with the white light and fluorescence image signals when the living tissues are irradiated with the excitation light,
• wherein the image processing system employs image signals, obtained from an image, outputted from the single imaging device as a first field of image signals of an interlaced image, and employs image signals obtained by performing an arithmetical operation for image signals, obtained from a plurality of images, outputted from the single imaging device as a second field of image signals of the interlaced image, and
• wherein one frame of each of the normal image and fluorescence image is configured with the first field of image signals and the second field of image signals.