Endoscope system

An endoscope system which is adjustable to a plurality of object distances and which is provided with a photographing optical system to display an image for magnifying observation, comprising:

• an optical system which allows switching between a normal observation image and a near observation image by operation of a focus adjustment device for changing a focal length and a working distance;
• a solid-state image sensor which photographs an image formed by said optical system;
• an image display unit which displays the image;
• an image control device which generates an image to be displayed on said image display unit on the basis of information from said solid-state image sensor and which controls switching between image processing modes;
• a calculating device which calculates optical amounts representing a situation of said optical system;
• and
• an optical system control device which controls said optical system;
• wherein in operation of said focus adjustment device, the following conditions are satisfied:
• WDwide>WDtele
• fwide≧ftele
• Ntele<Ftele<Nwide<Fwide
• where fwide is a focal length in a normal observation mode, WDwide is a working distance in the normal observation mode, Nwide, Fwide are a near end position and a far end position, respectively, of a depth of field in the normal observation mode in reference to an endoscope distal end position, ftele is a focal length in a near observation mode, WDtele is a working distance in the near observation mode, and Ntele, Ftele are a near end position and a far end position, respectively, of a depth of field in the near observation mode in reference to the endoscope distal end position,
• wherein said image control device controls a ratio of an amount of information α possibly appearing on said solid-state image sensor to an amount of image information β displayed on said image display unit in the near observation mode to be α/β≧1,
• wherein said image control device performs switching of the image processing modes in accordance with the situation of said optical system on the basis of a signal which is generated by said optical system control device and which is supplied to said focus adjustment device, and
• wherein said image control device performs processing such that a calculation result of the optical amounts, which is obtained by said calculating device on the basis of the signal supplied to said focus adjustment device and which represents the situation of said optical system, is displayed on said display unit.