Patent ID: 8444548

Claim:
An electronic endoscope comprising: an elongate insertion unit: an objective optical system provided at a distal end of the insertion unit and having a predetermined view angle to form an optical image of a subject; a solid image capturing element comprising a predetermined number of pixels in which the objective optical system forms an optical image of the subject; a lens moving unit that, when on the basis of a brightness signal generated from an image signal resulting from image capturing of the subject comprising a black band and a white band which have the same width, a maximum value of a brightness signal for the white subject is defined as Imax, a minimum value of a brightness signal for the black subject is defined as Imin, and a contrast I is defined by I=(Imax−Imin)/(Imax+Imin), moves at least some lenses constituting the objective optical system between two or more setting positions including a first setting position and a second setting position corresponding to at least the two positions, the two positions being a position on a far point side located at a first object distance from a distal end of the insertion unit, and a position on a near point side located at a second object distance smaller than the first object distance, to vary a focal distance of the objective optical system so that the depth of field has an overlapping part, in order to capture each subject at at least the two positions, at a contrast I of at least a predetermined value by the objective optical system; and a channel through which a treatment tool can be inserted and which is formed to be opened so as to locate the distal end of the treatment tool projected by the second object distance, within a view angle when set by the lens moving unit so as to focus on the position on the near point side, wherein the lens moving unit is configured to be able to set at least some of the lenses constituting the objective optical system, at the two setting positions corresponding to the near point side and the far point side, so that the objective optical system has a depth of field at which, in a setting state to the focal distance to focus on the position on the near point side, the subject comprising a 35-μm pitch black and white band pair can be captured at a contrast I of at least almost 10% and at which, in a setting state to the focal distance to focus on position on the far point side, the subject having a 0.5-mm pitch black and white band pair can be captured at a contrast I of at least almost 10% at a distance of 50 mm from the distal end of the insertion unit.