| 摘要 |
PURPOSE:To set the light distribution characteristics of illumination light automatically to characteristics suitable to a subject by detecting the flat state of the subject from an image pickup signal. CONSTITUTION:A driving circuit 50 is so controlled as to widen the directivity of the illumination light and light the entire surface of the subject uniformly. The frame 60 of a lens 22a of a condenser lens 22 is connected to the tip of a wire 56. When the subject in a tube such as the esophagus, the brightness of its peripheral part increases, the brightness of the center part decreases, and the output of a subtracter 48 increases. The circuit 50 rotates a motor 52 corresponding to draw the wire 60 through a wire driving member 54, thereby moving the frame 60 of the lens 22a to the front side. Consequently, the illumination light has narrow directivity and the center part is lighted concentrically to uniform the brightness of the entire surface, thereby observing the entirely in the tube.
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