Electronic endoscope

A video-processor of an electronic endoscope, to which a proximal end of a video-scope and a monitor for displaying an object image are respectively connected, said video-scope having an image sensor provided at a distal end of said video-scope, on which an object image is formed, and a light guide provided throughout said video-scope, to guide light from the proximal end of said video-scope to the distal end of said video-scope, said video-processor processing image-pixel signals corresponding to said object image, read from said image sensor successively, so as to generate video signals and feed said video-signals to said monitor, said video processor comprising:

• a light source provided in said video-processor such that light, emitted from said light source, is guided through said light guide and radiates from the distal end of said video-scope;
• a luminance value calculator adapted to successively calculate a luminance value indicating brightness of said object image on the basis of said image-pixel signals;
• a stop provided between said light source and the proximal end of said video-scope, adapted to regulate a quantity of light radiating from the distal end of said video-scope;
• a motor adapted to drive said stop, said stop being connected to said motor such that said stop is driven in accordance with a motion of said motor;
• a drive-amount setter adapted to set a target drive-amount of said stop, to make brightness of said object image constant, on the basis of said luminance value;
• a stop-controller adapted to adjust the quantity of light radiating from the distal end of said video-scope by controlling said stop in accordance with said target drive-amount at regular time-intervals, wherein said stop opens and closes such that the brightness of said object image displayed on said monitor is maintained at constant level;
• and
• a drive-amount determiner adapted to determine whether said target drive-amount exceeds a tolerable drive-amount, said stop-controller adapted to at least suspend a drive of said stop at the next adjustment of the quantity of light when said target drive-amount exceeds said tolerable drive-amount;
• wherein when a drive-time of said stop, depending on the target drive-amount, exceeds the time-interval for performing the adjustment of the quantity of light, said stop-controller suspends the drive of said stop for at least the next adjustment of the quantity of light and substantially prevents hunting.