Patent ID: 8167792

Claim:
An endoscope system comprising: a passage position setting section configured to: extract a dark region in an image picked up by an image pickup section arranged to a distal end portion of an insertion portion of an endoscope, and set a pixel position that is the center of the dark region as an initially-determined passage position of the distal end portion of the insertion portion of the endoscope; and a passage position correction section configured to: set a circle imitating a distal end face of the distal end portion, the circle being set in the center of the image and having a predetermined radius, extract a brightest region in the image and a boundary line of the brightest region, linearize a portion of the boundary line that is the interior of the circle, calculate a first vector having the center of the circle as a first vector initial point, a direction of the normal to the linearized portion of the boundary line as a first vector direction, and the radius of the circle as a first vector magnitude, calculate a second vector having the center of the circle as a second vector initial point, and a second vector direction and a second vector magnitude defined by the second vector initial point and the initially-determined passage position as a second vector end point, and set a pixel position that corresponds to an end point of a combination of the first vector and second vector as a corrected passage position of the distal end portion of the insertion section of the endoscope.