Patent ID: 8517928

Claim:
A capsule-type endoscope comprising: an image pickup unit that includes an objective optical system and an image pickup element; at least one illumination light source; and a transparent cover; wherein an inner surface of the transparent cover is shaped into an ellipsoid, D1 is greater than (β1) 2 /(4·α1), where D1 is a distance between a center of an entrance pupil of the objective optical system and a center of the inner surface of the transparent cover, the center of the inner surface being a center of the ellipsoid determined as an intersection of a major axis and a minor axis of the ellipsoid, β1 equals a minor diameter of the ellipsoid divided by 2, and α1 equals a major diameter of the ellipsoid divided by 2, the center of the ellipsoid coincides with an intersection of a perpendicular drawn from a vertex of the inner surface of the transparent cover to a plane Qm that contains a light emitting surface of the illumination light source, and the entrance pupil of the objective optical system lies in the plane Qm.