Patent ID: 7915572

Claim:
An endoscope including an optical axis, the endoscope comprising: a spherical or nearly spherical transparent viewing port; an objective lens that includes at least one aspheric surface and that optically forms an image of an object, said objective lens being formed as a single lens element; and a solid-state image sensor for converting said image into an electronic signal; wherein the following condition is satisfied −0.6 <k<− 0.85 where k is the eccentricity of said aspheric surface; and the shape of said aspheric surface is defined according to the following equation X=C·S 2 /[1+(1−( k+ 1)· C 2 ·S 2 ) 1/2 ] where X is the length of a line segment from a point on said aspheric surface at a distance S from an axis of symmetry of said objective lens as measured perpendicular to said axis of symmetry to the plane that is tangent to the vertex of said aspheric surface; and C=1/R, where R is the radius of curvature of said aspheric surface on said optical axis.