A rigid tip portion for an endoscope for inserting into a lumen of a human body, wherein the rigid tip portion has a center axis extending from a distal end of the rigid tip portion to a proximal end of the rigid tip portion; at each position along the center axis, a respective cross-section of the rigid tip portion perpendicular to the center axis is elliptical with a long axis and a short axis not longer than the long axis; the long axis and the short axis cross on the center axis; the rigid tip portion accommodates a sensor system comprising a single objective lens; and an image sensor, wherein a sensor area of the image sensor for photoelectrically converting an optical image taken through the single objective lens into an electrical image signal is arranged in an image plane of the single objective lens; a front lens on an object side of the single objective lens is arranged at the distal end of the rigid tip portion, characterized in that the single objective lens has a field of view of not less than 180°; the image plane is located such that the objective lens images a portion of a sphere on the image plane; the sphere has a radius of not less than 8 mm and not more than 12 mm; a center of the sphere is located not less than 0 mm and not more than 4 mm towards the image sensor from an apex of the objective lens on a side opposite to a side where the image sensor is located; and the objective lens consists of, in order from the object side to an image side: the front lens being a first meniscus lens having a convex side towards the object side; a second lens; a first condensing unit configured to condense light from the second lens; an aperture stop; a second condensing unit configured to condense light from the aperture stop; wherein a total number of lenses in the first and second condensing units is not less than 4 and not more than 6; the second lens is a second meniscus lens having a convex side towards the object side; an apex of the second meniscus lens is spaced apart from the first meniscus lens; if a radius of the first meniscus lens on the image side is denoted r2, a radius of the second meniscus lens on the object side is denoted r3, and a radius of the second meniscus lens on the image side is denoted r4, at least two of the following three conditions are fulfilled: r2/r4 ≥ 1.40; r4/r3 ≥ 0.111; and r2/r3 ≥ 0.16. the rigid tip portion has a center axis extending from a distal end of the rigid tip portion to a proximal end of the rigid tip portion; at each position along the center axis, a respective cross-section of the rigid tip portion perpendicular to the center axis is elliptical with a long axis and a short axis not longer than the long axis; the long axis and the short axis cross on the center axis; the rigid tip portion accommodates a sensor system comprising a single objective lens; and an image sensor, wherein a sensor area of the image sensor for photoelectrically converting an optical image taken through the single objective lens into an electrical image signal is arranged in an image plane of the single objective lens; a front lens on an object side of the single objective lens is arranged at the distal end of the rigid tip portion, characterized in that the single objective lens has a field of view of not less than 180°; the image plane is located such that the objective lens images a portion of a sphere on the image plane; the sphere has a radius of not less than 8 mm and not more than 12 mm; a center of the sphere is located not less than 0 mm and not more than 4 mm towards the image sensor from an apex of the objective lens on a side opposite to a side where the image sensor is located; and the objective lens consists of, in order from the object side to an image side: the front lens being a first meniscus lens having a convex side towards the object side; a second lens; a first condensing unit configured to condense light from the second lens; an aperture stop; a second condensing unit configured to condense light from the aperture stop; wherein a total number of lenses in the first and second condensing units is not less than 4 and not more than 6; the second lens is a second meniscus lens having a convex side towards the object side; an apex of the second meniscus lens is spaced apart from the first meniscus lens; if a radius of the first meniscus lens on the image side is denoted r2, a radius of the second meniscus lens on the object side is denoted r3, and a radius of the second meniscus lens on the image side is denoted r4, at least two of the following three conditions are fulfilled: r2/r4 ≥ 1.40; r4/r3 ≥ 0.111; and r2/r3 ≥ 0.16. the front lens being a first meniscus lens having a convex side towards the object side; a second lens; a first condensing unit configured to condense light from the second lens; an aperture stop; a second condensing unit configured to condense light from the aperture stop; wherein a total number of lenses in the first and second condensing units is not less than 4 and not more than 6; the second lens is a second meniscus lens having a convex side towards the object side; an apex of the second meniscus lens is spaced apart from the first meniscus lens; if a radius of the first meniscus lens on the image side is denoted r2, a radius of the second meniscus lens on the object side is denoted r3, and a radius of the second meniscus lens on the image side is denoted r4, at least two of the following three conditions are fulfilled: r2/r4 ≥ 1.40; r4/r3 ≥ 0.111; and r2/r3 ≥ 0.16.