Endoscope system and endoscope

An endoscope system, comprising:

• a first endoscope that includes a first distal end portion, a first observation window provided at the first distal end portion, a first objective optical system optically coupled to the first observation window and having a first viewing angle, and a first treatment instrument channel opening into which a first treatment instrument is inserted;
• and
• a second endoscope that includes a second distal end portion, a second observation window provided at the second distal end portion, a second objective optical system optically coupled to the second observation window and having a second viewing angle different from the first viewing angle, and a second treatment instrument channel opening into which a second treatment instrument is inserted, wherein
• under a condition where an amount of projection of the first treatment instrument from the first treatment instrument channel opening is substantially the same as an amount of projection of the second treatment instrument from the second treatment instrument channel opening, a first distance between the first treatment instrument channel opening and the first observation window and a second distance between the second treatment instrument channel opening and the second observation window are set so that the first treatment instrument is in the first viewing angle and the second treatment instrument is in the second viewing angle.

An endoscope used in a system, comprising:

• a first distal end portion;
• a first objective optical system which has at least a first viewing angle and is provided in the first distal end portion;
• and
• a first treatment instrument channel opening into which a first treatment instrument is inserted and which is provided in the first distal end portion, wherein
• a first distance between the first treatment instrument channel opening and the first objective optical system at the first distal end portion is longer than a second distance between a second treatment instrument channel opening provided in a second distal end portion and a second objective optical system having a second viewing angle narrower than the first viewing angle, the second distal end portion, the second objective optical system, and the second treatment instrument channel opening constituting another endoscope used in the system.

An endoscope comprising:

• a distal end portion;
• an objective optical system having at least a predetermined viewing angle and provided in the distal end portion;
• and
• a treatment instrument channel opening into which a treatment instrument is inserted and is disposed at a distance, determined based on the viewing angle, away from the objective optical system.

An endoscope comprising:

• a distal end portion;
• an objective optical system having at least a first viewing angle and provided in the distal end portion;
• and
• a solid imaging element having a number of pixels larger than that of another solid imaging element for an objective optical system having a second viewing angle narrower than the first viewing angle.