Patent ID: 6923758

Claim:
An endoscope comprising: a slender insertion portion; an illuminational optical system which is arranged at the tip portion of the insertion portion and which emits transmitted illumination light onto a subject side; a first frame member provided with the illuminational optical system; an observational optical system for forming an optical image of the subject illuminated by the illuminational optical system; a second frame member provided with the observational optical system; a liquid-tight joint portion which is arranged at the end portion facing the outside of the first frame member and which is joined liquid-tight to a first lens member constituting the illuminational optical system and the first frame member; and a steam-tight joint portion which is arranged at the end portion facing the outside of the second frame member and which joins steam-tight a second lens member constituting the observational optical system and the second frame member, wherein the steam-tight joint portion has a characteristic different from that of the liquid-tight portion.