Optical unit, endoscope apparatus, and manufacturing method of optical unit

An optical unit comprising:

• a cylindrical member whose thickness varies in a circumferential direction;
• a transparent member disposed at one end, in an axial direction, of the cylindrical member;
• and
• a joining member which joins the transparent member to the cylindrical member and thereby seals the cylindrical member at the one end in the axial direction,
• wherein a portion, joining a side surface of the transparent member to an inner circumferential surface of the cylindrical member, of the joining member has radially a thicker portion adjoining where the cylindrical portion is thick and a thinner portion adjoining where the cylindrical member is thin,
• wherein an end surface, located at the one end in the axial direction of the cylindrical member, is formed with an annular stepped portion on an inner circumference side of the end surface,
• wherein the stepped portion is formed with a brim which supports an outer peripheral portion of the transparent member and an annular groove which is provided between the brim and a part, other than the brim, of the cylindrical member in the circumferential direction and in which a part of the joining member is placed,
• wherein the part of the joining member placed in the annular groove is in contact with a part of a surface, at an other end in the axial direction, of the transparent member, and
• wherein an interval between the side surface of the transparent member and the inner circumferential surface of the cylindrical member is longer at the position where the cylindrical member is thick than at the position where the cylindrical member is thin.