Lens unit and lens alignment method

A lens alignment method for aligning a first lens and a second lens adjacent to each other in an optical axis direction, the lens alignment method comprising:

• providing an annular contacting portion in contact with the first lens on an outer peripheral side of a lens surface of the second lens on the first lens side and providing an annular contacted portion in contact with the contacting portion on an outer peripheral side of a lens surface of the first lens on the second lens side,
• bringing the contacting portion and the contacted portion into line contact with each other;
• and
• vibrating one of the first lens and the second lens until an annular contact line along which the contacting portion and the contacted portion are in contact with each other is located on a virtual perpendicular plane that is coaxial with an optical axis of the first lens and is perpendicular to the optical axis,
• wherein a cross-section of the contacting portion cut along the optical axis is an arc that is curved in a direction away from the first lens toward the outer peripheral side, and
• the contacted portion is a tapered surface extending to the second lens side toward the outer peripheral side.