Lens unit with dual O-ring sealing

A lens unit comprising:

• a first lens and a second lens disposed in order from an object side to an image side;
• a first lens barrel comprising an annular accommodating portion which accommodates an outer peripheral-edge portion of the first lens;
• a second lens barrel which accommodates a second lens and is held on an inner peripheral side of the first lens barrel;
• a third lens disposed on the image side of the second lens;
• a first O-ring;
• a second O-ring disposed between the second lens and the third lens;
• and
• a laminated body comprising a plurality of lenses laminated in an optical axis direction along an optical axis of the first lens, the laminated body being accommodated in the second lens barrel, wherein
• the first lens has an end surface facing the image side on an outer peripheral side of a lens surface;
• the accommodating portion comprises a peripheral wall surface located on an outer peripheral side of the second lens barrel and facing the first lens from an outer side in a radial direction, a support surface extending from an end on the image side of the peripheral wall surface to an inner peripheral side and facing the end surface from the image side, and a caulking portion which is brought into contact with the first lens from the object side at a position overlapping the support surface when viewed from the optical axis direction;
• the second lens comprises an annular contact portion which is in surface contact with the end surface of the first lens on an inner peripheral side of the support surface;
• the first O-ring is compressed between the first lens and the peripheral wall surface or between the first lens and the support surface;
• the second lens barrel accommodates the third lens and the second O-ring, comprises an annular second caulking portion which is bent from a distal end part on the object side to an inner peripheral side and is brought into contact with an outer peripheral-edge portion of the second lens from the object side, and comprises a first stepped portion on an inner peripheral surface;
• the first stepped portion comprises an annular first seating surface facing the object side at a position overlapping the caulking portion when viewed from the optical axis direction and an inner peripheral-surface portion extending from an end on an inner peripheral side of the annular first seating surface to the image side;
• the outer peripheral-edge portion of the second lens is located between the caulking portion and the annular first seating surface;
• the third lens is laminated on the object side of the laminated body and is supported from the image side by the laminated body;
• and
• the second O-ring is compressed in the optical axis direction at a position adjacent to the inner peripheral-surface portion in the radial direction and exerts an urging force to urge the third lens toward the object side and to urge the third lens toward the image side.