Lens unit
A lens unit includes a lens, a lens barrel, a housing groove, and a vent hole. The lens barrel houses the lens. The housing groove is formed in the lens barrel and houses an adhesive for bonding the lens and the lens barrel. The vent hole is a hole for discharging air and is formed in the housing groove.
1. A lens unit comprising:
a first lens having a first surface and a second surface opposite the first surface;
a second lens having a third surface and a fourth surface opposite the third surface, the third surface of the second lens facing the second surface of the first lens;
a lens barrel having a flange portion including a first cylindrical shape and a body portion including a second cylindrical shape and located inside the flange portion, the flange portion having a wider width than the body portion, the flange portion having a bottom portion and a wall portion surrounding the bottom portion, the bottom portion of the flange portion having a fifth surface and sixth surface opposite the fifth surface and located between the wall portion of the flange portion and the body portion, the bottom portion of the flange portion connecting the wall portion of the flange portion and body portion, the flange portion housing the first lens, the body portion housing the second lens, the body portion having an abutting portion contacting on the second surface of the first lens; and
an adhesive for bonding the first lens and the lens barrel,
wherein the lens barrel has a groove having an annular shape and located between an outer surface of the abutting portion of the body portion and an inner surface of the wall portion of the flange portion,
wherein the adhesive is disposed at least in the groove and bonds a part of the second surface of the first lens, the outer surface of the abutting portion of the body portion, the inner surface of the wall portion of the flange portion, and the fifth surface of the bottom portion of the flange portion,
wherein the flange portion of the lens barrel includes:
a first hole for discharging air, the first hole being formed in the groove of the flange portion; and
a second hole for injecting the adhesive, the second hole being formed in the groove of the flange portion;
wherein the first hole passes from an outer surface of the wall portion to the inner surface of the wall portion along a direction perpendicular to an optical axis direction and connects the groove, and
wherein the second hole passes from the sixth surface of the bottom portion to the fifth surface of the bottom portion along the optical axis direction and connects the groove.
2. The lens unit according to claim 1 , wherein
the groove is filled with the adhesive,
the first hole is at least partially filled with the adhesive, and
the second hole is at least partially filled with the adhesive.
3. The lens unit according to claim 2 wherein
the first lens is located at the inner surface of the wall portion of the flange portion, and
the second lens is located at an inner surface of the body portion.
4. The lens unit according to claim 3 , wherein
the second lens is fitted in an upper distal end portion of the body portion inside the flange portion.
5. The lens unit according to claim 1 , wherein each of the first hole and the second hole has a circular cross-sectional shape.
6. The lens unit according to claim 2 , wherein each of the first hole and the second hole has a diameter equal to or larger than 0.02 mm.