Lens unit

1. A lens unit comprising:

a lens including a first circular shaped portion and a second circular shaped portion arranged in a row along an optical axis direction, the first circular shaped portion including a face that curves with a convex profile in an optical axis direction and the second circular shaped portion including a face that curves with a convex profile in an opposite optical axis direction from the first circular shaped portion;

a lens-barrel formed of a resin and formed in a tubular shape, the lens-barrel including:

a first inner peripheral face to which the first circular shaped portion is fitted, and

a second inner peripheral face to which the second circular shaped portion is fitted and which is positioned separated in the optical axis direction from a fitting section where the first circular shaped portion and the first inner peripheral face are fitted, wherein the second inner peripheral face contacts with a circumferential edge of the second circular shaped portion at three or more portions in a circumferential direction; and

a spacing ring formed in a ring shape and that holds the lens by contacting the face of the second circular shaped portion.

2. The lens unit of claim 1 , wherein:

the second inner peripheral face is formed with a polygonal profile when viewed from the optical axis direction; and

contact portions at the second inner peripheral face that contacts with the second circular shaped portion have flat faces that forms each side of the polygonal profile.

3. The lens unit of claim 2 , wherein the second inner peripheral face includes curved faces formed to link adjacent of the flat faces together.

4. The lens unit of claim 2 , wherein the first circular shaped portion and the first inner peripheral face contact each other at three or more portions in a circumferential direction.

5. The lens unit of claim 4 , wherein the first inner peripheral face has a polygonal profile when viewed from the optical axis direction.

6. The lens unit of claim 5 , wherein the first inner peripheral face is configured including flat faces forming each side of the polygonal profile, and circular arc shaped connection portions connecting adjacent of the flat faces together.

7. The lens unit of claim 5 , wherein:

the first inner peripheral face is positioned further to a radial direction outside than the second inner peripheral face; and

flat faces forming each side of the first inner peripheral face and flat faces forming each side of the second inner peripheral face are formed at the same circumferential direction positions with each other, when viewed from the optical axis direction.

8. The lens unit of claim 1 , wherein a curved face is formed at a contact portion at the second inner peripheral face where contact is made with the second circular shaped portion, the curved face being depressed toward a radial direction outside of the lens-barrel when viewed from the optical axis direction and making face-to-face contact with the second circular shaped portion.

9. The lens unit of claim 1 , wherein the first inner peripheral face is positioned further to a radial direction outside than the second inner peripheral face.

10. The lens unit of claim 9 , wherein a length of the first circular shaped portion in the optical axis direction is shorter than a length of the second circular shaped portion in the optical axis direction.

11. The lens unit of claim 1 , wherein:

at least one of the first inner peripheral face or the second inner peripheral face includes an inclined face inclined with respect to the optical axis direction; and

of the first circular shaped portion or the second circular shaped portion, a circular shaped portion that fits together with the inclined face is inclined to correspond to the inclined face.

12. The lens unit of claim 1 , wherein the lens unit is a lens unit employed onboard a vehicle or employed for surveillance.