Imaging device

1. An imaging device comprising:

a case which includes a bottom plate portion and a top plate portion with an accommodation space interposed therebetween;

a dome cover which protrudes outward from the case through an opening formed in the top plate portion;

a lens unit which includes a lens;

an annular support member surrounding the lens unit which allows a circumferential edge portion of the dome cover to be interposed between the support member and the top plate portion;

and

an elastic member which is disposed between the bottom plate portion and the lens unit and allows the lens unit to be biased in a direction approaching the dome cover,

wherein the lens unit includes

an outer circumferential portion which is disposed on outside of the lens in a direction along the bottom plate portion and is engaged with an inside opening of the support member, and

a stepped portion which is provided in the outer circumferential portion and restricts movement of the lens unit in the direction approaching the dome cover by abutting the support member.

2. The imaging device according to claim 1 , further comprising:

a lens holder which is fixed to the bottom plate portion and holds the lens unit via the elastic member,

wherein the lens unit includes an engagement member in an end portion on the bottom plate portion side, and

the lens holder includes, in an end portion on the top plate portion side, an engagement portion which is engaged with the engagement member by a biasing force of the elastic member.

3. The imaging device according to claim 1 ,

wherein the elastic member is a coil spring which is disposed coaxially with the lens unit.

4. The imaging device according to claim 1 ,

wherein the case includes a first case having the bottom plate portion and a second case having the top plate portion,

the dome cover and the support member are provided in the first case, and

the lens unit and the elastic member are provided in the second case.

5. The imaging device according to claim 1 , wherein the dome cover is formed so that a ratio of a difference between thicknesses of the dome cover to a radius of the dome cover is 0.75% or higher and 6% or lower.

6. The imaging device according to claim 1 , wherein the shape of the annular support member conforms to the circumferential edge portion of the dome cover.

7. The imaging device according to claim 1 , wherein the annular support member is positioned entirely behind the dome cover.

8. The imaging device according to claim 1 , wherein the annular support member is a plate.

9. The imaging device according to claim 1 , wherein the stepped portion extends in a radial direction.

10. An imaging device comprising:

a case which includes a bottom plate and a top plate with an accommodation space interposed therebetween;

a dome cover which protrudes outward from the case through an opening formed in the top plate;

a ring-shaped annular support which allows a circumferential edge of the dome cover to be interposed between the ring-shaped annular support and the top plate;

a lens unit which includes a lens; and

a spring which is disposed between the bottom plate and the lens unit and allows the lens unit to be biased in a direction approaching the dome cover, wherein the lens unit further includes:

an outer circumferential support disposed on outside of the lens in a direction along the bottom plate and engaged with an inside opening of the ring-shaped annular support, and

a flange provided in the outer circumferential support which restricts movement of the lens unit in the direction approaching the dome cover by abutting the ring-shaped annular support.

11. The imaging device according to claim 10 , further comprising a lens holder which is fixed to the bottom plate and which holds the lens unit via the spring, wherein:

the lens unit includes a tab in an end on the bottom plate, and

the lens holder includes, in an end portion on the top plate, a recess which is engaged with the tab by a biasing force of the spring.

12. The imaging device according to claim 10 , wherein the spring is a coil spring which is disposed coaxially with the lens unit.

13. The imaging device according to claim 10 , wherein:

the case includes a first case including the bottom plate and a second case including the top plat,

the dome cover and the ring-shaped annular support are provided in the first case, and

the lens unit and the spring are provided in the second case.

14. The imaging device according to claim 10 , wherein the dome cover is formed such that a ratio of a difference between thicknesses of the dome cover to a radius of the dome cover is 0.75% or higher and 6% or lower.

15. The imaging device according to claim 10 , wherein the shape of the ring-shaped annular support conforms to the circumferential edge of the dome cover.

16. The imaging device according to claim 10 , wherein the ring-shaped annular support is positioned entirely behind the dome cover.

17. The imaging device according to claim 10 , wherein the ring-shaped annular support member is a plate.

18. The imaging device according to claim 10 , wherein the flange extends in a radial direction.