Driving mechanism for optical element

1. An optical element driving mechanism, comprising:

a movable portion, used for connecting to an optical element having a main axis;

a fixed portion, wherein the movable portion is movable relative to the fixed portion and arranged with the fixed portion along the main axis, and the fixed portion comprises a base;

a driving assembly for driving the movable portion to move relative to the fixed portion; and

an assist assembly for limiting a movement of the movable portion relative to the fixed portion, wherein the assist assembly comprises a limit element, a support element is disposed in an opening of the limit element, the main axis passes through the opening, and the limit element is disposed on a top surface of the base, wherein the limit element comprises a bottom perpendicular to the main axis and a limit portion vertically extending from the bottom along the main axis, the limit portion is in contact with the support element, the bottom is spaced apart from the support element, wherein the bottom and limit portion extend in different directions, and the bottom has a larger diameter than the limit portion in a plane perpendicular to the main axis.

2. The optical element driving mechanism as claimed in claim 1 , wherein the support element is disposed between the movable portion and the fixed portion to allow the movable portion to rotate relative to the fixed portion in two axes extending in a first direction and a second direction, and the first direction is not parallel to the second direction.

3. The optical element driving mechanism as claimed in claim 2 , wherein the support element further allows the movable portion to rotate relative to the fixed portion in an axis extending in a third direction, and the third direction is not parallel to the first direction or the second direction.

4. The optical element driving mechanism as claimed in claim 3 , wherein the assist assembly further comprises a magnetic permeable element, wherein a material of the support element comprises metal, and a magnetic force is generated between the magnetic permeable element and the support element to attract the magnetic permeable element and the support element.

5. The optical element driving mechanism as claimed in claim 2 , wherein a diameter of the opening of the limit element is greater than a diameter of the support element, and a diameter of the limit element is greater than a diameter of an opening of the base.

6. The optical element driving mechanism as claimed in claim 1 , further comprising a photo sensor that at least partially overlaps the driving assembly when viewed in a direction that is perpendicular to the main axis.

7. The optical element driving mechanism as claimed in claim 1 , further comprising an optical module, and the optical element is disposed in the optical module.

8. The optical element driving mechanism as claimed in claim 7 , wherein the optical module partially overlaps the driving assembly when viewed in a direction that is perpendicular to the main axis.

9. The optical element driving mechanism as claimed in claim 7 , further comprising a circuit board, wherein the optical module further comprises a substrate, and an extension of the substrate and an extension of the circuit board are positioned on different sides of the optical element driving mechanism.

10. The optical element driving mechanism as claimed in claim 9 , wherein the substrate at least partially overlaps the circuit board along the main axis.

11. The optical element driving mechanism as claimed in claim 1 , wherein the driving assembly comprises at least three driving magnets.

12. The optical element driving mechanism as claimed in claim 11 , wherein at least one of the driving magnets has a different shape than the other driving magnets.

13. The optical element driving mechanism as claimed in claim 11 , further comprising at least three position sensors, wherein each of the position sensors is positioned at a same side of the optical element driving mechanism with one of the driving magnets, for detecting magnetic fields of the driving magnets.

14. The optical element driving mechanism as claimed in claim 13 , wherein directions of the magnetic fields that are detected by two of the position sensors are parallel.

15. The optical element driving mechanism as claimed in claim 14 , wherein a direction of a magnetic field that is detected by one of the position sensors is not parallel to the directions of the magnetic fields that are detected by the two of the position sensors.

16. The optical element driving mechanism as claimed in claim 11 , wherein the driving magnets are multipolar magnets.

17. The optical element driving mechanism as claimed in claim 16 , wherein the magnets are arranged in different directions.

18. The optical element driving mechanism as claimed in claim 1 , wherein the movable portion comprises a wall that extends along the main axis and is adjacent to the driving assembly.