Driving mechanism

1. A driving mechanism for moving an optical unit, comprising:

a fixed part;

a movable part, movably connected to the optical unit and the fixed part; and

a driving unit, configured to impel the movable part and the optical unit relative to the fixed part, wherein the driving unit comprises an SMA element that has a first length when the movable part is in a first position relative to the fixed part, and when a current signal is applied to the SMA element, the SMA element shrinks from a first length to a second length and impels the movable part from the first position to a second position relative to the fixed part;

a slider, movably disposed on the movable part and connected to the SMA element, wherein the fixed part forms a longitudinal guiding structure, the slider contacts a first end of the guiding structure when the movable part is in the first position relative to the fixed part, and when the slider is impelled by the SMA element along the guiding structure from the first end to a second end of the guiding structure, the movable part is pushed by the slider from the first position to the second position;

a housing, wherein the movable part and the fixed part are received in the housing; and

a smooth element, disposed on an inner surface of the housing and facing the slider.

2. The driving mechanism as claimed in claim 1 , wherein the guiding structure comprises a longitudinal slot.

3. The driving mechanism as claimed in claim 2 , wherein the fixed part has a polygonal shape, and a tilt angle is formed between the guiding structure and a side of the fixed part.

4. The driving mechanism as claimed in claim 3 , wherein the tilt angle is 45 degree.

5. The driving mechanism as claimed in claim 1 , wherein the movable part has an annular structure with a longitudinal rail formed on it, and the slider extends through the rail to the guiding structure.

6. The driving mechanism as claimed in claim 5 , wherein the rail extends in a first direction, and the guiding structure extends in a second direction that is not parallel to the first direction.

7. The driving mechanism as claimed in claim 6 , wherein the second direction is not perpendicular to the first direction.

8. The driving mechanism as claimed in claim 7 , wherein an included angle is formed between the first and second directions, and the included angle ranges from 20 degree to 70 degree.

9. The driving mechanism as claimed in claim 1 , wherein the fixed part has a polygonal shape, and the slider is located close to a corner of the fixed part.

10. The driving mechanism as claimed in claim 1 , further comprising a resilient element disposed on the fixed part, wherein the slider is located between the resilient element and the SMA element.

11. The driving mechanism as claimed in claim 1 , wherein the optical unit includes a first blade and a second blade pivotally connected to the fixed part for partially covering an opening of the fixed part, light enters the driving mechanism and propagates through the opening along an entry direction, and the first and second blades at least partially overlap when viewed along the entry direction.

12. The driving mechanism as claimed in claim 11 , wherein the optical unit further includes a third blade for partially covering the opening of the fixed part, and when viewed along the entry direction, the first and third blades at least partially overlap, and the second and third blades at least partially overlap.

13. The driving mechanism as claimed in claim 11 , further comprising a protecting element, wherein the protecting element and the optical unit at least partially overlap when viewed along the entry direction.

14. A driving mechanism for moving an optical unit, comprising:

a fixed part;

a movable part, movably connected to the optical unit and the fixed part;

a driving unit, configured to impel the movable part and the optical unit relative to the fixed part, wherein the driving unit comprises an SMA element that has a first length when the movable part is in a first position relative to the fixed part, and when a current signal is applied to the SMA element, the SMA element shrinks from a first length to a second length and impels the movable part from the first position to a second position relative to the fixed part;

a slider, movably disposed on the movable part and connected to the SMA element, wherein the fixed part forms a longitudinal guiding structure, the slider contacts a first end of the guiding structure when the movable part is in the first position relative to the fixed part, and when the slider is impelled by the SMA element along the guiding structure from the first end to a second end of the guiding structure, the movable part is pushed by the slider from the first position to the second position; and

a bottom plate, forming a longitudinal cavity, wherein the fixed part is located between the movable part and the bottom plate, and the slider extends through the movable part and the fixed part to the cavity.

15. The driving mechanism as claimed in claim 14 , wherein the longitudinal cavity is parallel to the guiding structure.

16. The driving mechanism as claimed in claim 14 , further comprising a sensing assembly disposed on the movable part and the bottom plate for measuring the displacement of the movable part relative to the fixed part.

17. A driving mechanism for moving an optical unit, comprising:

a fixed part;

a movable part, movably connected to the optical unit and the fixed part;

a driving unit, configured to impel the movable part and the optical unit relative to the fixed part, wherein the driving unit comprises an SMA element that has a first length when the movable part is in a first position relative to the fixed part, and when a current signal is applied to the SMA element, the SMA element shrinks from a first length to a second length and impels the movable part from the first position to a second position relative to the fixed part;

a slider, movably disposed on the movable part and connected to the SMA element, wherein the fixed part forms a longitudinal guiding structure, the slider contacts a first end of the guiding structure when the movable part is in the first position relative to the fixed part, and when the slider is impelled by the SMA element along the guiding structure from the first end to a second end of the guiding structure, the movable part is pushed by the slider from the first position to the second position; and

a magnetic element, disposed on the fixed part, wherein the SMA element is located between the magnetic element and the slider.