Bi-directional stiffness for optical image stabilization in a dual-aperture digital camera

1. A folded camera module, comprising:

a) a lens module having a lens optical axis,

b) an optical path folding element (OPFE) for folding light from a first optical path to a second optical path towards an image sensor, the second optical path being along the lens optical axis;

c) a lens actuation sub-assembly configured to actuate the lens module to be moved for auto-focus (AF) along a first direction substantially parallel to the second optical path and to be moved for optical image stabilization (OIS) along a second direction substantially orthogonal to both the first and second optical paths to compensate for tilt of the folded camera module around the first direction; and

d) an OPFE actuation sub-assembly configured to tilt the OPFE for OIS around an OPFE tilt axis which is parallel to the second direction to compensate for tilt of the folded camera module around the second direction,

wherein the lens actuation sub-assembly comprises a plurality of springs mechanically coupled to a lens support plate carrying the lens module, wherein the plurality of springs provides overall low stiffness to movement of the lens module in the first and second directions and high stiffness of the lens module to torsion, such that a ratio between natural frequencies arising from the high stiffness to torsion and the low stiffness to movement in each of the first and second directions is greater than 2.

2. The folded camera module of claim 1 , wherein the ratio between natural frequencies arising from the high stiffness to torsion and the low stiffness to movement in each of the first and second directions is greater than 3.

3. The folded camera module of claim 1 , wherein the ratio between natural frequencies arising from the high stiffness to torsion and the low stiffness to movement in each of the first and second directions is greater than 5.

4. The folded camera module of claim 1 , wherein the ratio between natural frequencies arising from the high stiffness to torsion and the low stiffness to movement in each of the first and second directions is greater than 10.

5. The folded camera module of claim 1 , wherein the lens actuation sub-assembly is dimensioned to accommodate the lens module without obstructing an optical path passing through the lens module.

6. The folded camera module of claim 1 , further comprising one or more position sensors that enable measurement of a position of the lens module along the first and second directions and measurement of the OPFE tilt.

7. The folded camera module of claim 6 , wherein the position sensors are Hall sensors.

8. The folded camera module of claim 1 , wherein the OPFE actuation sub-assembly includes a plurality of flexible hanging members.

9. The folded camera module of claim 1 , wherein the OPFE tilt axis is a virtual axis.

10. The folded camera module of claim 1 , wherein the OPFE actuation sub-assembly includes at least one coil-magnet pair for actuating the OPFE tilt.

11. The folded camera module of claim 1 , wherein the OPFE includes a prism or a mirror.

12. The folded camera module of claim 1 , wherein the lens actuation sub-assembly includes a plurality of coil-magnet pairs for actuating the lens module movement.

13. The folded camera module of claim 12 , wherein the plurality of coil-magnet pairs includes two coil-magnet pairs.

14. The folded camera module of claim 1 , wherein the folded camera module has a folded camera height in the range of 4-7 mm and wherein the lens module has an effective focal length EFL F in the range of 6-15 mm.

15. The folded camera module of claim 1 , included in a smart-phone.