Autofocus camera systems and methods
A method for focusing a miniature camera includes providing a current through a coil, moving a lens of a camera based on the current to adjust a focus of the camera, and limiting movement of the lens along an optical path of the camera.
1. A method, comprising:
providing a current through a coil; and
moving an optical element, based on the current, with respect to an image sensor by moving a movable portion of a stage assembly, the movable portion having the optical element and a magnet assembly disposed thereon, the magnet assembly being positioned adjacent the coil;
biasing the movable portion toward an initial position of the optical element; and wherein
the optical element moves along an optical axis of the optical element; and
the movable portion defines a plane and is constrained to movement substantially within the plane along an axis parallel to the optical axis.
2. The method of claim 1 , wherein the magnet assembly comprises at least one permanent magnet.
3. The method of claim 1 , wherein:
the stage assembly further includes a stationary portion; and
the movable portion is coupled to the stationary portion via at least one flexible structure; and
the at least one flexible structure facilitates movement of the movable portion along the axis parallel to the optical axis while inhibiting other movement thereof.
4. The method of claim 1 , further comprising controlling the current through the coil to adjust the focus of an image on the image sensor.
5. The method of claim 1 , wherein the step of moving the optical element comprises moving the movable portion against the biasing force.
6. The method of claim 5 , wherein the biasing force is exerted on the movable portion via the magnet assembly.
7. A device, comprising:
a coil;
circuitry for providing a variable current through the coil;
a stage assembly including a movable portion, the movable portion having an optical element and a magnet assembly disposed thereon, the magnet assembly being resiliently suspended adjacent to the coil for movement relative to the coil;
a biasing member disposed to bias the movable portion toward an initial position; and wherein
the optical element moves along an optical axis of the optical element; and
the movable portion defines a plane and is constrained to movement substantially within the plane along an axis parallel to the optical axis.
8. The device of claim 7 , wherein the magnet assembly comprises at least one permanent magnet.
9. The device of claim 7 , wherein the stage assembly further includes a snubber assembly configured to constrain movement of the movable portion to substantially rectilinear movement along the axis parallel to the optical axis.
10. The device of claim 9 , wherein:
the stage assembly further includes a stationary portion; and
the movable portion is coupled to the stationary portion via at least one flexible structure; and
the at least one flexible structure facilitates movement of the movable portion along the axis parallel to the optical axis while inhibiting other movement thereof.
11. The device of claim 10 , wherein the at least one flexible structure comprises a plurality of flexures formed monolithically with the movable portion and the stationary portion.
12. The device of claim 11 , wherein the movable portion, the stationary portion, and the plurality of flexures are formed in silicon.
13. The device of claim 7 , wherein the biasing member comprises a spring disposed to apply a biasing force to the magnet assembly.
14. A method, comprising:
coupling an optical element to a magnet via a movable portion of a stage assembly, the movable portion defining a plane and being disposed between the magnet and the optical element;
coupling the movable portion to a biasing member such that the movable portion is biased toward an initial position;
suspending the magnet adjacent to a coil so that the optical element and the magnet move conjointly in response to a current through the coil, the optical element moving along an optical axis of the optical element; and
constraining movement of the movable portion to within the plane of the movable portion and along an axis parallel to the optical axis.
15. The method of claim 14 , wherein the magnet comprises a permanent magnet.
16. The method of claim 14 , wherein the step of constraining movement of the movable portion comprises positioning a set of snubbers around the movable portion.
17. The method of claim 14 , wherein the step of coupling the movable portion to a biasing member includes coupling the magnet to a spring.