Rotary actuation mechanism for variable focus spectacles
A rotary actuation mechanism for variable focus spectacles is disclosed. The spectacles include two variable focus lens units and a bridge therebetween. The actuation mechanism includes a rotary cam rotatably mounted on the bridge, a fingerwheel attached to the rotary cam to rotate it, a cam follower disposed in slidable contact with the peripheral surface of the rotary cam, and two elongated couplers pivotally mounted on the bridge. The peripheral surface of the rotary cam is spiral shaped to transfer the rotation of the rotary cam into a linear, or pivoting, motion of the cam follower. Each coupler has a proximate end in contact with or attached to the cam follower and a distal end coupled to a linkage anchor of a respective lens unit, to transfer the motion of the cam follower into simultaneous pivoting motions of the linkage anchors thereby adjusting the focal lengths of the lens units.
1. An actuation mechanism for spectacles, the spectacles including two variable focus lens units and a bridge therebetween, each variable focus lens unit having a linkage anchor, the actuation mechanism comprising:
a rotary cam mounted on the bridge and able to rotate around a rotation axis, the rotation axis being stationary with respect to the bridge, the rotary cam having a peripheral surface, wherein at least some points on the peripheral surface have radial distances, as measured from the rotation axis, that are different one from the other;
a cam follower disposed in slidable contact with the peripheral surface of the rotary cam; and
first and second elongated couplers, each pivotally mounted on the bridge, each having a proximate end engaged with the cam follower and a distal end coupled to the linkage anchor of a corresponding one of the lens units.
2. The actuation mechanism of claim 1 , further comprising a manually operable fingerwheel affixed to and rotatable with the rotary cam.
3. The actuation mechanism of claim 2 , wherein the fingerwheel is exposed by the bridge and accessible to a user, and wherein the fingerwheel defines a plurality of depressions on its exterior surface.
4. The actuation mechanism of claim 2 , wherein the fingerwheel and the rotary cam are formed as a single piece.
5. The actuation mechanism of claim 2 , wherein the finger wheel and the rotary cam define a through hole, and wherein the actuation mechanism further comprises a bearing shaft extending through the through hole.
6. The actuation mechanism of claim 1 , wherein the rotary cam is located near a center of the bridge, and where the first and second couplers are of substantially equal length.
7. The actuation mechanism of claim 1 , wherein a pivoting axis of each of the first and second couplers is located between the proximate and distal ends of the respective coupler and parallel to the rotation axis of the rotary cam.
8. The actuation mechanism of claim 1 , further comprising first and second adjusting screws respectively connecting, each via an adjustable distance, the distal end of the first and second couplers to the corresponding linkage anchors.
9. The actuation mechanism of claim 1 , wherein the rotary cam has a spiral shaped peripheral surface.
10. The actuation mechanism of claim 9 , wherein the peripheral surface of the rotary cam defines a plurality of steps, and wherein for each step a radial distance at its center is equal to or smaller than radial distances at its two ends.
11. The actuation mechanism of claim 1 , wherein the peripheral surface of the rotary cam defines a protrusion for engaging the cam follower, or the proximate end of the first or second coupler, when the rotary cam is rotated to an extreme position.
12. The actuation mechanism of claim 1 , wherein the cam follower is attached to the proximate end of the first coupler, and wherein the proximate end of the second coupler rests slidably on the cam follower.
13. The actuation mechanism of claim 12 , wherein cam follower defines a surface on which the proximate end of the second coupler rests.
14. The actuation mechanism of claim 1 , wherein the cam follower includes two parts, each being correspondingly attached to the proximate end of either the first, or the second, coupler.
15. The actuation mechanism of claim 1 , wherein the rotary cam is formed of PEEK or Torlon.