Micromirror unit with torsion connector having nonconstant width
A micromirror unit is provided which includes a frame, a mirror forming base upon which a mirror surface is formed, and a torsion connector which includes a first end connected to the mirror forming base and a second end connected to the frame. The torsion connector defines a rotation axis about which the mirror forming base is rotated relative to the frame. The torsion connector has a width measured in a direction which is parallel to the mirror surface and perpendicular to the rotation axis. The width of the torsion connector is relatively great at the first end. The width becomes gradually smaller from the first end toward the second end.
1. A micromirror unit comprising:
a first frame;
a mirror forming base provided with a mirror surface; and
a first torsion connector connecting the first frame to the mirror forming base and defining a first axis about which the mirror forming base is rotated relative to the first frame,
wherein the first torsion connector includes at least two torsion bars each having a first end connected to the mirror forming base and a second end connected to the first frame, the first ends of said at least two torsion bars being spaced from each other by a first distance, the second ends of said at least two torsion bars being spaced from each other by a second distance which is smaller than the first distance, the second ends being connected to different portions of the first frame.
2. The micromirror unit according to claim 1 , further comprising a second frame and a second torsion connector, wherein the second torsion connector connects the second frame to the first frame and defines a second axis about which the first frame and the mirror forming base are rotated relative to the second frame.
3. The micromirror unit according to claim 2 , wherein the second torsion connector includes at least two additional torsion bars each having a first end connected to the first frame and a second end connected to the second frame, the first ends of said at least two additional torsion bars being spaced from each other by a third distance, the second ends of said at least two additional torsion bars being spaced from each other by a fourth distance which is smaller than the first distance.
4. The micromirror unit according to claim 2 , wherein the first frame is provided with a third comb-teeth electrode, and the second frame is provided with a fourth comb-teeth electrode cooperating with the third comb-teeth electrode for moving the first frame and the mirror forming base relative to the second frame.
5. The micromirror unit according to claim 1 , further comprising a first potential conducting path and a second potential conducting path, wherein each of said at least two torsion bars is connected to one of the first and the second potential conducting paths.
6. The micromirror unit according to claim 1 , wherein the spacing between said at least two torsion bars becomes monotonically smaller from the mirror forming base to the first frame.
7. The micromirror unit according to claim 1 , wherein each of the at least two torsion bars has one of a rectangular cross section, a circular cross section and an elliptical cross section.
8. The micromirror unit according to claim 1 , wherein each of said at least two torsion bars has a hollow structure.
9. The micromirror unit according to claim 1 , wherein each of said at least one of the first and second ends of each torsion bar has a curved portion for prevention of stress concentration.
10. The micromirror unit according to claim 1 , wherein the mirror forming base is provided with a first comb-teeth electrode and the first frame is provided with a second comb-teeth electrode cooperating with the first comb-teeth electrode for moving the mirror forming base relative to the first frame.
11. The micromirror unit according to claim 1 , further comprising a support base facing the mirror forming base, wherein the support base is provided with a first electrode facing the mirror forming base, and the mirror forming base is provided with a second electrode facing the first electrode.
12. The micromirror unit according to claim 1 , wherein at least a part of the first frame has a multi-layer structure including a plurality of conductive layers and an insulating layer disposed between the conductive layers.