Micro mirror unit and method of making the same
A micro mirror unit includes a moving part carrying a mirror portion, a frame and torsion bars connecting the moving part to the frame. The moving part, the frame and the torsion bars are formed integral from a material substrate. The frame includes a portion thicker than the moving part.
1. A micro mirror unit comprising a moving part, a frame and a torsion bar connecting the moving part to the frame,
wherein the moving part, the frame and the torsion bar are formed integral from a common material substrate having a layered structure including an intermediate layer and silicon layers sandwiching the intermediate layer,
wherein the moving part includes: a first intermediate portion originating from the intermediate layer; a first structural member held in contact with the first intermediate portion and provided with a mirror portion; and a second structural member held in contact with the first intermediate portion on a side opposite to the first structural member;
wherein the frame includes: a second intermediate portion originating from the intermediate layer; a third structural member held in contact with the second intermediate portion on a same side as the first structural member; and a fourth structural member held in contact with the second intermediate portion on a same side as the second structural member; and
wherein the third structural member extends beyond the first structural member in a layering direction of the layered structure.
2. The micro mirror unit according to claim 1 , wherein the moving part includes a first comb-like electrode, the frame including a second comb-like electrode for operation of the moving part by static electric force generated between the first and the second comb-like electrodes.
3. The micro mirror unit according to claim 2 , wherein the first comb-like electrode is formed in the first structural member, the second comb-like electrode being formed in the fourth structural member at a portion contacting the second intermediate portion.
4. The micro mirror unit according to claim 1 , wherein the moving part includes: a relay frame connected to the frame via the torsion bar; a mirror-formed portion spaced from the relay frame; and a relay bar connecting the relay frame to the mirror-formed portion, the relay bar extending in a direction across a direction in which the torsion bar extends.
5. The micro mirror unit according to claim 4 , wherein the mirror-formed portion includes a third comb-like electrode, the relay frame including a fourth comb-like electrode for operation of the mirror-formed portion by static electric force generated between the third and the fourth comb-like electrodes.
6. The micro mirror unit according to claim 5 , wherein the third comb-like electrode is formed in the first structural member, the fourth comb-like electrode being formed in the second structural member.