Micromachined torsional scanner
First Claim
1. A torsional scanner comprising:
- a planar micromachined mirror formed in a surface layer of a silicon wafer section, said mirror having a mirror surface;
a pair of opposed torsion bars for supporting said mirror as an island within the wafer section, said mirror thus supported within the wafer section by said torsion bars exhibiting a plurality of vibrational modes including a principal torsional vibrational mode about an axis that is collinear with said torsion bars, a vertical shaking vibrational mode, a vertical rocking vibrational mode, a lateral shaking vibrational mode, and a lateral rocking vibrational mode, each such vibrational mode of said mirror having a vibrational frequency, the vibrational frequency of the principal torsional vibrational mode being lower by at least 20% than the vibrational frequency of any other vibrational mode of said mirror; and
drive means for communicating a reciprocating torsional force to said mirror, thereby establishing a rotary motion of said mirror about the axis that is collinear with said torsion bars.
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Abstract
A frequency-locked torsional scanner of the type having a micromachined mirror formed on a surface of a silicon wafer section supported within a larger wafer section by a pair of opposed torsion bars. The principal vibrational frequency of the mirror is selected to be at least 20% higher than other modes of vibration. To prevent breakage, the torsion bars are hardened by conversion of at least a surface layer to silicon carbide or nitride. A pair of scanners with orthogonal torsion bars may be mounted in a vacuum enclosure for two-dimensional scanning at different rates suitable for television display. In alternate embodiments, a detector and a scanner may be built on a plate on the same supported wafer section or two scanners may be independently supported or one scanner and one detector may be independently supported as two plates. The mirror may be driven electrostatically, magnetically, or by both methods.
851 Citations
41 Claims
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1. A torsional scanner comprising:
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a planar micromachined mirror formed in a surface layer of a silicon wafer section, said mirror having a mirror surface; a pair of opposed torsion bars for supporting said mirror as an island within the wafer section, said mirror thus supported within the wafer section by said torsion bars exhibiting a plurality of vibrational modes including a principal torsional vibrational mode about an axis that is collinear with said torsion bars, a vertical shaking vibrational mode, a vertical rocking vibrational mode, a lateral shaking vibrational mode, and a lateral rocking vibrational mode, each such vibrational mode of said mirror having a vibrational frequency, the vibrational frequency of the principal torsional vibrational mode being lower by at least 20% than the vibrational frequency of any other vibrational mode of said mirror; and drive means for communicating a reciprocating torsional force to said mirror, thereby establishing a rotary motion of said mirror about the axis that is collinear with said torsion bars. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A micromachined scanner assembly comprising:
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a micromachined mirror formed on a surface of a silicon wafer island supported within a first wafer section by a pair of opposed torsion bars, said mirror thus supported within the wafer section by said torsion bars exhibiting a plurality of vibrational modes including a principal torsional vibrational mode about an axis that is collinear with said torsion bars, a vertical shaking vibrational mode, a vertical rocking vibrational mode, a lateral shaking vibrational mode, and a lateral rocking vibrational mode, each such vibrational mode of said mirror having a vibrational frequency, the vibrational frequency of the principal torsional vibrational mode being lower by at least 20% than the vibrational frequency of any other vibrational mode of said mirror; and magnetic drive means for communicating a torsional force to said silicon wafer island, said magnetic drive means including; a conductive coil disposed on said silicon wafer island; and a magnetic field means disposed adjacent to said silicon wafer island in a galvanometric relationship with said conductive coil.
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8. A torsional scanner assembly comprising:
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a planar frame having opposed, axially aligned torsion bars that support a planar, central mirror plate, said frame, torsion bars and mirror plate all monolithically fabricated from a planar semiconductor stress-free single crystal silicon layer of a substrate;
said central mirror plate thus supported within the planar frame by said torsion bars having a center, defining a mirror rest plane if no external force is applied to said central mirror plate, and also exhibiting a plurality of vibrational modes including a principal torsional vibrational mode about an axis that is collinear with said torsion bars, a vertical shaking vibrational mode, a vertical rocking vibrational mode, a lateral shaking vibrational mode, and a lateral rocking vibrational mode, each such vibrational mode of said central mirror plate having a vibrational frequency, the vibrational frequency of the principal torsional vibrational mode being lower by at least 20% than the vibrational frequency of any other vibrational mode of said central mirror plate; anddrive means for imparting rotary motion to said central mirror plate about the axis that is collinear with said torsion bars. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41)
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Specification