Note: Descriptions are shown in the official language in which they were submitted.
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OPTICAL MICROSWITCH
WITIi ROTARY ELECTROSTATIC MICROACTUATOR
The present invention relates generally to optical microswitches and more
particularly to optical
microswitches utilizing electrostatic microactuators with comb drive
assemblies.
Optical switches have heretofore been provided. Many of such switches use
macroscopic rotators.
Switches utilizing electromagnetic motors have been disclosed to move either
an input optical fiber or a refractive
or reflective element interspersed between input and output optical fibers.
Examples of such designs that use
piezoelectric elements to move refractive or reflective elements are shown in
U.S. Patent Nos. 5,647,033 to
Laughlin, 5,748,813 to Buchin and 5,742,712 to Pan et al. All of switches are
relatively large and expensive.
A micromachined optical switch is disclosed in U.S. Patent No. 5,446,811 to
Field et al, and uses a
bimetallic element to displace an optical fiber into alignment with one or
more optical fibers. Such switch, however,
is not easily extendable to a switch having a relatively large number of
output fibers and bimetallic actuators are
relatively slow.
Micromachined devices to tilt or rotate mirrors are known in the prior art,
but suffer from various
limitations. A one dimensional or two dimensional mirror rotator that tilts
about axes in the plane of the substrate
used to fabricate the device is disclosed in Dhuler et al., "A Novel Two Axis
Actuator for High Speed Large
Angular Rotation", Transducers '97, Vol. 1, pp. 327-330. The actuator uses a
variable gap parallel plate capacitor
as the drive element, which suffers from non-linear response of force or
angular displacement as a function of
applied voltage. A similar type of tilting mirror is descnbed in Kruth et al.,
"Silicon Mirrors and Micromirror
Arrays for Spatial Laser Beam Modulation", Sensors and Actuators A 66 ( 1998),
pp. 76-82. Such mirrors are
typically designed for use in projection displays or in scanners for bar code
reading. A scanner using surface
nucromachining technology and having a mirror that is tilted out of the plane
of the fabrication is described in
Kung et al., "Surface-Micromachined Electrostatic-Comb Driven Scanning
Micromirrors for Barcode Scanners",
Ninth Annual Int. Workshop on Micro Electro Mechanical Systems, San Diego,
1996, pp. 192-19997. All of such
devices tend to have difficulty in maintaining flatness and smoothness in the
mirror elements and may have
difficulty in precise static positioning of the mirror due to hysteresis in
the coupling between the electrostatic comb
drive actuator in the plane of the substrate and the mirror element out of the
substrate plane.
In general, it is an object of the present invention to provide a relatively
inexpensive optical microswitch
having a small form factor.
Another object of the invention is to provide an optical microswitch of the
above character in which the
reflective face of a micromirror can rotate in the focal plane of a focusing
lens.
Another object of the invention is to provide an optical microswitch of the
above character in which first
and second micromirrors can be closely packed and disposed in the focal plane
of a focusing lens.
Another object of the invention is to provide an optical microswitch of the
above character which is
capable of coupling visible or infrared light into an optical fiber with low
transmission losses.
Another object of the invention is to provide an optical microswitch of the
above character which has
relatively fast switching times.
Another object of the invention is to provide an optical microswitch of the
above character in which the
mirror is capable of angular rotations over a relatively large range.
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The accompanying drawings, which are somewhat schematic in many instances and
are incorporated in
and form a part of this specification, illustrate several embodiments of the
invention and, together with the
description, serve to explain the principles of the invention.
FIG. 1 is a perspective view of an optical microswitch with rotary
electrostatic microactuator of the present
invention.
FIG. 2 is a plan view of a rotary electrostatic microactuator for use in the
optical microswitch of FIG. 1.
FIG. 3 is a cross-sectional view of the rotary electrostatic microactuator of
FIG. 2 taken along the Iine 3-3
of FIG. 2.
FIG. 4 is a plan view of another embodiment of a rotary electrostatic
microactuator for use in the optical
microswitch of FIG. 1.
FIG. 5 is a plan view of a further embodiment of a rotary electrostatic
microactuator for use in the optical
microswitch of FIG. 1.
FIG. 6 is a perspective view of another embodiment of an optical microswitch
with rotary electrostatic
microactuator of the present invention.
Optical microswitch 11, shown schematically in FIG. 1, is formed from a
support body 12 of any suitable
size and shape and made from any suitable material such as a ceramic material.
Body 12 shown in FIG. 1 has a base
13 and a back 14 secured to the base and extending perpendicularly from the
base. Support body 12 is optionally
coupled to one and as shown a plurality of output optical fibers 16, which can
be either single mode or multi-mode
fibers. In this regard, a bundle 21 of such output fibers 16 is secured
together by a tube 22 mounted on base 13
by any suitable means such as bracket 23. The plurality of optical fibers 16
includes first and second optical fibers
16a and 16b. Tube 22 and output bundle 21 terminate at an end 31. A
conventional focusing lens such as a GRIN
lens 32 is disposed adjacent the end 31 of the fiber optic output bundle 21
and is mounted to base 13 by any suitable
means such as bracket 33. Lens 32 has a sufficient field of view to
accommodate all of fibers 16 in output bundle
21.
At least one and as shown a plurality of input optical fibers 41 can
optionally be coupled to support body
13 for providing laser light to optical microswitch 11. The input optical
fibers 41 are aaanged in a bundle 42
secured together by any suitable means such as tube 43. Input fibers 41
terminate at respective ends 44. Input
bundle 42 is secured to base 13 by any suitable means such as bracket 46. A
conventional collimating lens such
as GRIN lens 47 is disposed adjacent ends 44 and secured to base 13 by bracket
48 or any other suitable means.
Lens 47 is perpendicular to lens 32. An input laser beam 51 from a laser
source (not shown) is directed on a path
by one of input optical fibers 41 through lens 47 to optical microswitch 11.
The glass surfaces of fibers 16 and 41
and lenses 32 and 47 are coated in a conventional manner with an anti-
reflective material.
First and second rotary electrostatic microactuators 56 and 57 are carried by
support body 12 for
alternatively coupling input laser beam 51 into first output fiber 16a or
second output fiber 16b. First planar
microactuator 56 is formed from a first planar rotator chip 58 secured to base
13 by any suitable means such as an
adhesive (not shown). For simplicity, first microactuator 56 and first rotator
chip 58 are shown schematically in
FIG. 1. The first microactuator 56 is preferably disposed perpendicular to
input laser beam 51 and parallel to the
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central longitudinal axis of output of lens 32. A first micromachined mirror
61 extends out of the plane of first
microactuator 56 and is secured to the first microactuator by mean of a post
62 preferably formed integral with the
micromachined mirror 61. Mirror 61 and post 62 are preferably micromachined
separately from microactuator 56.
Post 62 is joined at its base to the microactuator 56 by an adhesive (not
shown) or any other suitable means. First
mirror 61 has a reflective face or surface 63 and is rotatable by first
microactuator 56 about an axis of rotation 64
extending through post 62 and disposed perpendicular to the plane of first
microactuator 56. The axis of rotation
64 preferably intersects the reflective face 63 of micromirror 61 to ensure
that face 63 is undergoing pure rotation.
In addition, axis of rotation 64 is preferably placed at the focal plane of
output lens 32.
Second planar microactuator 57 extends in a second plane and is substantially
identical to first
microactuator 56. The second microactuator 57 is formed from a second planar
rotator chip 67 mounted to block
14 by any suitable means such as an adhesive (not shown). For simplicity,
second microactuator 57 and second
rotator chip 67 are shown schematically in FIG. I . Second microactuator 57 is
suspended over first microactuator
56 and is disposed perpendicular to the plane of the first microactuator. A
second mirror 68 is carried by second
microactuator 57 and is disposed out of the plane of the microactuator 57.
Second micromachined mirror 68 is
preferably formed with an L-shaped post 71 having a base portion or base 71 a
and a cantilever portion or extension
71b. Base 71 a is secured to the microactuator 57 by an adhesive (not shown)
or any other suitable means. Mirror
68 rotates about an axis of rotation 72 extending along base 71 a and disposed
perpendicular to the plane of second
microactuator 57. The axis of rotation 64 of first mirror 61 and the axis of
rotation 72 of second mirror 68 are
preferably disposed in a plane extending perpendicular to the first and second
microactuators 56 and 57. The
mirrors 61 and 68 each have a sufficient range of rotation to permit the
mirror 61 to direct laser beam 51, by means
of lens 32, onto the core of each of optical fibers 16. Extension 71b is
centered on an axis 73 extending parallel
to the plane of second microactuator 57. Axis of rotation 64 of the first
microactuator 56 and axis 73 are preferably
disposed in a plane extending perpendicular to the first microactuator and
parallel to the second microactuator.
Second mirror 68 has a reflective face or surface 74 which is thus centered on
the focal plane of lens 32. Reflective
~~ 25 surfaces 63 and 74 of respective micromirrors 61 and 68 are highly
reflective at the particular wavelength of laser
beam 51.
Any suitable micromachined actuator can be utilized for first and second
microactuators 56 and 57.
Several prefeaed microactuators are disclosed in International Publication No.
WO 00/36740 having a priority date
of December 15, 1999, the entire contents of which is incorporated herein by
this reference. One particularly
preferred rotary electrostatic microactuator 101, shown in FIGS. 2 and 3, is
formed on a planar substrate 102 of the
respective rotator chip 58 or 67. A rotatable member or circular mirror holder
103 overlies the substrate 102. A
plurality of first and second comb drive assemblies 106 and 107 are carried by
substrate 102 for rotating mirror
holder 103 in first and second opposite angular directions about an axis of
rotation 108 extending through the center
of the circular mirror holder 103 perpendicular to planar substrate 102 and
thus FIG. 2. Axis of rotation 108
corresponds to axes of rotations 64 and 72 of the respective microactuators 56
and 57. Each of the first and second
comb drive assemblies 106 and 107 includes a first comb drive member or comb
drive 111 mounted on substrate
102 and a second comb drive member or comb drive 112 overlying the substrate
102. First and second
w v ~cW11Ct1 CND
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spaced-apart springs 113 and 114 are included in microactuator 101 for
supporting or suspending second comb
drives 112 and mirror holder 103 above the substrate 102 and for providing
radial stiffness to the movable second
comb drives 112 and thus the mirror holder 103.
Substrate 102 is made from any suitable material such as silicon and is
preferably formed from a silicon
wafer. The substrate has a thickness ranging from 200 to 600 microns and
preferably approximately 400 microns.
Mirror holder 103, first and second comb drive assemblies 106 and 107 and
first and second springs 113 and 114
are formed atop the substrate 102 by a second or top layer 116 made from a
wafer of any suitable material such as
silicon. Top wafer 116 has a thickness ranging from 10 to Z00 microns and
preferably approximately 85 microns
and is secured to the substrate 102 by any suitable means. The top wafer 116
is preferably fusion bonded to the
substrate 102 by means of a silicon dioxide layer 117 having a thickness
ranging from 0.1 to two microns and
preferably approximately one micron. Top wafer 116 may be lapped and polished
to the desired thickness. The
mirror holder 103, the first and second comb drive assemblies 106 and 107 and
the first and second springs 113
and 114 are formed from the top wafer 116 by any suitable means. Preferably,
such structures are etched from
wafer 116 using deep reactive ion etching (DRIE) techniques. Mirror holder 103
is spaced above substrate 102 by
an air gap 118, that ranges from three to 30 microns and preferably
approximately 15 microns, so as to be
electrically isolated from the substrate.
At least one and preferably a plurality of first comb drive assemblies 106 are
included in rotary electrostatic
microactuator 101 and disposed about axis of rotation 108, shown as a point in
FIG. 2, for driving mirror holder
103 in a clockwise direction about axis 108. At least one second comb drive
assembly 107 and preferably a
plurality of second comb drive assemblies 107 can be included in microactuator
101 for driving the mirror holder
in a counterclockwise direction about the axis of rotation 108. Each of the
first and second comb drive assemblies
106 and 107 extends substantially radially from axis of rotation 108 and, in
the aggregate, subtend an angle of
approximately 180° so as to provide rotary microactuator 101 with a
semicircular or fanlike shape when viewed
in plan (see FIG. 2). More specifically, microactuator 101 has three first
comb drive assemblies 106a, 106b and
106c and three second comb drive assemblies 107a, 107b and 107c. Rotary
microactuator 101 has a base 119
extending along a diameter of the semicircle formed by the microactuator 101
and has an outer radial extremity 121
resembling the arc of a semicircle. Radial extremity 121 has first and second
ends which adjoin the first and second
opposite ends of base 119. The radial extremity 121 is defined by the outer
radial extremities of first and second
comb drive assemblies 106 and 107. Mirror holder 103 and axis of rotation 108
are disposed at the center of the
semicircle adjacent base 119.
First and second comb drive assemblies 106 and 107 are interspersed between
each other, that is, a second
comb drive assembly 107 is disposed between each pair of adjacent first comb
drive assemblies 106. The first comb
drive assemblies 106 are symmetrically disposed relative to the second comb
drive assemblies 107 about the radial
centerline of rotary electrostatic microactuator 101, that is the imaginary
line extending in the plane of substrate
102 through axis of rotation 108 and perpendicular to base 119. Each of the
first and second comb drive assemblies
106 and 107 has a length ranging from 200 to 2,000 microns and more preferably
approximately 580 microns.
Rotary microactuator 101 has a length measured along base I 19 ranging from
500 to 5,000 microns and more
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preferably approximately 1,800 microns.
First comb drive 111 of each of first and second comb drive assemblies 106 and
107 is mounted to
substrate 102 by means of silicon dioxide layer 117. As such, the first comb
drives 111 are immovably secured to
substrate 102. Each of the first comb drives 111 has a radially-extending bar
122 provided with a first or inner
radial portion 122a and a second or outer radial portion 122b. Outer portion
122b extends to outer radial extremity
121 of microactuator 101. A plurality of comb drive fingers 123 are
longitudinally spaced apart along the length
of bar 122 at a separation distance ranging from eight to 50 microns and
preferably approximately 24 microns. The
comb drive forgers 123 extend substantially perpendicularly from bar 122 and
are each arcuate in shape. More
specifically, each comb forger 123 has a substantially constant radial
dimension relative to axis of rotation 108 as
it extends outwardly from the bar 122. Fingers 123 have a length ranging from
approximately 22 to 102 microns
and increase substantially linearly in length from bar inner portion 122a to
bar outer portion 122b. Although the
comb fingers 123 can vary in width along their length, the comb forgers 123
are shown as having a constant width
ranging from two to 12 microns and preferably approximately six microns. Bar
inner portions 122a for first comb
drive assemblies 106a and 106b and second comb drive assemblies 107b and 107c
are joined to a base member 124
which serves to anchor such bars 122 to substrate I 02 and permit such bar
inner portions 122a to thus have a smaller
width and the related comb drives 123 to have a corresponding longer length.
Second comb drives 112 are spaced above substrate 102 by air gap 118 so as to
be movable relative to
substrate 102 and relative to first comb drives 111. The second comb drives I
12 have a construction similar to the
first comb drives I 11 discussed above and, more specifically, are formed with
a bar 126 that extends radially
outwardly from axis of rotation 108. The bar 126 has a first or inner radial
portion 126a in close proximity to axis
108 and a second or outer radial portion 126b that extends to radial extremity
121. A plurality of comb drive forgers
127 are longitudinally spaced apart along the length of bar 126 and are
substantially similar to comb forgers 123.
Arcuate comb fingers 127 are offset relative to comb fingers 123 so that the
comb forgers 127 on second comb drive
112 can interdigitate with comb fingers 123 on first comb drive 111 when the
second comb drives 112 are rotated
about axis 108 towards the stationary first comb drives 111. Each of first and
second comb drive assemblies 106
and 107 resembles a sector of the semicircular microactuator 101.
Means including first and second spaced-apart springs 113 and 114 are included
within rotary electrostatic
microactuator 101 for movably supporting second comb drives 112 over substrate
102. First and second suspension
elements or springs 113 and 114 each have a length which preferably
approximates the length of first and second
comb drive assemblies 106 and 107, however springs having lengths less than
the length of the comb drive
assemblies can be provided. Although first and second springs 113 and 114 can
each be formed from a single
spring member, the springs 113 and 114 are each preferably U-shaped or V-
shaped in conformation so as to be a
folded spring. As shown, springs 113 and 114 are substantially U-shaped. Each
of springs 113 and 114 is made
from first and second elongate spring members 131 and 132. First or linear
spring member 131 has first and second
end portions 131a and 131b and second or linear spring member 132 has first
and second end portions 132a and
132b.
The first end portion 131 a of each folded spring 113 and 114 is secured at
its end to substrate 102 adjacent
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axis of rotation 108 by means of silicon dioxide layer 117 (see FIG. 3). The
balance of the spring is spaced above
the substrate by air gap 118. Second end portion 131b of each spring 113 and
114 is secured to first end portion
132a of the second spring member 132. First and second beam-like spring
members 131 and 132 each extend
radially outwardly from axis of rotation 108 and preferably have a length
approximating the length of first and
second comb drive assemblies 106 and 107. The spring members 131 and 132 are
preferably approximately equal
in length and each have a length of approximately 500 microns. As such, spring
first end portions 131 a are secured
to substrate 102 adjacent spring second end portions 132b. Although first end
portion 131 a of each spring 113 and
114 can be secured to substrate 102 adjacent mirror holder 103 or adjacent
outer radial extremity 121, the first end
portion 131a is preferably secured to substrate 102 adjacent outer radial
extremity 121. First and second spring
members 131 and I32 each have a width ranging from one to 10 microns and
preferably approximately four
microns. First and second thin, elongate sacrificial bars I33 and 134, of a
type described in U.S. Patent No.
5,998,906 and in copending U.S. patent application Serial No. 09/135,236 filed
August 17, 1998, the entire contents
of each of which are incorporated herein by this reference, extend along each
side of each spring member 131 and
132 for ensuring even etching and thus the desired rectangular cross section
of the spring members. Sacrificial bars
133 and 134 are disposed along opposite sides of the spring members and extend
parallel to the respective spring
member.
Second end portion 132b of each spring 113 and 114 is secured to at least one
of second comb drives 112.
In this regard, first and second movable frame members or frames 141 and 142,
spaced above substrate 102 by air
gap 118, are provided in rotary electrostatic microactuator 101. Each of the
frames 141 an 142 is substantially U-
shaped in conformation and includes as side members bars 126 of the adjoining
second comb drives 112. More
specifically, first movable frame 141 includes bar 126 of second comb drive
assembly 107a, bar 126 of first comb
drive assembly 106a and an arcuate member 143 which interconnects such bar
outer portions 126b. Second
movable frame 142 is similar in construction and includes as side members bar
126 of second comb drive assembly
107c, bar 126 of first comb drive assembly 106c and an arcuate member 144
which interconnects such bar outer
portions 126b. Second end portion 132b of first spring I 13 is secured to
arcuate member 143 adjacent to bar outer
portion 126b of second comb drive assembly 107a, while the second end portion
132b of second spring 114 is
secured to arcuate member 144 adjacent bar outer portion 126b of first comb
drive assembly 106c. In this manner,
first folded spring 113 is disposed inside first movable frame 142 and second
folded spring 114 is disposed inside
second movable frame 142. Bar inner portion 126a of second comb drive assembly
107a is joined to mirror holder
103 and serves to secure first spring 113 to the mirror holder. Similarly, bar
inner portion 126a of fast comb drive
assembly 106c is joined to mirror holder 103 for intercormecting second spring
114 to the mirror holder.
First and second movable frames 141 and 142 are symmetrically disposed about
the radial centerline of
rotary electrostatic microactuator 101. At least one comb drive assembly and
preferably at least one first comb drive
assembly 106 and at least one second comb drive assembly 107 are disposed
between first and second movable
frames 141 and 142 and thus first and second springs 113 and 114. More
specifically, first comb drive assemblies
106a and 106b and second comb drive assemblies 107b and 107c are disposed
between frames I41 and 142. Bar
126 of second comb drive assembly 107b and bar 126 of first comb drive
assembly 106b are joined back to back
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to form a third movable frame 147 preferably extending along the centerline of
microactuator 1 O 1 between movable
frames 141 and 142. An inner arcuate member or shuttle 148 is joined at
opposite ends to first and second movable
frames 141 and 142. One end of rigid shuttle 148 is secured to bar inner
portion 126a of first comb drive assembly
106a while the second end of the shuttle 148 is secured to bar inner portion
126a of second comb drive assembly
107c. Third movable frame 147 is joined to the middle of the shuttle 148 so as
to rotate in unison with first and
second movable frames 141 and 142 about axis 108. An additional arcuate member
151 is provided in
microactuator 101 for rigidly securing together second end portions 131b of
first and second springs 113 and 114.
The arcuate member 151 overlies substrate 102 and extends at least partially
around the axis of rotation 108.
Member 151 is disposed between shuttle 148 and mirror holder 103 and rotates
about axis 108 free of mirror holder
103. The suspended structures of microactuator 101, that is mirror holder 103,
second comb drives 112, first and
second springs 131 and 132 and first and second movable frames 141 and 142,
each have a thickness ranging from
10 to 200 microns and preferably approximately 85 microns.
Second comb drives I 12 of first and second comb drive assemblies 106 and 107
are movable in a direction
of travel about axis of rotation 108 by means of movable frames 141, 142 and
147 between respective first
positions, as shown in FIG. 2, in which comb drive fingers 123 and 127 of the
first and second comb drives are not
substantially fully interdigitated and respective second positions, not shown,
in which the comb drive forgers 123
and 127 are substantially fully interdigitated. Although comb drive fingers
123 and 127 can be partially
interdigitated when secoad comb drives 112 are in their first positions, the
comb forgers 123 and 127 are shown
as being fully disengaged and thus are not interdigitated when second comb
drives 112 are in their first positions.
When in their second positions, comb forgers 127 of second comb drives 112
extend between respective comb drive
fingers 123 of the first comb drives 111. Comb fingers 127 approach but
preferably do not engage bar 122 of the
respective first comb drives 111 and similarly comb drive fingers 123 approach
but preferably do not engage bar
126 of the respective second comb drives 112. Rigid movable frames 141, 142
and 147 are constructed as light
weight members to decrease the mass and moment of inertia of the movable
portions of microactuator 101 and thus
facilitate rotation of second comb drives 112 and mirror holder 103 about axis
of rotation 108. Each of the movable
frames 141, 142 and 147 is substantially hollow and formed with a plurality of
internal beams or trusses 152 for
providing rigidity to the movable frame.
Electrical means is included within microactuator 101 for driving second comb
drives 112 between their
first and second positions. Such electrical means includes a controller and
voltage generator 161 that is electrically
connected to a plurality of electrodes provided on substrate 102 by means of a
plurality of electrical leads 162.
Controller 161 is shown schematically in FIG. 2. A first ground electrode 166
and a second ground electrode 167
are formed on substrate 102 and are respectively joined to the first end
portion 131 a of first and second springs 113
and 114 for electrically grounding second comb drives 112 and mirror holder
103. Electrodes 166 and 167 serve
as the attachment points for spring first end portions 131 a to the substrate
102. First comb drives 111 of first comb
drive assemblies 106 can be supplied a voltage potential from controller 161
by means of an electrode 171
electrically coupled to bar outer portion 122b of first comb drive assembly
106a and an additional electrode 172
electrically coupled to the first comb drive 111 of first comb drive assembly
106b and to first comb drive 11 I of
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first comb drive assembly 106c by lead 173. An electrode 176 is secured to the
first comb drive 11 I of second
comb drive assembly 107a by means of lead 177 and to second comb drive
assembly 107b and an electrode 179
is joined to bar outer portion 122b of second comb drive assembly 107c for
providing a voltage potential to the first
comb drives of second comb drive assemblies 107. A metal layer 181 made from
aluminum or any other suitable
material is created on the top surface of top wafer 116 for creating
electrodes 166, 167, 171, 172, 176 and 179 and
for creating leads 173,174,177 and 178 (see FIG. 2). First and second pointers
186 extend radiaIly outwardly from
the outer end of third movable frame 147 for indicating the angular position
of mirror holder 103 about axis 108
on a scale 187 provided on substrate 102.
Means in the form of a closed loop servo control can be included in
microactuator 101 for monitoring the
position of second comb drives 112 and thus mirror holder 103. For example,
controller 161 can determine the
position of the movable comb drives 112 by means of a conventional algorithm
included in the controller for
measuring the capacitance between comb drive fingers 127 of the movable comb
drives 112 and the comb drive
fingers 123 of the stationary comb drives 111. A signal separate from the
drive signal to the comb drive members
can be transmitted by controller 161 to the microactuator for measuring such
capacitance. Such a method does not
require physical contact between the comb drive forgers. Alternatively, a
portion of the output optical energy
coupled into the output fiber 16 can be diverted and measured and the drive
signal from the controller 161 to the
microactuator 101 adjusted until the measured optical energy is maximized.
In operation and use of optical microswitcb 11, first and second
microactuators 56 and 57 are utilized to
respectively rotate first and second mirrors 61 and 68 to direct input laser
beam 51 to either first or second output
fibers 16a or 16b or any of the other optical fibers 16 of output bundle 21.
Mirror holder 103 of the respective
microactuator 101 can be rotated in opposite first and second directions of
travel about axis of rotation 108 by
means of controller I61. The amount of rotation can be controlled by the
amount of voltage supplied to the
appropriate first comb drives 111 of the microactuator 101. As shown in FIG.
1, laser beam 51 is launched by input
lens 57 onto the reflective surface 74 of second mirror 68, from which the
beam S la is reflected onto surface 63
of first mirror 61. Input laser beam 51 b is reflected by the first mirror 61
onto the desired portion of the image plane
of output lens 32 so that the laser beam 51 is focused and coupled by lens 32
into the appropriate optical fiber 16
of output bundle 21.
Rotation of second mirror 68 in first and second opposite directions about
axis of rotation 72 by second
microactuator 57 controls the vertical position relative to first
microactuator 56 at which the reflected beam S l a
strikes reflective face 63 on the axis of rotation 64 of the first mirror 61.
Rotation of the first mirror 61 about axis
of rotation 64 by first microactuator 56 controls the horizontal position
relative to the first microactuator 56 at which
the beam 5 lb reflected by the first mirror strikes output lens 32. In this
manner, input laser beam 51 can be directed
by the first and second mirrors 61 and 68 into any one of the optical fibers
of output bundle 21. For example,
rotation of first micromirror 61 to a first position and rotation of second
micromirror 68 to a first position reflects
the laser beam 51 to first output fiber 16a, while rotation of first
micromirror 61 to a second position and rotation
of second micromirror 68 to a second position reflects the laser beam 51 to
second output fiber 16b. The position
of the mirror holders 103 of microactuators 56 and 57 and thus mirrors 61 and
68 can optionally be monitored in
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the manner discussed above with respect to microactuator 101. Micromirrors 61
and 68 are each capable ofrotating
at speeds less than five milliseconds between fibers 16 with optical losses of
less than one dB.
In its rest position, second mirror 68 is aligned on second microactuator 57
so its reflective surface 74 is
capable of reflecting input laser beam 51 from the center of input lens 47
onto the center of the first mirror 61.
Similarly, first mirror 61 is angularly disposed relative to first
microactuator 56 so that when the first mirror is in
its rest position, the input beam 51 a impinging the first mirror 61 is
reflected by the first mirror onto the center of
output lens 32. Such positioning of first and second mirrors 61 and 68
relative to first and second microactuators
56 and 57 minimizes the rotational travel of the mirrors during the operation
of optical microswitch 11. The first
and second mirrors 61 and 68 are each capable of +/- six degrees angular
rotation, that is a rotation of six degrees
in both the clockwise and counterclockwise directions for an aggregate
rotation of twelve degrees.
The fanlike shape of first and second microactuators 56 and 57 permits
respective first and second mirrors
61 and 68 to be mounted along the base 119 of the respective microactuator
101. For example, the placement of
first mirror 61 on such base 119 of first microactuator 56 permits the
microactuator 56 to be positioned along one
side of first rotator chip 58 and support base 13 so that input laser beam 51
has a path to second mirror 68 that is
unobstructed by the microactuator 56. Second mirror 68 overhangs such side of
rotator chip 58. Similarly, the
fanlike shape of second microactuator 57 permits the microactuator 57 to
overhang fu~st microactuator 56. Second
mirror 68 advantageously rotates about axis 72 disposed along the base 119 of
second microactuator 57 and
overhangs second microactuator 57 so as to be in close proximity to first
mirror 61. This close placement of first
and second mirrors 61 and 68 minimizes the length of base 71 a of second
mirror post 71 and the optical path of
input laser beam 51.
The separate fabrication of first and second mirrors 61 and 68 allows for
larger choice of reflective coatings
for the mirrors, including multilayer dielectric mirrors, enhanced metallic
mirrors and metallic mirrors otherwise
incompatible with micromachining fabrication steps such as sacrificial release
or high temperature processing. The
separate mirrors 61 and 68 can be fabricated on relatively thick and very
smooth flat substrates, which is difficult
to achieve with an integrated micromachined process. In addition, mirrors
rotating above and out of the plane of
the substrate 102 allow for novel mechanical layout and packaging of
microswitch 11, particularly the close
coupling of microactuators 56 and 57.
The utilization of rotary electrostatic microactuators, and particularly
electrostatic microactuators having
a fanlike shape or other shape that permits the axis of rotation to be placed
along a side of the microactuator, allows
the optical microswitch 11 to have a relatively small form factor of less than
approximately one cubic centimeter.
Microactuators 56 and 57 desirably require relatively low power and permit
rapid switching between fibers.
Microswitch 11 is particularly suited for use as an optical switch in a fiber
optic network of a telecommunications
system. However, the optical microswitch 11 can be used in other applications,
such as in computer data storage
systems, and more specifically in an optics module of a magneto-optical data
storage system. Other applications
include data networks and cable television systems.
Although optical microswitch 11 is shown for use with a plurality of input
optical fibers 41, a single input
fiber 41 can be prow ided. Alternative, input laser beam 51 can be supplied
from any other suitable source, such as
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directly from a laser in close proximity to or mounted on support body 12. In
addition, it should be appreciated that
microswitch I 1 can be bidirectional, that is optical fibers 16 can serve as
input fibers and optical fibers 41 can serve
as output fibers.
Another rotary electrostatic microactuator disclosed in International
Publication No. WO 00/36740 having
S a priority date of December 15, 1999 and suitable for use as first and/or
second microactuators 56 and 57 in optical
microswitch 11 is shown in FIG. 4. Microactuator 201 therein has similarities
to microactuator 101 and like
reference numerals have been used to describe like components of
microactuators 1 J 1 and 201. A rotatable member
or mirror holder 202 overlies substrate 102 of the respective rotator chip 58
or 67. A plurality of first and second
comb drive assemblies 203 and 204 are carried by the substrate 102 for
rotating the mirror holder 202 in first and
second opposite direction about an axis of rotation 206 extending
perpendicular to planar substrate 102. Axis of
rotation 206 corresponds to axes of rotations 64 and 72 of the respective
microactuators 56 and 57. The axis of
rotation is shown as a point in FIG. 4 and labeled by reference line 206. Each
of the first and second comb drive
assemblies 203 and 204 includes a first drive member or comb drive 211 mounted
on substrate 102 and a second
comb drive member or comb drive 212 overlying the substrate. First and second
spaced-apart springs 213 and 214
are included in microactuator 201 for supporting or suspending second comb
drives 212 and mirror holder 202
above the substrate 102 and for providing radial stiffness to the second comb
drives 212 and the mirror holder 202.
The mirror holder 202, first and second comb drive assemblies 203 and 204 and
first and second springs 213 and
214 are formed from top layer 116 by any suitable means such as discussed
above for microactuator 101. Mirror
holder 202, second comb drives 212 and first and second springs 213 and 214
are spaced above substrate 102 by
air gap 188 and have thicknesses similar to those discussed above for the like
components of microactuator 101.
At least one and preferably a plurality of first comb drive assemblies 203 are
included in rotary electrostatic
microactuator 201 and disposed about axis of rotation 206 for driving mirror
holder 202 in a clockwise direction
about axis of rotation 206. At least one and preferably a plurality of second
comb drive assemblies 204 can be
included in microactuator 201 for driving the mirror holder in a
counterclockwise direction about the axis of rotation
~'25 206. Each of the first and second comb drive assemblies 203 and 204
extends substantially radially from axis of
J rotation 108 and the assemblies 203 and 204, in the aggregate, subtend an
angle of approximately 180° to provide
the semicircular or fanlike shape to microactuator 201. More particularly,
microactuator 201 has four first comb
drive assemblies 203a, 203b, 203c and 203d and four second comb drive
assemblies 204a, 204b, 204c and 204d.
The first comb drive assemblies 203 are interspersed between the second comb
drive assemblies 204. The rotary
microactuator 201 has a base 219 substantially similar to base 119 and an
outer radial extremity 221 substantially
similar to outer radial extremity 121. First comb drive assemblies 203 are
symmetrically disposed relative to second
comb drive assemblies 204 about the radial centerline of rotary electrostatic
microactuator 201, that is the imaginary
line extending in the plane of substrate 102 through axis of rotation 206
perpendicular to base 219. Mirror holder
202 and axis of rotation 206 are disposed at the center of microactuator 201
adjacent base 219. The rotary
microactuator has a length measured along base 219 ranging from 500 to 5,000
microns and preferably
approximately 2,000 microns.
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First comb drive 211 of each of first and second comb drive assemblies 203 and
204 is mounted to
substrate 101 in the manner discussed above with respect to fast comb drives
111. Each of the fast comb drives
211 has a radial-extending bar 226 provided with a fast or inner radial
portion 226a and a second or outer radial
portion 226b. The outer portion 226b of each fast comb drive 211 extends to
outer radial extremity 221. A
plurality of comb drive forgers 227 are longitudinally spaced apart along the
length of bar 226 at a separation
distance ranging from eight to 50 microns and preferably approximately 35
microns. The comb drive fingers 227
extend substantially perpendicularly from bar 226 and, like comb drive fingers
123, are each arcuate in shape.
Fingers 227 have a length ranging from 25 to 190 microns and increase
substantially linearly in length from bar
inner portion 226a to bar outer portion 226b. Each of the comb drive forgers
227 has a proximal portion 227a and
a distal portion 227b. The proximal portion 227a has a width ranging from four
to 20 microns and preferably
approximately 10 microns, and the distal portion 227b has a width less than
the width ofproximal portion 227a and,
more specifically, ranging from two to 12 microns and preferably approximately
six microns.
Second comb drives 212 and mirror holder 202 are part of a movable or
rotatable frame 231 spaced above
substrate 102 by air gap 118 so as to be electrically isolated from the
substrate and movable relative to the substrate
and fast comb drives 211. Frame 231 includes a fast arm 232, a second arm 233,
a third arm 236 and a fourth arm
237, each of which extend in a substantial radial direction from axis of
rotation 206. First and fourth arms 232 and
237 are symmetrically disposed relative to the centerline of microactuator 101
and second and third arms 233 and
236 are also symmetrically disposed relative to such centerline. First and
fourth arms 232 and 237 are each U-
shaped in conformation and formed from fast and second bars 241 and 242. The
fast bar 241 has a fast or inner
radial portion 241a in close proximity to axis 206 and a second or outer
radial portion 241b that extends to outer
radial extremity 221. Similarly, second bar 242 has a fast or inner radial
portion 242a and a second or outer radial
portion 242b. Outer radial portions 241 b and 242b are joined by a base member
243 at outer radial extremity 221.
Inner radial portion 241a of the first bar 241 is joined to mirror holder 202,
while inner radial portion 242a of
second bar 242 extends freely adjacent the mirror holder 202. Second and third
arms 233 and 236 are joined at their
inner portions to mirror holder 202.
First bar 241 of fast arm 232 forms part of second comb drive 212 of fast comb
drive assembly 203a,
while second bar 242 of fast arm 232 serves as part of the second comb drive
212 of second comb drive assembly
204a. A plurality of comb drive fingers 251 are longitudinally spaced apart
along the length of such fast bar 241
for forming the comb drive forgers of fast comb drive assembly 203a, while a
plurality of comb drive fingers 251
are longitudinally spaced apart along the length of second bar 242 of such
fast arm 232 for forming the comb drive
forgers of lust comb drive assembly 204a. Comb drive fingers 251 are
substantially similar to comb drive forgers
22? and have a fast or proximal portion 251 a joined to the respective bar 241
or 242 and a second or distal portion
251 b extending from such proximal portion 251 a. Distal portions ZS lb have a
width less than the width of proximal
portions 251a. Arcuate comb drive forgers 251 are offset relative to comb
drive fingers 227 so that comb drive
forgers 251 can interdigitate with comb drive fingers 227. First bar 241 of
fourth arm 237 similarly serves as part
of second comb drive 212 of second comb drive assembly 204d, while second bar
242 of the fourth arm 237 serves
as part of the second comb drive 212 for fast comb drive assembly 203d. Comb
drive forgers 251 extend from fast
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and second bars 241 and 242 of fourth arm 237.
Second and third arms 233 and 236 are included in second comb drives 212 of
first comb drive assemblies
203b and 203c and second comb drive assemblies 204b and 204c. The second arm
233 has a first or inner radial
portion 233a joined to mirror holder 202 and a second or outer radial portion
233b adjacent outer radial extremity
221. Third arm 236 is similar in constnrction to second arm 233 and has a
first or inner radial portion 236a and a
second or outer radial portion 236b. A first plurality of comb drive fingers
251 are longitudinally spaced apart
along the length of one side of second arm 233 for forming the second comb
drive of second comb drive assembly
204b and a second plurality of comb drive fingers 251 are longitudinally
spaced apart along the length of the other
side of second arm 233 for forming the second comb drive of first comb drive
assembly 203b. Similarly, a first
plurality of comb drive forgers 251 are longitudinally spaced apart along one
side of third arm 236 for forming
second comb drive 212 of first comb drive assembly 203c and a second plurality
of comb drive forgers 251 are
longitudinally spaced apart along the opposite side of the third arm 236 for
forming second comb drive 212 of
second comb drive assembly 204c. The second and third arms 233 and 236 can
optionally be joined by a link 252
at the respective inner radial portions 233 and 236a for enhancing the
rigidity of the arms 233 and 236.
Means including first and second spaced-apart springs 213 and 214 are included
within rotary electrostatic
microactuator 201 for movably supporting mirror holder 202 and second comb
drives 212 over substrate 102.
Springs 213 and 214 are symmetrically disposed about the centerline of
microactuator 201 and preferably have a
length which approximates the length of at least some of first and second comb
drive assemblies 203 and 204. Base
219 of microactuator 201 includes an attachment or bracket member 253 which
has a portion intersecting axis of
rotation 206 and serves to secure first and second springs 213 and 214 to
substrate 102. Each of the springs 213
and 214 is formed from a single beam-like spring member 256 having a first or
inner radial end portion 256a joined
at its end to bracket member 253 and a second or outer radial end portion 256b
joined to base member 243 of the
respective first arm 232 or fourth arm 237. More specifically, first spring
213 extends from bracket member 253
up the center of first arm 232 for joinder to the center of base member 243.
Second spring 214 extends from bracket
member 253 radially outwardly through the center of fourth arm 237 for joinder
to the center of base member 243.
Inner end portions 256a of spring members 256 are joined to the bracket member
253 at axis of rotation 206. The
spring members 256 have a width ranging from one to 10 microns and preferably
approximately four microns.
Respective first and fourth arms 232 and 237 serve to secure outer end
portions 256b of the first and second springs
213 and 214 to mirror holder 202.
At least one comb drive assembly and preferably at least one first comb drive
assembly 203 and at least
one second comb drive assembly 204 is disposed between first and second
springs 213 and 214. More specifically,
first comb drive assemblies 203b and 203c and second comb drive assemblies
204b and 204c, each of which is
formed in part by second and third arms 233 and 236, are angularly disposed
between first and second springs 213
and 214. Additionally, first comb drive assembly 203a and second comb drive
assembly 204d, symmetrically
disposed relative to each other about the centerline of microactuator 201, are
angularly disposed between first and
second springs 213 and 214.
Comb drive forgers 227 and 251 of first and second comb drives 211 and 212 are
not substantially fully
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interdigitated when in their first or rest positions shown in FIG. 4. Although
the teen not substantially fully
interdigitated is broad enough to cover comb drive fingers which are not
interdigitated when in their rest positions,
such as comb drive forgers 123 and 127 of microactuator 101 shown in FIGS. 2
and 3, such term also includes
comb drive forgers which are partially interdigitated when in their rest
positions. In microactuator 201, distal
portions 227b and 251b of the comb drive fingers are substantially
interdigitated when the comb drives 211 and
212 are in their at rest positions.
At least one and as shown all oi' first and second comb drive assemblies 203
and 204 are not centered along
a radial extending outwardly from axis of rotation 206. In this regard, distal
ends 261 of comb drive fingers 227
for each comb drive assembly 203 or 204 are aligned along an imaginary line
that does not intersect axis of rotation
206 and, as such, is spaced-apart from the axis 206. Similarly, distal ends
262 of comb forgers 251 extend along
an imaginary line which does not intersect axis of rotation 206. Each of first
and second comb drive assemblies
203 and 204 thus resembles a sector of a semicircle that is offset relative to
a radial of such semicircle.
Second comb drives 212 of first and second comb drive assemblies 203 and 204
are each movable in a
direction of travel about axis of rotation 206 between a first or rest
position, as shown in FIG. 4, in which comb
~~ 15 drive fingers 227 and 251 are not substantially fully interdigitated and
a second position (not shown) in which comb
drive forgers 227 and 251 are substantially fully interdigitated such as
discussed above with respect to comb fingers
123 and 127 of microactuator 101. Second comb drives 212 of first comb drive
assemblies 203 are in their second
positions when second comb drives 212 of second comb drive assemblies 204 are
in their first positions and,
similarly, the second comb drives 212 of assemblies 204 are in their second
positions when the second comb drives
212 of assemblies 203 are in their first positions.
Electrical means is included within microactuator 201 for driving second comb
drives 212 between their
first and second positions. Such electrical means can include a controller and
voltage generator 161 electrically
connected to a plurality of electrodes provided on the substrate 102 by means
of a plurality of electrical leads 162.
For simplicity, controller 161 and leads 162 are not shown in FIG. 4. Such
electrodes, each of which is substantially
similar to the electrodes discussed above with respective to microactuator
101, include a common electrode 266
electrically coupled by lead 267 to bracket member 253, at least one drive
electrode 271 coupled directly or by
means of lead 272 to first comb drive 211 of first comb drive assemblies 203
and one or more drive electrodes 273
coupled directly or by means of lead 274 to first comb drives 211 of second
comb drive assemblies 204. Several
leads 274 extending out of the plane of microactuator 201 are shown in phantom
lines in FIG. 4. The position of
mirror holder 202 and thus mirrors 61 and 68 can optionally be monitored in
the manner discussed above with
respect to microactuator 101.
The rotary electrostatic microactuators of microswitch 11 can utilize other
than radially-extending comb
drive assemblies. An exemplary push-pull microactuator using coupled linear
electrostatic micromotors is described
in International Publication No. WO 00/36?40 having a priority date of
December 15, 1999 and shown in FIG. 5.
Rotary electrostatic microactuator 401 therein is similar in certain respects
to microactuators 101 and 201 and like
reference numerals have been used to describe like components of the
microactuators 101, 201 and 401. The
microactuator 401 includes a rotatable member 402 comprising a mirror holder,
for mounting to the
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microactuator 401 a micromirror 403 extending out of the plane of
microactuator 401, and a T-shaped bracket 404
secured to micromirror 403. The profile of micromirror 403 is shown in FIG. 5.
The rotatable member 402 rotates
about an axis of rotation 406 extending perpendicular to planar substrate 102
of the respective rotator chip 68 or
67. Axis of rotation 406 corresponds to axes of rotations 64 and 72 of the
respective microactuators 56 and 57.
The axis of rotation 406 intersects micromirror 403 at its reflective surface
403a and is identified as a point by
reference numeral 406 in FIG. 5. Microactuator 401 is provided with at least
one side 407 and rotatable member
402 is disposed adjacent the side 407. The microactuator 401 bas fu~st and
second linear micromotors 408 and 409
and first and second couplers 41 I and 412 for respectively securing first and
second micromotors 408 and 409 to
bracket 404.
First and second micromotors 408 and 409 are substantially identical in
construction and are formed atop
the substrate 102 from upper layer 116. The micromotors each includes at least
one comb drive assembly and
preferably includes at least one first comb drive assembly 416 and at least
one second comb drive assembly 417.
As shown, each of the micromotors 408 and 409 includes a plurality of four
first comb drive assemblies 416 and
a plurality of four second comb drive assemblies 471 aligned in parallel.
First comb drive assemblies 416 are
disposed side-by-side in a group and second comb drive assemblies 417 are
similarly disposed side-by-side in a
group. The group of assemblies 416 are disposed in juxtaposition to the group
of assemblies 417.
Comb drive assemblies 416 and 417 can be of any suitable type. In one
preferred embodiment, the comb
drive assemblies are similar to the comb drive assemblies described in U.S.
Patent No. 5,998,906 issued December
7, 1999 and in copending U.S. patent application Serial No. 09/135,236 filed
August 17, 1998. The comb drive
assemblies 416 and 417 are each provided with a first comb drive member or
comb drive 421 mounted on substrate
102 and a second comb drive 422 overlying the substrate. First comb drives 421
are each formed from an elongate
bar 426 having first and second end portions 426a and 426b. A plurality of
linear comb drive forgers 427, shown
as being linear, are secured to one side of the bar in longitudinally spaced-
apart positions along the length of the
bar. Comb drive fingers or comb fingers 427 extend perpendicularly from bar
426 and, as shown, can be of equal
length and have a constant width along their length. Second comb drives 422
are similar in construction to first
comb drives 421 and are each formed from a bar 431 having first and second end
portions 431a and 431b. A
plurality of linear comb fingers 432, shown as being linear, extend from one
side of the bar 431 in longitudinally
spaced-apart positions. Comb fingers 432 are substantially identical to comb
fingers 427, but are offset relative to
the comb forgers 427. When comb drive assemblies 416 and 417 are in their home
or rest positions, comb forgers
427 and 432 are not substantially fully interdigitated and, preferably, are
partially interdigitated as shown in FIG.
5.
An elongate member or shuttle 436 is included in each of first and second
micromotors 408 and 409.
Shuttle 436 has first and second end portions 436a and 436b. First end portion
431 a of each of bars 431 is secured
to shuttle 436 so that bars 431 extend perpendicularly from one side of the
shuttle 436 between shuttle end portions
436a and 436b.
First and second spaced-apart spring members 437 and 438 are included in each
of micromotors 408 and
409. Springs 437 and 438 can be of any suitable type and are preferably formed
from at least one elongate beam-
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like member. In one preferred embodiment, springs 437 and 438 each consist of
a single such beam-like member
similar to first spring member 131 and to second spring member 132 discussed
above. Springs 437 and 438 are
substantially identical in construction and each include first and second
sacrificial bars 133 and 134 disposed along
opposite sides of the springs for the purposes discussed above. First spring
437 has first and second end portions
S 437a and 437b and second spring 438 has first and second end portions 438a
and 438b. The spring second end
portion 437b is secured to shuttle first end portion 436a and the spring
second end portion 438b is secured to shuttle
second end portion 436b. As a result, at least one and as shown all of first
and second comb drive assemblies 416
and 417 are disposed between first and second springs 437 and 438. The springs
437 and 438 preferably extend
perpendicular to shuttle 436 when comb drive assemblies 416 and 417 are in
their home or rest positions. Each of
the first and second springs 437 and 438 preferably has a length approximating
the length of comb drive assemblies
416 and 417 so that first end portions 437a and 438a are disposed adjacent the
second end portions 426b and 431b
of the comb drive bars 426 and 431. An attachment block 439 is secured to
substrate 102 for each spring 437 and
438 and serves to attach the first end portions 437a and 438a of the first and
second springs to the substrate 102.
Second comb drives 422, shuttle 436 and first and second springs 437 and 438
are spaced above substrate
102 by air gap 1 I 8 so as to be electrically isolated from the substrate and
movable relative to the substrate. These
structures can have any suitable thickness and preferably each have a
thickness ranging from 10 to 200 microns
and more preferably approximately 85 microns. First and second springs 437 and
438 are included within the
means of microactuator 401 for suspending and movably supporting second comb
drives 422 over substrate 102.
The second comb drives 422 are movable in a linear direction of travel
relative to first comb drives 421
between first positions, as shown in FIG. 5, in which comb fingers 427 and 432
are not substantially fully
interdigitated and second positions in which the comb fingers 427 and 432 are
substantially fully interdigitated.
When in their second positions, comb fingers 432 extend between respective
comb fingers 427 and approach but
preferably do not engage first comb drive bar 426. Second comb drive members
422 of first comb drive assemblies
416 are in their second positions when second comb drives 422 of second comb
drive assemblies 417 are in their
first positions. Conversely, the second comb drives of first comb drive
assemblies 416 are in their first positions
when the second comb drives of second comb drive assemblies 417 are in their
second positions.
The movement of second comb drives 422 to their first and second positions
causes shuttle 436 to move
in opposite first and second linear directions relative to substrate 102. Such
directions of travel are substantially
perpendicular to the disposition of the elongate first and second comb drive
assemblies 416 and 417. A plurality
of first stops 441 are secured to substrate 102 for limiting the travel of
second comb drives 422 of first comb drive
assemblies 416 towards their respective first comb drives 421. A plurality of
similar second stops 442 are secured
to the substrate for limiting the travel of second comb drives 422 of second
comb drive assemblies 417 towards
their respective first comb drives 421. In one preferred embodiment, first and
second micromotors 408 and 409
are disposed in juxtaposition so that respective shuttles 436 are disposed
side-by-side in parallel with each other.
Second end portions 436b of the shuttles 436 each generally point towards
micromirror 403 and are centered
relative to axis of rotation 406.
First and second couplers 41 I and 412 are suspended above substrate 102 by
air gap 118 and have a first
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end secured to shuttle second end portion 436b and a second end secured to the
bracket 404. The couplers 411 and
412 are preferably symmetrically disposed relative to each other with respect
to axis of rotation 406. First coupler
411 secures shuttle 436 of the first micromotor 408 to one side of bracket 404
and second coupler 412 secures
second micromotor 409 to the other side of bracket 404. In one preferred
embodiment, each of the first and second
couplers has at least one spring member or coupling spring to provide a non-
rigid connection between the shuttle
436 and the bracket 404. In a particular preferred embodiment, each of the
first and second couplers 411 and 412
includes a rigid strip 446 secured at one end to shuttle 436 by means of a
first coupling spring 437 and secured at
its other end to bracket 404 by a second coupling spring 448.
Electrical means is included within microactuator 401 for driving second comb
drives 422 of the first and
second micromotors 408 and 409 between their first and second positions. Such
electrical means includes a suitable
controller and voltage generator such as controller and voltage generator 161
electrically coupled to a plurality of
electrodes by means of a plurality of electrical leads 162. For simplicity,
controller 161 and leads 162 are not shown
in FIG. 5. Such electrodes, each of which is substantially similar to the
electrodes described above with respect to
microactuator 101, include first and second ground electrodes 453 which are
electrically coupled by means of
respective leads 454 to attachment block 439 for first springs 437 so as to
electrically ground first and second
springs 437 and 438, shuttle 436 and second comb drives 422 of each of the
micromotors 408 and 409. A first drive
electrode 457 is electrically coupled, either directly or by means of leads
458, to first comb drives 421 of the first
comb drive assemblies 416 of each micromotor 409 and 409. A second drive
electrode 461 is electrically coupled,
either directly or by means of lead 462, to the first comb drives 421 of the
second comb drive assemblies 417 of
the micromotors 408 and 409. An additional stop 463 secured to substrate 102
can additionally be provided for
each micromotor 408 and 409 to limit the forward travel of shuttle 436 towards
rotatable member 402. The position
of rotatable member 402 and thus mirrors 61 and 68 can optionally be monitored
in the manner discussed above
with respect to microactuator 101.
Other optical microswitches utilizing rotary electrostatic microactuators can
be provided. Optical
microswitch 501 shown in FIG. 6 is formed from a support body 502 of any
suitable size and shape and made from
any suitable material such as a ceramic material. Support body 502 has a base
503 and is preferably coupled to a
plurality of optical fibers. As shown in FIG. 6, a plurality of five optical
fibers 506 are coupled to base 503 by any
suitable means such as block 507. The fibers 506 include an input fiber 506a
and a plurality of output fibers which
can be any of the fibers 506. First and second output fibers 506b and 506c are
identified in FIG. 6. The optical
fibers 506 are secured to a planar surface 508 of block 507 by any suitable
means such as an adhesive (not shown).
Fibers 506 extend parallel to each other and are preferably arranged in
juxtaposition on surface 508 with respective
end surfaces 511 linearly aligned across the block 507. Input fiber 506a is
preferably at the center of fibers 506.
A conventional collimating and focusing lens such as GRIN lens 512 is disposed
adjacent end surfaces S11 of
optical fibers 506 and is mounted on base 503 by any suitable means such as an
adhesive (not shown). Lens 512
has a sufficient field of view to accommodate all of fibers 506. The glass
surfaces of fibers 506 and lens 512 are
coated in a conventional manner with an anti-reflective material. An input
laser beam 516 is directed from input
fiber 506a along a path.
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A rotary electrostatic microactuator 521 is carried by support body 502 for
directing input laser beam 516
to first output fiber 506b, second output fiber 506c or any of the other
fibers 506. Microactuator 521 is formed from
a planar rotator chip 522 secured to base 503 by any suitable means such as an
adhesive (not shown). For
simplicity, microactuator 521 and rotator chip 522 are shown schematically in
FIG. 6. The microactuator 521 is
disposed on base 503 such that the plane of the microactuator is parallel to
input laser beam 516. Microactuator
521 is fanlike in shape and is arranged on support body 502 such that the
diametric base 523 of microactuator 521,
corresponding for example to base 119 of microactuator 101, is disposed
adjacent lens 512 and perpendicular to
input laser beam 516. A micromachined mirror 526 substantially similar to
first mirror 61 discussed above is
included in optical microswitch 501. Micromachined mirror 526 extends out of
the plane of microactuator 521 and
is secured to the microactuator by means of a post 527 preferably formed
integral with micromirror 526. Post 527
is joined at its base to microactuator 521 by an adhesive (not shown) or any
other suitable means. Micromirror 526
has a reflective face or surface 528 rotatable by microactuator 521 about an
axis of rotation 529 extending through
post 527 and disposed perpendicular to the plane of microactuator 521 and to
input beam 516. Axis of rotation 529
is preferably disposed at the focal plane of lens 512 and mirror 526 has a
sufficient range of rotation to permit the
~~ 15 mirror to direct output beam 531, by means of lens 512, onto the core of
each of optical fibers 506.
Any suitable micromachined actuator can be utilized for microactuator 521,
including any of the
microactuators disclosed in International Publication No. WO 00/36740 having a
priority date of December I5,
1999 and any of such microactuators 101, 201 and 401 discussed above.
In operation and use, microactuator 521 is utilized to rotate micromirror 526
to reflect input laser beam
516 and cause the output laser beam 531 to impinge the image plane of lens 512
for coupling into first or second
output optical fibers 506b or 506c. Rotation of micromirror 526 about axis of
rotation 529 controls the position
at which output laser beam 531 impinges lens 512 and thus the optical fiber
506 into which output beam 531 is
directed. In its rest position, micromirror 526 is preferably aligned on
microactuator 521 so that its reflective
surface 528 is parallel with base 523 of the microactuator 521. Additionally,
as disclosed above, it is preferable
that input fiber 506a be one of the centenmost optical fibers 506. Such
central disposition of input fiber 506a and
the disposition of micromirror 526 parallel to base 528 minimizes the
rotational travel of the micromirror when
directing the output beam 521 to the desired output fiber 506. For example,
micromirror 526 need be rotated only
slightly in the clockwise direction for directing output laser beam 531 into
first output fiber 506b. Similarly, slight
counterclockwise rotation of micromirror 526 about axis 529 results in output
laser beam 531 being directed into
second output fiber 506c, as shown in FIG. 6. In addition, use of the central
fiber 506 as the input fiber facilitates
the input beam S 16 impinging reflective surface 528 on the axis of rotation
of micromirror 526. Micromirror 526
is capable of +/- six degrees angular rotation, that is a rotation of six
degrees in both the clockwise and
counterclockwise directions for an aggregate rotation of twelve degrees,
although approximately +/_ four degrees
or less of angular rotation is sufficient in microswitch 501.
The disposition of axis of rotation 529 adjacent the base 523 of microactuator
521 facilitates placement
of the reflective face 528 of micramirror S26 in the focal plane of lens 512.
Bidirectional optical microswitch 501
has a relatively small form factor of less than approximately one cubic
centimeter. The microswitch 501 is suitable
. . ........-r. n~ ~rrt
CA 02356905 2001-06-14
WO 00/36447 PGTNS99/29715
-18-
for use in a fiber optic network of a telecommunications system, but can also
be used in other applications such as
in a computer data storage system.
As can be seen from the foregoing, a relatively inexpensive optical
niicroswitch having a small form factor
has been provided. The microswitch has a micromirror with a reflective face
that rotates in the focal plane of a
focusing lens. The microswitch can optionally be provided with first and
second micrornirrors that are closely
packed and disposed in the focal plane of a focusing lens. The microswitch is
capable of coupling visible light into
a single mode or mufti-mode optical fiber with low transmission losses and has
relatively fast switching times. The
mirror of the microswitch is capable of angular rotations over a relatively
large range.
