Digital Camera Patent AbstractA digital camera is constructed with multiple lenses mounted in
a pair of tubular elements which are nested together for relative
axial movement. Movement is provided by piezoelectric actuators
mounted externally to a support tube on flexible printed circuit
board elements. Each lens tube is provided with a drive rail which
extends at least partially over the length of the lens tube and
projects radially outward from the periphery of each of the tubes.
The rails are accessible to the engagement pads of the piezoelectric
actuators to allow the transmission of drive forces to each of the
tubes.
Digital Camera Patent ClaimsWe claim:
1. An adjustable support for an optical system of a digital camera
comprising: a support tube having a longitudinal axis, said support
tube being secured within said camera; a first lens tube in which
at least one lens element is fixed, said first lens tube being mounted
for relative movement coaxially on said support tube; a drive rail
fixed to said first lens tube and extending radially outward therefrom
through a slot constructed in said support tube; and at least one
piezoelectric actuator mounted on said support tube in operative
association with said drive rail, wherein said at least one piezoelectric
actuator engages said drive rail to cause movement of said first
lens tube along said axis.
2. An adjustable support for an optical system of a digital camera,
as described in claim 1, wherein said at least one piezoelectric
actuator is mounted on a flexible printed circuit board.
3. An adjustable support for an optical system of a digital camera,
as described in claim 2, wherein said printed circuit board is substantially
U-shaped and wherein the at least one piezoelectric actuator comprises:
a pair of piezoelectric elements mounted on opposing surfaces of
said U-shaped printed circuit board wherein said U-shaped printed
circuit board is mounted on said support tube with said drive rail
extending between said elements.
4. An adjustable support for an optical system of a digital camera,
as described in claim 3, wherein said drive rail is constructed
with a wedge-shaped cross section having inclined engagement surfaces;
and further comprising a spring cup for securing said U-shaped printed
circuit board to said support tube in a manner to exert a bias force
on said U-shaped printed circuit board in a manner which tends to
urge said piezoelectric elements into engagement with said drive
rail and thereby exert a radially outward force on said drive rail.
5. An adjustable support for an optical system of a digital camera,
as described in claim 1, wherein supporting surfaces constructed
between said lens tube and the support tube are very close to, or
centered with, engagement pads constructed on the piezoelectric
actuator.
6. An adjustable support for an optical system of a digital camera,
as described in claim 1, wherein said lens tube is forced against
said support tube by spring forces in the radial direction.
7. An adjustable support for an optical system of a digital camera,
as described in claim 1, wherein said lens tube is forced against
said support with magnetic forces in the radial direction.
8. An adjustable support for an optical system of a digital camera,
as described in claim 1, wherein said drive rail is constructed
with a wedge-shaped cross section having inclined engagement surfaces,
wherein engagement of said at least one piezoelectric actuator exerts
a radially outward force.
9. An adjustable support for an optical system of a digital camera,
as described in claim 1, further comprising a position sensor mounted
on said support tube in operative association with said first lens
tube to monitor the axial position of said first lens tube.
10. An adjustable support for an optical system of a digital camera,
as described in claim 9, wherein said position sensor comprises
an optical sensor in line of sight communication with said first
lens tube through said support tube.
11. An adjustable support for an optical system of a digital camera,
as described in claim 9, wherein said position sensor is mounted
on said flexible printed circuit board.
12. An adjustable support for an optical system of a digital camera,
as described in claim 1, further comprising: a second lens tube
in which at least one lens element is fixed, said second lens tube
being mounted on said support tube for axial movement relative to
said first lens tube; a second drive rail fixed to said second lens
tube and extending radially outward therefrom through a slot constructed
in said support tube; and at least one piezoelectric actuator mounted
on said support tube in operative association with said second drive
rail, wherein said at least one piezoelectric actuator engages said
second drive rail to cause movement of said second lens tube along
said axis relative to said first lens tube.
13. An adjustable support for an optical system of a digital camera,
as described in claim 12, further comprising: multiple projections
extending radially outward from said second lens tube; travel grooves
constructed in said first lens tube to receive the projections of
said second lens tube for axial motion in said grooves.
14. An adjustable support for an optical system of a digital camera,
as described in claim 13, wherein said projections and said travel
grooves are constructed within mating surfaces which are beveled
in order to maintain a consistent radial position of said second
lens tube within said first lens tube.
15. An adjustable support for an optical system of a digital camera,
as described in claim 12, wherein said at least one piezoelectric
actuator in operative association with said second lens tube is
mounted on a second flexible printed circuit board.
16. An adjustable support for an optical system of a digital camera,
as described in claim 15, wherein said second flexible printed circuit
board is substantially U-shaped and wherein the at least one piezoelectric
actuator comprises: a pair of piezoelectric elements mounted on
opposing surfaces of said U-shaped printed circuit board wherein
said U-shaped printed circuit board is mounted on said support tube
with said second drive rail extending between said elements.
17. An adjustable support for an optical system of a digital camera,
as described in claim 16, wherein said second drive rail is constructed
with a wedge-shaped cross section having inclined engagement surfaces;
and further comprising a spring clip for securing said second U-shaped
printed circuit board to said support tube in a manner to exert
a bias force on said second U-shaped printed circuit board in a
manner which tends to urge said piezoelectric elements into engagement
with said second drive rail and thereby exert a radially outward
force on said second drive rail.
18. An adjustable support for an optical system of a digital camera,
as described in claim 12, wherein said second drive rail is constructed
with a wedge-shaped cross section having inclined engagement surfaces,
wherein engagement of said at least one piezoelectric actuator exerts
a radially outward force on said second drive rail.
19. An adjustable support for an optical system of a digital camera,
as described in claim 12, further comprising a second position sensor
mounted on said support tube in operative association with said
second lens tube to monitor the axial position of said second lens
tube.
20. An adjustable support for an optical system of a digital camera,
as described in claim 19, wherein said second position sensor comprises
an optical sensor in line of sight communication with said second
lens tube through said support tube.
21. An adjustable support for an optical system of a digital camera,
as described in claim 19, wherein said second position sensor is
mounted on said second flexible printed circuit board.
22. An adjustable support for an optical system of a digital camera,
as described in claim 12, wherein said first and second drive rails
are spaced symmetrically around the periphery of said support tube.
23. An adjustable support for an optical system of a digital camera
comprising: a support tube having a longitudinal axis, said support
tube being secured within said camera; a first and second lens tubes
each having a lens system fixed therein, said first and second lens
tubes being mounted for relative movement coaxially on said support
tube; first and second drive rails fixed to said first and second
lens tubes respectively, each of said drive rails extending radially
outward from respective lens tubes through a slot constructed in
said support tube; and at least two piezoelectric actuators mounted
on said support tube in operative association with said first and
second drive rails, wherein said at least two piezoelectric actuators
engage said first and second drive rails to cause axial movement
of said first and second lens tubes relative to said support tube.
24. An adjustable support for an optical system of a digital camera,
as described in claim 23, wherein said first and second drive rails
are spaced symmetrically around the periphery of said support tube.
25. An adjustable support for an optical system of a digital camera,
as described in claim 23, wherein said first and second drive rails
are spaced asymmetrically around the periphery of said support tube.
26. An adjustable support for an optical system of a digital camera,
as described in claim 23, wherein said support tube and said first
lens tube are constructed with aligned spaces to allow said second
lens tube to be assembled in a motion transverse to said support
tube axis.
27. An adjustable support for an optical system of a digital camera,
as described in claim 23, further comprising: a projection extending
radially outward from each of said first and second lens tubes;
a pair of travel grooves constructed in said support tube to receive
the projections of said first and second lens tubes for axial motion
in said grooves; and wherein said projections and said travel grooves
are constructed within mating surfaces which are beveled in order
to maintain a consistent radial position of said first and second
lens tubes within said support tube.
28. An adjustable support for an optical system of a digital camera,
as described in claim 27, wherein said first and second drive rails
are constructed with a wedge-shaped cross section having inclined
engagement surfaces, wherein engagement of said piezoelectric actuators
exert a radially outward forces on said first and second drive rails
to maintain engagement between said projections of said first and
second lens tubes and said travel grooves.
29. An adjustable support for an optical system of a digital camera,
as described in claim 23, wherein said at least two piezoelectric
actuators in operative association with said first and second lens
tubes are mounted on separate flexible printed circuit boards mounted
on said support tube.
30. An adjustable support for an optical system of a digital camera,
as described in claim 29, wherein said flexible printed circuit
boards are substantially U-shaped and wherein each of the at least
two piezoelectric actuators comprises: a pair of piezoelectric elements
mounted on opposing surfaces of each of said U-shaped printed circuit
boards, wherein said U-shaped printed circuit boards are mounted
on said support tube with said first and second drive rails extending
between said elements.
31. An adjustable support for an optical system of a digital camera,
as described in claim 30, wherein said first and second drive rails
are constructed with wedge-shaped cross sections having inclined
engagement surfaces; and further comprising a spring clip for securing
said second U-shaped printed circuit board to said support tube
in a manner to exert a bias force on said second U-shaped printed
circuit board in a manner which tends to urge said piezoelectric
elements into engagement with said second drive rail and thereby
exert a radially outward force on said second drive rail.
32. An adjustable support for an optical system of a digital camera,
as described in claim 23, wherein said drive rails are constructed
with a wedge-shaped cross section having inclined engagement surfaces,
wherein engagement of said at least two piezoelectric actuators
with said drive rails exerts a radially outward force on said drive
rails.
33. An adjustable support for an optical system of a digital camera,
as described in claim 23, further comprising a pair of position
sensors mounted on said support tube in operative association with
said first and second lens tubes to monitor the axial position of
said first second lens tubes.
34. An adjustable support for an optical system of a digital camera,
as described in claim 33, wherein said position sensors comprise
optical sensors in line of sight communication with said first and
second lens tubes through said support tube.
35. An adjustable support for an optical system of a digital camera,
as described in claim 33, wherein said position sensors are mounted
on said first and second flexible printed circuit boards. Digital Camera Patent DescriptionBACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an assembly of optical components
for a miniature digital camera, including piezoelectric actuators
for moving the optical components to provide focusing, zoom, and
other functions. In particular an arrangement of the components
is described that reduces the overall size and facilitates assembly.
2. Brief Description of Related Developments
The components of electronic cameras require low power consumption,
low weight and cost efficiency. These design criteria are challenged
by the demand for optically adjustable cameras that provide autofocus,
zoom optics, or both. These features require the relative movement
of optical elements to provide the adjustment. The required motion
is typically linear but may use a rotating motor combined with a
motion-converting mechanism such as a lead-screw. The motion range
is often in the order of millimeters. It is a purpose of this invention
to provide a mechanism for adjusting the position of the optical
elements in an electronic camera.
One component that has been used in numerous applications is a
bimorph piezoelectric element, such elements are constructed of
multiple layers of piezoelectric material wherein each layer is
connected for independent excitation. In U.S. Pat. No. 4,291,958,
a bimorph piezoelectric cantilever beam is used in combination with
a magnifying lever for focusing a camera. However, the necessary
stroke of such a focusing device results in a poor stiffness of
the device. In electronic camera applications, space is a crucial
factor. There is thus a need for simple drive elements that can
operate in narrow spaces with limited mechanical support. It is
a purpose of this invention to utilize a bimorph piezoelectric element
to adjust the position of a lens in an optical system of a digital
camera.
A camera system using a piezoelectric actuator is described in
commonly owned, related application for patent, Ser. No. 10/163,111
referenced above. The disclosure of this application is incorporated
herein by reference. In this application, a lens element is mounted
within a camera on a tubular member. The lens tube is in turn mounted
on a support tube for movement along the longitudinal axis of the
tubular member. The adjustment movement is provided by means of
multiple bimorph piezoelectric elements, for example by three elements,
spaced symmetrically around the circumference of the support tube.
The piezoelectric elements are connected to and mounted on a flexible
printed circuit board which may contain other electronic components
associated with the lens drive system. The flexible printed circuit
board is mounted on the support tube and is in turn connected to
a voltage source such as a battery. The flexibility of the printed
circuit board allows it to be formed to the shape of the support
tube and for the piezoelectric element to be positioned in engagement
with the lens tube.
The bimorph piezoelectric element used in the mechanism of the
cited application is constructed of at least two layers of piezoelectric
material which are independently energized to provide relative deformation
between the two layers. This piezoelectric element is formed in
the shape of a beam having an engagement pad extending transverse
to the plane of the element from its midpoint. The beam is fixed
to the circuit board close to ends or nodal positions. The beam
comprises a pair of bimorph piezoelectric elements extending to
either side of the engagement pad. Each of the bimorph elements
has dual active layers. The differential deformation generated by
energizing only one of the two layers will cause the piezoelectric
elements to bend, moving the outer end of the engagement pad into
contact with the movable lens tube. By altering the excitation of
the piezoelectric elements, the engagement pad causes movement in
an axial direction, thereby adjusting the position of the lens.
A pattern of excitation is devised to provide movement in discrete
steps.
In the system of the cited application, a processor is connected
in the printed circuit board to provide the main control for the
digital camera and is constructed to generate a drive voltage pattern
in accordance with the desired movement of the lens.
The movement generated by the piezoelectric element provides a
high resolution, but there are no structural features that provide
a reference in order to obtain accurate repeatability. The step
length provided by the piezoelectric element can vary with operational
and environmental conditions. In order to obtain the precision required
in some optical designs, a position sensor is used to monitor the
position of the movable tubes. An optical sensor is used to view
a reflecting surface, which is mounted on the moveable tube. The
reflecting surface consists of a gray-scale incorporated into the
surface treatment of the moveable tube. This configuration will
provide accurate positional monitoring of a moveable tube.
It is a purpose of this invention to provide a miniature digital
camera system of the type described above in which the components
are arranged to facilitate their assembly in an over all package
that is smaller. It is another purpose of this invention to provide
a rail system external to the lens support tubes for engagement
by piezoelectric actuators.
SUMMARY OF THE INVENTION
A digital camera is constructed with multiple lenses mounted in
a pair of tubular elements, which are nested together for relative
axial movement to provide a zoom function. The lens tube assembly
is in turn mounted on a support tube. The lens tube assembly is
moveable within said support tube with respect to an image plane
to provide an autofocus function. Movement is provided by piezoelectric
actuators mounted externally to the support tube on flexible printed
circuit board elements. Each lens tube is provided with a drive
rail which extends at least partially along the length of the lens
tube and project radially outward from the periphery of each of
the tubes. The rails are accessible to the engagement pads of the
piezoelectric actuators to allow the transmission of drive forces
to each of the tubes. Slots are constructed in the support tube
to allow the drive rails to project through the support tube. The
piezoelectric actuators are mounted to permit engagement by a pair
of actuators on either side of the rail.
The rails are constructed having a wedge shaped cross section which
narrows radially inward towards the axis of the system. The piezoelectric
elements are mounted on opposing surfaces of U-shaped flexible printed
circuit boards with a rail in between. In this manner, the piezoelectric
elements are positioned for engagement with the tapered sides of
the rail. A mounting bracket is provided in which is secured the
printed circuit board. The clip like mounting bracket exerts a spring
force on the printed circuit board or the piezoelecric element itself
to bias the piezoelectric elements into engagement with the rail.
This bias force also has a radial component which is applied outward
on the tube element to maintain the tubes in axial alignment and
minimize function effects. Position sensors are mounted on the U-shaped
printed circuit board in optical communication with reflective surfaces
of respective lens tubes.
In one embodiment, the rails are positioned concentrically on the
tube assembly. In a second embodiment the rails are positioned in
the same quadrant of the tube assembly circumference. In the latter
embodiment the engagement forces are applied eccentrically to the
tube elements. To assist in maintaining tube alignment, wedge shaped
grooves and mating surfaces are formed on the engaging surfaces
of the lens tube assembly and the support tube.
BRIEF DESCRIPTION OF THE DRAWINGS
The digital camera system of this invention is explained in more
detail below with reference to the accompanying drawing, in which:
FIG. 1 is an axially exploded, perspective view of an embodiment
of a camera system, according to this invention;
FIG. 2 is an enlarged, exploded perspective view of the lens elements
of FIG. 1;
FIG. 3 is an enlarged exploded, perspective view of the piezoelectric
drive system of FIG. 1;
FIG. 4a is a transverse sectional view of the embodiment of this
invention shown in FIG. 1, taken along section lines 4A--4A of FIG.
4b;
FIG. 4b is a side view of the assembled optical assembly of FIG.
1;
FIG. 5 is an axially exploded, perspective view of an embodiment
of a camera system, according to an alternative embodiment of this
invention; and
FIG. 6 is a transverse sectional view of the alternate embodiment
of this invention shown in FIG. 5.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, a digital camera 1 is constructed with a pair
of lens systems 2 and 3 mounted in a pair of tubular elements 4
and 5. Lens tubes 4 and 5 are nested together for relative movement
along axis x--x to provide a multiple optical functions, such as
auto focus and zoom. The assembled lens tubes 4 and 5, assembly
6, is in turn mounted on a support tube 7 for axial movement within
said support tube 7 with respect to an image plane 8. A filter 9
may be positioned in front of image plane 8. An image sensor 10
is mounted on main circuit board 11 on which may also be mounted
the control and processing components of the digital camera. Lens
tubes 2 and 3 may have multiple cooperating lens mounted within.
Support tube 7 is constructed to receive the lens tubes 4 and 5
in an interior passage 12. Movement is provided by piezoelectric
actuators 13 16 mounted externally to the support tube on flexible
printed circuit board elements 17 and 18. Spring clip mounting brackets
19 and 20 secure the piezoelectric modules in place within a cover
tube 21.
Referring to FIG. 2, lens tubes 4 and 5 are nested together for
sliding movement. As shown lens tube 5 is constructed with rounded
surfaces 22 provided on the outer periphery of a trio of projections
23 25. The projections 23 25 extend through mating slots 26 28 in
lens tube 4. Slots 26 28 are constructed with tapered surfaces 29
which engage opposing tapered surfaces 30 on projections 23 25.
Each of lens tubes 4 and 5 is provided with a drive rail 31 and
32 respectively which extends at least partially over the length
of the lens tubes 4 and 5 and project radially outward from the
periphery of each of the tubes. As shown in FIG. 3, the rails 31
and 32 are accessible to the engagement pads 33 36 of the piezoelectric
actuators 13 16 to allow the transmission of drive forces to each
of the tubes 4 and 5. Slots 37 are constructed in the support tube
7 to allow the drive rails 31 and 32 to project through the support
tube 7.
As shown in FIG. 3, the piezoelectric actuators 13 16 are independently
mounted on flexible printed circuit boards 17 and 18. Printed circuit
boards 38 and 39 are formed in the shape of a U having opposing
arms 40 and 41. The printed circuit board is constructed having
circuit paths (not shown) to supply power to the piezoelectric actuators
13 16. Optical sensors 42 and 43 may also be fixed to the printed
circuit boards 17 and 18. As shown, the actuators 13 16 are mounted
in pairs on opposing arms 40 and 41. The assembly is fixed to the
support tube 7 in a position to permit engagement by a pair of actuators,
such as 15 and 16, on either side of the rails 31 and 32.
Lens tubes 4 and 5 have to be aligned with the support tube 7 with
minimum friction forces. The friction forces will result in a torque
that tend to rotate the lens tube away from axial alignment. If
the supporting surfaces between the lens tubes 4 and 5 and the supporting
tube 7 are very close to, or centered with, the engagement pads
of the drive elements, the torque will be reduced due to a shorter
torque lever. To maintain these advantageous conditions the lens
tubes 4 and 5 have to be pressed against the supporting tube 7 with
a controlled force. This desired bias force in the radial direction
can be created by several means with their respective advantages
and disadvantages. The bias force can be achieved by a flexible
spring (not shown) of e.g. steel or rubber that forces the lens
tubes against the support tube with a minimum of axial forces. The
flexible spring could either be in frictional contact with the lens
tube, e.g. the lens tube is moving within a slot in the support
tube, or fixed directly to the lens tube, e.g. a thin metal wire
that can easily bend in the axial direction. Another solution that
could be used in particular cases is bias forces created by permanent
magnets.
In one embodiment, shown in FIG. 4a, the rails 31 and 32 can be
constructed having a wedge shaped cross section which narrows radially
inward towards the axis of the system. The piezoelectric elements
13 16 are mounted on opposing surfaces of U-shaped flexible printed
circuit boards 17 and 18 with a rail 31 or 32 in between. In this
manner, the piezoelectric elements are positioned for engagement
with the tapered sides of the rail. Spring clips 19 and 20 are provided
in which are secured the printed circuit boards 17 and 18. The spring
clips 19 and 20 exert a spring force on the printed circuit boards
to bias the piezoelectric elements into engagement with their respective
rail. This bias force also has a radial component which is applied
outward on the tube element to maintain the tubes in axial alignment
and minimize binding. Optical sensors 42 and 43 are mounted on the
U-shaped printed circuit boards in optical communication with reflective
surfaces 44 and 45 of respective lens tubes 4 and 5. As shown in
FIG. 3, sensor ports 46 (not shown) and 47 are provided in support
tube 7 to provide access for the optical sensors 42 and 43. The
optical sensors are responsive to provide a position indication
for the lens tubes as they are moved by actuators 13 16. Optical
sensors are shown for illustration, but other types of position
sensors may be adapted for the same purpose, for example, a resistive
position sensor.
For illustration of the basic structure of this invention, two
lens tubes are shown, however, it should be understood, that more
complex lens configurations may be constructed which would require
a greater number of lens tubes. Multiple lens tubes may be nested
for relative movement and driven as shown and described in this
application. Each of the lens tubes may contain lens system comprised
of multiple lens elements.
In one embodiment, the rails are positioned concentrically on the
tube assembly, as shown in FIG. 1. In a second embodiment the rails
are positioned in the same quadrant of the tube assembly circumference,
as shown in FIGS. 5 and 6. In the latter embodiment the engagement
forces are applied eccentrically to the tube elements. To assist
in maintaining tube alignment, wedge shaped grooves 150 and 154
and mating surfaces 151 and 153 are formed on the engaging surfaces
of the lens tube assembly and the support tube, as shown in FIG.
6.
Referring to FIG. 5, the optical system 101 of the second embodiment
is constructed with dual lens tubes 104 and 105. Lens tubes 104
and 105 contain the lenses of the optical system 101 mounted within
support tube 107. A cover tube 121 encloses the optical assembly.
More lens tubes could be employed if a more complex optical system,
i.e., more lenses, is desired.
Similarly to the first embodiment, the optical system 101 is mounted
on printed circuit board 108 to transmit light from an image (not
shown) to an image sensor 110 at an image plane 111. The printed
circuit board may also contain the control circuit 162 for the digital
camera and provide means to connect the optical system to a power
source such as a battery.
Lens tubes 104 and 105 are nested for movement along axis y--y
within support tube 107. This movement includes sliding movement
of lens tube 105 relative to lens tube 104 and movement of the lens
tube 104 within support tube 107. In the embodiment of FIGS. 5 and
6, the lens tubes are nested in a different manner. Lens tube 104
has only a partial tubular surface 152 which has an outer surface
151 for engagement with a groove 150 on the inner surface of passage
112 in support tube 107. The engaging surfaces provide a track in
which the lens tube 104 is moved by the action of piezoelectric
elements 115 and 116. A rail 131 is constructed on the surface 152,
extending radially upward according to FIG. 6. Rail 131 extends
through a slot 137 constructed for this purpose in support tube
107. Rail 131 is shaped with a wedge shaped cross section which
provides surfaces for the engagement of the piezoelectric actuators
115 and 116. These slanted surfaces 155 and 156 cause the engagement
force of the piezoelectric actuators 115 and 116 to apply a radial
outward component of force, which tends to maintain alignment of
the lens tube 104 within the groove 150.
Lens tube 105 may be assembled by insertion through opening 157
in support tube 107 in a motion transverse to the axis y--y. Lens
tube 105 is also constructed with an engagement surface 153 which
extends axially on its outer periphery. A groove 154 is constructed
in the inner surface of passage 112 approximately 90.degree. from
groove 150 to receive engagement surface 153. A rail 132 extends
radially outward from surface 154 through a slot 158 constructed
in support tube 107.
In a manner similar to the first embodiment piezoelectric actuators
113 116 are mounted on the opposing surfaces of U-shaped printed
circuit boards 117 and 118. Circuit boards 117 and 118 are secured
to support tube 107 by spring clips 119 and 120. A pair of outward
extending flanges 160 and 161 may be formed on support tube 107
to receive printed circuit boards 117 and 118. Clips 119 and 120
engage the flanges to secure the circuit boards in place. As shown
in FIG. 6, piezoelectric actuator's 115 and 116 engage slanted surfaces
155 and 156 of rail 131 and are urged into engagement by bias force
exerted by spring clip 119. The radial component of this force urges
the optical tube 104 outward and into engagement with groove 150.
An identical assembly secures the piezoelectric actuators 113 and
114 on support tube 107 and urges the actuators into engagement
with rail 132.
The configuration and operation of the piezoelectric elements are
described in more detail in the parent application referenced above
and incorporated herein.
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