Digital Camera Patent Abstract
A support for an optical system of a digital camera is constructed
which provides adjustable positioning of the lens elements in response
to signals from the camera control processor. The support comprises
multiple tubes, mounted for relative coaxial movement, which support
a lens element. At least one of the tubes is adjustable in position
relative to a main support tube. The adjustable tube is engageable
by piezoelectric elements. Each piezoelectrical element is mounted
to a flexible printed circuit board which contains the camera operating
system and is mounted on the support tube. Digital Camera Patent Claims
What is claimed is:
1. An adjustable support for an optical system of a digital camera
comprising: a fixed tubular support having a longitudinal axis,
said fixed tubular support being secured within said camera; a moveable
tubular support mounted for relative movement doaxially on the fixed
tubular support; a lens, mounted on the moveable tubular support
in operative association with said optical system; a flexible printed
circuit board mounted on the fixed tubular support; and at least
one piezoelectric element having at least two active volumes which
are independently excitable, said at least one piezoelectric element
mounted and connected to said flexible printed circuit board, said
piezoelectric element being deformable in response to an applied
voltage to engage the moveable support and move said support along
said longitudinal axis.
2. An adjustable support for an optical system of a digital camera,
as described in claim 1, wherein said piezoelectric element is constructed
in the shape of a beam; said beam having a longitudinal axis and
further comprising: first and second piezoelectric sections, each
constructed having at least two active volumes; a passive part forming
a fixed connection between said first and second piezoelectric sections,
said piezoelectric sections extending longitudinally outward on
either side of said passive part towards opposite ends; an engagement
pad extending outward from said passive part transverse to said
longitudinal axis to provide a surface for engagement with said
moveable tubular support; and wherein said beam is mounted on the
fixed tubular support and said engagement surface is in operative
contact with said moveable tubular support.
3. An adjustable support for an optical system of a digital camera,
as described in claim 2, wherein said active volumes comprise at
least two parallel layers of piezoelectric material connected by
electrodes to a source of voltage, said electrodes connected to
said applied voltage to provide independent excitation of said active
volumes.
4. An adjustable support for an optical system of a digital camera,
as described in claim 2, wherein said applied voltage is varied
to cause a distortion of said piezoelectric beam into engagement
with said moveable tubular support and further to cause distortion
of said piezoelectric beam to provide axial movement.
5. An adjustable support for an optical system of a digital camera,
as described in claim 4, wherein said voltage is varied according
to a predetermined pattern.
6. An adjustable support for an optical system of a digital camera,
as described in claim 1, wherein said moveable support tube is mounted
within the fixed support tube for coaxial movement therein.
7. An adjustable support for an optical system of a digital camera,
as described in claim 1, wherein said lens provides an autofocus
function for the digital camera.
8. An adjustable support for an optical system of a digital camera,
as described in claim 1, wherein said flexible printed circuit board
is wrapped on said fixed tubular support and assumes a tubular shape
consistent with said fixed tubular support.
9. An adjustable support for an optical system of a digital camera,
as described in claim 8, wherein said flexible printed circuit board
is wrapped on an outer surface of said fixed tubular support and
further comprising: a flexible resilient damping band wrapped on
said fixed tubular support around said flexible printed circuit
board; and a split band shaped spring element positioned over said
damping band to hold said damping band and printed circuit board
in place.
10. An adjustable support for an optical system of a digital camera,
as described in claim 1, wherein said at least one piezoelectric
element comprises a plurality of piezoelectric elements positioned
symmetrically on the fixed tubular support.
11. An adjustable support for an optical system of a digital camera,
as described in claim 1, wherein said at least one piezoelectric
element comprises a plurality of piezoelectric elements positioned
symmetrically on the outer surface of the fixed tubular support
and wherein said piezoelectric elements engage said moveable tubular
support through an access opening in said fixed tubular support.
12. An adjustable support for an optical system of a digital camera,
as described in claim 1, wherein said piezoelectric element is constructed
in the shape of a beam and is mounted on the fixed support, said
beam extending parallel to said axis from said fixed support in
a cantilever fashion towards a moveable end.
13. An adjustable support for an optical system of a digital camera,
as described in claim 12, wherein said active volumes comprise at
least two parallel layers of piezoelectric material separated by
electrodes and extending from a fixed end to said moveable end,
said electrodes connected to said applied voltage to provide independent
excitation of said active volumes.
14. An adjustable support for an optical system of a digital camera,
as described in claim 12, wherein said applied voltage is varied
to cause a radial bending of said piezoelectric element into engagement
with said moveable support and further to cause an expansion or
contraction of said piezoelectric element to provide axial movement.
15. An adjustable support for an optical system of a digital camera,
as described in claim 12, wherein said voltage is varied according
to a predetermined pattern.
16. An adjustable support for an optical system of a digital camera,
as described in claim 15, wherein the predetermined pattern of voltage
is devised to move said moveable end of said piezoelectric element
in an elliptical pattern.
17. An adjustable support for an optical system of a digital camera,
as described in claim 12, wherein said at least one piezoelectric
element comprises a plurality of piezoelectric elements positioned
symmetrically on the support tube.
18. An adjustable support for an optical system of a digital camera,
as described in claim 1, further comprising: a second moveable tubular
support mounted for movement on said moveable tubular support; a
second lens mounted on said second tubular support in operative
association with said optical system to provide a zoom capability;
and at least one auxiliary piezoelectric element having at least
two active volumes which are independently excitable, said at least
one auxiliary piezoelectric element secured to the moveable tubular
support and extending between said moveable tubular support and
said second moveable tubular support, said auxiliary piezoelectric
element being deformable in response to an applied voltage to engage
the second moveable support and move said second moveable support
on said moveable support.
19. An adjustable support for an optical system of a digital camera,
as described in claim 1, further comprising a position sensor mounted
on the flexible printed circuit board for sensing the position of
said moveable tube in order to provide a position reference to control
the movement of said moveable tube.
20. An adjustable support for an optical system of a digital camera,
as described in claim 19, wherein the position sensor comprises
an optical sensor which senses reflected light from an optical scale
on said moveable tube.
21. An adjustable support for an optical system of a digital camera
comprising: a fixed tubular support having a longitudinal axis,
said fixed tubular support being secured within said camera; a moveable
tubular support mounted for relative movement coaxially on the fixed
tubular support; a lens, mounted on the moveable tubular support
in operative association with said optical system; at least one
piezoelectric element constructed in the shape of a beam; said beam
having a longitudinal axis, and first and second ends, said beam
secured to the fixed tubular support close to said first and second
ends, said beam further comprising: first and second piezoelectric
sections, each of said sections constructed having at least one
active volume each, said piezoelectric sections being selectively
deformable in response to an applied voltage to engage the moveable
support and move said support along said longitudinal axis; a passive
part forming a fixed connection between said first and second piezoelectric
sections, said piezoelectric sections extending longitudinally outward
on either side of said passive part towards opposite ends; an engagement
pad extending outward from said passive part transverse to said
longitudinal axis to provide a surface for engagement with said
moveable tubular support; and wherein said beam is connected to
the fixed tubular support in a manner that allows said engagement
surface to be in operative contact with said moveable tubular support.
22. An adjustable support for an optical system of a digital camera,
as described in claim 21, further comprising a flexible printed
circuit board mounted on the fixed tubular support, wherein said
at least one piezoelectric element is mounted directly on and connected
to said flexible printed circuit board.
23. An adjustable support for an optical system of a digital camera,
as described in claim 22, wherein said active volumes are connected
to a voltage source by electrodes connected through said flexible
printed circuit board.
24. An adjustable support for an optical system of a digital camera,
as described in claim 22, further comprising: a flexible resilient
damping band wrapped on said fixed tubular support around said flexible
printed circuit board; and a split band shaped spring element positioned
over said damping band to hold said damping band and printed circuit
board in place.
25. An adjustable support for an optical system of a digital camera
system, as described in claim 21, wherein said at least one piezoelectric
element comprises a plurality of piezoelectric elements positioned
symmetrically on the support tube.
26. An adjustable support for an optical system of a digital camera,
as described in claim 21, wherein said applied voltage is varied
to cause a distortion of said piezoelectric beam into engagement
with said moveable tubular support and further to cause distortion
of said piezoelectric beam to provide axial movement.
27. An adjustable support for an optical system of a digital camera,
as described in claim 26, wherein said voltage is varied according
to a predetermined pattern.
28. An adjustable support for an optical system of a digital camera,
as described in claim 21, wherein said flexible printed circuit
board is wrapped on an outside surface of said fixed tubular support
and assumes a tubular shape consistent with said fixed tubular support.
29. An adjustable support for an optical system of a digital camera,
as described in claim 21, wherein said at least one piezoelectric
element comprises a plurality of piezoelectric elements positioned
symmetrically on the support tube.
30. An adjustable support for an optical system of a digital camera,
as described in claim 21, wherein said at least one piezoelectric
element comprises a plurality of piezoelectric elements positioned
symmetrically on an outer surface of the fixed tubular support and
wherein said plurality of piezoelectric elements engage said moveable
tubular support through an access opening in said fixed tubular
support.
31. A digital camera system comprising: a main camera control circuit
board, mounted in said camera; an optical system mounted on said
main printed circuit board to receive and process images; an adjustable
support for said optical system further comprising: a fixed tubular
support having a longitudinal axis, said fixed tubular support being
mounted on said main printed circuit board; a moveable tubular support
mounted for relative movement coaxially on the fixed tubular support;
a lens, mounted on the moveable tubular support in operative association
with said optical system; a flexible printed circuit board mounted
on the fixed tubular support; and at least one piezoelectric element
having at least two active volumes which are independently excitable,
said at least one piezoelectric element mounted and connected to
said flexible printed circuit board, said piezoelectric element
being deformable in response to an applied voltage to engage the
moveable support and move said support along said longitudinal axis.
32. A digital camera system, as described in claim 31, wherein
said at least one piezoelectric element is constructed in the shape
of a beam; said beam having a longitudinal axis and further comprising:
first and second piezoelectric sections, each constructed having
at least one active volume each; a passive part forming a fixed
connection between said first and second piezoelectric sections,
said piezoelectric sections extending longitudinally outward on
either side of said passive part towards opposite ends; an engagement
pad extending outward from said passive part transverse to said
longitudinal axis to provide a surface for engagement with said
moveable tubular support; and wherein said beam is mounted on the
fixed tubular support and said engagement surface is in operative
contact with said moveable tubular support.
33. A digital camera system, as described in claim 32, wherein
said active volumes comprise at least two parallel layers of piezoelectric
material connected by electrodes to said applied voltage to provide
independent excitation of said active volumes.
34. A digital camera system, as described in claim 32, wherein
said applied voltage is varied to cause a distortion of said piezoelectric
beam into engagement with said moveable tubular support and further
to cause distortion of said piezoelectric beam to provide axial
movement.
35. A digital camera system, as described in claim 34, wherein
said voltage is varied according to a predetermined pattern.
36. A digital camera system, as described in claim 32, further
comprising a flexible printed circuit board mounted on the fixed
tubular support, wherein said at least one piezoelectric element
is mounted directly on and connected to said printed circuit board.
37. A digital camera system, as described in claim 36, wherein
said flexible printed circuit board is wrapped on said fixed tubular
support and assumes a tubular shape consistent with said fixed tubular
support.
38. A digital camera system, as described in claim 37, wherein
said flexible printed circuit board is wrapped on an outer surface
of said fixed tubular support and further comprising: a flexible
resilient damping band wrapped on said fixed tubular support around
said flexible printed circuit board; and a split band shaped spring
element positioned over said damping band to hold said damping band
and printed circuit board in place.
39. A digital camera system, as described in claim 31, wherein
said moveable support tube is mounted within the fixed support tube
for coaxial movement therein.
40. A digital camera system, as described in claim 31, wherein
said lens provides an autofocus function for the digital camera.
41. A digital camera system, as described in claim 31, wherein
said at least one piezoelectric element comprises a plurality of
piezoelectric elements positioned symmetrically on the fixed tubular
support.
42. A digital camera system, as described in claim 31, wherein
said at least one piezoelectric element comprises a plurality of
piezoelectric elements positioned symmetrically on the outer surface
of the fixed tubular support and wherein said at least one piezoelectric
element engages said moveable tubular support through an access
opening in said fixed tubular support.
43. A digital camera system, as described in claim 31, wherein
said piezoelectric element is constructed in the shape of a beam
and is mounted on the fixed support, said beam extending parallel
to said axis from said fixed support in a cantilever fashion towards
a moveable end.
44. A digital camera system, as described in claim 43, wherein
said active volumes comprise at least two parallel layers of piezoelectric
material separated by electrodes and extending from a fixed end
to said moveable end, said electrodes connected to said applied
voltage to provide independent excitation of said active volumes.
45. A digital camera system, as described in claim 43, wherein
said applied voltage is varied to cause a radial bending of said
piezoelectric element into engagement with said moveable support
and further to cause an expansion or contraction of said piezoelectric
element to provide axial movement.
46. A digital camera system, as described in claim 43, wherein
said voltage is varied according to a predetermined pattern.
47. A digital camera system, as described in claim 46, wherein
the predetermined pattern of voltage is devised to move said moveable
end of said piezoelectric element in an elliptical pattern.
48. A digital camera system, as described in claim 43, wherein
said at least one piezoelectric element comprises a plurality of
piezoelectric elements positioned symmetrically on the inner surface
of the support tube.
49. A digital camera system, as described in claim 31, further
comprising: a second moveable tubular support mounted for movement
on said moveable tubular support; a second lens mounted on said
second tubular support in operative association with said optical
system to provide a zoom capability; and at least one auxiliary
piezoelectric element having at least two active volumes which are
independently excitable, said at least one auxiliary piezoelectric
element secured to the moveable tubular support and extending between
said moveable tubular support and said second moveable tubular support,
said auxiliary piezoelectric element being deformable in response
to an applied voltage to engage the second moveable support and
move said second moveable support on said moveable support.
50. A digital camera system comprising: a main camera control circuit
assembled on a flexible circuit board, an optical system contained
within said camera to receive and process images; an adjustable
support for said optical system further comprising: a fixed tubular
support having a longitudinal axis, said fixed tubular support being
secured within said camera, and wherein said flexible printed circuit
board is mounted thereon; a moveable tubular support mounted for
relative movement coaxially on the fixed tubular support; a lens,
mounted on the moveable tubular support in operative association
with said optical system; at least one piezoelectric element constructed
in the shape of a beam; said beam having a longitudinal axis, said
beam secured to the fixed tubular support by said flexible printed
circuit board and extending between said fixed tubular support and
said moveable tubular support, said beam further comprising: first
and second piezoelectric sections, each of said sections constructed
having at least two active volumes, which are independently excitable,
said piezoelectric sections being selectively deformable in response
to an applied voltage to engage the moveable support and move said
support along said longitudinal axis; a passive part forming a fixed
connection between said first and second piezoelectric sections,
said piezoelectric sections extending longitudinally outward on
either side of said passive part towards opposite ends; an actuating
lever extending outward from said passive part transverse to said
longitudinal axis to provide a surface for engagement with said
moveable tubular support; and wherein said beam is mounted on the
fixed tubular support in a manner that allows said engagement surface
to be in operative contact with said moveable tubular support.
51. A digital camera system, as described in claim 50, wherein
said active volumes are connected to a voltage source by electrodes
connected through said flexible printed circuit board.
52. A digital camera system, as described in claim 50, wherein
said at least one piezoelectric element comprises a plurality of
piezoelectric elements positioned symmetrically on the inner surface
of the support tube.
53. A digital camera system, as described in claim 50, wherein
said applied voltage is varied to cause a distortion of said piezoelectric
beam into engagement with said moveable tubular support and further
to cause distortion of said piezoelectric beam to provide axial
movement.
54. A digital camera system, as described in claim 53, wherein
said voltage is varied according to a predetermined pattern.
55. A digital camera system, as described in claim 50, wherein
said flexible printed circuit board is wrapped on said fixed tubular
support and assumes a tubular shape consistent with said fixed tubular
support.
56. A digital camera system, as described in claim 55, wherein
said flexible printed circuit board is wrapped on an outer surface
of said fixed tubular support and further comprising: a flexible
resilient damping band wrapped on said fixed tubular support around
said flexible printed circuit board; and a split band shaped spring
element positioned over said damping band to hold said damping band
and printed circuit board in place.
57. A digital camera system, as described in claim 50, wherein
said at least one piezoelectric element comprises a plurality of
piezoelectric elements positioned symmetrically on an outer surface
of the fixed tubular support and wherein said at least one piezoelectric
element engages said moveable tubular support through an access
opening in said fixed tubular support.
58. A digital camera system, as described in claim 50, further
comprising: a second moveable tubular support mounted for movement
on said moveable tubular support; a second lens mounted on said
second tubular support in operative association with said optical
system to provide a zoom capability; and at least one auxiliary
piezoelectric element having at least two active volumes which are
independently excitable, said at least one auxiliary piezoelectric
element secured to the moveable tubular support and extending between
said moveable tubular support and said second moveable tubular support,
said auxiliary piezoelectric element being deformable in response
to an applied voltage to engage the second moveable support and
move said second moveable support on said moveable support.
59. An adjustable support for an optical system of a digital camera
comprising: a fixed tubular support having a longitudinal axis,
said fixed tubular support being secured within said camera; a moveable
tubular support mounted for relative movement coaxially on the fixed
tubular support; a flexible printed circuit board mounted on the
fixed tubular support; wherein said moveable tubular support further
comprises: a front section and a rear section mounted on said fixed
tubular support for both relative movement between said sections
and for movement in tandem; at least one first lens mounted on said
front section for movement therewith; at least one second lens mounted
on said rear section for movement therewith; and wherein said at
least one first and second lenses optically cooperating to provide
an optical function; and at least one first piezoelectric element
having at least two active volumes which are independently excitable,
said at least one first piezoelectric element mounted and connected
to said flexible printed circuit board, said at least one first
piezoelectric element being deformable in response to an applied
voltage to engage said front section and move said front section
along said longitudinal axis; and at least one second piezoelectric
element having at least two active volumes which are independently
excitable, said at least one second piezoelectric element mounted
and connected to said flexible printed circuit board, said at least
one second piezoelectric element being deformable in response to
an applied voltage to engage said rear section and move said rear
section along said longitudinal axis.
60. An adjustable support for an optical system of a digital camera,
as described in claim 59, wherein said at least one first and second
lenses cooperated to provide a zoom function.
61. An adjustable support for an optical system of a digital camera,
as described in claim 59, wherein said at least one first lens is
a zoom lens and said at least one second lens is a focus lens.
62. An adjustable support for an optical system of a digital camera,
as described in claim 59, further comprising a first optical sensor
mounted and connected to said flexible printed circuit board, said
first optical sensor positioned to sense light reflected from a
surface of said front section and a second optical sensor mounted
and connected to said flexible printed circuit board, said second
optical sensor positioned to sense light reflected from a surface
of said rear section.
Digital Camera Patent Description
TECHNICAL FIELD
The present invention relates generally to a mechanism for moving
the lens elements of an electronic camera.
BACKGROUND OF THE INVENTION
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.
SUMMARY OF THE INVENTION
A miniaturized digital camera is constructed for use with a mobile
communication device or other compact appliance. The optical system
of such a camera may consist of a small lens assembly having single
or multiple lens components. The optical system transmits the image
received from an external source to a sensor array which converts
the optical signal to a digital signal for processing. In multiple
lens configurations, the lenses in the optical system are moved
in relation to each other to provide autofocus and zoom capability.
In the simplest of applications a single primary lens may be provided
with sufficient movement to provide autofocus in accordance with
the sensed location of the subject. For simplicity the subject invention
is first described with reference to a single adjustable lens application,
although multiple lens configurations may be constructed utilizing
multiple drive mechanisms as disclosed in this application.
According to this invention, 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 subject mechanism
is constructed of at least two layers of piezoelectric material
which are independently energized to provide relative deformation
between the two layers. The piezoelectric element used in the system
of one embodiment of this invention 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 outer end of the engagement
pad is free to move in operative association with the movable lens
tube. In the preferred embodiment, the beam comprises a pair of
bimorph piezoelectric elements extending to either side of the engagement
pad. Each of the bimorph elements have 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.
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.
In a second embodiment of this invention a pair of lenses are used
to provide a zoom function. In this embodiment the moveable tube
is divided into a front lens support section and rear lens support
section and each of the sections is driven separately by piezoelectric
elements in a manner similar to that described above. If the application
warrants, an optical sensor can be provided to monitor the position
of both sections.
Further embodiments can be constructed which combine the autofocus
and zoom functions.
In this manner a miniature drive system is provided to move the
lens within the camera while using a minimum of power and space.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is described in more detail below with reference
to the accompanying drawings, in which:
FIG. 1 is a schematic view of a simple optical system for use in
a digital camera in accordance with the preferred embodiment of
this invention;
FIG. 2 is a sectional view of the optical system of this invention
shown in FIG. 1, taken along section lines a--a;
FIG. 3 is a block diagram of a control system for a digital camera
according to a preferred embodiment of this invention;
FIGS. 4a-4e are enlarged views of the piezoelectric element shown
in FIGS. 1 and 2 at various conditions of excitation;
FIG. 5 is an exploded perspective view of the components of the
optical system of this invention;
FIG. 6 is a schematic view of an alternate embodiment of the optical
system of this invention;
FIG. 7 is an end view of the optical system of this invention as
shown in FIG. 6; and
FIG. 8 is a schematic illustration of a alternate embodiment of
a piezoelectric element for use in the embodiment of FIGS. 6 and
7;
FIGS. 9a and 9b are schematic diagrams of possible optical systems
having moveable lens modules to provide both autofocus and zoom
capabilities;
FIG. 10 is a schematic drawing of a circuit for driving a bimorph
piezoelectric element;
FIG. 11 is a schematic cut away view of an alternate embodiment
of an optical system showing the use of a position sensor according
to this invention;
FIG. 12a is an exploded view of the basic elements of the alternate
embodiment of FIG. 11;
FIG. 12b is a sectional view of the assembled embodiment of FIG.
12a, along an axial section line;
FIG. 12c is a sectional view of the assembled embodiment of FIG.
12a, along a section line transverse to the axis of the device;
FIG. 13 is a schematic cut away view of a further alternative embodiment
of. the optical system of this invention;
FIG. 14(a) is a perspective schematic view of the spring support
and flexible printed circuit board of embodiment of FIG. 13;
FIG. 14(b) is a schematic end view of the spring and flexible printed
circuit board assembly of the embodiment of FIG. 13;
FIG. 15 is a perspective schematic view of the moveable tube of
the embodiment of FIG. 13; and
FIG. 16 is a perspective schematic view of the support tube of
the optical system of this invention with a position monitor.
DETAILED DESCRIPTION OF THE INVENTION
A typical optical lens system 1 for a camera having an autofocus
capability is depicted schematically in FIG. 1. It generally will
consist of a primary lens 2, which operates to project a focused
image of subject 8 on image plane 5. As shown, the primary lens
2 is adjustable in the range x-y. Lens system 1 is used in a digital
camera system 6, as shown in FIG. 3. Lens system 1 is secured within
a housing (not shown) to project an image on an image sensor 7 positioned
at the image plane 5 of the camera system 6. The primary lens 2
is adjustable to obtain an autofocus function. The single adjustable
lens configuration is chosen for ease of illustration. It should
be recognized that multiple lens adjustment could be obtained to
provide a zoom capability. Examples of such systems are shown in
FIGS. 9a and 9b. In the latter instances, multiple piezoelectric
drive groups may be constructed to provide independent adjustment
motion of the autofocus and zoom lenses.
The lens assembly 1, as shown in FIG. 1, consists of a support
tube 9 and a lens tube 10. Lens tube 10 holds the lens 2 and is
mounted coaxially within support tube 9. Lens tube 10 is adjustable
to provide an autofocus capability for the camera system 6. To provide.
the necessary adjustment, lens tube 10 is supported within the support
tube 9 for movement in an axial direction. Support and motion for
the lens tube 10 is provided by multiple bimorph piezoelectric elements
11, 12, and 13, as shown in FIGS. 1 and 2. The lens tube can be
driven by two or even one element if there is no need for high axial
forces.
The circuit board for the piezoelectric drive is a flexible printed
circuit board 14 arranged about the outer cylindrical surface 15
of the support tube 9. The piezoelectric elements 11-13 and their
associated components are connected and supported directly by the
flexible circuit board 14. The image processing and related elements
of the camera system 6, as shown in FIG. 3, are connected and supported
by a separate printed circuit board, such as shown at reference
number 73 in FIG. 12. A power supply 22, such as a battery, will
be connected to printed circuit boards 14 and 73 in a well known
manner. A resilient insulating sheet 15 is wrapped around flexible
circuit board 14. The assembly of flexible circuit board and insulating
sheet 15 is held in place on support tube 9 by a split ring shaped
spring 16. Damping sheet 15 and spring 16 may be eliminated by incorporating
these functions into the construction of flexible circuit board
14. Contacts 20 are formed on flexible circuit board 14 to provide
means to connect the flexible circuit board 14 a power supply 22.
Sheet 15 provides a resilient damping of the piezoelectric distortion
within the assembly while allowing the necessary flexing and the
damping of acoustic noise.
As illustrated in FIGS. 1 and 2, the piezoelectric elements are
mounted on the flexible circuit board 14 on the outer periphery
of the support tube 9. Elements 11-13 are identical and each is
constructed with a pair of elements 30 and 31, as shown in FIG.
4e. Element 11 is formed by bimorph sections 30 and 31 which are
connected to form a beam by a passive member 32 at the midpoint
of the beam. An engagement pad 33 extends outward from the passive
member 32 transverse to the longitudinal axis of the beam. Bimorph
section 30 is constructed of dual piezoelectric volumes 30A and
30B which are both active and connected to flexible circuit board
14 though contacts 34. Each volume could consist of several layers
connected and polarized to act as one piezoelectric layer. This
reduces the necessary driving voltages. It is also possible to use
only one piezoelectric volume in each bimorph section if the corresponding
deformation is sufficient. Similarly section 31 is constructed of
dual piezoelectric layers 31A and 31B connected to flexible circuit
board 14 though contacts 35. Engagement pad 33, in the assembled
condition, is aligned with an opening 18 in support tube 9 to allow
engagement of the outer engagement end 36 of pad 33 with the lens
support tube 9.
The piezoelectric elements 11-13 are excited in accordance with
a predetermined pattern to cause the attachment levers 33 of elements
11-13 to engage the lens tube 10 and adjust its axial position.
The amount of this adjustment will be in accordance with a signal
from an autofocus sensor 23 which senses the distance d of the subject
8. Using appropriate algorithms, it is possible to obtain the auto-focus
setting data directly from the image sensor, thereby eliminating
the need for a separate sensor element. In the event that multiple
lens movement is provided to allow a zoom function, a manual zoom
control 24 is provided to signal the camera control processor to
cause movement, for example, of a zoom lens as shown in FIG. 9a.
The camera system 6 consists of a primary control processor 21 which
receives power from power supply 22 to drive the components of the
system 6. Adjustment signals are provided by autofocus sensor 23
which senses the distance d of the subject from the optical system
1.
The camera control processor 21 generates a signal and sends it
to an actuator control processor 25. The actuator control processor
25 generates a predetermined control voltage pattern to cause the
piezoelectric elements to deform in response to signals from the
camera control processor 21. The voltage pattern is designed to
cause movement of the adjustable lens tube 10 in the axial direction
in the amount indicated by the autofocus sensor 23. The optical
elements project the image of subject 8 onto the image sensor 7
located at the focal plane 5 of the camera system 6. Image sensor
7 generates a signal indicative of the image which is projected.
The image signal is converted to a digital signal in image processor
26. The digital image signal is stored in a memory section of camera
control processor 21.
An example of actuator control processor 25 is shown in the circuit
diagram of FIG. 10. The circuit shown is designed to control two
piezoelectric volume elements 201 and 202. By driving an output
bridge 210, comprising transistors 211, 212, 213, 214, to control
piezoelectric element 201 and another separate bridge 220, comprising
the transistors 221, 222, 223, 224, to control another piezoelectric
element 202. The transistors of bridges 210 and 220 can be either
bipolar or Field Effect (FET) devices or a combination thereof.
Bridge 210 is controlled by bridge control signals 231, 232, 233,
234 and bridge 220 is controlled by signals 241, 242, 243, 244.
The transistors of the bridges 210 and 220 can either be discrete
or integrated in the control circuit. 0 indicates circuit ground
and + indicates the supply bus. In operation the half bridge, comprising
transistors 211 and 212, can be controlled by the bridge control
signals 231, 232 to output any voltage between 0 and + and the other
half bridge, comprising transistors 213, 214, of bridge 210 can
be controlled by the bridge control signals 233, 234 to output a
complementary voltage.
Thus the full supply bus voltage can be applied over the element
201 either way. The control signals 231, 232, 233, 234 can also
easily be arranged to completely switch off all transistors in bridge
210. In the same way the controller 25 can control the bridge 220
to output a voltage either way over the element 202 or keep the
element 202 unconnected. All needed volume element movements can
be implemented by the controller 25 by separately controlling two
or more elements at the same time.
FIG. 4a-4e show a double bimorph piezoelectric element 11 which
is constructed to engage lens tube 10 to adjust the axial position
of lens tube 10. As previously described, the element 11 and its
associated elements 12 and 13 are each constructed in the same manner.
In each of the elements 11, a pair of bimorph elements 30 and 31
are mechanically connected through passive part 32 to form a beam
4. Each of the sections are constructed similarly, therefore only
one is described herein. The bimorph section 30 comprises two active
volumes 30A and 30B separated by a middle electrode 34A. The upper
active volume 30A is shown as a single layer, but may have multiple
layers. Similarly, the lower active volume 30B may comprise a number
of piezoelectric layers, but only one is shown for simplicity. The
bottom electrode (34C) of active volume 30B is connected to GND
in one embodiment. In other embodiments all electrodes (34A-C, 35A-C)
can be controlled individually. If a soft piezoelectric material,
i.e. a material that is easy to polarize, is used, the upper electrode
of active volume 30A is connected to a voltage higher than the peak
voltage applied to signal electrode 34A. If a hard piezoelectric
material is used, a polarization opposite to the electric field
can be used and the upper electrode can be connected to ground.
By applying a voltage between selected electrodes, the active volumes
30A and 30B can be excited individually. By applying a voltage over
the active volume 30A, the piezoelectric layer expands in the electrical
field direction, i.e. each layer becomes thicker, if the electric
field and polarization have the same direction, however, at the
same time, the active volume 30A will contract in the longitudinal
direction. This contraction and expansion is related to the characteristic
coefficients of the piezoelectric material chosen. If the active
volume 30A is unaltered as active volume 30B is excited, the decreased
length of the active volume 30B will cause the bimorph piezoelectric
section 30 to distort and bend upwards as shown in FIG. 4a. By reversing
this excitation in section 31, the opposite distortion is obtained
which will result in the distortion of the beam 4 as illustrated
in FIG. 4a. A pattern of excitation and distortion is derived to
provide steps of motion, as shown in FIGS. 4a-d. These steps can
be repeatedly activated by appropriate signals.
The bimorph element 11, as shown in FIG. 4e, is comprised of two
adjacent piezoelectric beams or sections 30 and 31 separated by
passive part or member 32. There are three points of contact for
the element 11 one close to either end of the combined beams and
another at the engagement end 36 of pad 33. In order to allow the
necessary distortion of the beam sections and overall beam that
comprises element 11, the ends of the beam should be flexibly mounted
to the flexible circuit board 14 to provide a degree of rotation
at the corresponding contact points.
There are, therefore, four independent active volumes, 30A, 30B,
31A and 31B that make up beam 4. Dynamic excitation of one to four
of the four active volumes provides motion of the engagement pad
33 in both the z and the x directions. By exciting the active volumes
in cooperation the motions illustrated in FIGS. 4a-4d are obtained.
Note that all motions of the piezoelectric element are exaggerated
in the figures, in order to illustrate the motion principles. At
ultrasonic frequencies this provides an elliptic type of motion
of the engagement pad 33, which will cause a movement of the lens
support tube in the X direction.
Piezoelectric actuating elements of this type are described in
copending U.S. application Ser. No. 09/739,906, filed Dec. 20, 2000.
The disclosure of this application is incorporated herein in its
entirety by reference.
In an alternate embodiment as shown in FIGS. 6-8, the piezoelectric
element 11A comprises a cantilevered beam having two active volumes
40A and 40B supported by passive part 42 which is mounted on flexible
circuit board 14. The piezoelectric element 11A has at least two
parallel active volumes 40A and 40B. Each of the active volumes
40A and 40B comprises at least one piezoelectric layer. The active
volumes 40A and 40B can be activated individually by electrodes
43 (only one is illustrated in the figure) arranged in parallel
with the active volumes 40A and 40B. At the moveable tip 45 of the
piezoelectric element 11A is an engaging surface 48, which is brought
into contact with the adjustable tube 10 during operation of the
autofocus function of camera system 6. flexible circuit board 14
supports the element 11A at the passive part 32 and is connected
to electrodes 43 through appropriate means (not shown). In this
embodiment, the flexible circuit board 14 is fixed to the interior
surface 15 of the support tube 9. Support tube 9 is fixed within
the body of the camera system 6 (not shown).
By applying the same voltage on both volumes 40A and 40B, the element
llA can be caused to contract in the axial direction. By combining
different voltages on the respective volumes 40A and 40B the actuating
surface 48 can be moved in a two-dimensional space (X and Z), as
illustrated by the elliptical path shown in FIG. 8. In order to
move adjustable tube 10, the element 11A is forced to bend against
it for frictional engagement. A different excitation of the active
volumes 40A and 40B can be accomplished to provide an expansion
of the element 11A which will provide movement of the adjustable
tube 10 in the opposite axial direction.
In either embodiment, by deriving a pattern of voltage signals
to be applied to electrodes of piezoelectric element 11, a desired
pattern of movements can be obtained which are consistent with the
desired function. The particular motion performed is responsive
to the signals from the camera control processor 20.
In order to obtain the precision required in some optical designs,
a position sensor 70 is used to monitor the position of the movable
tubes, as shown in FIGS. 11 and 12a-c. The optical system of this
embodiment includes support tube 17 and moveable lens tube 10 as
previously described. These components are mounted directly on printed
circuit board 73 by holder 74 (see FIG. 11). Printed circuit board
73 contains the image sensor 7, image processor 26 and related components
(not shown). An optical sensor 71 is mounted and connected to flexible
circuit board 14 and is used to view a reflecting surface 76 mounted
on the moveable tube 10. Optical sensor 71 may be a commercially
available, subminiature, reflective type, photointerrupter, such
as model GP2S60, available from Sharp Microelectronics of the Americas,
Camas, Wash. Optical monitor 70 includes a reflecting surface 76
as shown in the embodiment of FIG. 15, which consists of a gray-scale
incorporated into the surface treatment of the moveable tube. In
FIG. 15, the reflecting surface 76 is shown in the rear section
120 of moveable tube 110. The assembly of this embodiment also includes
flexible circuit board 14 wrapped around support tube 17 and held
in place by spring element 16. Piezoelectric elements 1-13 are mounted
on flexible circuit board 14 in a position to enable the engagement
pads of these elements to engage the lens tube 10 through openings
76-78 in support tube 17. Visual access for position sensor 71 is
provided by port 79 in support tube 17. This configuration will
provide accurate monitoring of a moveable tube in a wide variety
of embodiments. An appropriate opening must be provided in the intervening
components of optical system 1 to enable the optical sensor 51 to
have visual access to the moveable tubes 10 or 110 (in FIG. 13).
The piezoelectric drive systems described above can be readily
adapted to move multiple lenses either through an appropriate linkage
system to a single drive or by independent multiple drives to provide
the required adjustability for both autofocus and zoom capabilities.
FIGS. 9a and 9b show two possible lens configurations for providing
autofocus and zoom. In the system of FIG. 9a, a primary lens 51
is mounted on a support tube for movement relative to focal plane
5, a zoom assembly is provided which consists of a pair of lenses
52 and 53. The zoom lenses are mounted for movement relative to
the primary lens 51 and focal plane 5. The zoom pair is also mounted
for movement with the primary lens for focus adjustment. This system
is designed to use a piezoelectric drive for the primary lens support
movement which would include the zoom components and a second drive
to provide movement of the zoom lenses relative to the primary lens
support.
In FIG. 9b, a zoom system is shown using a pair of lens 61 and
62. This configuration would also be adaptable to a pair of drives
as indicated above for movement in ranges 63 and 64 as shown in
FIG. 9b. In these configurations, a second moveable support tube
may be provided which is mounted for movement within the primary
lens support tube 10. In general, to provide the zoom function,
at least two groups of lenses are provided, one group for adjusting
the zoom ration and another for compensating for changes in focus.
A piezoelectric driven optical system for providing a zoom function
is shown in FIGS. 13-15. There are myriad configurations of lens
systems which can be adapted to a system of this invention depending
on the needs of a particular application. The systems described
herein are designed for applications where size, weight, and energy
use need to be minimized.
In the multiple lens system of the embodiment shown in FIGS. 13-16,
an optical system 101 is mounted directly to the main printed circuit
board 122 which includes an image sensor (not shown). Optical system
101, as shown in FIGS. 13-15, consists of a second lens element
102 and a first lens element 103 with an infra red filter 104. Optical
system 101 is mounted on moveable tube 110. In this configuration,
moveable tube 110 is split into two sections, a front section 121
in which is mounted the first lens element 103 and a rear section
120 in which is mounted the second lens element. The sections of
the moveable tube 110 are moveable with respect to each other. For
example, front section 121 may be moveable on rear section 120,
as shown in FIG. 15. Front section 121 may also be connected to
a bellows 105 to provide a seal for the optical system 101.
As shown in FIG. 14(b), each section of moveable tube 110 is driven
independently by a pair of piezoelectric elements, piezoelectric
elements 112 and 113 may power the rear section 120 and piezoelectric
elements 111 and 131 may power the front section 121. To increase
the effectiveness of the engagement with the piezoelectric drives,
drive pad contact surfaces 125 and 126 are constructed on the front
section 121 and rear section 120 respectively. The pads may be formed
by alteration of the surface finish in the proper location.
Optical sensors, such as 123, may be provided in this embodiment
for each of the sections 120 and. 121, mounted directly on the flexible
printed circuit board 114. An opening 127 is constructed in the
support tube 117 to provide optical exposure to reflective surface
76 on rear tube section 120.
In this manner a versatile drive mechanism is provided which fulfills
the design requirements of space, power consumption and weight.
It will be understood by those skilled in the art that various modifications
and changes may be made to the above described embodiments without
departure from the scope of the invention as defined in the claims.
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