U.S. patent application number 14/708163 was filed with the patent office on 2015-11-05 for miniature optical zoom lens.
The applicant listed for this patent is DYNAOPTICS PTE LTD. A SINGAPORE PRIVATE LIMITED COMPANY. Invention is credited to Koon Lin Cheo, Chang Lun HOU.
Application Number | 20150316748 14/708163 |
Document ID | / |
Family ID | 54355144 |
Filed Date | 2015-11-05 |
United States Patent
Application |
20150316748 |
Kind Code |
A1 |
Cheo; Koon Lin ; et
al. |
November 5, 2015 |
MINIATURE OPTICAL ZOOM LENS
Abstract
Miniature zoom lens systems and methods of manufacturing thereof
are described. An exemplary system includes a first prism
positioned to receive incident light from an entrance to the
miniature lens system, at least a first varifocal lens positioned
to receive the light that exits the prism, at least one base lens
positioned to receive the light after passing through the first
varifocal lens, a detector positioned to receive the light after
passing through the base lens, and a first actuator configured to
move the first varifocal lens in at least a direction perpendicular
to propagation axis of the light passing through the first
varifocal lens. The miniature lens system has a small z-height and
can be implemented in mobile devices such as mobile phones.
Inventors: |
Cheo; Koon Lin; (Singapore,
SG) ; HOU; Chang Lun; (Singapore, SG) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DYNAOPTICS PTE LTD. A SINGAPORE PRIVATE LIMITED COMPANY |
Singapore |
|
SG |
|
|
Family ID: |
54355144 |
Appl. No.: |
14/708163 |
Filed: |
May 8, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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PCT/IB2013/002905 |
Nov 8, 2013 |
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14708163 |
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PCT/IB2015/000409 |
Jan 8, 2015 |
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PCT/IB2013/002905 |
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61874333 |
Sep 5, 2013 |
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61724221 |
Nov 8, 2012 |
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61925215 |
Jan 8, 2014 |
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Current U.S.
Class: |
359/694 |
Current CPC
Class: |
G02B 7/005 20130101;
G02B 15/16 20130101; G02B 13/009 20130101; G02B 7/04 20130101; G02B
7/026 20130101; G02B 13/0065 20130101; G02B 7/102 20130101; G02B
13/004 20130101; G02B 13/0045 20130101; G02B 13/007 20130101; G02B
13/0075 20130101; G02B 13/0085 20130101; G02B 3/0081 20130101; G02B
15/177 20130101 |
International
Class: |
G02B 13/00 20060101
G02B013/00; G02B 7/04 20060101 G02B007/04; G02B 7/02 20060101
G02B007/02; G02B 7/00 20060101 G02B007/00 |
Claims
1. A miniature zoom lens system, comprising: a first prism
positioned on an optical axis to receive incident light from an
entrance to the miniature lens system through a first face of the
first prism and to bend the received light by approximately 90
degrees before allowing the light to exit from a second face of the
first prism; a pair of varifocal lenses, each comprising at least
two optical elements and each optical element having at least one
optical surface defined by a polynomial, and wherein at least one
of the pair of varifocal lenses is positioned to receive light that
exits from the second face of the prism; each of the optical
elements being formed integrally with a frame, at least one base
lens positioned substantially along the optical axis to receive
light after passing through the pair of varifocal lenses; and a
first actuator configured to connect to the frames of the optical
elements to move the pair of varifocal lenses in a direction
substantially perpendicular to optical axis.
2. The system of claim 1, wherein the lens and frame are formed
integrally by injection molding.
3. The system of claim 1, wherein the first varifocal lens is one
of the following: a liquid crystal lens, a liquid lens, or an
Alvarez-like lens.
4. The system of claim 1 wherein at least two surfaces of at least
one of the optical elements are defined by polynomials.
5. The system of claim 1, wherein the first actuator comprises one
of a coil or a magnet.
6. The system of claim 1, further comprising a structural platform
to allow one of the following to be directly molded onto,
fabricated onto, or integrated with the structural platform: the
first prism, a second prism, the first varifocal lens, or a second
varifocal lens.
7. The system claim 6, wherein the structural platform comprises a
spring flexure element.
8. The system claim 6, wherein the structural platform includes a
frame and an arm.
9. The system claim 8, wherein: the structural platform frame
comprises a lead frame metal structure that is one or more of: a
metal-stamped structure, a laser-cut structure, a milled structure,
an etched structure, or a molded structure; the arm is molded on
the lead frame structure; and one or more of the first prism, a
second prism, the first varifocal lens, or a second varifocal lens
is molded onto the lead frame.
10. The system of claim 6, wherein a wafer-level optical component
with a preformed lens element is bonded to the platform.
11. The system claim 1, wherein the first actuator is a voice-coil
actuator with a bidirectional drive.
12. The system claim 1, comprising second actuator configured to
move an optical component other than the first varifocal lens
within the miniature zoom lens system.
13. The system of claim 12, wherein the second actuator and the
first actuator are configured to displace both the optical
component other than the first varifocal lens and the first
varifocal lens by the same distance and in the same direction.
14. The method of claim 13, wherein the optical component other
than the first varifocal lens is one of: a second varifocal lens,
the at least one base lens, the first prism, or a second prism.
15. The system claim 1, wherein the first varifocal lens has a
rectangular or an oval-shaped cross section encompassing only an
essential active area of the first varifocal lens.
16. The system claim 1, further comprising a second varifocal lens
positioned to receive the light exiting the first varifocal lens
before reaching the at least one base lens.
17. The system of claim 16, wherein the second varifocal lens has a
rectangular or an oval-shaped cross section encompassing only an
essential active area of the second varifocal lens.
18. The system of claim 16, wherein the optical elements of both
the first and the second varifocal lenses are movable with respect
to one another so as to provide optical zoom capability for the
lens system.
19. The system claim 1, wherein the at least one base lens is
configured to move along the optical axis of the system to provide
optical focusing ability for the lens system.
20. A miniature zoom lens system, comprising: a first varifocal
lens positioned to receive incident light from an entrance to the
miniature lens system, the first varifocal lens comprising at least
two optical elements, each formed integrally with a frame; a first
prism positioned to receive light from the first varifocal lens
through a first face of the first prism and to bend the received
light by approximately 90 degrees before allowing the light to exit
from a second face of the first prism; a second varifocal lens
positioned to receive the light that exits the second face of the
prism, the second varifocal lens comprising at least two optical
elements, each formed integrally with a frame; at least one base
lens positioned to receive the light after passing through the
second varifocal lens; a second prism positioned to receive the
light that exits the at least one base lens through a first face of
the second prism and to bend the light received by the second prism
by approximately 90 degrees before allowing the light to exit from
a second face of the second prism; and at least one actuator
configured to connect to the frames of the optical elements to move
the optical elements of one or both of the first varifocal and
second varifocal lenses in at least a direction perpendicular to an
optical axis of the system.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of PCT
Application No. PCT/IB2013/002905, entitled "MINIATURE OPTICAL ZOOM
LENS", filed on Nov. 8, 2013, which in turn is a PCT conversion of
U.S. Provisional Patent Application No. 61/724,221, entitled
"INTEGRATED ELASTIC SUSPENSION PLATFORM WITH OPTICAL COMPONENTS"
filed on Nov. 8, 2012, and also of U.S. Provisional Patent
Application No. 61/874,333, entitled "MINIATURE OPTICAL ZOOM LENS"
filed on Sep. 5, 2013. This application is further a
continuation-in-part of PCT Application No. PCT/IB2015/000409,
entitled `LENS ASSEMBLIES AND ACTUATORS FOR OPTICAL SYSTEMS AND
METHODS THEREFOR", filed on Jan. 8, 2015, which in turn is a
conversion of U.S. Provisional Patent Application No. 61/925,215,
filed on Jan. 8, 2014, Each of the foregoing applications is
incorporated herein by reference, and the present application
claims the benefit of priority from each of the foregoing.
BACKGROUND
[0002] The present disclosure relates to optical systems and
methods of manufacturing thereof and more particularly to zoom lens
systems and methods of manufacturing.
[0003] The alignment of components in an optical system is an
important factor in achieving optimal system performance and a
desired image quality. Proliferation of small-scale optical systems
for use in, for example, a variety of handheld devices, such as
cell phones and hand-held cameras, places additional challenges on
alignment tolerances due to the small dimensions of optical
components within such devices. As such, there exists a need to
improve the alignment of components in an optical system in order
to achieve optimal performance while minimizing the system's
overall form factor. Further, it is essential to minimize the size
of the optical systems that are used in, for example, consumer
devices, such as phones and hand-held cameras.
SUMMARY
[0004] The disclosed embodiments relate to systems and methods for
improving the alignment of optical components within an optical
systems. The disclosed embodiments further relate to miniature zoom
lens systems and methods for their manufacture and assembly that
allow the production of small lens systems in a streamlined
fashion. In some exemplary embodiments, the disclosed embodiments
are used to align varifocal lenses of an optical system to decrease
the overall size of the system while optimizing its
performance.
[0005] In systems with moving optical components, such as zoom lens
systems, alignment of optical components is complicated due to
their mobility. In some systems, optical components are moved only
along the optical axis (i.e., along the z-axis), which makes
alignment along the optical axis particularly important.
Alternatively, or additionally, in some systems, such as in an
Alvarez lens configuration, optical components can move
perpendicular to the optical axis, which makes proper alignment of
the elements in multiple dimensions even more challenging.
Alignment issues can be further exacerbated in systems where
components with aspheric or free-form surfaces are used since such
components may not have an axis of symmetry.
[0006] The disclosed embodiments seek to provide methods and system
for properly aligning optical components by moving them both along
and perpendicular to the z-axis (i.e., the optical axis) in order
to minimize the length of the optical path while maintaining the
quality of images captured by such optical systems. By using
freeform lenses, such as Alvarez lenses, it is possible to achieve
optimal focusing and zooming of an image within a diminutive amount
of space by actuating lenses at right angles to the z-axis in
addition to moving the lenses and other optical components along
the z-axis.
[0007] This reduction in the optical path's length enables a
reduction in the overall size of the optical system, since less
space would be required to carry an image through the system's
lenses. As such, optimized alignment of the lens elements in a
miniature optical system in accordance with the disclosed
embodiments leads to smaller optical systems in devices that use
such systems, such as cell phones and digital cameras. This
reduction in optical system size allows such devices to have more
room for other components, such as batteries and processors, or
allows them to achieve an overall reduction in size altogether. As
these devices become smaller and smaller, the need for such
miniaturization of key technological components will be paramount
to maintaining a competitive edge for those companies that
manufacture and sell such devices.
[0008] One aspect of the disclosed embodiments relates to an
integrated optical device that includes an elastic suspension
fixture fabricated using a first process, and an optical element
integrated into the elastic suspension fixture. The optical element
is fabricated using a second process. In one exemplary embodiment,
the first process comprises one of the following processes: an
injection molding process, an in-mold decoration process, a hot
stamping process, a metal stamping process, a micro-fabrication
process that produces a chip-based mold, or an insert molding
process. In another exemplary embodiment, the second process
comprises one of the following processes: an injection molding
process, a casting from a mold process, an in-mold decoration
process, a hot stamping process, a metal stamping process, a
micro-fabrication process that produces a chip-based mold, or an
insert molding process.
[0009] According to one exemplary embodiment, the integrated
optical device further includes one or more of the following: a
frame, one or more alignment structures, an actuator configured to
displace the optical element, one or more additional optical
elements, one or more additional elastic elements, and one or more
rigid elements. In yet another exemplary embodiment, the elastic
fixture is configured to allow movement of the optical element in
one or more directions. In still another exemplary embodiment, the
elastic fixture is configured to allow movement of the optical
element in three dimensions.
[0010] In one exemplary embodiment, the integrated optical device
further includes an actuator configured to displace the elastic
feature and to thereby displace the optical element. In another
exemplary embodiment, the optical element comprises at least one of
the following surfaces: a spheric surface, an aspheric surface, or
a free-form surface.
[0011] Another aspect of the disclosed embodiments relates to a
zoom lens that includes the above noted integrated optical device.
Yet another aspect of the disclosed embodiments relates to a
handheld electronic device comprising the above noted integrated
optical device.
[0012] In another embodiment, the optical element and frame
structure is molded in a single step. Alignment of the optical
element is controlled through the molding process and one less
assembly step is needed. The lens element and frame structure is
then made of the same material. The material of choice is a balance
of fulfilling optical requirements such as refractive index for the
lens element and mechanical requirements such as yield strength for
the frame. Typical materials for polymers include but are not
limited to Zeonex and polycarbonates.
[0013] Additional post-processing steps can be performed to address
the requirements. For example, diamond-like coating can be coated
on the integrated structure on the non-optical portions to increase
structural strength as well as reduce friction. An opaque coating
can be used to reduce light transmission through the integrated
lens structure other than the active lens element area.
[0014] Another aspect of the disclosed embodiments relates to a
method for fabricating an integrated optical device, that includes
obtaining a first mold that is structured to form an elastic
suspension fixture, injecting a first injection material into the
first mold, and placing a second mold in contact with the first
mold and the first injection material within the first mold, where
the second mold is structured to form an optical element. The
method also includes injecting a second injection material into the
second mold, removing the second mold, and removing the first mold
to obtain the elastic suspension fixture with the optical element
integrated thereto
[0015] In one exemplary embodiment, the first injection material
comprises a first polymer suitable for formation of the elastic
suspension fixture, and the second injection material comprises a
polymer suitable for formation of the optical element. In another
exemplary embodiment, the method further includes further refining
structure of the integrated optical device using a precision
machining tool. In still another exemplary embodiment, the method
further includes, prior to removing the first mold, placing a third
mold in contact with the first mold and the first injection
material, where the third mold is structured to form an additional
element, and injecting a third injection material into the third
mold.
[0016] According to another exemplary embodiment, the additional
element is one of: an additional optical element, an additional
elastic fixture; or a rigid fixture. In one exemplary embodiment,
the additional element is an alignment fixture. In yet another
exemplary embodiment, components within the integrated optical
devices are positioned according to a tolerance in the range of 1
to 5 microns. In another exemplary embodiment, the third injection
material is the same material as one of the first injection
material and the second injection material.
[0017] In one exemplary embodiment, the first mold is additionally
structured to comprise a groove for placement of an actuation
mechanism. In another exemplary embodiment, the above method
further includes integrating a metallic frame into the elastic
suspension fixture. In another exemplary embodiment, the metallic
frame is formed using a metal stamping technique.
[0018] Another aspect of the disclosed embodiments relates to a
method for fabricating an integrated optical device that includes
obtaining a first mold that is structured to form an elastic
suspension fixture and an optical element, injecting a first
injection material into the first mold, injecting a second
injection material into the first mold, and removing the first mold
to obtain the elastic suspension fixture with the optical element
integrated thereto.
[0019] Another aspect of the disclosed embodiments relates to a
method for fabricating an integrated optical device that includes
obtaining a mold that is structured to form an elastic suspension
fixture and to house an optical element, placing the optical
element in the mold, injecting a first injection material into the
mold to form an elastic suspension fixture, and removing the mold
to obtain the elastic suspension fixture with the optical element
integrated thereto. In one exemplary embodiment, the optical
element is cast from a mold prior to placing the optical element in
the mold.
[0020] Another aspect of the disclosed embodiments relates to a
miniature zoom lens system that includes a first prism positioned
to receive incident light from an entrance to the miniature lens
system through a first face of the first prism and to bend the
received light by approximately 90 degrees before allowing the
light to exit from a second face of the first prism, and at least a
first varifocal lens positioned to receive the light that exits the
second face of the prism. The miniature zoom lens system further
includes at least one base lens positioned to receive the light
after passing through the first varifocal lens, a detector
positioned to receive the light after passing through the base
lens, and a first actuator configured to move the first varifocal
lens in at least a direction perpendicular to propagation axis of
the light passing through the first varifocal lens.
[0021] In one exemplary embodiment, at least one face of the first
prism has a freeform surface. In another exemplary embodiment, the
first varifocal lens is one of the following: a liquid crystal
lens, a liquid lens, or an Alvarez-like lens. In another exemplary
embodiment, the detector comprises a complementary metal-oxide
semiconductor (CMOS). In yet another exemplary embodiment, the
first actuator comprises one of a coil or a magnet. In still
another exemplary embodiment, the above miniature zoom lens system
includes a structural platform to allow one of the following to be
directly molded onto, fabricated onto, or integrated with the
structural platform: the first prism, a second prism, the first
varifocal lens, or a second varifocal lens. In one exemplary
embodiment, the structural platform comprises a spring flexure
element. In another exemplary embodiment, thee structural platform
includes a frame and an arm.
[0022] According to another exemplary embodiment, the structural
platform frame comprises a lead frame metal structure that is one
or more of: a metal-stamped structure, a laser-cut structure, a
milled structure, an etched structure, or a molded structure. In
such an exemplary embodiment, the arm is molded on the lead frame
structure, and one or more of the first prism, a second prism, the
first varifocal lens, or a second varifocal lens is molded onto the
lead frame.
[0023] In one exemplary embodiment, a wafer-level optical component
with a preformed lens element is bonded to the platform. In another
exemplary embodiment, the first actuator is a voice-coil actuator
with a bidirectional drive. In yet another exemplary embodiment,
the miniature zoom lens system also includes a second actuator
configured to move an optical component other than the first
varifocal lens within the miniature zoom lens system. In still
another exemplary embodiment, the second actuator and the first
actuator are configured to displace both the optical component
other than the first varifocal lens and the first varifocal lens by
the same distance and in the same direction. In one exemplary
embodiment, the optical component other than the first varifocal
lens is one of: a second varifocal lens, the at least one base
lens, the first prism, or a second prism.
[0024] According to another exemplary embodiment, the first
varifocal lens has a rectangular or an oval-shaped cross section
encompassing only an essential active area of the first varifocal
lens. In another exemplary embodiment, the miniature zoom lens
system further includes a second varifocal lens positioned to
receive the light exiting the first varifocal lens before reaching
the at least one base lens. In still another exemplary embodiment,
the second varifocal lens has a rectangular or an oval-shaped cross
section encompassing only an essential active area of the second
varifocal lens. In yet another exemplary embodiment, both the first
and the second varifocal lenses are movable with respect to one
another so as to provide optical zoom capability for the lens
system.
[0025] In one exemplary embodiment, the at least one base lens is
configured to move along optical axis of the base lens so as to
provide optical focusing ability for the lens system through only
movement of the base lens. In another exemplary embodiment, one or
more of the first varifocal lens, the second varifocal lens or the
at least one base lens is a liquid lens, a liquid crystal lens, a
MEMS-based lens, an Alvarez-like lens, a piezo-based lens, or a
combination thereof. In another exemplary embodiment, the spring
flexure is one of a simple beam flexure or a cascaded beam
flexure.
[0026] An embodiment includes a first varifocal lens positioned to
receive the incident light from an entrance to the miniature lens
system, a first prism positioned to receive the light that exits
the first varifocal lens through a first face of the first prism
and to bend the light received by the first prism by approximately
90 degrees before allowing the light to exit from a second face of
the first prism, and a fixed lens or lens group is positioned to
receive the light that exits the first prism.
[0027] A second varifocal lens is positioned after the lens or lens
group. At least one base lens positioned to receive the light after
passing through the second varifocal lens, a second prism may or
may not be necessarily positioned to receive the light that exits
the at least one base lens through a first face of the second prism
and to bend the light by approximated 90 degrees before allowing
the light to exit from a second face of the second prism, a
detector positioned to receive the light after exiting the second
prism, and at least one actuator configured to move one or both of
the first varifocal lenses in at least a direction perpendicular to
propagation axis of the light passing through the first of the
second varifocal lenses. The second prism serves to position the
detector in a smaller configuration such that the z-axis height of
the module can be minimized. The material selection of the second
prism also serves to correct for chromatic aberration in the
image.
[0028] With the fixed lens or lens group after the first prism, the
optical power of the varifocal lenses can be reduced. The reduction
in optical power helps in the profile gradient of the varifocal
lenses, resulting in better manufacturability. The material of the
fixed lens or lens group can also be chosen to help in correcting
chromatic aberrations which is a key aberration for zoom
lenses.
[0029] Another embodiment includes a first varifocal lens
positioned to receive the incident light from an entrance to the
miniature lens system, a first prism positioned to receive the
light that exits the first varifocal lens through a first face of
the first prism and to bend the light received by the first prism
by approximately 90 degrees before allowing the light to exit from
a second face of the first prism, a fixed freeform lens is
positioned to receive the light that exits the first prism.
[0030] A second varifocal lens is positioned after the fixed
freeform lens. At least one base lens positioned to receive the
light after passing through the second varifocal lens, a second
prism may or may not be necessarily positioned to receive the light
that exits the at least one base lens through a first face of the
second prism and to bend the light by approximated 90 degrees
before allowing the light to exit from a second face of the second
prism, a detector positioned to receive the light after exiting the
second prism, and at least one actuator configured to move one or
both of the first varifocal lenses in at least a direction
perpendicular to propagation axis of the light passing through the
first of the second varifocal lenses. The second prism serves to
position the detector in a smaller configuration such that the
z-axis height of the module can be minimized. The material
selection of the second prism also serves to correct for chromatic
aberration in the image.
[0031] The fixed freeform lens serves to reduce the optical power
of the varifocal lenses. The additional freedom that a freeform
lens provides additional tools to correct for other aberrations in
the optical system. For example, correcting distortions and other
asymmetries in the beam profile due to the varifocal lenses. The
material of the freeform lens can also be chosen to help in
correcting chromatic aberrations which is a key aberration for zoom
lenses.
[0032] Another embodiment includes a first varifocal lens
positioned to receive the incident light from an entrance to the
miniature lens system, a first prism positioned to receive the
light that exits the first varifocal lens through a first face of
the first prism and to bend the light received by the first prism
by approximately 90 degrees before allowing the light to exit from
a second face of the first prism, a second varifocal lens is
positioned after prism.
[0033] The second varifocal lens is an Alvarez-lens pair with an
additional freeform lens moving in tandem with one of the lenses in
the Alvarez-lens pair. This allows the gradient of the profile in
the Alvarez-lens group to be reduced for ease of manufacturability.
The additional freedom in the lens profile helps to correct for
asymmetry in the aberrations.
[0034] At least one base lens positioned to receive the light after
passing through the second varifocal lens, a second prism may or
may not be necessarily positioned to receive the light that exits
the at least one base lens through a first face of the second prism
and to bend the light by approximated 90 degrees before allowing
the light to exit from a second face of the second prism, a
detector positioned to receive the light after exiting the second
prism, and at least one actuator configured to move one or both of
the first varifocal lenses in at least a direction perpendicular to
propagation axis of the light passing through the first of the
second varifocal lenses. The second prism serves to position the
detector in a smaller configuration such that the z-axis height of
the module can be minimized. The material selection of the second
prism also serves to correct for chromatic aberration in the
image.
[0035] An embodiment includes a first varifocal lens positioned to
receive the incident light from an entrance to the miniature lens
system, a first prism positioned to receive the light that exits
the first varifocal lens through a first face of the first prism
and to bend the light received by the first prism by approximately
90 degrees before allowing the light to exit from a second face of
the first prism.
[0036] A second varifocal lens is positioned after first prism. At
least one base lens positioned to receive the light after passing
through the second varifocal lens. A freeform lens is placed
together with the base lens for additional aberration
correction.
[0037] A second prism may or may not be necessarily positioned to
receive the light that exits the at least one base lens through a
first face of the second prism and to bend the light by
approximated 90 degrees before allowing the light to exit from a
second face of the second prism, a detector positioned to receive
the light after exiting the second prism, and at least one actuator
configured to move one or both of the first varifocal lenses in at
least a direction perpendicular to propagation axis of the light
passing through the first of the second varifocal lenses. The
second prism serves to position the detector in a smaller
configuration such that the z-axis height of the module can be
minimized. The material selection of the second prism also serves
to correct for chromatic aberration in the image.
[0038] An embodiment includes a first varifocal lens positioned to
receive the incident light from an entrance to the miniature lens
system, a first prism positioned to receive the light that exits
the first varifocal lens through a first face of the first prism
and to bend the light received by the first prism by approximately
90 degrees before allowing the light to exit from a second face of
the first prism.
[0039] A second varifocal lens is positioned after first prism. At
least two base lens which serves as a lens group is positioned to
receive the light after passing through the second varifocal lens.
Of the at least two base lens, at least one of them is fixed, the
other base lenses are movable, changing the optical power of the
base lens group. The variable optical power aids in the focusing of
the image as well as reducing the optical power change the
varifocal lenses has to undertake to perform zoom. That helps in
manufacturability of the profiles of the lenses or an increase to
the overall optical power change the whole optical system can
undertake.
[0040] A second prism may or may not be necessarily positioned to
receive the light that exits the at least one base lens through a
first face of the second prism and to bend the light by
approximated 90 degrees before allowing the light to exit from a
second face of the second prism, a detector positioned to receive
the light after exiting the second prism, and at least one actuator
configured to move one or both of the first varifocal lenses in at
least a direction perpendicular to propagation axis of the light
passing through the first of the second varifocal lenses. The
second prism serves to position the detector in a smaller
configuration such that the z-axis height of the module can be
minimized. The material selection of the second prism also serves
to correct for chromatic aberration in the image.
[0041] Another aspect of the disclosed embodiments relates to a
miniature zoom lens system that includes a first prism positioned
to receive incident light from an entrance to the miniature lens
system through a first face of the first prism and to bend the
received light by approximately 90 degrees before allowing the
light to exit from a second face of the first prism, and a first
varifocal lens positioned to receive the light that exits the
second face of the prism. Such a miniature zoom lens system also
includes a second varifocal lens positioned to receive the light
that exits first varifocal lens, at least one base lens positioned
to receive the light after passing through the second varifocal
lens, a second prism positioned to receive the light that exits the
at least one base lens through a first face of the second prism and
to bend the light received by the second prism by approximately 90
degrees before allowing the light to exit from a second face of the
second prism, a detector positioned to receive the light after
exiting the second prism, and at least one actuator configured to
move one or both of the first varifocal and second varifocal lenses
in at least a direction perpendicular to propagation axis of the
light passing through the first or the second varifocal lenses.
[0042] Another aspect of the disclosed embodiments relates to a
miniature zoom lens system that includes a first varifocal lens
positioned to receive the incident light from an entrance to the
miniature lens system, a first prism positioned to receive the
light that exits the first varifocal lens through a first face of
the first prism and to bend the light received by the first prism
by approximately 90 degrees before allowing the light to exit from
a second face of the first prism, a second varifocal lens
positioned to receive the light that exits first prism, at least
one base lens positioned to receive the light after passing through
the second varifocal lens, a second prism positioned to receive the
light that exits the at least one base lens through a first face of
the second prism and to bend the light received by the second prism
by approximately 90 degrees before allowing the light to exit from
a second face of the second prism, a detector positioned to receive
the light after exiting the second prism, and at least one actuator
configured to move one or both of the first varifocal and second
varifocal lenses in at least a direction perpendicular to
propagation axis of the light passing through the first or the
second varifocal lenses.
[0043] In one exemplary embodiment, the second prism is orientated
such as to allow placement of the detector on the same side of the
miniature zoom lens system as the entrance to the miniature zoom
lens system. In another exemplary embodiment, the second prism is
orientated such as to allow placement of the detector on a side of
the miniature zoom lens system that is opposite to the entrance to
the miniature zoom lens system.
[0044] Another aspect of the disclose embodiments relates to a
miniature zoom lens system that includes a first varifocal lens
positioned to receive the incident light from an entrance to the
miniature lens system, a first prism positioned to receive the
light that exits the first varifocal lens through a first face of
the first prism and to bend the light received by the first prism
by approximately 90 degrees before allowing the light to exit from
a second face of the first prism, a second varifocal lens
positioned to receive the light that exits first prism, at least
one base lens positioned to receive the light after passing through
the second varifocal lens, a detector positioned along the optical
axis of the at least one base lens to receive the light after
exiting the at least one base lens, and at least one actuator
configured to move one or both of the first varifocal and second
varifocal lenses in at least a direction perpendicular to
propagation axis of the light passing through the first or the
second varifocal lenses.
[0045] In one exemplary embodiment, the first varifocal lens and
the first prism are formed as an integrated structure thereby
reducing optical path length of light propagating through the
miniature lens system. In another exemplary embodiment, one or more
optical elements of the first varifocal lens are positioned to
configure the first varifocal lens as a lens with a negative
optical power, and one or more optical elements of the second
varifocal lens are positioned to configure the second varifocal
lens as a lens with a positive optical power.
[0046] In yet another exemplary embodiment, one or more optical
elements of the first varifocal lens are positioned to configure
the first varifocal lens as a lens with a positive optical power,
and one or more optical elements of the second varifocal lens are
positioned to configure the second varifocal lens as a lens with a
negative optical power. In still another exemplary embodiment, one
or more optical elements of the first varifocal lens are movable so
as to allow an optical power of the first varifocal lens to change
in response to the movement of the one or more optical elements of
the first varifocal lens. In one exemplary embodiment, one or more
optical elements of the second varifocal lens are movable so as to
allow an optical power of the second varifocal lens to change in
response to the movement of the one or more optical elements of the
first varifocal lens.
[0047] Another aspect of the disclosed embodiments relates to an
Alvarez lens configuration that includes a first optical element
and a second optical element, where each optical element includes
two surfaces that are substantially perpendicular to an optical
axis of the lens configuration, and a first surface of each the
optical elements is a plane surface and a second surface of each of
the optical elements is a surface characterized by a polynomial.
Alternatively, both surfaces of either or both of the first and
second optical elements can be characterized by a polynomial, or
different polynomials. The different polynomials can have different
terms, different coefficients, or both. The first optical element
is positioned at a particular distance from the second optical
element such that the second surface of the first optical element
faces the second surface of the second optical element, where each
of the first and the second optical elements is configured to move
substantially perpendicular to the optical axis.
[0048] Another aspect of the disclosed embodiments relates to an
Alvarez lens configuration that includes a first optical element
and a second optical element, where each optical element includes
two surfaces that are substantially perpendicular to an optical
axis of the lens configuration. A first surface of each the optical
elements is a freeform surface and a second surface of each of the
optical elements is a surface characterized by a polynomial. The
first optical element is positioned at a particular distance from
the second optical element such that the second surface of the
first optical element faces the second surface of the second
optical element, where each of the first and the second optical
elements is configured to move substantially perpendicular to the
optical axis.
[0049] In one exemplary embodiment, the first optical element is
configured to move synchronously with the second optical element
and in opposite direction of the movement of the second optical
element. In another exemplary embodiment, the first and the second
optical elements are configured to move perpendicular to the
optical axis by the same amount but in opposite directions.
[0050] In some embodiments with any of the above described systems,
a z-height of no more than 6 mm is achieved, and a z-height in the
range of 4-7 mm can be achieved over a range of optical powers, for
example in the range of 1.times. to 6.times.. In some embodiments
with any of the above described systems, a field of view in the
range 60 degrees to 75 degrees is achieved.
[0051] Another aspect of the disclosed embodiments relates to a
method for manufacturing a miniature lens system that includes
producing a structural platform comprising a frame and an arm, and
molding a plurality of optical elements onto the frame of the
structural platform subsequent to, and as a separate step from,
producing the structural platform, the plurality of optical
components comprising: a first varifocal lens, a first prism and a
first base lens. In one exemplary embodiment, producing the
structural platform comprises molding the arm onto the frame of the
structural platform. In another exemplary embodiment, the above
noted method further includes connecting one or more actuators to
the arm of the structural platform, the one or more actuators being
coupled to one or more of the optical elements to allow movement of
the one or more optical elements. In still another exemplary
embodiment, the above noted method further comprises bonding a
wafer-level optical component with a preformed lens element to the
structural platform.
BRIEF DESCRIPTION OF THE DRAWINGS
[0052] FIG. 1 depicts the dimensional tolerance versus component
dimension for a precision injection molding regime that is
implemented in accordance with the disclosed embodiments and other
techniques.
[0053] FIG. 2 illustrates a sequence of operations that can be
carried out to fabricate an integrated optical system in accordance
with an exemplary embodiment.
[0054] FIG. 3 illustrates a top view of a fabricated molded
structure in accordance with an exemplary embodiment.
[0055] FIG. 4 illustrates a set of operations that can be carried
out to produce an integrated optical device in accordance with an
exemplary embodiment.
[0056] FIG. 5 illustrates a set of operations that can be carried
out to produce an integrated optical device in accordance with an
exemplary embodiment.
[0057] FIG. 6 illustrates a set of operations that can be carried
out in accordance with another exemplary embodiment to produce an
integrated optical device.
[0058] FIG. 7 depicts an optical system in which the optical path
is folded twice and varifocal lenses are located in between the
folding optics in accordance with an exemplary embodiment.
[0059] FIG. 8 depicts an optical system with varifocal lenses
located at the window, the optical path being folded before
reaching the second varifocal lens and folded again before reaching
the complementary metal-oxide semiconductor (CMOS) detector in
accordance with an exemplary embodiment.
[0060] FIG. 9 depicts an optical system comprising a varifocal lens
element integrated with a prism element and a CMOS detector placed
vertically upright in accordance with an exemplary embodiment.
[0061] FIG. 10 is a ray diagram for an optical system in accordance
with an exemplary embodiment.
[0062] FIG. 11 is a ray diagram for an optical system in accordance
with another exemplary embodiment.
[0063] FIG. 12 illustrates a pair of varifocal lenses that include
planar surfaces in accordance with an exemplary embodiment.
[0064] FIG. 13 illustrates a pair of varifocal lenses that include
freeform surfaces in accordance with an exemplary embodiment.
[0065] FIG. 14 depicts the active area of an Alvarez-like lens in
accordance with an exemplary embodiment.
[0066] FIG. 15 depicts an exemplary prism element with a freeform
surface that can be utilized within at least one optical system of
the disclosed embodiments.
[0067] FIG. 16 depicts an integrated lens platform and its
associated components in accordance with an exemplary
embodiment.
[0068] FIG. 17 illustrates a set of operations that can be carried
out in accordance with an exemplary embodiment to produce a
miniature lens system.
[0069] FIG. 18 illustrates an embodiment of a miniaturized optical
zoom lens system comprising, in sequence along a light path, a
first varifocal lens, a prism and optional iris, a second varifocal
lens, and a base lens group, all configured to create an image on a
image sensor or detector.
[0070] FIG. 19 illustrates an embodiment of a miniature optical
zoom lens system comprising, in sequence along a light path, a
first varifocal lens, a prism and optional iris, a single fixed
freeform lens, a second varifocal lens, and a base lens group, all
configured to create an image on a image sensor.
[0071] FIG. 20 illustrates an embodiment of a miniature optical
zoom lens system comprising, in sequence along a light path, a
first varifocal lens, a prism and optional iris, a second varifocal
lens group comprising three freeform lenses in which two move
together, and a base lens group, all configured to create an image
on an image sensor.
[0072] FIG. 21 illustrates an embodiment of a miniature optical
zoom lens system comprising, in sequence along a light path, a
first varifocal lens, a prism and optional iris, a second varifocal
lens, a base lens group, and a freeform lens, all configured to
create an image on an image sensor.
[0073] FIG. 22 illustrates an embodiment of a miniature optical
zoom lens system comprising, in sequence along a light path, a
first varifocal lens, a prism and optional iris, a fixed
rotationally symmetric lens, a second varifocal lens, and a base
lens, all configured to create an image on an image sensor.
[0074] FIG. 23 illustrates an embodiment of a miniature optical
zoom lens system comprising, in sequence along a light path, a
first varifocal lens, a prism and optional iris, a second varifocal
lens, a first base lens group which is movable, and a fixed base
lens group, all configured to create an image on an image
sensor.
[0075] FIG. 24 illustrates in detail a configuration of the
elements of a varifocal lens wherein each of the optically
important surfaces are defined by polynomials, although the
polynomial defining each surface can vary from the polynomial
defining the other surfaces, including varying the number of terms
and the coefficients.
[0076] The disclosed embodiments relate to methods, devices, and
fabrication processes that facilitate design and manufacturing of
optical systems with improved alignment capabilities and reduced
overall size, in addition to disclosing systems and methods for
configuring components within an optical system.
[0077] To achieve movement of an optical component, such as a lens,
along the optical axis (i.e., z-axis) or perpendicular to the
optical axis (i.e., along the x- and y-axes), in an embodiment
spring flexures can be utilized to allow the optical component to
move laterally. The spring flexures can be simple beams or cascaded
beam flexures. Alternatively, voice coil motors can be used to
achieve the necessary movement.
[0078] In one approach, the lens element in an optical system can
be fabricated through a molding process whereby a mold is created
and liquid plastic resin is injected into the mold and hardened
through UV or heat. The spring flexures can be fabricated
separately, for example using micro fabrication processes. The lens
element and the spring flexures can then be assembled. In this
approach, however, alignment can be one major concern. For example,
unlike typical spherical lens elements, free-form surfaces may not
have rotational symmetry. Thus, besides the usual in-plane
positioning issues, there is an additional rotational alignment
between the lens element and the spring flexure structure. The
actual step of assembly, whether through adhesives or other means,
may also potentially disturb the alignment process.
[0079] The disclosed embodiments facilitate alignment of optical
components in an optical system that can include optical components
with spheric, aspheric, and/or free-form surfaces that may further
move in any direction within the optical system. In some
embodiments, monolithic integration of the lens element, spring
flexures, and supporting structures minimizes the number of
post-assembly steps for integration and reduces possible
misalignment issues.
[0080] Some of the disclosed embodiments rely on injection
precision molding to fabricate optical systems that can include
lenses and other optical components, as well as mechanical
components such as flexible or rigid fixtures. FIG. 1 provides a
comparison of dimensional tolerance versus component dimensions for
a precision injection molding regime that is implemented in
accordance with the disclosed embodiments. As illustrated in FIG.
1, precision injection molding enables the manufacture of smaller
components with better tolerances compared to other techniques. As
will be described in the sections that follow, multiple shots of
injection molding can be sequentially introduced to produce
integrated micro-optic devices in accordance with the techniques of
the disclosed embodiments.
[0081] According to the disclosed embodiments, the lens and the
flexures of an integrated optical device can be fabricated in a
single step. This can be achieved in several ways. The lens element
is essentially a refractive element with a certain surface profile.
The required surface profile can be fabricated through casting from
a mold. Fabrication of the lens together with the spring flexures
can be accomplished by turning the additional spring flexures on
the same mold as the lens. As such, when the plastic resin is
injected into the mold, the resulting structure is a lens element
with the spring flexures attached thereto. In this way, lens
elements casted out separately can be assembled with the supporting
structure. Other parts of the structure can be molded in the same
step, as well. By way of example, and not by limitation, such other
parts can include structures for assembly with other lens elements
or structures for positioning and alignment.
[0082] In scenarios where a single-shot molding process is not
feasible due to, for example, limitations in design flexibility, a
multi-shot (e.g., two-shot, three-shot, four-shot, etc.) precision
injection molding fabrication process can be used to fabricate the
integrated optical system. For example, in a two-shot fabrication
process, the first shot can cast out the spring flexures, and the
second mold for the second shot can cast out the lens element
integrated with the previously cast spring flexures. As the mold is
removed, further fine-tuning on the dimensions can be done, if
needed, through on-the-spot micromachining, such as with a
precision computer numerical control (CNC) machine.
[0083] According to some embodiments, metal stamping can
additionally, or alternatively, used to mass-produce parts in a
cost-efficient manner. In this case, the metal stamping mold can
create the spring flexure skeleton structure that can be used to
reinforce the subsequent molding step. The molding step can then
cast out the lens element on the metal skeleton structure.
[0084] Besides molding the lens element on the metal skeleton
structure, the lens elements can be molded in a separate process.
This may be carried out to minimize the stress on the active lens
area during the molding process. In such scenarios, the lens
elements can be assembled onto the skeleton structure through a
separate process such as ultrasonic welding or adhesives
[0085] According to some embodiments, micro-fabrication methods can
additionally, or alternatively, be used to produce a chip-based
mold. The chip or wafer produced using micro-fabrication techniques
can include etched-out grooves that correspond to the locations of
the spring flexures. The lens element can then be cast out
separately and positioned on individual chips or wafers.
Ultraviolet (UV) or heat-curable resin can then be poured to fill
out the grooves together with the lens elements and subsequently
cured. The resulting plastic piece is now a lens element with the
spring flexures attached and aligned.
[0086] In another iteration, the above described fabricated
integrated spring-flexure-lens can then be further assembled either
with other components or another spring-flexure-lens assembly using
one or more of the above-described techniques. As such, other
structures can be incorporated into the molding process. Since
other components also need to be assembled, some alignment
structures can be molded as part of the overall structure.
[0087] In embodiments that require the movement of one or more
optical components, an actuation mechanism is needed to move the
lens. This actuation mechanism can also be incorporated into the
mold design. For example, electromagnetic actuation can be
implemented using a miniature coil of wire that is assembled on the
integrated spring-flexure-lens. To this end, a groove can be
designed to hold the miniature coil of wire on the integrated
spring-flexure-lens.
[0088] As noted earlier, further refinements can be undertaken
immediately after the plastic resin step through, for example, a
precision micromachining that is performed on the cast plastic
structure to further improve the tolerance of the components.
[0089] FIG. 2 illustrates a sequence of operations that can be
carried out to fabricate an integrated optical system in accordance
to an exemplary embodiment of the invention. The operations in FIG.
2 start with the creation of the elastic suspension mold. Next, the
first shot of elastic suspension material is injected into the
mold. Then, a second shot casts out the lens. Upon removal of the
lens mold (in (d)) and removal of the integrated device (in (e)),
the elastic suspension frame and the micro lens is obtained.
Although the exemplary operations in FIG. 2 depict the fabrication
process for a single-lens assembly with elastic suspension
structures, it is understood that additional optical, mechanical
(including alignment) structures can be integrated into the optical
system through the existing or additional injection molding steps.
Moreover, these additional structures can be rigid or elastic.
[0090] FIG. 3 illustrates a top view of a molded structure
fabricated in accordance with an exemplary embodiment of the
invention. The structure that is illustrated in FIG. 3 includes a
supporting structure, a lens element, a holder for the lens
actuator and elastic (e.g., spring) fixtures that allow the lens to
be moved in the up/down direction indicated by the arrow. While the
exemplary structure of FIG. 3 only shows movement of the lens in a
single direction, it is understood that movement of the lens in
three dimensions can be enabled. For example, additional elastic
fixtures and appropriate actuation mechanisms can be included in
the structure.
[0091] Further, alternate or additional optical components can be
incorporated into the integrated systems that are fabricated in
accordance with the disclosed embodiments. These components can
include, but are not limited to, lenses, gratings, diffractive
optical elements and the like. The disclosed embodiments provide
for a sequence of manufacturing processes with tolerances in the
region of 1 to 5 microns for an integrated platform incorporating
elastic suspension, rigid frames, and optical components. The cost
of manufacturing these components is estimated to be much lower
than conventional MEMS micro fabrication.
[0092] Precision manufacturing technologies that are used for
fabrication of the integrated systems in accordance with the
disclosed embodiments can include injection molding, in-mold
decoration, hot stamping, and/or insert molding. These processes
allow mass manufacturing of integrated optical systems that can
include a microlens on an elastic suspension platform. In some
embodiments, the elastic suspension is made with a metal backbone
that is fabricated using, for example, metal stamping followed by a
polymer molding (first shot). The metallic frames can enhance the
elasticity of the suspension and robustness of the frame. In some
embodiments, the elastic suspension is made without the metal
backbone. The second shot can be a polymer material suitable for an
optical lens. This component is then assembled into a larger
structure making up an optical lens module. Multiple shots of
injection molding process steps can be incorporated for
multi-component integration.
[0093] FIG. 4 illustrates a set of operations 400 that can be
carried out in accordance with an exemplary embodiment to produce
an integrated optical device. At 402 a first mold is obtained that
is structured to form an elastic suspension fixture. At 404, a
first injection material is injected into the first mold. At 406 a
second mold is placed in contact with the first mold and with the
first injection material within the first mold. The second mold is
structured to form an optical element. At 408, a second injection
material is injected into the second mold. At 410 the second mold
is removed and at 412 the first mold is removed to obtain the
elastic suspension fixture with the optical element integrated
thereto.
[0094] FIGS. 5 and 6 illustrate two sets of operations 500 and 600,
respectively, that can be carried out in accordance with other
exemplary embodiments to produce an integrated optical device. In
the exemplary embodiment of FIG. 5, at 502, a first mold is
obtained that is structured to form an elastic suspension fixture
and an optical element. At 504, a first injection material is
injected into the first mold and, at 506, a second injection
material is injected into the first mold. At 508, the first mold is
removed to obtain the elastic suspension fixture with the optical
element integrated thereto. In the exemplary operations 600 of FIG.
6, at 602, a mold is obtained that is structured to form an elastic
suspension fixture and to house an optical element. At 604, the
optical element is placed in the mold and, at 606, a first
injection material is injected into the mold to form an elastic
suspension fixture. At 608, the mold is removed to obtain the
elastic suspension fixture with the optical element integrated
thereto.
Zoom Lens Configuration
[0095] In applications with limited space (e.g., in a camera phone)
the configuration of optical components significantly influences
the size of the overall camera module that can be achieved. In such
systems, the thickness (e.g., the thickness of the device in
z-direction or "z-height") of the module is paramount. In order to
deliver the smallest possible optical configuration for a zoom lens
system, several configurations are disclosed in this
application.
[0096] As shown in FIG. 7, one embodiment features a light
path-bending element, such as a prism 702 or a mirror, which is
used to bend incoming rays 90 degrees, sending them through two
varifocal lenses 704, 706 and another prism 708, which bends the
optical path again for it to reach the detector (e.g., CMOS
detector 710). In an exemplary embodiment, the fixed/base lens 714
is integrated with the prism 708, and the aperture 712 is placed
in-between the two varifocal lenses 704, 706. Such a configuration
offers the shortest z-height possible but suffers from limited
field of view (FOV) and f-numbers. In this configuration, while it
is possible to achieve a thin z-height of 6 mm, the FOV is limited
to about 30.degree..
[0097] In order to increase the FOV, in some embodiments, at least
one of the varifocal lenses may be located at the entrance of the
optical system, as shown in FIG. 8. In the exemplary configuration
of FIG. 8, a prism 802 is placed in-between the two varifocal
lenses 804, 806 to bend the optical path 90 degrees and another
prism 808 is used to bend the light an additional 90 degrees before
reaching the detector (e.g., the CMOS detector 810). The aperture
812 is located between the prism 802 and the varifocal lens 806.
The exemplary configuration of FIG. 8 allows a FOV of 60.degree. to
75.degree.. The z-height has to be increased to about 8 mm. FIG. 8
illustrates an exemplary configuration in which the detector is
placed on the same side as the entrance of the optical system.
However, it is understood that the detector can be placed on the
side opposite to the entrance of the optical system (as, for
example, illustrated in the configuration of FIG. 7). Placing the
detector at the same side can minimize the z-height of the module
since the increase in z-height is primarily due to the additional
height of the lens and detector elements. Thus placing the detector
810 on the same side as the entrance window means that the z-height
is increased only by the thicker of the two elements. However,
since the optical path to reach the detector is relatively long,
considering the need for the path to be folded before reaching the
detector, the aperture and beam diameter is still relatively large
in this configuration. An approach to shorten the optical path
length to reach the detector can reduce the z-height even
further.
[0098] To reduce the optical path length to reach the detector, in
accordance with some embodiments, the detector is placed vertically
upright and therefore closer to the lenses, as shown in FIG. 9. In
the exemplary configuration of FIG. 9, a prism-like element 904
that includes a first varifocal lens integrated with a prism
component is placed between the window receiving the incident light
and the second varifocal lens 906. Thus, the need for a second
prism element is removed. The aperture 912 is located between the
integrated varifocal lens and prism 904 and the second varifocal
lens 906. The overall optical path length can be reduced from about
23 mm to about 18 mm. The reduction in optical path length allows a
smaller aperture diameter along with smaller lens elements and
therefore also smaller z-height. A z-height of approximately 6 mm
can be obtained in this configuration. As another example, a
z-height of between about 4-7 mm can be achieved, with the
particular z-height affected by the optical power of a particular
design. Without the varifocal lens integrated with the prism, the
z-height will have to be increased slightly, to about 6.5 mm, to
accommodate the gap between the varifocal lens and prism. In this
configuration, a FOV in the range of 60.degree.-75.degree. can be
achieved. Depending on the application, optical specification of
the disclosed zoom lenses can be modified to meet the required size
and form factor. For example, the z-height can be further reduced
to meet specific implementation requirements.
[0099] FIG. 10 illustrates a ray diagram for a miniature lens
configuration in accordance with an exemplary embodiment. The
configuration of FIG. 10 provides a specific example of the lens
system of FIG. 9 in which both varifocal lenses 1004 and 1006 are
alvarez-like lenses. In addition, the various optical components in
FIG. 10 are positioned to obtain the desired zoom capability. In
particular, the first pair of Alvarez lenses 1004 is positioned to
receive incident light from the entrance to the miniature lens
system, and direct the light to the integrated prism. Although the
exemplary diagram of FIG. 10 shows an integrated Alvarez
lens-prism, it is understood that in some embodiments, the first
Alvarez lens and the prism may be separate components. Referring
back to FIG. 10, the light that enters the integrated prism is bent
by 90 degrees before exiting the prism. The light is then received
by the second Alvarez lens 1006, and subsequently travels through
the Fixed/base lens group 1014 before reaching the detector 1010.
In the example diagram of FIG. 10, by moving the two elements of
the first Alvarez lenses 1004 perpendicular to the optical axis at
opposite directions (e.g., one lens element is moved out and the
other lens element is moved into the page), a negative optical
power is produced. Further, in the exemplary diagram of FIG. 10, by
moving the two elements of the second Alvarez lens 1006
perpendicular to the optical axis at opposite directions, a
positive optical power is effectuated. The movement of the lens
elements can be achieved using one or more actuators that are
coupled to the lens elements. The exemplary configuration of FIG.
10 produces a miniature lens system with a small height, which
makes this configuration particularly advantageous for
implementation in devices with thin form factors, such as a cell
phone or tablet.
[0100] FIG. 11 illustrates a ray diagram for a miniature lens
configuration in accordance with another exemplary embodiment. The
configuration of FIG. 11 provides yet another specific example of
the lens system of FIG. 9 in which both varifocal lenses 1104 and
1106 are alvarez-like lenses. In addition, the various optical
components in FIG. 11 are positioned to obtain the desired zoom
capability. In particular, the first pair of Alvarez lenses 1104 is
positioned to receive incident light from the entrance to the
miniature lens system, and direct the light to the integrated
prism. The light that enters the integrated prism is bent by 90
degrees before exiting the prism. The light is then received by the
second Alvarez lens 1106, and subsequently travels through the
Fixed/base lens group 1114 before reaching the detector 1110. In
the example diagram of FIG. 11, by moving the two elements of the
first Alvarez lenses 1104 perpendicular to the optical axis at
opposite directions (e.g., one lens element is moved out and the
other lens element is moved into the page), a positive optical
power is produced. Further, in the exemplary diagram of FIG. 11, by
moving the two elements of the second Alvarez lens 1106
perpendicular to the optical axis at opposite directions, a
negative optical power is effectuated. The movement of the lens
elements can be achieved using one or more actuators that are
coupled to the lens elements. As is illustrated in FIG. 11 by the
circled X and circled dot markings on the Alvarez lens elements,
the movements of the lens elements are opposite to those
illustrated in FIG. 10. By changing the optical power of the two
pairs of Alvarez lenses, the focal length of optical system
changes. In the exemplary diagram of FIG. 10, the lens system
operates as a telescope with a long focal length.
[0101] FIG. 12 illustrates a lens configuration that includes two
varifocal lenses in accordance with an exemplary embodiment. Each
of the first varifocal lens 1202 and the second varifocal lens 1204
comprises two lens elements comprises two elements (FIG. 12
illustrates elements 1 and 2 for the first lens 1202, and elements
3 and 4 for the second lens 1204). Each element is considered a
thin plate, where each plate is characterized by two surfaces that
are generally perpendicular to the optical axis. One surface is a
plane surface and the other surface is a polynomial surface which
is characterized by a function (e.g., a polynomial). The non-planar
surface is designated as Alvarez surface in FIG. 12. For each of
the lenses 1202 and 1204, by placing the two plates at a small
distance from one another, and with the polynomial surfaces facing
one another, an optical power is generated. By moving the two
elements perpendicular to the optical axis at opposite directions
synchronously, the optical power can be varied.
[0102] FIG. 13 illustrates a lens configuration that includes two
varifocal lenses in accordance with another exemplary embodiment.
The exemplary configuration of FIG. 13 includes a first varficoal
lens 1302 and a second varifocal lens 1304 similar to those
depicted in FIG. 12. However, instead of plane surfaces, the
elements 1, 2, 3 and 4 in FIG. 13 each include a freeform surface
that is shaped to correct aberrations in the optical system.
[0103] In each of the disclosed embodiments, the varifocal lenses
can be, among other types, liquid crystals, liquid lenses, or
Alvarez-like lenses. The varifocal lenses can also be made up of
multiple lens elements, as in the case of Alvarez-like lenses. For
each of the embodiments, it would not be feasible to configure
conventional lenses for a small z-height module since a
conventional lens moving along the optical axis would increase the
z-height significantly. Further, to achieve a large FOV, at least
one varifocal lens must be located at the entrance of the optical
module.
Lens Active Area
[0104] The disclosed embodiments include additional improvements
that further reduce the z-height of the optical module. In some
embodiments that use Alvarez-like lenses, the Alvarez-like lenses
are moved perpendicular to the optical path (instead of along the
optical path) to perform tuning. Moreover, displacement of the
Alvarez-like lenses perpendicular to the optical axis has a
significant impact on the performance of the optical module. In
particular, a larger displacement of the lens can result in a
greater change of optical power. However, given that only a portion
of the lens area is being utilized at a given position of the
lenses (i.e., an "actual active area" of the lens), a larger
displacement of the lenses also results in requiring a larger
circular lens diameter to cover the active area. This scenario can
be further illustrated with the aid of FIG. 14, in which the small
circles represent two actual active areas of a varifocal lens at
two different lens positions (i.e., displaced from one another
perpendicular to the optical axis). While the diagram in FIG. 14
shows active areas of the same size for illustration purposes, the
sizes of the actual active areas may not be the same. In the
exemplary diagram of FIG. 14, the optical axis pointing in and out
of the page. The large circle in FIG. 14 represents the circular
area needed to encompass the active area of any single lens as the
lens moves in x- and/or y-directions. The rectangular area
represents the smaller single lens profile that is sufficient for
the operation of the lens. The length of the rectangular area would
typically represent the direction of motion.
[0105] In some embodiments, instead of a circular lens, a
rectangular or oval-shaped lens that only covers the essential
active area of the lenses is used. Such a lens in rectangular
format is shown by the rectangular block in FIG. 14. In this
manner, the actuation range can be increased without affecting the
overall optical module size. Rotational alignment can be improved
during assembly and fabrication.
Freeform Prism
[0106] According to some embodiments, the size of the optical
system can be further reduced by combining the prism and varifocal
lens elements. This is particularly relevant when Alvarez-like
lenses are used. Using this technique, one of the sides of the
prism can be molded with a freeform surface, as shown in FIG. 15,
allowing additional gap space between the varifocal lens surfaces
to be removed.
Integrated Platform
[0107] In moving lenses perpendicular to the optical axis, the
mechanism has to be small, compact, and easily aligned and
manufactured. Having the lens element integrated with a structural
platform is a way of fulfilling these requirements. FIG. 16 shows
an integrated platform in accordance with an exemplary embodiment.
As shown in FIG. 16, the integrated platform comprises a frame that
serves as a structural guide and an arm element that connects to an
actuator element, such as a coil or magnet. The lens element can be
directly molded or fabricated onto the frame with the correct
orientation. A spring flexure element may or may not be
incorporated with the integrated platform. In one embodiment, the
platform frame and arm are molded in one step and the lens element
molded after that. In another embodiment, the frame can be made of
a lead frame metal structure. The lead frame can be metal-stamped,
laser-cut, milled, etched, or molded. The arm element can be molded
on the lead frame structure by an injection molding process, with
the lens element molded onto the lead frame after the rest of the
structures are completed.
[0108] In order for the molded lens to be aligned accurately,
alignment structures can be incorporated onto the platform. Besides
insert molding the lenses, a wafer-level optical component with a
preformed lens element can be bonded to the platform in a separate
step. All of these processes are intended to allow the
manufacturing process to be automated, keeping the overall
structure compact and ensuring accurate alignment between
structures and lens elements.
[0109] In actuating the integrated lens platform, incorporating a
spring flexure element may or may not be necessary. A spring
flexure primarily serves to provide a restoring force to the
platform. This is necessary if the actuation mechanism is only
capable of providing a force in a single direction, as in the case
with a voice-coil actuator with a single-direction drive. A
voice-coil actuator with a bidirectional drive can remove the need
for a flexure-restoring element. Without the spring flexure
element, the actuation range can be easily increased. By adding a
position sensor on the system, the position of the lens platform
can be well determined through a closed-loop control.
[0110] In some embodiments, the actuation requirement is simplified
when two or more lenses are designed to move with the same
displacement and direction. In this way, instead of having
individual actuators for each lens element, one actuator is used to
move two or more lenses. A mechanical structure can be designed to
link the multiple lenses together. The structure is then actuated
by an actuator.
Zoom and Focus Decouple Operation
[0111] Focusing and zoom are two operations that the optical system
has to be able to perform. Regardless of the configuration that is
used, the first varifocal lens element can be used for focusing
purposes when the second varifocal lens is kept constant at a
particular optical power. Operation in such a manner can be very
elegant given the cost of more complex electronics and more
constraints in terms of the optical optimization that has to be
performed on the optical system.
[0112] To simplify the operation of the system, in some
embodiments, the zoom and focusing operations are decoupled. Zoom
is delivered through the tuning of the two varifocal lenses.
Focusing can be performed through moving the base lens system along
the optical axis. This simplifies the image optimization process
and controls. In such embodiments, an actuator group actuates the
varifocal lenses as a group. Focusing can be achieved through
either moving the base lens group along the optical axis or a
tunable lens element or elements in the base lens group. Suitable
elements are optical lenses that can change their optical power,
such as liquid lenses, liquid crystals, MEMS-based lenses,
Alvarez-like lenses, and piezo-based lenses.
[0113] FIG. 17 illustrates a set of operations 1700 that can be
carried out in accordance with an exemplary embodiment to produce a
miniature lens system. At 1702, a structural platform comprising a
frame and an arm is produced. At 1704, a plurality of optical
elements are molded onto the frame of the structural platform
subsequent to, and as a separate step from, producing the
structural platform. The plurality of optical components
comprising: a first varifocal lens, a first prism and a first base
lens. In one exemplary embodiment, producing the structural
platform comprises molding the arm onto the frame of the structural
platform. In another exemplary embodiment, the above noted method
further includes connecting one or more actuators to the arm of the
structural platform. The one or more actuators are coupled to one
or more of the optical elements to allow movement of the one or
more optical elements. In yet another exemplary embodiment, the
above method further includes bonding a wafer-level optical
component with a preformed lens element to the structural
platform.
[0114] FIGS. 18-23 illustrate various alternative embodiments of
miniature optical lens systems, all configured to create an image
on an image sensor which is typically supplied separately from the
present invention. In particular, FIG. 18 illustrates an embodiment
of a miniaturized optical zoom lens system comprising, in sequence
along an optical path, a first varifocal lens 1800 comprised of a
pair of Alvarez-like optical elements 1805 and 1810, a prism 1815
and optional iris 1820, a second varifocal lens 1825 again
comprised of a pair of Alvarez-like optical elements 1830 and 1835,
and a base lens group 1840 comprising a plurality of rotationally
symmetric lenses, illustrated as 1840A-C, all configured to create
an image on a image sensor or detector. The optical elements 1805,
1810, 1830 and 1835 of the first and second varifocal lenses 1800
and 1825, respectively, are configured to move perpendicularly to
the light path to provide at least variable optical power, and one
or both of the optically important surfaces of each optical element
can be, depending on the implementation requirements, defined by a
polynomial as described in greater detail hereinafter in connection
with FIG. 24. The movement of the optical elements may either be
individual or as pairs, such as, for example, a pairing of
1805-1830 and 1810-1835, or 1805-1835 and 1810-1830, all as taught
in greater detail in commonly assigned PCT patent application
PCT/IB2015/000409, incorporated herein by reference. The base lens
group moves along the optical path and optically combines with the
varifocal lenses to provide a focused image on a
separately-supplied sensor. An actuator, which may comprise a
plurality of actuators, [not shown for clarity of illustration]
provides relative movement of the varifocal lenses as well as the
base lens group. In some embodiments a second prism may be
positioned between the base lens group and the sensor to again bend
the light 90 degrees and enable reduced z-height of the camera,
since, in the absence of the second prism, the size of the sensor
may require a greater z-height of the completed camera once the
sensor is mated to the lens system of the present invention. It
will also be appreciated that, in some embodiments, the sensor
itself can be moved along the optical path for purposes of, for
example, achieving improved or simplified focusing, or the entire
lens system can be moved relative to the sensor for these same
purposes. In an embodiment suitable for use in a mobile device, the
travel of the sensor can be in the range of 0.2 mm to 1 mm. A
separate actuator can be implemented to control such movement. It
will be appreciated by those skilled in the art that the above
description of individual or pair-wise movements, actuators, second
prism, and so on, apply to each of the alternatives described
herein and, for the sake of clarity, will not be repeated.
[0115] Referring next to FIG. 19, the alternative embodiment
illustrated therein comprises in sequence along the optical path, a
first varifocal lens 1900 comprised of a pair of Alvarez-like
optical elements 1905 and 1910, a prism 1915 and optional iris
1920, a single fixed Alvarez-like freeform lens or optical element
1925, a second varifocal lens 1930 comprising a pair of
Alvarez-like optical elements 1935 and 1940, and a base lens group
1950 comprising, for example, rotationally symmetrical lenses
1950A-C, all configured to create an image on an image sensor 1955.
The freeform lens 1925 is fixed in position and can have one or
both surfaces defined by the same or different polynomials, and
also the same as or different from the polynomial(s) that define
the surfaces of the varifocal lenses 1900 and 1925, as discussed in
greater detail hereinafter in connection with FIG. 24. As discussed
above, optical elements 1905, 1910, 1925 and 1930 move
perpendicularly to the optical axis. The combination of the fixed
optical element 1925 with the varifocal lenses can aid in focusing
and aberration and distortion correction as well as reducing the
optical power that must otherwise be provided by varifocal lenses
1900 and 1930.
[0116] Next, with reference to FIG. 20, an embodiment of a
miniature optical zoom lens system is illustrated which comprises,
in sequence along the optical path, a first varifocal lens 2000
comprising Alvarez-like optical elements 2005 and 2010, a prism
2015 and optional iris 2020, a second varifocal lens group 2025
comprising three freeform optical elements 2030, 2035 and 2040, in
which optical elements 2030 and 2040 move together along the same
path while optical element 2035 moves in the opposite direction,
and a base lens group 2045 comprising rotationally symmetrical
lenses 2045A-C, all configured to create an image on an image
sensor 2050. As with the embodiment of FIG. 19, the addition of
optical element 2030 can aid in focusing, aberration and distortion
correction, as well as reducing the optical power required from the
remaining Alvarez-like elements.
[0117] FIG. 21 illustrates an embodiment of a miniature optical
zoom lens system comprising, in sequence along the optical path, a
first varifocal lens 2100 comprising Alvarez-like optical elements
2105 and 2110, a prism 2115 and optional iris 2120, a second
varifocal lens 2125 comprising optical elements 2130 and 2135, a
base lens group 2140 comprising, for example, symmetrical lenses
2140A-C, and a freeform lens 2145 which can be either fixed or
movable, depending upon the design requirements of the
implementation, all configured to create an image on an image
sensor 2150. The varifocal lenses are configured and operate as
described above, and the freeform lens element 2145 can have one or
both surfaces defined by the same or different polynomials, again
as described in connection with FIG. 24. Depending upon the
particular design requirements, the lens element 2145 can aid in
focusing, aberration and distortion correction, as well as
providing optical power in some instances.
[0118] Referring next to FIG. 22, the embodiment of a miniature
optical zoom lens system illustrated therein comprises, in sequence
along the optical path, a first varifocal lens 2200 comprising
Alvarez-like optical elements 2205 and 2210, a prism 2215 and
optional iris 2220, a rotationally symmetric lens 2225, a second
varifocal lens 2230 comprising Alvarez-like optical elements 2235
and 2240, and a base lens 2245 and comprising, for example, three
rotationally symmetrical lenses 2245A-C, all configured to create
an image on an image sensor 2250. The lens 2225 is shown as fixed,
but in some embodiments can be movable along the optical axis. As
before, the lens 2225 can aid in focusing and aberration and
distortion correction, and may in some embodiments aid in providing
optical power.
[0119] FIG. 23 illustrates an embodiment of a miniature optical
zoom lens system comprising, in sequence along a light path, a
first varifocal lens 2300 comprising Alvarez-like optical elements
2305 and 2310, a prism 2315 and optional iris 2320, a second
varifocal lens 2325 comprising optical elements 2330 and 23355, a
first base lens group 2340, illustrated as having, for example, two
rotationally symmetrical lenses 2340A-B, and a second base lens
group 2345, shown as fixed and comprising a single rotationally
symmetrical lens but which, depending upon the design requirements,
can be movable along the optical axis and may comprise more than
one lens. As before, the overall function of the lens system of the
present invention is to create a clear image on an image sensor
which benefits for variable optical power. The separation of the
base lens into two groups can facilitate focusing as well as
aberration and distortion correction.
[0120] FIG. 24 illustrates in detail a configuration of the
elements of a varifocal lens 2400 and having Alvarez-line optical
elements 2405 and 2410 wherein each of the optically important
surfaces are defined by polynomials, although the polynomial
defining each surface can vary from the polynomial defining the
other surfaces, including varying the number of terms and the
coefficients.
[0121] It is understood that the operations that are described in
the present application are presented in a particular sequential
order in order to facilitate understanding of the underlying
concepts. It is also understood, however, that such operations may
be conducted in a different sequential order, and further, that
additional or fewer steps may be used to carry out the various
disclosed operations.
[0122] The foregoing description of embodiments has been presented
for purposes of illustration and description. The foregoing
description is not intended to be exhaustive or to limit
embodiments of the present invention to the precise form disclosed,
and modifications and variations are possible in light of the above
teachings or may be acquired from practice of various embodiments.
The embodiments discussed herein were chosen and described in order
to explain the principles and the nature of various embodiments and
their practical application to enable one skilled in the art to
utilize the present invention in various embodiments and with
various modifications as are suited to the particular use
contemplated. The features of the embodiments described herein may
be combined in all possible combinations of methods, apparatus,
modules, systems, and articles of manufacture.
* * * * *