U.S. patent application number 13/533565 was filed with the patent office on 2013-05-16 for laser ultrasonic measurement system with movable beam delivery.
The applicant listed for this patent is Thomas E. Drake, Marc Dubois. Invention is credited to Thomas E. Drake, Marc Dubois.
Application Number | 20130120758 13/533565 |
Document ID | / |
Family ID | 41340786 |
Filed Date | 2013-05-16 |
United States Patent
Application |
20130120758 |
Kind Code |
A1 |
Dubois; Marc ; et
al. |
May 16, 2013 |
LASER ULTRASONIC MEASUREMENT SYSTEM WITH MOVABLE BEAM DELIVERY
Abstract
A laser ultrasonic measurement system includes a first and a
second laser source configured to generate a first and a second
laser beam, respectively. A movable mechanical link is arranged to
transmit the first laser beam. The movable mechanical link is
formed by a plurality of rigid sections interconnected by rotating
joints. A robot is configured to support and control the movement
of at least a section of the mechanical link to transmit the first
laser beam to an object. An optical scanner is positioned proximate
to the mechanical link. The optical scanner is configured to direct
the first and second laser beams onto the object. An interferometer
is optically coupled to the optical scanner. The interferometer is
configured to receive reflected light from the object and in
response generate an electrical signal. The first laser source is
kinematically mounted in a housing assembly.
Inventors: |
Dubois; Marc; (Keller,
TX) ; Drake; Thomas E.; (Fort Worth, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Dubois; Marc
Drake; Thomas E. |
Keller
Fort Worth |
TX
TX |
US
US |
|
|
Family ID: |
41340786 |
Appl. No.: |
13/533565 |
Filed: |
June 26, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12464571 |
May 12, 2009 |
8243280 |
|
|
13533565 |
|
|
|
|
61054801 |
May 20, 2008 |
|
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Current U.S.
Class: |
356/482 ;
356/502 |
Current CPC
Class: |
G01B 11/16 20130101;
G01B 11/161 20130101; G01N 29/2418 20130101; G01N 29/265 20130101;
G01B 17/00 20130101; G01B 9/02049 20130101; G01B 11/00
20130101 |
Class at
Publication: |
356/482 ;
356/502 |
International
Class: |
G01B 9/02 20060101
G01B009/02 |
Claims
1. A laser ultrasonic measurement system, comprising: a first and a
second laser source configured to generate a first and a second
laser beam, respectively; a movable mechanical link having a first
end and a second end arranged to optically transmit at least one of
the laser beams from its laser source to the second end, the
moveable mechanical link formed by a plurality of rigid sections
interconnected by one or more rotating joints; a robot configured
to support and control the movement of at least a section of the
mechanical link to transmit at least one of the laser beams to an
object; at least one optical element proximate to the second end of
the moveable mechanical link, the at least one optical element
configured to direct the first and second laser beams onto the
object; and an interferometer optically coupled to the at least one
optical element, the interferometer configured to receive reflected
light from the object and to generate an electrical signal in
response.
2. The laser ultrasonic measurement system of claim 1, wherein the
at least one optical element comprises at least one optical
scanner.
3. The laser ultrasonic measurement system of claim 1, wherein the
second laser beam is transmitted proximate to the at least one
optical element by an optical link.
4. The laser ultrasonic measurement system of claim 3, wherein the
optical link comprises an optical fiber.
5. The laser ultrasonic measurement system of claim 1, wherein the
second laser source is placed proximate to the at least one optical
element.
6. The laser ultrasonic measurement system of claim 2, wherein the
first and second laser beams are optically coupled to the at least
one optical scanner using optics and mirrors.
7. The laser ultrasonic measurement system of claim 2, wherein the
at least one optical scanner is mounted on a rotating axis.
8. The laser ultrasonic measurement system of claim 1, wherein at
least one of the laser sources is kinematically mounted in a
housing assembly by a plurality of supports to isolate the laser
source from stress.
9. The laser ultrasonic measurement system of claim 2, wherein the
robot is configured to provide displacement to the mechanical link
for translational and rotational movements of the at least one
optical scanner proximate to the mechanical link.
10. The laser ultrasonic measurement system of claim 9, wherein the
robot includes a robotic arm configured to support and control
movement of the mechanical link for translational and rotational
movements of the at least one optical scanner proximate to the
mechanical link.
11. The laser ultrasonic measurement system of claim 1, wherein a
load support mechanism supports at least a section of the
mechanical link.
12. The laser ultrasonic measurement system of claim 1, wherein the
robot is mounted on a track.
13. The laser ultrasonic measurement system of claim 1, further
comprising at least two reflecting mirrors arranged in each
rotatable joint to transfer at least one of the laser beams between
adjacent rigid sections.
14. The laser ultrasonic measurement system of claim 1, wherein the
first and second laser beams are rendered substantially collinear
prior to being directed onto the object by the at least one optical
element.
15. A laser ultrasonic measurement system, comprising: a first and
a second laser source configured to generate a first and a second
laser beam, respectively, the first laser source being a CO2 laser
kinematically mounted in a housing assembly by a plurality of
supports; a moveable mechanical link having a first end coupled to
the first laser source and a second end, the moveable mechanical
link being arranged to optically transmit the first laser beam from
the first laser source to the second end, the moveable mechanical
link formed by a plurality of rigid sections interconnected by one
or more rotating joints; a robot having a robotic arm configured to
support and control movement of at least a section of the
mechanical link to transmit at least one of the laser beams to an
object; an optical scanner proximate to the second end of the
moveable mechanical link, the optical scanner configured to direct
the first and second laser beams onto the object; and an
interferometer optically coupled to the optical scanner, the
interferometer configured to receive reflected light from the
object and to generate an electrical signal in response.
16. The laser ultrasonic measurement system of claim 15, wherein
the first and second laser beams are optically coupled to the
optical scanner using optics and mirrors.
17. The laser ultrasonic measurement system of claim 15, wherein
the robot is configured to provide displacement to the mechanical
link for translational and rotational movements of the optical
scanner proximate to the mechanical link.
18. The laser ultrasonic measurement system of claim 15, further
comprising at least two reflecting mirrors arranged in each
rotatable joint to transfer at least one of the laser beams between
adjacent rigid sections.
19. The laser ultrasonic measurement system of claim 15, wherein
the first and second laser beams are rendered substantially
collinear prior to being directed onto the object by the optical
scanner.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. Non-Provisional
application Ser. No. 12/464571, entitled LASER ULTRASONIC
MEASUREMENT SYSTEM WITH MOVABLE BEAM DELIVERY, filed May 12, 2009,
which claims priority to U.S. Provisional Patent Application No.
61/054801, entitled IMPROVED LASER-ULTRASONIC INSPECTION OF COMPLEX
PARTS USING AN ARTICULATED BEAM DELIVERY SYSTEM, filed May 20,
2008, both of which are hereby incorporated by reference for all
purposes.
FIELD OF THE INVENTION
[0002] The invention generally relates to laser ultrasonic
measurement, and more particularly to a laser ultrasonic
measurement system with movable beam delivery.
BACKGROUND OF THE INVENTION
[0003] Laser ultrasonic measurement systems are frequently used for
structural analysis of parts and components. These systems offer
advantages over non-laser type systems (e.g., piezoelectric
transducer-based systems). Laser ultrasonic systems are typically
non-contact systems that test a structure by measuring ultrasonic
waves induced in a structure. Typically, a first laser beam,
referred to as a generation beam, is directed to a structure
causing thermal expansion of the structure, which generates
ultrasonic waves. A second laser beam, referred to as a detection
beam, is used to illuminate the structure. Reflected light from the
structure is processed for analysis of the structure.
[0004] Laser ultrasonic systems are well suited for many industrial
applications, such as measurement of steel at high temperature,
measurement of paint thickness and non-destructive testing of
complex structures.
[0005] One drawback of existing laser ultrasonic measurement
systems is the difficulty of delivering the generation and
detection beams to a structure or a part that may not be easily
accessible. Since existing systems are not easily movable, delivery
of the generation and detection beams to a structure that is not
easily accessible can be challenging. The generation beam, in
particular, may be difficult to deliver to such a structure because
its wavelength may preclude delivery via a fiber optic cable. Also,
large peak power or large average power of the generation beam
increases the difficulty of delivery to the structure.
SUMMARY
[0006] In one embodiment, a laser ultrasonic measurement system
includes a first and a second laser source configured to generate a
first and a second laser beam, respectively. A movable mechanical
link is arranged to transmit the first laser beam. The mechanical
link is formed by a plurality of rigid sections interconnected by
rotating joints. In one implementation, at least two reflecting
mirrors are arranged in the joint to transfer the first laser beam
between adjacent rigid sections.
[0007] A robot is configured to support and control the movement of
at least a section of the mechanical link. The robot enables the
mechanical link to transmit the first laser beam to an object. An
optical scanner is positioned proximate to the mechanical link. The
optical scanner directs the first and second laser beams onto the
object. The optical scanner is mounted on a rotating axis. An
interferometer is optically coupled to the optical scanner. The
interferometer is configured to receive reflected light from the
object and in response generate an electrical signal.
[0008] In one embodiment, the second laser beam is transmitted
proximate to the optical scanner by an optical link. The first
laser source is kinematically mounted in a housing assembly by a
plurality of supports to isolate the laser source from stress.
[0009] The robot is configured to provide displacement to the
mechanical link for translational and rotational movements of the
optical scanner proximate to the mechanical link. The robot
includes a robotic arm configured to support and control the
movement of the mechanical link for translational and rotational
movements of the optical scanner proximate to the mechanical
link.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] For a more complete understanding of the features, example
embodiments and possible advantages of the present invention,
reference is now made to the detailed description of the invention
along with the accompanying figures and in which:
[0011] FIG. 1 illustrates a laser ultrasonic measurement system in
accordance with an embodiment;
[0012] FIG. 2 illustrates two link sections coupled by a rotating
joint;
[0013] FIG. 3 illustrates an exemplary implementation of a laser
source coupled to a movable mechanical link;
[0014] FIG. 4 illustrates a plane constraint, a line constraint and
a point constraint;
[0015] FIG. 5 shows the system of FIG. 1 mounted on a rail;
[0016] FIG. 6 shows the system of FIG. 1 conducting inspection of a
structure; and
[0017] FIG. 7 illustrates a laser head assembly in accordance with
one implementation.
DETAILED DESCRIPTION OF THE INVENTION
[0018] FIG. 1 illustrates a laser ultrasonic measurement system 100
in accordance with an embodiment. The system 100 includes a laser
source 104 that generates a laser beam (not shown in FIG. 1).
Although the system 100 is illustrated as having only a single
laser source, it will be appreciated that the system 100 may be
implemented with two or more laser sources, each configured to
generate a laser beam. The system 100 includes a movable mechanical
link 108 coupled to the laser source 104. The movable mechanical
link 108 is configured to transmit the laser beam from the laser
source 104 to a desired location or an object. The laser beam, for
example, may be directed to a part or a component that is being
analyzed. The mechanical link 108 may be configured to transmit
multiple laser beams, each originating from an independent laser
source.
[0019] The system 100 includes a robot 110 configured to support
and control the movement of at least a section of the mechanical
link 108. In one implementation, the robot 110 may include a
robotic arm 116 to support and guide the mechanical link 108. It
will be apparent to those skilled in the art that the system 100
may be implemented with a robot without the robotic arm.
[0020] The robotic arm 116 provides mobility to the system 100 by
guiding the mechanical link 108 proximate to the part or component
being tested. In one implementation, the mechanical link 108 is
formed by a plurality of link sections 114 interconnected by joints
112. The joints 112 may, for example, be rotating-type joints,
which allow the link sections 114 to rotate about the joints 112.
The rotating joints 112 provide the link sections 114 with a wide
degree of angular freedom of movement. In one implementation, the
robotic arm 116 is configured to provide displacement to the
mechanical link 108 for translational movement. The movement range
of the mechanical link 108 may be extended by the robotic arm 116
by appropriate movement, as will be apparent to those skilled in
the art. In one implementation, the robotic arm 116 comprises a
plurality of interconnected arm sections 120 cooperatively
controlling the movement of the mechanical link 108.
[0021] FIG. 2 illustrates two link sections 114A and 114B coupled
by a rotating joint 112. A pair of mirrors 204A and 204B is
arranged in the rotating joint 112 to transfer the laser beam 208
between the pair of link sections 114A and 114B. The mirrors 204A
and 204B are arranged in a manner to enable the transfer of the
laser beam 208 regardless of the angular orientation of the link
sections 114A and 114B. In one implementation, the link sections
114A and 114B are rigid tubes capable of transmitting a laser
beam.
[0022] In one embodiment, a laser head assembly 124 is coupled to
the mechanical link 108. The laser head assembly 124 is configured
to receive the laser beam and to direct the laser beam to the
object being tested. An optical scanner (not shown in FIG. 1) is
mounted in the head assembly 124. The optical scanner may be a
scanner mounted on a rotating axis proximate to the laser beam.
[0023] In one embodiment, a laser ultrasonic measurement system
includes a first and a second laser source (not shown in FIG. 1)
configured to generate a first and a second laser beam,
respectively. The first laser source is coupled to the movable
mechanical link 108, which directs the first laser beam to the
object being tested. The second laser source is coupled to an
optical link that directs the second laser beam to the object. In
one implementation, the optical link is an optical fiber that is
supported by the robot 110. Alternatively, the second laser source
may be mounted in the head assembly 124 or on any part of robot 110
in a manner to allow the second laser beam to be directed to the
object.
[0024] The first laser beam creates ultrasonic waves in the object
while the second laser beam illuminates the object. It will be
appreciated that part of the second laser beam is reflected by the
object. The reflected beam is phase shifted by the ultrasonic waves
in the object.
[0025] The reflected beam is received by an interferometer (not
shown in FIG. 1), which is coupled to the optical scanner. The
interferometer generates an ultrasonic signal responsive to the
reflected beam. More precisely, the interferometer generates the
ultrasonic signal responsive to the phase shift in the reflected
beam.
[0026] In one implementation, the laser source includes a resonator
configured to generate a laser beam. FIG. 3 illustrates an
exemplary implementation of a laser source 300 coupled to a movable
mechanical link 108. The laser source 300 includes a resonator 308
configured to generate a laser beam from a lasing material. In one
implementation, the resonator 308, for example, may include a gas
vessel 304 containing a gaseous substance configured to generate a
laser beam. One end of the mechanical link 108 is attached to the
laser resonator 308 and aligned so that the laser beam can
propagate through the full length of the mechanical link 108. Once
aligned, the end of the mechanical link 312 is locked onto the
laser resonator 308. The direction of propagation of a laser beam
is defined by the resonator 308 position. The construction of the
resonator 308 will be apparent to those skilled in the art.
[0027] The gas vessel 304 is mounted in an assembly or frame (not
shown in FIG. 3). The resonator 308 is kinematically mounted on gas
vessel 304 via a plurality of supports. In one implementation, the
resonator 308 is kinematically mounted via supports 316, 320 and
324 to isolate from stress and deformation. For example, the
support 316 may provide a plane constraint, the support 320 may
provide a line constraint, while the support 324 may provide a
point constraint, as illustrated in FIG. 4. The construction of the
supports will be apparent to those skilled in the art. The plane,
line and point constraints isolate the resonator 308 from stress
and deformations, thereby enabling the laser beam to exit the
resonator 308 at a fixed orientation relative to resonator 308.
Because the mechanical link is aligned and locked in place
relatively to the resonator 308, any movement of the resonator due
to the gas vessel stress or deformation will maintain the laser
beam alignment into the mechanical link.
[0028] In one implementation, the laser ultrasonic measurement
system includes a first laser source and a second laser source,
wherein the first laser source is a gas laser (e.g., CO2 laser) and
the second laser source is a solid state laser or a fiber-type
laser. The second laser source may be a hybrid laser built with
solid state and fiber components. In one implementation, the second
laser source is a stable low-power single-frequency laser amplified
by one or more stages of amplification. The single-frequency laser
and the amplification stages can be based on fiber laser
technologies, solid-state laser technologies, flash-lamp
technologies, or a combination of those technologies. The first
laser (e.g., CO2 laser) generates a first laser beam used to create
ultrasonic waves in the object being analyzed, while the second
laser generates a second laser beam which illuminates the object.
In one implementation, only the first laser source is kinematically
mounted, as illustrated in FIG. 3.
[0029] FIG. 5 illustrates an implementation according to which the
system 100 is mounted on a rail 504 to provide increased mobility.
By mounting the system 100 on the rail 504, the total inspection
range is significantly increased. FIG. 6 shows the system 100
mounted on the rail 504 conducting inspection of a structure
608.
[0030] FIG. 7 illustrates the laser head assembly 124 in accordance
with one implementation. The laser head assembly 124 is attached to
the robot arm 116 (not shown in FIG. 7) at attachment 760. One end
of the mechanical link 108 (not shown in FIG. 7) is attached to the
laser head 124 at attachment 764, transmitting the first laser beam
208 to the laser head 124. The second laser source (not shown in
FIG. 7) is optically coupled to the laser head 124 through an
optical fiber 724, transmitting a second laser beam 728 to laser
head 124. The first and second laser beams 208 and 728 are
optically coupled to an optical scanner 704 using optics and
mirrors 730, 732, 734, 736, 738, and 740. The optical scanner 704
is mounted on a rotating axis 708, in which the rotation axis is
concentric with the optical axis defined by laser beams 208 and
728. The optical scanner 704 aids in directing the laser beams 208
and 728 to an object being tested.
[0031] In one embodiment, the optical scanner includes two mirrors
712 and 714, each mounted on a galvanometer (not shown in FIG. 7)
in a manner to direct the laser beams 208 and 728 onto the object.
Light 744 from the second laser beam 728 reflected by the object is
optically transmitted from the optical scanner 704 to an optical
fiber 750 through optics and mirror 746 and 734. The mirror 738 is
made small enough to allow reflected light 744 to reach optical
fiber 750. An optical fiber 750 transmits reflected light 744 to an
interferometer (not shown in FIG. 7). The interferometer is
therefore optically coupled to the optical scanner through mirror
734, optics 746, and fiber 750.
[0032] It will also be appreciated that one or more of the elements
depicted in the drawings/figures can also be implemented in a more
separated or integrated manner, or even removed or rendered as
inoperable in certain cases, as is useful in accordance with a
particular application.
[0033] As used in the description herein and throughout the claims
that follow, "a," "an" and "the" include plural references unless
the context clearly dictates otherwise. Also, as used in the
description herein and throughout the claims that follow, the
meaning of "in" includes "in" and "on" unless the context clearly
dictates otherwise.
[0034] The foregoing description of illustrated embodiments of the
present invention, including what is described in the Abstract, is
not intended to be exhaustive or to limit the invention to the
precise forms disclosed herein. While specific embodiments of, and
examples for, the invention are described herein for illustrative
purposes only, various equivalent modifications are possible within
the spirit and scope of the present invention, as those skilled in
the relevant art will recognize and appreciate. As indicated, these
modifications may be made to the present invention in light of the
foregoing description of illustrated embodiments of the present
invention and are to be included within the spirit and scope of the
present invention.
[0035] Thus, while the present invention has been described herein
with reference to particular embodiments thereof, a latitude of
modification, various changes and substitutions are intended in the
foregoing disclosures, and it will be appreciated that in some
instances some features of embodiments of the invention will be
employed without a corresponding use of other features without
departing from the scope and spirit of the invention as set forth.
Therefore, many modifications may be made to adapt a particular
situation or material to the essential scope and spirit of the
present invention. It is intended that the invention not be limited
to the particular terms used in the following claims and/or to the
particular embodiment disclosed as the best mode contemplated for
carrying out this invention, but that the invention will include
any and all embodiments and equivalents falling within the scope of
the appended claims. Thus, the scope of the invention is to be
determined solely by the appended claims.
* * * * *