Optics: measuring and testing – For light transmission or absorption
Reexamination Certificate
1999-06-30
2003-10-14
Font, Frank G. (Department: 2877)
Optics: measuring and testing
For light transmission or absorption
C356S502000
Reexamination Certificate
active
06633384
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to an apparatus and method of non-destructive evaluation of materials, and more particularly, to an apparatus and method of processing optical information to detect ultrasonic surface displacements through the use of at least one laser to perform a non-destructive evaluation of a material.
BACKGROUND OF THE INVENTION
In recent years, the use of advanced composite structures has experienced tremendous growth in the aerospace, automotive, and many other commercial industries. While composite materials offer significant improvements in performance, they require strict quality control procedures in the manufacturing processes. Specifically, non-destructive evaluation (“NDE”) methods are required to assess the structural integrity of composite structures, for example, to detect inclusions, delaminations and porosities. Conventional NDE methods, however, are very slow, labor-intensive, and costly. As a result, testing procedures adversely increase the manufacturing costs associated with composite structures.
Various methods and apparatuses have been proposed to assess the structural integrity of composite structures. One method to generate and detect ultrasound using lasers is disclosed in U.S. Pat. No. 5,608,166, issued Mar. 4, 1997, to Monchalin et al. (the “'166 Patent”). The '166 Patent discloses the use of a first modulated, pulsed laser beam for generating ultrasound on a work piece and a second pulsed laser beam for detecting the ultrasound. Phase modulated light from the second laser beam is then demodulated to obtain a signal representative of the ultrasonic motion at the surface of the work piece. A disadvantage associated with this approach is that the first pulsed laser beam must be modulated. Other U.S. Patents issued to Monchalin et al. and relating to the subject matter of ultrasonic material testing include the following:
U.S. Pat. No.
Title
Issue Date
5,608,166
Generation and Detection of
Mar. 4, 1997
Ultrasound with Long Pulse
Lasers
4,966,459
Broadbank Optical Detection
Oct. 30, 1990
of Transient Motion from a
Scattering Surface
5,131,748
Broadbank Optical Detection
Jul. 21, 1992
of Transient Motion from a
Scattering Surface by Two-
Wave Mixing in a
Photorefractive Crystal
5,402,235
Imaging of Ultrasonic-
Mar. 29, 1995
Surface Motion by Optical
Multiplexing
4,633,715
Laser Heterodyne
Jan. 6, 1987
Interferometric Method and
Apparatus for Measuring
Ultrasonic Displacements
5,080,491
Laser Optical Ultrasound
Jan. 14, 1992
Detection Using Two
Interferometer Apparatuses
5,137,361
Optical Detection of a
Aug. 11, 1992
Surface Motion of an Object
Using a Stabilized
Interferometric Cavity
4,426,155
Method and Apparatus for the
Jan. 17, 1984
Interferometric Wavelength
Measurement of Frequency
Tunable C. W. Lasers
5,608,166
Generation and Detection of
Mar. 4, 1997
Ultrasound with Long Pulse
Lasers
4,820,981
Method and Apparatus for
Apr. 11, 1989
Measuring Magnetic Losses in
Ferromagnetic Materials
Based on Temperature
Modulation Measurements
4,659,224
Optical Interferometric
Apr. 21, 1987
Reception of Ultrasonic
Energy
4,607,341
Device for Determining
Aug. 19, 1986
Properties of Materials from
a Measurement of Ultrasonic
Absorption
Although these patents describe operable techniques for optically detecting transient motion from a scattering surface, which techniques are useful for ultrasonic composite materials non-destructive test and evaluation, these techniques have numerous failings.
To begin, none of the Monchalin and other known techniques provide the ability to perform with high signal-to-noise-ratios (SNR) at large distances from typically very dark composite materials using small aperture high-speed optical scanning methods. The ability to operate in such a mode has the distinct advantage of increasing the optical scan area coverage and providing substantially improved depth-of-field thereby eliminating the need for active focusing mechanisms.
Other known techniques do not posses the desirable feature of removing common-mode noise from the laser signals using a fully self-referenced interferometric configuration that uses all of the available light without the use of separate stabilization measurements.
Another limitation associated with the Monchalin and other known apparatuses relates to their inability to operate at very high scan rates and process ultrasonic data in real-time. This limitation makes such apparatuses only marginally useful for testing and evaluating composite materials.
Other limitations associated with existing apparatuses relate to general inflexibility of such apparatuses, which may hold all distances low, result in small depth of field performance and only minimal extraction of information from the back scattered signals. These limitations make industrial application of the ultrasonic testing method generally impractical.
SUMMARY OF THE INVENTION
The present invention provides an apparatus and method for generating and detecting ultrasonic surface displacements on a remote target that substantially eliminates or reduces disadvantages and problems associated with previously developed laser ultrasonic systems and methods.
More specifically, the present invention provides a method and system for generating and detecting ultrasonic surface displacements on a remote target. The system includes a first pulsed laser to generate a first pulsed laser beam. The first pulsed laser beam produces ultrasonic surface displacements on a surface of the remote target. A second pulsed laser generates a second pulsed laser beam coaxial with said first pulsed laser beam to detect the ultrasonic surface displacements on the surface of the remote target. Collection optics to collect phase modulated light from the second pulsed laser beam either reflected or scattered by the remote target and optionally optically processed to increase the light intensity. An interferometer to process the phase modulated light and generate at least one output signal. A processor for processing the at least one output signal obtains data representative of the ultrasonic surface displacements on the surface of the remote target.
In another embodiment, a method for ultrasonic laser testing in accordance with the invention comprises using a first pulsed laser beam to generate ultrasonic surface displacements on a surface of a remote target. A second pulsed laser beam coaxial is used with the first pulsed laser beam to detect the ultrasonic surface displacements on the surface of the remote target collecting phase modulated light from the second pulse laser beam either reflected or scattered by the remote target also occurs, processing the phase modulated light to obtain data representative of the ultrasonic surface displacements on the surface of the remote target.
A technical advantage of the present invention is that a method for ultrasonic laser testing is provided. The personal invention provides rapid, non-contact, and non-destructive inspection techniques that can be applied to complex composite structures. The present invention provides a flexible, accurate and cost effective method for inspecting complex composite structures. The present invention is able to rapidly scan and test large-sized composite structures. The present invention is able to inspect at angles off normal (i.e., up to ±45 degrees). The present invention does not require expensive fixturing to test composite structures. The present invention does not require the shape of the part to be known prior to testing. The present invention does not require access to both sides of a composite structure to test it for defects.
REFERENCES:
patent: 4659224 (1987-04-01), Monchalin
patent: 5042952 (1991-08-01), Opsal et al.
patent: 5080491 (1992-01-01), Monchalin et al.
patent: 5286313 (1994-02-01), Schultz et al.
patent: 5317383 (1994-05-01), Berni
patent: 5402235 (1995-03-01), Monchalin
patent: 5414510 (1995-05-01), Schultz et al.
patent: 5608166 (1997-03-01), Monchalin et al.
patent: 5638396 (1997-06-01), Klimek
patent: 5724138 (1998
Drake, Jr. Thomas E.
Osterkamp Mark A.
Font Frank G.
Koestner Bertani LLP
Lockheed Martin Corporation
Natividad Phil
LandOfFree
Method and apparatus for ultrasonic laser testing does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for ultrasonic laser testing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for ultrasonic laser testing will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3167508