System and method for ultrasonic laser testing using a laser source to generate ultrasound having a tunable wavelength
First Claim
1. A method for controllably generating ultrasonic displacements at a remote target, comprising the steps of:
- generating a laser beam of pulses at a first known wavelength;
directing the laser beam to a point on the remote target for producing ultrasonic displacement on the remote target;
sensing ultrasonic displacements at the remote target;
tuning the first known wavelength of said laser beam to a second wavelength in the 3- to 4-micron range for altering the ultrasonic displacements occurring at the remote target in response to said laser beam, said tuning for generating optimal resolution of said ultrasonic displacements during said sensing.
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Abstract
A system and method for generating ultrasonic displacements on a remote target. The method of the present invention includes the steps of first using a laser to generate a beam having a first wavelength to produce ultrasonic displacements at the remote target. This laser beam will have a first wavelength which can be modulated to alter characteristics of the ultrasonic displacements. These ultrasonic displacements at the remote target can be optimized to enhance the detection optics for collecting phase modulated light from the second pulsed laser beam either reflected or scattered by the remote target; an interferometer to process the phase modulated light and generate at least one output signal, and means for processing the at least one output signal to obtain data representative of the ultrasonic surface displacements on the surface of the remote target.
30 Citations
53 Claims
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1. A method for controllably generating ultrasonic displacements at a remote target, comprising the steps of:
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generating a laser beam of pulses at a first known wavelength;
directing the laser beam to a point on the remote target for producing ultrasonic displacement on the remote target;
sensing ultrasonic displacements at the remote target;
tuning the first known wavelength of said laser beam to a second wavelength in the 3- to 4-micron range for altering the ultrasonic displacements occurring at the remote target in response to said laser beam, said tuning for generating optimal resolution of said ultrasonic displacements during said sensing. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
an inspection acoustic frequency; and
a depth of penetration.
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12. The method of claim 11, wherein the long pulse laser source is encoded with a tone burst to control the inspection acoustic frequency.
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13. The method of claim 11, wherein the long pulse laser source is encoded with a chirp to control the inspection acoustic frequency.
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14. The method of claim 11, wherein the long pulse laser source is varied based on a specific composite formulation of the remote target.
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15. The method of claim 11, wherein the long pulse laser source is varied based on a geometry of the remote target.
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16. The method of claim 11, wherein the long pulse laser source is varied based on a database used to determine the optimal inspection acoustic frequency and depth of penetration.
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17. The method of claim 1, wherein the first laser has a repetition rate greater than 400 Hz.
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18. The method of claim 1, wherein the first laser is selected from the group consisting of CO2 Laser, Nd:
- YAG laser, alexandrite laser, titanium sapphire laser, lamp pumped laser, and diode pumped laser.
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19. The method of claim 1, wherein the first laser is a solid state laser.
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20. The method of claim 1, wherein the long pulse laser source is controllably varied based on a specific composite formulation of the remote target.
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21. The method of claim 1, wherein the step of tuning the first known wavelength of the laser beam to a second wavelength is realized by combining the first laser with a second laser to produce a third laser at a second wavelength.
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22. A method for controllably producing laser radiation with a tunable wavelength and temporal shape comprising:
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generating a laser beam of pulses having a first known wavelength;
directing said laser beam to a point on the remote target for producing ultrasonic displacements on the remote target;
sensing the ultrasonic displacements on the remote target;
tuning the first known wavelength of said laser beam to a second wavelength in the 3- to 4-micron range for altering the ultrasonic displacement occurring at the remote target in response to said laser beam, said controllable shifting for generating optimal resolution of said ultrasonic displacements during said sensing. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39)
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40. A system for producing laser radiation with a tunable wavelength and temporal shape comprising:
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a laser for generating a pulsed laser beam having a first known wavelength;
a laser beam directing mechanism for directing said laser beam to a point on the remote target;
an ultrasonic displacement sensor for sensing ultrasonic displacements at the remote target;
a wavelength shifting device for tuning the first known wavelength to a second wavelength in the 3- to 4-micron range for generating optimal resolution of said ultrasonic displacements for said ultrasonic displacement sensor. - View Dependent Claims (41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53)
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Specification