Non-destructive estimation of coating layer thickness based on sweep frequency photo acoustic guided wave technique

1 . A processor implemented method for non-destructive estimation of coating layer thickness based on sweep frequency photo acoustic guided wave technique, comprising:

generating a plurality of photoacoustic guided waves from a plurality of samples, via one or more hardware processors, by irradiating the plurality of samples by an intensity modulated Continuous Wave (CW) laser diode at a pre-defined angle and a pre-defined sweep frequency, wherein the plurality of samples absorb laser radiation and undergoes thermoelastic expansion and during relaxation the plurality of samples releases the plurality of photoacoustic guided waves having a same frequency as excited frequencies, wherein the plurality of photoacoustic guided waves are received by an ultrasound sensor in contact with the plurality of samples via a coupling medium and then the plurality of photoacoustic guided waves are acquired by a Vector Network Analyzer (VNA), wherein the plurality of photoacoustic guided waves exhibit a maximum amplitude near a resonance frequency of the plurality of samples, and wherein the plurality of samples is associated with a known-thickness parameter;

determining a frequency spectrum of the plurality of photoacoustic guided waves generated from the each of the plurality of samples, via the one or more hardware processors, based on a frequency spectra determination technique;

determining the resonance frequency from the frequency spectrum, via the one or more hardware processors, based on a sweep frequency photoacoustic guided wave technique, wherein the sweep frequency is a narrow band of frequencies, wherein a sweep frequency acoustic signal is sensed by the ultrasound sensor and acquired by the Vector Network Analyzer, wherein the VNA plots a magnitude of the sweep frequency photoacoustic signal at different frequencies to obtain the frequency spectrum from the each of the plurality of samples; and

plotting a calibration curve based on the resonance frequency, via the one or more hardware processors, wherein the calibration curve associates the resonance frequency of each of the plurality of samples is associated with the known-thickness parameter of each of the plurality of samples.

2 . The processor implemented method of claim 1 , wherein the calibration curve is utilized for non-destructive estimation of coating layer thickness of a sample under test (SUT), comprises:

generating a plurality of test photoacoustic guided waves from the sample under test (SUT), via the one or more hardware processors, by irradiating the SUT by the intensity modulated Continuous Wave (CW) laser diode at the pre-defined angle and the pre-defined sweep frequency;

determining a test frequency spectrum of the plurality of test photoacoustic guided waves generated from the each of the plurality of SUT, via the one or more hardware processors, based on the frequency spectrum determination technique;

determining a test resonance frequency from the test frequency spectrum, via the one or more hardware processors, based on the sweep frequency photoacoustic guided wave technique; and

estimation a coating layer thickness of the SUT using the calibration curve and the test resonance frequency, via the one or more hardware processors.

3 . The processor implemented method of claim 1 , wherein the intensity modulated Continuous Wave (CW) laser diode is a CW laser diode with an intensity modulated at the pre-defined sweep frequency, wherein a Laser Driver Module (LDM) is configured to modulate the intensity of the CW laser diode in accordance with the predefined sweep frequency, wherein the pre-defined sweep frequency refers to excitation of the intensity modulated CW laser diode based on one of the plurality of samples and the SUT, wherein the predefined sweep frequency ranges between 100 kHz to 300 kHz.

4 . The processor implemented method of claim 1 , wherein the pre-defined angle is incidence of the intensity modulated CW laser diode irradiation at an optimal angle of 45 degrees on one of the plurality of samples and the SUT, wherein the intensity modulated CW laser diode is of wavelength 808 nm.

5 . The processor implemented method of claim 1 , wherein the frequency spectra determination technique is chosen based on a heuristic technique close to the resonance frequency of one of the plurality of samples and the SUT.

6 . The processor implemented method of claim 1 , wherein the sweep frequency photo acoustic guided wave technique uses a narrow band of frequencies such that a high frequency noise and the resonance frequency is exceeding a threshold of a signal to noise ratio (SNR).

7 . A system for non-destructive estimation of coating layer thickness based on sweep frequency photo acoustic guided wave technique, comprising:

a sensor module, and

an analysis module comprising a one or more hardware processors(s), an Input/Output interface(s), a memory, and a database, wherein the one or more hardware processors are configured by the instructions to:

generate a plurality of photoacoustic guided waves from a plurality of samples, via one or more hardware processors, by irradiating the plurality of samples by an intensity modulated Continuous Wave (CW) laser diode at a pre-defined angle and a pre-defined sweep frequency, wherein the plurality of samples absorb laser radiation and undergoes thermoelastic expansion and during relaxation the plurality of samples releases the plurality of photoacoustic guided waves having a same frequency as excited frequencies, wherein the plurality of guided photoacoustic waves are received by an ultrasound sensor in contact with the plurality of samples via a coupling medium and then the plurality of photoacoustic guided waves are acquired by a Vector Network Analyzer (VNA), wherein the plurality of photoacoustic guided waves exhibit a maximum amplitude near a resonance frequency of the plurality of samples, and wherein the plurality of samples is associated with a known-thickness parameter;

determine a frequency spectrum of the plurality of photoacoustic guided waves generated from the each of the plurality of samples, via the one or more hardware processors, based on a frequency spectra determination technique;

determine the resonance frequency from the frequency spectrum, via the one or more hardware processors, based on a sweep frequency photoacoustic guided wave technique, wherein the sweep frequency is a narrow band of frequencies, wherein a sweep frequency acoustic signal is sensed by the ultrasound sensor and acquired by the Vector Network Analyzer, wherein the VNA plots a magnitude of the sweep frequency photoacoustic signal at different frequencies to obtain the frequency spectrum from the each of the plurality of samples; and

plot a calibration curve based on the resonance frequency, via the one or more hardware processors, wherein the calibration curve associates the resonance frequency of each of the plurality of samples is associated with the known-thickness parameter of each of the plurality of samples.

8 . The system of claim 7 , wherein the calibration curve is utilized for non-destructive estimation of coating layer thickness of a sample under test (SUT), comprises:

generate a plurality of test photoacoustic guided waves from the sample under test (SUT), via one or more hardware processors, by irradiating the SUT by the intensity modulated Continuous Wave (CW) laser diode at the pre-defined angle and the pre-defined sweep frequency;

determine a test frequency spectrum of the plurality of test photoacoustic guided waves generated from the each of the plurality of SUT, via the one or more hardware processors, based on the frequency spectrum determination technique;

determine a test resonance frequency from the test frequency spectrum, via the one or more hardware processors, based on the sweep frequency photoacoustic guided wave technique; and

estimate a coating layer thickness of the SUT using the calibration curve and the test resonance frequency, via the one or more hardware processors.

9 . The system of claim 7 , wherein the intensity modulated Continuous Wave (CW) laser diode is a CW laser diode with an intensity modulated at the pre-defined sweep frequency, wherein a Laser Driver Module (LDM) is configured to modulate the intensity of the CW laser diode in accordance with the predefined sweep frequency, wherein the pre-defined sweep frequency refers to excitation of the intensity modulated CW laser diode based on one of the plurality of samples and the SUT, wherein the predefined sweep frequency ranges between 100 kHz to 300 kHz.

10 . The system of claim 7 , wherein the pre-defined angle is incidence of the intensity modulated CW laser diode irradiation at an optimal angle of 45 degrees on one of the plurality of samples and the SUT, wherein the intensity modulated CW laser diode is of wavelength 808 nm.

11 . The system of claim 7 , wherein the frequency spectra determination technique is chosen based on a heuristic technique close to the resonance frequency of one of the plurality of samples and the SUT.

12 . The system of claim 7 , wherein the sweep frequency photo acoustic guided wave technique uses a narrow band of frequencies such that a high frequency noise and the resonance frequency is exceeding a threshold of a signal to noise ratio (SNR).

13 . One or more non-transitory machine-readable information storage mediums for non-destructive estimation of coating layer thickness based on sweep frequency photo acoustic guided wave technique comprising one or more instructions which when executed by one or more hardware processors cause:

generating a plurality of photoacoustic guided waves from a plurality of samples, by irradiating the plurality of samples by an intensity modulated Continuous Wave (CW) laser diode at a pre-defined angle and a pre-defined sweep frequency, wherein the plurality of samples absorb laser radiation and undergoes thermoelastic expansion and during relaxation the plurality of samples releases the plurality of photoacoustic guided waves having a same frequency as excited frequencies, wherein the plurality of photoacoustic guided waves are received by an ultrasound sensor in contact with the plurality of samples via a coupling medium and then the plurality of photoacoustic guided waves are acquired by a Vector Network Analyzer (VNA), wherein the plurality of photoacoustic guided waves exhibit a maximum amplitude near a resonance frequency of the plurality of samples, and wherein the plurality of samples is associated with a known-thickness parameter;

determining a frequency spectrum of the plurality of photoacoustic guided waves generated from the each of the plurality of samples, based on a frequency spectra determination technique;

determining the resonance frequency from the frequency spectrum, based on a sweep frequency photoacoustic guided wave technique, wherein the sweep frequency is a narrow band of frequencies, wherein a sweep frequency acoustic signal is sensed by the ultrasound sensor and acquired by the Vector Network Analyzer, wherein the VNA plots as magnitude of the sweep frequency photoacoustic signal at different frequencies to obtain the frequency spectrum from each of the plurality of samples; and

plotting a calibration curve based on the resonance frequency, wherein the calibration curve associates the resonance frequency of each of the plurality of samples is associated with the known-thickness parameter of each of the plurality of samples.

14 . The one or more non-transitory machine-readable information storage mediums of claim 13 , wherein the calibration curve is utilized for non-destructive estimation of coating layer thickness of a sample under test (SUT), comprising generating a plurality of test photoacoustic guided waves from the sample under test (SUT, by irradiating the SUT by the intensity modulated Continuous Wave (CW) laser diode at the pre-defined angle and the pre-defined sweep frequency;

determining a test frequency spectrum of the plurality of test photoacoustic guided waves generated from the each of the plurality of SUT, based on the frequency spectrum determination technique;

determining a test resonance frequency from the test frequency spectrum, based on the sweep frequency photoacoustic guided wave technique, wherein the sweep frequency photo acoustic guided wave technique uses a narrow band of frequencies such that a high frequency noise and the resonance frequency is exceeding a threshold of a signal to noise ratio (SNR); and

estimation a coating layer thickness of the SUT using the calibration curve and the test resonance frequency.

15 . The one or more non-transitory machine-readable information storage mediums of claim 13 , wherein the intensity modulated Continuous Wave (CW) laser diode is a CW laser diode with an intensity modulated at the pre-defined sweep frequency, wherein a Laser Driver Module (LDM) is configured to modulate the intensity of the CW laser diode in accordance with the predefined sweep frequency, wherein the pre-defined sweep frequency refers to excitation of the intensity modulated CW laser diode based on one of the plurality of samples and the SUT, wherein the predefined sweep frequency ranges between 100 kHz to 300 kHz,

wherein the pre-defined angle is incidence of the intensity modulated CW laser diode irradiation at an optimal angle of 45 degrees on one of the plurality of samples and the SUT, wherein the intensity modulated CW laser diode is of wavelength 808 nm,

wherein the frequency spectra determination technique is chosen based on a heuristic technique close to the resonance frequency of one of the plurality of samples and the SUT, and

wherein the sweep frequency photo acoustic guided wave technique uses a narrow band of frequencies such that a high frequency noise and the resonance frequency is exceeding a threshold of a signal to noise ratio (SNR).