Laser ultrasonic frequency-domain imaging and phase weighted optimization based on full matrix capture

Area of Science:

• Materials Science
• Nondestructive Testing
• Ultrasonic Imaging

Background:

• Far-field laser technology advances bulk structure nondestructive ultrasonic imaging.
• Thermoelastic excitation causes low signal-to-noise ratios, limiting image resolution and contrast.

Purpose of the Study:

• To develop a frequency-domain phase weighted imaging method for superior laser ultrasonic defect imaging.
• To enhance image quality, resolution, and noise suppression in laser ultrasonic testing.

Main Methods:

• Laser ultrasonic scanning with a cylindrical lens focused line source for enhanced body wave signals.
• Frequency-domain phase shift migration (PSM) for multimode imaging (F-SAFT, F-TFM) using full matrix capture.
• Phase circular statistical vector (PCSV) for weighted optimization to suppress noise and artifacts.

Main Results:

• Frequency-domain imaging outperformed time-domain results.
• Phase weighting further improved image quality and significantly reduced the detection blind zone.
• The method effectively suppressed background noise and multimode artifacts.

Conclusions:

• The developed frequency-domain phase weighted imaging method offers a significant advancement for laser ultrasonic defect detection.
• This technique enables rapid, high-quality defect imaging in bulk structures.
• The PCSV approach provides effective noise and artifact reduction for improved imaging accuracy.