Laser-ultrasonic non-destructive, non-contacting inspection system

A method of inspecting an area in a workpiece, said workpiece also including an outer surface, comprising the steps of:

• generating an array of acoustic waves in said workpiece that arrive substantially in phase with respect to each other at said inspection area and propagate through and/or reflect from said inspection area to arrive at an area on an outer surface of said workpiece, with said waves arriving substantially in phase with respect to each other over a locus at said outer surface, thereby vibrating said outer surface over said locus,
• detecting said acoustic waves over said locus by directing an optical read-out beam to said vibrating surface and distributing it over said locus so that said read-out beam is phase modulated by said vibrations and reflected from said surface, and
• extracting information about said inspection area from said detected acoustic waves.

A weld inspection system for on-line inspection of a weld site between first and second workpieces, each of said workpieces including an outer surface, comprising:

• an acoustic wave generator for generating an array of acoustic waves in said first workpiece that arrive substantially in phase with respect to each other at said weld site such that a portion of said waves reflect from said weld site and propagate back through said first workpiece to arrive at and vibrate an area on the outer surface of said first workpiece, with said waves arriving substantially in phase with respect to each other over a locus at said outer surface, and another portion of said acoustic waves propagate into said second piece through said weld site as a weld joint forms,
• an acoustic wave receiver that detects said acoustic waves over said locus by directing an optical read-out beam to said vibrating surface and distributing it over said locus so that the read-out beam is phase modulated by the vibrations along said locus and reflected from said surface, and
• a signal monitor for extracting information about said weld site from said acoustic wave receivers.

A weld inspection system for off-line inspection of a weld joint between first and second workpieces, each of said workpieces also including an outer surface, comprising:

• an acoustic wave generator for generating an array of acoustic waves in said first workpiece that arrive substantially in phase with respect to each other at said weld joint such that a portion of said waves propagate through said weld joint to arrive at and vibrate an area on the outer surface of said second workpiece, with said waves arriving substantially in phase with respect to each other over a locus at said outer surface,
• an acoustic wave receiver that detects said acoustic waves over said locus by directing an optical read-out beam to said vibrating surface and distributing it over said locus so that the read-out beam is phase modulated by the vibrations along said locus and reflected from said surface, and
• a signal monitor for extracting information about said weld site from said acoustic wave receivers.

A laser-ultrasonic, non-contacting inspection system, comprising:

• an acoustic wave generator for generating an array of acoustic waves in a workpiece that arrive substantially in phase with respect to each other at a desired inspection area in said workpiece and propagate through and/or reflect from said inspection area to illuminate an area on an outer surface of said workpiece, with said waves arriving substantially in phase with respect to each other over a locus at said outer surface, thereby vibrating the illuminated surface, said generator comprising an optical beam generator that directs an optical beam that has a power density sufficient to generate an array of acoustic waves in said workpiece through either thermoelastic or ablation effects onto said workpiece so that said beam is symmetric about said inspection area,
• an acoustic wave receiver that detects said acoustic waves over said locus, said acoustic wave receiver comprising an optical beam generator that directs a read-out beam onto said vibrating surface so that said read-out beam falls within a ring-shaped pattern on said vibrating surface that is symmetric about said inspection area, said read-out beam being phase modulated by said vibrations and reflected from said surface, and
• a signal monitor for extracting information about said inspection area from said acoustic wave receiver.

A method of inspecting an area in a workpiece, said workpiece also including an outer surface, comprising the steps of:

• generating an array of acoustic waves in said workpiece that arrive substantially in phase with respect to each other at said inspection area and propagate through and/or reflect from said inspection area to illuminate an area on an outer surface of said workpiece, with said waves arriving substantially in phase with respect to each other over a locus at said outer surface, thereby vibrating the illuminated surface, said acoustic waves being generated in said workpiece by directing an optical beam that has a power density sufficient to generate an array of acoustic waves in said workpiece through either thermoelastic or ablation effects onto said first workpiece so that said beam is symmetric about said inspection area,
• detecting said acoustic waves over said locus by directing a read-out beam onto said vibrating surface so that said read-out beam falls within a ring-shaped pattern on said vibrating surface that is symmetric about said inspection area, is phase modulated by said vibrations and is reflected from said surface, said read-out beam illuminating a half to full ring-shaped pattern on said vibrating surface, and
• extracting information about said inspection area from said detected acoustic waves.