Pulse stretching technique for laser bond inspection, laser ultrasonic inspection, and laser peening

An inspection system comprising:

• an end effector;
• a positioning system configured to adjust a position of the end effector;
• a laser system provided within the end effector, the laser system comprising:
• a laser configured to provide a laser pulse,
• a plurality of pulse stretchers coupled together in series, the plurality of pulse stretchers configured to stretch a pulse width of the laser pulse so as to obtain a stretched laser pulse, wherein one or more pulse stretchers of the plurality of pulse stretchers includes two beamsplitting elements and an optical ring cavity that are configured to split a received laser pulse into a plurality of overlapping laser pulses with different time delays, thereby lengthening a pulse width of the received laser pulse, wherein the two beamsplitting elements include (i) a first beamsplitting element that splits the received laser pulse into a first beam that enters the optical ring cavity for generating a delayed first beam and a second beam and (ii) a second beamsplitting element that splits the second beam and the delayed first beam into two beams where one beam is output as the stretched laser pulse and the other enters the optical ring cavity, wherein the one or more pulse stretchers of the plurality of pulse stretchers includes an optical delay controller through which the first beam travels during generation of the delayed first beam, wherein the optical delay controller includes a plurality of reflective surfaces establishing a closed optical loop and an actuator to adjust a separation distance between at least two of the plurality of reflective surfaces so as to adjust the time delay of the first beam, wherein one of the plurality of reflective surfaces permits a portion of the first beam that has achieved a desired delay to exit the closed optical loop;
• and
• a lens assembly configured to direct the stretched laser pulse to a workpiece bondline;
• a feedback module configured to control a shape of the stretched laser pulse output by the plurality of pulse stretchers, wherein the feedback module includes one or more pulse delay comparators and a computing device, each pulse delay comparator configured to compare the received laser pulse to a corresponding stretched laser pulse that has been stretched by the plurality of pulse stretchers, and the computing device is configured to output a control signal to the optical delay module, based on a result of the comparing by the one or more pulse delay comparators, indicating an adjustment to the time delay;
• and
• a detector configured to detect a response of the workpiece bondline to the stretched laser pulse.

A method for inspecting a workpiece bondline comprising:

• adjusting a position of an end effector so as to adjust a position at which laser pulses output by a laser system contact a workpiece, wherein the laser system is provided within the end effector;
• providing a laser pulse using the laser system;
• stretching a pulse width of the laser pulse using a plurality of pulse stretchers coupled in series so as to obtain a stretched laser pulse, wherein the plurality of pulse stretchers are provided within the end effector, wherein one or more pulse stretchers of the plurality of pulse stretchers includes two beamsplitting elements and an optical ring cavity that are configured to split a received laser pulse into a plurality of overlapping laser pulses with different time delays, thereby lengthening a pulse width of the received laser pulse, wherein the two beamsplitting elements include (i) a first beamsplitting element that splits the received laser pulse into a first beam that enters the optical ring cavity for generating a delayed first beam and a second beam and (ii) a second beamsplitting element that splits the second beam and the delayed first beam into two beams where one beam is output as the stretched laser pulse and the other enters the optical ring cavity, wherein the one or more pulse stretchers of the plurality of pulse stretchers includes an optical delay controller through which the first beam travels during generation of the delayed first beam, wherein the optical delay controller includes a plurality of reflective surfaces establishing a closed optical loop and an actuator to adjust a separation distance between at least two of the plurality of reflective surfaces so as to adjust the time delay of the first beam, wherein one of the plurality of reflective surfaces permits a portion of the first beam that has achieved a desired delay to exit the closed optical loop;
• controlling a shape of the stretched laser pulse output by the plurality of pulse stretchers, by a feedback module including one or more pulse delay comparators and a computing device, each pulse delay comparator configured to compare the received laser pulse to a corresponding stretched laser pulse that has been stretched by the plurality of pulse stretchers, and the computing device is configured to output a control signal to the optical delay module, based on a result of the comparing by the one or more pulse delay comparators, indicating an adjustment to the time delay;
• and
• delivering the stretched laser pulse to a workpiece bondline;
• and
• detecting a response of the workpiece bondline to the stretched laser pulse.