Abstract: A system for non-destructively inspecting or testing for faults or damage in or beneath the surface of structures, such as debonds or delaminations in composite materials, or cracks, broken stringers, delaminations and the like in structures. High energy acoustic impulses are focused onto a sample point or local area for vibrationally exciting the surface of the structure under inspection. A laser Doppler camera system directs a laser beam onto the excited area and derives from reflected light energy information including time domain signals. A Fast Fourier Transform (FFT) is constructed for each sample point and an analysis made to set aside FFTs deviating from a preselected standard which represent damaged or other anomalous areas. The remaining FFTs represent an average or statistical FFT spectrum of the undamaged or fault-free area. The average FFTs and the deviating FFTs are then subtracted to provide a clear and unambiguous signal of the fault and other anomalous areas in the structure under test.

Abstract: Apparatus for non-destructively inspecting for faults in or beneath the surface of structures, such as debonds or delaminations in composite materials, or cracks, broken stringers, delaminations and the like in semi-monocoque structures, includes at least one spark gap discharge device displaced from the test object which focuses an acoustic pulse onto a small local area of the object for vibrationally exciting the surface of that area. A laser Doppler camera system, also displaced from the test object directs a laser beam onto the excited area and derives from light energy reflected back from the excited area the velocity of out-of-surface displacement of, and relaxation frequencies generated by, the surface of the excited area and provides an indication of whether a fault is present in that area.

Abstract: Apparatus for non-destructively inspecting for faults in or beneath the surface of structures, such as debonds or delaminations in composite materials, or cracks, broken stringers, delaminations and the like in semi-monocoque structures, includes at least one spark gap discharge device displaced from the test object which focuses an acoustic pulse onto a small local area of the object for vibrationally exciting the surface of that area. A laser Doppler camera system, also displaced from the test object directs a laser beam onto the excited area and derives from light energy reflected back from the excited area the velocity of out-of-surface displacement of, and relaxation frequencies generated by, the surface of the excited area and provides an indication of whether a fault is present in that area.

Abstract: A semi-monocoque structure is nondestructively tested by affixing an exciter to the outer skin of the structure for causing it to vibrate with an out-of-plane motion in a nodal pattern. Sensors either attached to or spaced from the outer surface provide signals representative of phase and acceleration information at likely anti-nodal points from which a computer-programmed controller senses resonant frequencies and amplitude of displacement. The controller automatically scans the excitation frequency through a predetermined range, and upon sensing a resonant frequency examines the signal to ascertain phase and amplitude of displacement of the anti-nodes and automatically adjusts their amplitude of displacement until the anti-nodes are optimized to be either bi-concave or concave/convex.

Abstract: A solid-state laser oscillator/amplifier system, which combines in a single laser crystal the operations of a narrow beam oscillator and a large volume amplifier, utilizes the polarization feature of the laser beam to effect coupling of an amplified beam out of the resonator in a manner which efficiently utilizes the whole volume of the active medium. The system generates a high brightness laser beam with high output energy contained in a small divergence angle.