Patent ID: 8804132

Claim:
Apparatus for performing shearography from a platform that is moving at a known velocity above and over a surface, at a known distance above the surface, and the timing between pairs of coherent laser light pulses directed toward the surface from the moving platform is known, the apparatus comprising: (a) first laser means for generating a first of the pairs of pulses of coherent light onto the surface; (b) an optical receiver positioned a known distance from the first laser means for receiving the coherent light from the first laser means that is reflected from the surface; (c) second laser means for generating a second of the pairs of pulses of coherent light onto the surface, the second laser means being spaced a known distance from the first laser means, and the second laser means being movable to change the distance between the first laser means and the second laser means, and the optical receiver receives the coherent light from the second laser means that is reflected from the surface; and (d) means for changing the distance between the first laser means and the second laser means dependent on the velocity of the moving platform, the distance of the moving platform above the surface, and the timing between the first of each pair of pulses of coherent light and the second of each pair of pulses of coherent light, the changed distance between the first laser means and the second laser means permitting the shearography to be performed.