Patent ID: 8717577
Filing Date: 2014-05-06
Classification: G01B

Abstract:
1. Apparatus for performing shearography of a surface from a platform that is moving above and over the surface, the apparatus comprising: (a) first laser means for generating a first of a pair of pulses of coherent light that reflects off the surface to create a first image, the first laser means generating its first laser pulse from a first point in space; and (b) second laser means for generating a second of the pair of pulses of coherent light that reflects off the surface to create a second image, the second laser means being spaced a known distance from the first laser means, the second laser means generating its second pulse a known time after the first laser means generates its first pulse, and after the known time the second laser means is at the first point in space where it generates the second laser pulse; (c) optics for receiving both the first image and the second image reflected from the surface; (d) image passing means associated with the optics, wherein the image passing means passes the first image when the first laser means is at the first point in space, and after the known time the image passing means passes the second image when the second laser means is at the first point in space; (e) means for dividing the first image into two copies laterally displaced from each other on the same image plane, and for dividing the second image into two copies laterally displaced from each other on the same image plane; (f) means for capturing the two copies of the first image to create a first specklegram and subsequently capturing the two copies of the second image to create a second specklegram; (g) means for storing both the first specklegram and the second specklegram; and (h) means for combining the first specklegram and the second specklegram to create a sheargram image showing changes in the surface.