Double exposure holography is perhaps the most established interferometry-based optical non-destructive testing (NDT) technique since the invention of the laser. In tis paper, the reference and object beams are transmitted via optical fibres; the launcher for the object beam is attached to a translating stage. Shiftign the translating stage in prescribed direction and amount results in the generation of reference carrier fringes. During testing, a small load-increment is applied to the test object prior to the second exposure while the object beam is simultaneously translated. This results in the reference carrier fringe pattern being perturbed by the displacement of the object surface. With the rapid advancement of computer technology and image processign techniques, this paper uses a Fast Fourier Transform (FFT) algorithm to automatically extract the deformation fringe-phases, instead of manually counting and processing the visible fringes. To illustrate the method described in this paper, two sets of images that correspond to a centrally loaded disk and an industrial water filter under internal uniform pressure are presented.
展开▼
