Holographic Fringe Linearization Interferometry For Defect Detection

Holographic deformation measurements by Fourier transform technique with automatic phase unwrapping

“…This principle of shifting the object wavefront between exposures to create linear cosine fringes has been illustrated in the literature. 24 The fringes have a period p in object space, which is given by…”

Methods and Applications of Optical Holography

“…At the first step the image of untreated object is recorded and secondly, the second image is recorded after the object was treated mechanically, thermally etc. When the hologram is reconstructed in coherent light it generates two wavefronts -one from image of object in primary state and another from image of object after treatment [53,54]. The interference of both wavefronts produces fringes on reconstructed 3D image of object (Fig.…”

The Use of Carrier Fringes and FFT in Holographic Nondestructive Testing

“…whether the surface has moved toward or away from the observer, 1-2 and in assigning the correct fringe orders. In overcoming these difficulties, the carrier fringe technique [1][2][3][4][5][6] is frequently used. The basic principle of the technique is to introduce a known set of linear carrier fringes which modulates the conventional deformation fringes.…”

“…The fast Fourier transform (FFT) method of fringe pattern analysis is successfully used for extracting phase information from fringe patterns caused by the interference of tilted wavefronts. [2][3][4][5][6] Tilting the wavefront generates a linearised fringe pattern which facilitates the use of computerized automatic analysis. The FFT method for computing phases can produce phase maps automatically without the need for locating fringe centers or assigning fringe orders.…”