Beam-splitting cube for fringe-projection, holographic, and shearographic interferometry

We describe a simple method in which the techniques of fringe-projection, h olographic, and shearographic interferometry maybe readily realized with a commercial beam-splitting cube, a laser source, and abeam expander. With th e use of a computer algorithm, moire fringes maybe derived digitally from t he fringes that are projected onto a reference surface and onto an object s urface. Successful use of the beam-splitting cube for these optical methods is attributed to the refraction of the two split beams that exit from the two adjacent faces of the cube. By careful orientation of the cube, the two refracted fight beams will converge and interfere, resulting in the format ion of Young's interference fringes for the fringe-projection method. When the hypotenuse of the beam-splitting cube is placed nearly normal to an ill uminated object, both the image and the mirror image of the object will be formed behind the cube where a camera is placed. This optical setup thus fo rms the basis for double-exposure holography when these two images are full y overlapped and for shearography when the images are slightly laterally di splaced. (C) 2001 Optical Society of America.