Fringe multiplication methods for digital interferometric fringes.

Holographic moire fringes can be multiplied by using diffraction interferometry, an approach which is not applicable to some other interferometric techniques such as geometric moire. Three fringe multiplication methods are proposed which use a digital image processing technique to multiply various interferometric fringes. These methods are easy to handle and greatly improve the measurement accuracy. They enlarge the testing range for applying the interferometric techniques.