OPTICAL FRINGE MULTIPLICATION IN MOIRE INTERFEROMETRY

An optical method for multiplication of moire fringes is proposed to i ncrease the sensitivity of moire interferometry. The process involves two recording steps. In the first step, a traditional moire interferom etry setup is used. The moire pattern containing carrier fringes and l oad fringes is recorded onto a glass-based holographic plate. The carr ier frequency is much lower than that of the original specimen grating . The plate is then developed. In the second step, the holographic pla te, regarded as a distorted specimen grating, is further examined by a similar moire interferometry system. The frequency of the second virt ual grating is arranged to be 2n times that of the carrier fringes con tained in the recorded plate. As a result, the load fringes are reveal ed with a multiplication factor of 2n. The interpretation of the optic al multiplication method from wave-front interference theory is given and an experiment is conducted. (C) 1995 Optical Society of America