General considerations relevant to the design of moire interferometry apparatus are presented, followed by a description of the construction and adjustment of a particular 6-beam 3-axis device.

Approaches to design

There are three general design steps in the physical realization of a device for performing interferometry, including the moire variety. First, the needed special capabilities and tolerable limitations must be listed. Second, an optical arrangement that will satisfy the requirements must be designed. Finally, optical components must be obtained and arranged to perform the desired tasks.

Various optical arrangements for moire interferometry have been employed (Cloud and Herrera Franco 1986; Herrera Franco 1985; McDonach, McKelvie, and Walker 1980; Post 1980; Post 1987; Post and Baracat 1981; Post, Han, and Ifju 1994). Discussion of all the possibilities would be somewhat tedious and could be counterproductive in that the reader's attention might be distracted from the development process. Once the process is understood, the practitioner can review literature on the designs that have been employed and can then modify these designs or create new ones to fit the problems and resources at hand. For that reason, attention here is focused on the design and construction of a general-purpose 6-beam instrument with useful capabilities for experiments that require full knowledge of the surface strain fields in different types of specimens (Cloud, et al. 1987; Cloud, Herrera Franco, and Bayer 1989; Herrera Franco 1985).