Interferometric testing of cylindrical inner surface

Surface shape of precision ring is critical to its performance. To require the whole surface information, more requirements are needed for traditional measurement. A Fizeau type interferometric system is proposed, with a 90° conical mirror the whole cylindrical inner surface can be achieved through one measurement. Considering the introduced errors from the real experiment condition, it is almost impossible to get the real surface information from the inner surface. Any small angular deviation from the 90° cone and misplacement from its ideal position may result in large measurement errors. These errors are hard to be removed before their origins are figured out, also their influence on the measurement results are understood. The principle of the testing setup, the theoretical analysis of main errors based on a cylindrical coordinate, computer simulations by MatLab, and experimental validation are presented in this paper.