The current advent of consumer level optical see-through (OST) head-mounted displays (HMD's) has greatly broadened the accessibility of Augmented Reality (AR) to not only researchers but also the general public as well. This increased user base heightens the need for robust automatic calibration mechanisms suited for nontechnical users. We are developing a fully automated calibration system for two stereo OST HMD's, a consumer level and prototype model, based on the recently introduced interaction free display calibration (INDICA) method. Our current efforts are also focused on the development of an evaluation process to assess the performance of the system during use by non-expert subjects.