Practical Solutions for Calibration of Optical See-Through Devices

One of the most crucial tasks in a see-through augmented reality (AR) system is to register the virtual objects with the real world through a transparent display. The importance stems not only from the fact that registration requires careful calibration of the system but also from the necessity that any calibration procedure should take into account the users. Tuceryan et al. in [26] proposed a general method for calibrating any see-through AR system. This method is called the single point active alignment method (SPAAM) based on dynamic alignment of a set of displayed points with a single scene point at a time. Our experiences with this method on several optical see-through AR systems showed that although a powerful tool, users find alignment of many points overwhelming. This paper introduces several improvements to simplify the calibration process and increase the success rate. After identifying the causes where calibration parameters change from user to user, we propose ways of preventing most of the change by adopting particular configurations for tracker sensor and the see-through display. Then, a simple user interface is implemented where existing calibrations can be used. Furthermore, we have introduced a simpler model for the calibration that requires less number of user inputs, typically four, to calibrate the system.