Single point active alignment method (SPAAM) for optical see-through HMD calibration for AR

Augmented reality (AR) is a technology in which a user´s view of the real world is enhanced or augmented with additional information generated from a computer model. In order to have a working AR system, the see-through display system must be calibrated so that the graphics is properly rendered. The optical see-through systems present an additional challenge because we do not have access to the image data directly as in video see-through systems. This paper reports on a method we developed for optical see-through head-mounted displays. The method integrates the measurements for the camera and the magnetic tracker which is attached to the camera in order to do the calibration. The calibration is based on the alignment of image points with a single 3D point in the world coordinate system from various viewpoints. The user interaction to do the calibration is extremely easy compared to prior methods, and there is no requirement for keeping the head static while doing the calibration