Optical see-through HMD calibration: a stereo method validated with a video see-through system

We present initial results from ongoing work to calibrate optical see-through head-mounted displays (HMDs). We have developed a method to calibrate stereoscopic optical see-through HMDs based on the 3D alignment of a target in the physical world with a virtual object in the user's view. This is an extension of the single point active alignment method (SPAAM) (Tuceryan and Navab, 2000) developed for monocular HMDs. Going from the monocular to the stereoscopic optical HMDs for calibration purposes is not straightforward. This is in part due to the perceptual complexity of the stereo fusion process bringing up completely new challenges including the choice of the shape of the virtual object, the physical target and how to display the virtual object without any knowledge of the characteristics of the HMD and eye combination, i.e. the projection model. We have addressed these issues and proposed a solution for the calibration problem which we have validated through experiments on the see-through HMD system described in (Sauer et al., 2000). By experimenting, we have found the appropriate type of virtual objects and physical features to be used in the 3D alignment. Furthermore, we have measured how good the alignment and calibration actually are.